spinal and cranial nerves

IV. PERIPHERAL PART OF SOMATIC NERVOUS SYSTEM
SPINAL NERVES
Because the central parts of somatic nervous system are the spinal cord and brain, that corresponding peripheral parts are the spinal and cranial nerves.
Anterior roots of the spinal cord are formed by axons of motor neurons of anterior horns of
spinal cord therefore they are motor. The posterior roots are formed by central processes of cells
of spinal ganglions and they are sensory. The peripheral processes of spinal ganglion’s cells originate by receptors.
Anterior and posterior roots fuse together laterally to spinal ganglion and in intervertebral foramen form mixed spinal nerve (n. spinalis). The total number of spinal nerves – 31 pair: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal (correspond to segments of spinal cord).
After exit through intervertebreal foramen each nerve divides into four branches. The anterior
one (r. ventralis) and posterior (r. dorsalis) are continuation of nerve; other two: meningeal
branch (r. meningeus) go to meninges of spinal cord, and white communicating one (r. communicans albus) connects with sympatetic ganglion.
The inflammation of anterior or posterior roots of spinal cord is called radiculitis; of trunk of
spinal nerve – funiculitis; of peripheral branches – neuritis.
Figure 17. Scheme of main sensory and motor neurons of spinal nerves and their communications with spinal cord.
1- skin, 2- nerve fibers from skin receptors, 3- posterior branch, 4- anterior branch, 5- skeletal
muscle, 6- spinal ganglion of posterior root, 7 - vegetative branch, 8 - sympathetic ganglion, 9 anterior root, 10 - intestine.
The posterior roots always more thiner than anterior ones. Each posterior branch (exept I
cervical nerve) is divided on medial and lateral branches. The posterior cervical branches supply
skin and muscles of posterior cervical region. First posterior branch is motor and named suboccipital nerve (n. suboccipitalis), which supplies the short occipito-vertebral muscles (rectus
capitis posterior major and minor muscles, obliquus capitis superior and inferior muscles). The
second posterior branch is the largest of all posterior cervical branches. Its medial cutaneous
branch perforates the tendon of trapezius muscle and appears under skin as greater occipital
nerve (n. occipitalis major) and supplies the skin of occipital region. The rest posterior cervical
branches are very short and supply skin and autochtonous muscles of the back.
The posterior branches of thoracic and lumbar nerves supply skin and proper muscles of the
back. Branches of superior lunbar nerves reach gluteal skin and named superior clunial nerves
(nn. clunium superiores). The posterior branches of sacral nerves are very thin, exit through pos1
terior sacral foramina and form middle clunial nerves (nn. clunium medii). The posterior branch
of coccygeal nerve supplies skin over coccyx and around anus.
The meningeal branches go back through intervertebral foramina to vertebral canal and supply meninges and denticulate ligament of spinal cord. They contain sensory and sympathetic fibers.
The anterior branches of spinal nerves supply skin and muscles of anterior wall of body and
limbs. Unlike posterior branches their fibers intertwine and form nerve plexuses. There are four
large plexuses: cervical, brachial, lumbar and sacro-coccygeal. Only anterior branches of 12 thoracic nerves form no plexuses. Together with arteries and veins they pass in intercostal spaces
between external and internal intercostal muscles, along lower margin of rib in costal groove and
named intercostal nerves (nn. intercostales).
XII intercostal nerve lies under corresponding rib and named subcostal nerve. Six upper pairs
of intercostal nerves along intercostal spaces reach the sternum, and six lower ones reach anterior
abdominal wall and pass between transversus abdominis and internal oblique abdominis muscles
and enter rectus abdominis muscle sheath. Intercostal nerves supply deep muscles of thorax, all
abdominal muscles, the skin of chest (and mammary gland) and skin of abdomen.
THE CERVICAL NERVOUS PLEXUS
The cervical plexus (plexus cervicalis) is formed by anterior branches of four upper cervical
nerves and is located inside deep muscles of neck (prevertebral and anterior, middle and posterior scalene).
The branches of this plexus are subdivided into: a) motor, b) sensory and c) mixed.
The motor or muscular branches supply deep muscles of neck (rectus capitis anterior and lateralis muscles, longus capitis and colli muscles, scalene muscles). One of the motor branches
inferior root, radix inferior, crosses externally internal jugular vein and fuses with superior root
of hypoglossal nerve, forming the ansa cervicalis. Its branches supply infrahyoid muscles of
neck (the sternohyoid, sternothyroid, thyrohyoid and omohyoid).
The sensory branches of cervical plexus go out between superior and middle thirds of posterior margin of sternocleidomastoid muscle. They supply the skin of neck, occiput and chest in
infraclavicular region. The branches are:
– the lesser occipital nerve (n. occipitalis minor) – along the posterior margin of sternocleidomastoid muscle it goes upwards and supplies the skin of occipital region.
– the greater auricular nerve (n. auricularis magnus) – the largest cutaneous branch. It goes
upwards to auricle along external surface of sternocleidomastoid and supplies the skin of external acoustic meatus and convex part of auricule and the skin of parotideomasseteric region.
– the transverse cervical nerve (n. transversus colli) – cross transversely the sternocleidomastoid muscle and gives 4 branches. The upperst of them fuses with ramus colli of facial nerve.
It supplies the skin of anterior region of neck.
– the supraclavicular nerves (nn. supraclaviculares) descend and supply the skin above the
clavicle and pectoralis major and deltoid muscles.
The mixed branches: phrenic nerve (n. phrenicus) – the longest nerve of cervical plexus. It
descends in front of the anterior scalenus muscle, enters thoracic cavity: the left one crosses anteriorly aortic arch, the right goes externally to superior vena cava. Both go down to diaphragm in
front of roots of lungs on lateral surface of heart between pericardium and mediastinal pleura. Its
motor fibers supply the muscular part of diaphragm. The sensory ones – the mediastinal pleura,
pericardium and going through caval opening of diaphragm in abdominal cavity, supply a fibrous capsule of liver and its ligaments.
The phrenicus sign – Tenderness after pressing between crura of sternocleidomastoid muscle
above right clavicle. Pain radiates to liver area. It is positive in case of liver or gallbladder diseases.
THE BRACHIAL PLEXSUS
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The brachial plexus (plexus brachialis) is formed by anterior branches of the four lower
cervical nerves and the major part of first thoracic nerve (С5-С8, Th1). Conditionally the brachial
plexus is divided into supraclavicular and infraclavicular parts. First one is located in spatium
interscalenum above subclavian artery as three trunks: superior, middle and inferior. Second one
is in the axillary cavity and represented by 3 cords: the medial, lateral and posterior, which surround the axillary artery. Branches of brachial plexus are classified as short and long.
The short branches originate from supraclavicular part. Conditionally they are divided into
two groups: 1) nerves to scapula: dorsal scapular nerve (n. dorsalis scapulae) – it supplies levator scapulae muscle; suprascapular nerve (n. suprascapularis) with the same name artery supplies supraspinatus and infraspinatus muscles; subscapular nerves (nn. subscapulares) – by 2-3
branches supplies subscapular and teres major muscles; 2) nerves thorax: the medial and lateral
pectoral nerves (nn. pectorales medialis et lateralis) supply the pectoralis major and minor muscles; the long thoracic nerve (n. thoracicus longus) – it goes at external surface of serratus anterior muscle and supplies it; the thoracodorsal nerve (n. thoracodorsalis) – it goes along the lateral margin of scapula and supplies the latissimus dorsi muscle. And the thinest nerve of short
branches – the subclavian nerve (n. subclavius) goes in front of subclavian artery more laterally
to phrenic nerve and supplies subclavius muscle.
Figure 18. The cervical and brachial plexuses.
The long branches originate from infraclavicular part.
The branches of medial cord:
– the medial root of median nerve;
– the medial cutaneous brachial nerve (n. cutaneus brachii medialis) – it supplies the skin of
corresponding region;
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– the medial cutaneous antebrachial nerve (n. cutaneus antebrachii medialis) – it supplies
corresponding skin;
– the ulnar nerve (n. ulnaris), which is mixed.
The ulnar nerve gives no branches on arm, but goes through medial bicipital groove together
with median nerve and brachial artery, and then behind medial humeral epicondyle and in forearm goes through ulnar groove together with ulnar artery. It supplies the flexor carpi ulnaris and
medial half of flexor digitorum profundus muscles. Than on palm it is divided on deep (muscular) and superficial (sensory) branches. It supplies skin around V and medial half of IV finger
(1.5 fingers), dorsal skin of 2.5 fingers (V, IV medial half of III) and majority muscles of hand.
The branches of lateral cord:
– the lateral root o median nerve;
– the musculocutaneus nerve (n. musculocutaneus) – it supplies the anterior group of brachial
muscles, its continuation lateral cutaneous antebrachial nerve (n. cutaneus antebrachii lateralis) – skin of this region.
The median nerve (n. medianus) – mixed, it originates by two roots from lateral and medial
cords. It gives no branches for the arm, goes through medial bicipital groove, median groove of
forearm and supplies all anterior muscles of the forearm except flexor carpi ulnaris and medial
half of flexor digitorum profundus muscles. Through the carpal canal under retinaculum flexorum it enters the palm and is divided on common digital nerves. It supplies partly thenar muscles, I and II lumbrical muscles as well as and skin of 3.5 fingers (I, II, III and lateral half of IV).
From posterior cord:
– the axillary nerve (n. axillaris), it is thick and short (sometimes considered as short branch
of brachial plexus), it goes back through foramen quadrilaterum of posterior wall of axillary cavity. Its terminal branch is the superior lateral cutaneous brachial nerve. Its muscular branches
supply to the deltoid and teres minor muscles.
– the radial nerve (n. radialis) – the thickest branch of brachial plexus. It goes back through
humeromuscular canal together with deep brachial artery and veins. In cubital fossa it is divided
into superficial and deep branches. It supplies posterior group of arm and forearm muscles. Its
sensory branches supply skin of posterior side of arm, forearm and hand of 2.5 fingers (I, II and
lateral half of III). In such case it is named like «the king» of all posterior part of upper limb.
The abbreviation “UMRU” for marking of zones of skin innervations of hand and fingers: on
palm 1.5 fingers supplied by Ulnar nerve and 3.5 – Median, on the dorsal side laterally 2.5 – the
Radial and 2.5 – Ulnar one. But the skin of distal phalanges of fingers is supplied similar to palmar side: the medial 1.5 fingers by ulnar nerve, 3.5 fingers – by median nerve.
THE LUMBAR PLEXUS. SACROCOCCYGEAL PLEXUS
Common lumbosacral plexus (pl. lumbosacralis) is formed by all anterior branches of lumbar, sacral and coccigeal nerves according zones of innervation are subdivided on two plexuses:
the lumbar and sacrococcygeal.
The lumbar plexus (pl. lumbalis) is formed by anterior branches of XII thoracic (partially),
I, II, III, IV (partially) lumbar spinal nerves.
The muscular branches (rr. musculares) supply quadratus lumborum, psoas major and minor
muscles.
Iliohypogastric nerve (n. iliohypogastricus) lies on quadratus lumborum muscle parallel to
ХII intercostal nerve. Then it goes between transverse and internal oblique abdominis muscles,
ending in hypogastric region. It supplies anterior abdominal wall, and by anterior and posterior
branches supply the skin of suprapubic region and skin above the trochanter major.
Ilioinguinal nerve (n. ilioinguinalis) goes between abdominal muscles, but its cutaneous
branch - through inguinal canal and supplies to the skin of scrotum (or labia majora).
The lateral cutaneous femoral nerve (n. cutaneus femoris lateralis) goes under inguinal ligament and supplies the lateral surface of skin of thigh.
The genitofemoral nerve (n. genitofemoralis) is located at anterior surface the psoas major
muscle and separates on two branches: a) the genital (r. genitalis), which goes through inguinal
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canal and supplies to m. cremaster and skin of scrotum (in males), the round ligament of uterus
and skin of labia majora (in females); b) femoral (r. femorails), which goes through vascular lacuna and supplies the skin of thigh below inguinal ligament.
The largest branches of the plexus are the femoral and obturator ones.
The femoral nerve (n. femoralis) reach the thigh under inguinal ligament through the muscular lacuna together with iliopsoas muscle. At the thigh it divides at the following brunches: the
muscular (to iliopsoas, quadriceps femoris, sartorius and pectineus muscles); the anterior cutaneus femoral nerve and saphenous nerve (n. saphenus). The last one goes together with femoral
artery and femoral vein in adductor (Hunter’s) canal, descends on medial surface of leg around
the medial malleus and enters medial surface of foot and supple skin of these areas.
The obturator nerve (n. obturatorius) leaves lumbar plexus medially to psoas major muscle,
descends to lesser pelvis, on its lateral wall reaches the obturator canal. Through it goes at medial surface of the thigh and supplies the medial group of muscles and skin of medial surface of
inferior part of the thigh and hip joint.
Figure 19. The lumbar and sacral plexus.
1 – n. subcostalis. 2 – n. iliohypogastricus. 3 – n. ilioinguinalis. 4 – truncus lumbosacralis. 5
– n. cutaneus femoris lateralis. 6 – n. genitofemoralis. 7 – n. femoralis. 8 – n. obturatorius. 9 – pl.
sacralis. 10 – gangl. sympatica sacralia. 11 – truncus sympathicus. 12 – pl. aorticus abdominalis.
The sacral plexus (pl. sacralis) – the largest of plexuses and is formed by anterior branches
of IV (partially) and V lumbar, all sacral spinal nerves. It lies inside lesser pelvis on piriformis
muscle. Its branches exit pelvic cavity through supra- and infrapiriform foramina to gluteal region.
The branches of this plexus are subdivided at short and long ones.
The short branches: a) muscular – supply piriformis, internal obturatorius, gemelli superior
and inferior as well as quadratus femoris muscles; b) superior gluteal nerve (n. gluteus superior)
– goes through suprapiriform foramen and supplies to gluteus medius and minimus and tensor
fasciae latae muscles; b) the inferior gluteal nerve (n. gluteus inferior) – exits through infrapiriform foramen and supplies the gluteus maximus muscle; c) the pudendal nerve (n. pudendus)
– goes out with inferior gluteal nerve, surrounds sciatic spine and through the lesser sciatic foramen goes back to the pelvis, into ischiorectal faoosa, where it divides into the terminal branches:
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the inferior rectal (nn. rectales inferiores) – supply external anal sphincter and skin around anal
canal; perineal nerves (nn. perineales) – to skin and muscles of perineum; the posterior scrotal
or posterior labial (nn. scrotales s. labiales posteriores) supply to the skin of posterior part of
scrotum and labia majora; the dorsal nerve of penis or clitoris (n. dorsalis penis s. clitoridis) give
branches to corresponding organs and contain large number of vegetative fibers.
The long branches of sacral plexus: the posterior cutaneous femoral nerve and sciatic nerve.
The posterior cutaneous femoral nerve (n. cutaneus femoris posterior) – sensory, enters thigh
under inferior margin of gluteus maximus muscle and supplies the skin of inferior part of buttocks (nn. clunium inferiores), perineum, posterior surface of thigh, popliteal fossa.
The sciatic nerve (n. ischiadicus) is mixed. It is the largest nerve of human body. It goes out
through infrapiriform foramen, in gluteal region it lies under gluteus maximus muscle. Near its
inferior margin nerve is located just under fascia lata (the place of most variable damage of it).
At the thigh it goes between muscles of posterior group and supplies to them. In popliteal fossa
the sciatic nerve divides into tibial and common peroneal nerves.
The tibial nerve (n. tibialis). In poplitael fossa it gives off the medial sural cutaneous nerve
(n. cutaneus surae medialis), after that it goes within cruropoliteal canal together with posterior tibial artery and veins. Then it travels behind in the medial malleolus, goes to plantar surface of foot
and divides into terminal branches - the medial and lateral plantar nerve. Besides, tibial nerve
gives off also: muscular (to posterior muscles of leg) and articular branches (to knee and talocrural joints).
The medial sural cutaneous nerve (n. cutaneus surae medialis) goes between heads of gastrocnemius muscle and joins with the lateral sural cutaneous nerve, forming the sural nerve (n.
suralis), which behind the lateral malleolus continuous as the lateral dorsal cutaneous nerve (n.
cutaneus dorsalis lateralis), which supplies the lateral part of foot. On the leg medial sural cutaneous nerve supplies to the skin of posterior-medial surface. The medial plantar nerve supplies
to the flexor digitorum brevis muscle, I and II lumbrical muscles and the plantar skin of medial
3.5 toes. The lateral plantar nerve supplies to the rest of plantar muscles and the skin of the rest
1.5 toes and lateral half of the plantar surface.
Common peroneal nerve (n. peroneus (fibularis) communis) passes forwards around the neck of
the fibula within the substance of peroneus (fibularis) longus, where it terminates by dividing into
the superficial and deep peroneal (fibular) nerves. Before this, common peroneal nerve gives off
the lateral sural cutaneous nerve (n. cutaneus surae lateralis), supplying to the skin of posterior-lateral
surface of leg, and it joins the medial sural cutaneous nerve to form sural nerve.
The superficial peroneal nerve (n. peroneus (fibularis) superficialis) goes down inside musculoperoneal canal between fibula and origin of peroneal muscles, which it supplies), it continuous at dorsum of foot by two nerves: the medial and intermediate dorsal cutaneous nerves (n.
cutaneus dorsalis medialis et intermedius). They supply the skin of dorsal side of foot, except
first interdigital space.
The deep peroneal nerve (n. peroneus (fibularis) profundus) moves together with anterior tibial artery and veins between anterior muscles of leg and supplies to them. It gives off branches to
talocrural joint and dorsal muscles of foot and skin of first interdigital space.
So, the sciatic nerve and its branches supply to posterior muscles of thigh, all muscles of leg
and foot, skin of leg (except the medial surface) and foot (except the medial margin of dorsal
side).
The coccygeal plexus is created by V lumbar and coccygeal spinal nerves – it supplies the
skin over the coccyx.
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CRANIAL NERVES
Cranial nerves, nn. craniales, are nerves that are anatomically and functionally connected to the
brain. There are 12 pairs of cranial nerves, which are indicated by Roman digits:
I pair - olfactory nerves, nn. olfactorii;
II pair - optic nerve, n. opticus;
III pair - oculomotor nerve, n. oculomotorius;
IV pair - trochlear nerve, n. trochlearis;
V pair - trigeminal nerve, n. trigeminus;
VI pair - abducent nerve, n. abducens;
VII pair - facial nerve, n. facialis;
VIII pair - vestibulocochlear nerve, n. vestibulocochlearis;
IX pair - glossopharyngeal nerve, n. glossopharyngeus;
X pair - vagus nerve, n. vagus;
XI pair - accessory nerve, n. accessorius;
XII pair - hypoglossal nerve, n. hypoglossus;
Fig. 20. Internal surface of base of the skull with cranial nerves.
I and II pairs of cranial nerves are derived from the forebrain, III-XII pairs are related to
various parts of the brainstem. III and IV pairs are connected with the midbrain, V-VIII - with
the pons, and IX-XII - with the medulla oblongata.
According to the composition of the fibers, cranial nerves are divided into 3 groups:
1) sensory nerves - I, II and VIII pairs;
2) motor nerves - IV, VI, XI and XII pairs;
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3) mixed nerves - III, V, VII, IX and X pairs (taking into account that the parasympathetic part of the III nerve innervates exclusively muscles, this pair is also sometimes referred to as
motor nerves).
Sensory nerves are formed by centripetal fibers (central processes) of cells located in the
nasal mucosa for the I pair, in the retina for the II pair or in the sensory ganglion of the VIII pair.
The motor nerves are formed by axons of cells of the motor nuclei of the cranial nerves IV, VI, XI and XII pairs.
Mixed nerves have different fiber composition. The sensory component present in V, VII,
IX, and X pairs of cranial nerves is represented by central processes of pseudounipolar cells located in sensory ganglions. The motor component present in III-VII, IX-XII pairs of cranial
nerves is represented by axons of cells of the motor nuclei of the corresponding nerves. The parasympathetic component in the mixed nerves is found in III, VII, IX and X pairs of cranial
nerves. It is formed by preganglionic parasympathetic fibers extending from the parasympathetic
nuclei of the corresponding nerves to the autonomic ganglia or postganglionic fibers, which are
axons of the cells of these ganglions. The name, localization of the autonomic ganglions and
nerves containing parasympathetic fibers are indicated in the table (see below).
It should be noted that in the composition of the motor and mixed cranial nerves there are
also sympathetic postganglionic fibers originating from the superior cervical ganglion of the
sympathetic trunk.
PHILO- AND ONTOGENESIS OF CRANIAL NERVES
Phylogenetically the cranial nerves lost their initial segmental location and became highly
specialized. The olfactory and optic nerves are specific nerves of the sensory organs that develop
from the forebrain and are its outgrowths. They connect the organ of smell and the organ of vision to the brain.
The rest of cranial nerves are derived from the spinal nerves and are fundamentally similar to them. The III pair (oculomotor nerve), the fourth pair (trochlear nerve) and the VI pair (abducent nerve) developed in connection with the preauricular myotomes, innervates the muscles
of the eyeball that developed from these myotomes. These nerves, as well as the XI and XII
pairs, are similar to the anterior roots of the spinal nerves.
V, VII, VIII, IX and X pairs of cranial nerves are homologues of the posterior roots.
These nerves are associated with muscles developing from the muscles of the branchial apparatus and developed from the lateral plates of the mesoderm, therefore they innervate the skin,
muscles of the corresponding visceral branchial arches, and also contain visceral motor fibers,
innervating glands and organs of the head and neck.
A special place is occupied by the V pair (trigeminal nerve), which is formed by the fusion of two nerves - the deep optic nerve, innervating the skin of the anterior surface of the head,
and the trigeminal nerve itself, innervating the skin and muscles of the mandibular arch.
In development, the VIII pair (vestibulocochlear nerve) is separated from the facial nerve,
which carries out the specific innervation of the organ of hearing and balance. IX pair (glossopharyngeal nerve) and X pair (vagus nerve), which consists of visceral motor nerve fibers, develop by isolating the caudal part of the vagus nerve. The hypoglossal nerve is complex in
origin, as it is formed by the fusion of few spinal nerves, some of which move cranially and enter
the region of the medulla oblongata.
Thus, all 12 pairs of cranial nerves by origin can be divided into several groups:
1. Nerves - derivatives of the brain - I (n. olfactorius) and II pairs (n. opticus).
2. Nerves developing in connection with the head myotomes - III (n. oculomotorius), IV
(n. trochlearis), VI (n. abducent) pairs.
3. Nerves - derivatives of branchial arches - V (n. trigeminus), VII (n. facialis), VIII (n.
vestibulocochlearis), IX (n. glossopharyngeus), X (n. vagus), XI (n. accessorius) pairs.
4. The nerve that developed by the fusion of the spinal nerves - XII pair (n. hypoglossus).
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The cranial nerves, like the spinal nerves, have nuclei (accumulations of gray matter):
somatic sensory (corresponding to the posterior horns of the gray matter of the spinal cord), somatic motor (corresponding to the anterior horns) and vegetative (corresponding to the lateral
horns). Vegetative can be divided into visceral motor and visceral sensory, moreover, visceral
motor not only innervate unstriated (smooth) muscles, but also provide trophics to skeletal muscles. Given that the striated muscles received the features of somatic muscles, all the nuclei of
the cranial nerves related to such muscles are better designated as somatic motor.
As a result, the composition of the cranial nerves contains the same components as in the
spinal nerves.
Afferent components:
1) somatic sensory fibers coming from organs that perceive physical stimuli (pressure,
pain, temperature, sound and light) i.e. skin, organs of hearing and vision - II, V, VIII.
2) visceral sensory fibers coming from organs that perceive internal stimuli, i.e. from
nerve endings in the digestive organs and other viscera, from the special organs of the pharynx,
oral (gustatory organ) and nasal (olfactory organ) cavities - I, V, VII, IX, X.
Efferent components:
1) somatic motor fibers innervating voluntary muscles, namely: muscles originating from
head myotomes, eye muscles (III, IV, VI), sublingual muscles (XII), and skeletal muscles that
are secondarily displaced into the anterior digestive tract - the so-called muscles of the branchial
apparatus, which have become masticatory, facial, etc. in mammals and humans. (V, VII, IX, X,
XI);
2) visceral motor vegetative fibers (parasympathetic and sympathetic fibers) innervating
visceral muscles, i.e. involuntary muscles of blood vessels and internal organs, muscle of the
heart, as well as various glands (secretory fibers), - V, VII, IX, X.
Scheme for the studying and description of cranial nerves
1. Numbering and name of the nerve (English, Latin).
2. Functional characteristic (motor, sensory, mixed).
3. Source of nerve development.
4. Nerve nuclei (name, functional characteristic, topography).
5. The principle of nerve formation, sensory ganglions.
6. Place of entry (sensory) or exit (motor, parasympathetic) of nerves from the brain.
7. The place of entry or exit of nerves from the skull.
8. The passage of the nerve in the periphery.
9. Parasympathetic ganglions associated with nerves.
10. The main trunks and branches of the nerve, their area of innervation.
SENSORY GANGLIONS OF CRANIAL NERVES AND THEIR LOCALIZATION
Name of nerve and number of pair
Name of ganglion
Trigeminal nerve, n. trigeminus, V pair Ganglion trigeminale
Localization of ganglion
Facial nerve, n. facialis, VII pair
Ganglion geniculi
Vestibulocochlear nerve, n. vestibulocochlearis, VIII pair
Glossopharyngeal nerve, n. glossopharyngeus, IX pair
Vagus nerve, n. vagus, X pair
Ganglion vestibulare, ganglion cochleare
Ganglion superius, ganglion inferius
Trigeminal impression of anterior surface of temporal pyramid
Geniculum of facial canal in temporal
pyramid
Floor of internal acoustic meatus, spiral canal of cochlear modiolus
Jugular foramen, fossula petrosa
Ganglion superius, ganglion inferius
Jugular foramen, below to it
CRANIAL NERVES
9
Name of nerve
and number of
pair
I., nn. olfactorii (S)
Sourse of development
Nuclei and their topography
derivatives of the
forebrain
—
II. n. opticus (S)
derivatives of the
—
forebrain
III. n. oculomoto- Derivatives of the Nucleus n. oculomotorii
rius (M, P)
head myotomes (M). Tegmentum mesencephali, level of superior
colliculi
Nucleus accessorius (P)
and unpaired median (P).
the same place as previous one, somewhat medially and posteriorly
IV. n. trochlearis Derivatives of the Nucleusn. trochlearis (M)
(M)
head myotomes Tegmentum mesencephali, level of inferior colliculi
Place of exiting
Place of exiting
from cranial
from brain or enInnervated organs
cavity or entertering in it
ing in it
Bulbus olfactorius Lamina cribro- Regio olfactoria musa ossis eth- cosa of nasal cavity
moidalis
Chiasma opticum
Sulcus
Fissura orbitaloculomotorius,
is superior
fossa
interpeduncularis
Posteriorly to the
tegmentum of the
midbrain.
Pass
around
cerebral
peduncles
V. n. trigeminus Homologues of Nucleus motorius n. Anteriorly the mid(M, S)
the posterior roots trigemini (M). In superior dle cerebellar peof spinal nerves. part pars dorsalis pontis duncle
(anterior
Derivatives
of
part of linea tribranchial arches
gemino-facialis)
Nucleus pontinus n. trigemini (S). laterally to the
previous one
Nucleus
spinalis
n.
trigemini (S). Continuation
of the previous one along
all medulla oblongata.
Nucleus tractus mesencephalici n. trigemini (S). In
the tegmentum of the midbrain, laterally to the aqueduct.
VI. n. abducens Derivatives of the Nucleus n. abducentis
(M)
head myotomes (M). Dorsal part of pons,
in the area of colliculus
facialis
VII. n. facialis (n. Homologues of Nucleus n. facialis (M)
intermedius) (M, S, the posterior roots Dorsal part of pons, forP)
of spinal nerves. matio reticularis
Derivatives
of
branchial arches
Nucleus solitarius (S).
Dorsal part of pons
Nucleus
salivatorius
superior (P)
Formatio reticularis, pars
dorsalis pontis (posteriorly to nucleus of facial
nerve)
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Canalis opticus Retina of eyeball
М. Levator palpebrae
superioris, m. rectus
medialis,
m.
rectus
superior, m. rectus inferior,
m. obliquus inferior
M. ciliaris, m. sphincter pupillae
Fissura orbital- M. obliqus superior
is superior
N.
ophthalmicus – fissura
orbi-talis superior, n. maxillaris – foramen
rotun-dum, n.
mandibularis –
foramen ovale
(M) Mm. masticatores, m. tensor veli
palatini, m. tensor
tympani,
m.
mylohyoideus, venter
anterior m. digastrici
(S) Skin of frontal
and temporal regions,
skin of face.
(S) Mucosa of nasal
and oral cavities, anterior 2\3 of the
tongue, teeth, salivary glands, organs
and tissues of orbit,
dura matter of anterior and middle cranial
fossa
Posterior edge of Fissura orbital- M. rectus lateralis
pons, in the groove is superior
between pons and
pyramid.
Posteriorly to mid- Porus acusticus (M) Mm. faciales, m.
dle cerebellar pe- internus – cana- platysma,
venter
duncle (posterior lis facialis – posterior m. digapart of linea tri- foramen stylo- strici, m. stуlohygeminofacialis)
mastoideum
oideus, m. stapedius
(S) gustatory sense of
anterior 2/3 of the
tongue
(P) Glandula lacrimalis,
tunica mucosa oris,
tunica mucosa nasi
(glands), gl. sublingualis,
gl.
submandibularis,
glandulae
salivatoria
minores
VIII.
n.
Homologues
vestibulocochlearis of the posterior
(S)
roots of spinal
nerves.
Pars cochlearis
Derivatives
of
Pars vestibularis branchial arches
IX., n. glossophaHomologues
ryngeus (M, S, P) of the posterior
roots of spinal
nerves.
Derivatives
of
branchial arches
X. n. vagus (M, S, Homologues of
P)
the posterior roots
of spinal nerves.
Derivatives
of
branchial arches
XI. n. accessorius Homologues of
(M)
the posterior roots
of spinal nerves.
Derivatives
of
branchial arches
In the region of lateral
angle of rhomboid fossa
(area vestibularis)
Nuclei cochleares ventralis et dorsalis (S)
Nuclei vestibulares medialis, lateralis, superior et
inferior (S)
Nucleus solitarius (S)
Doraslly in the medulla oblongata, in the region of
trigonum n. vagi as a continuation of this nucleus
Nucleus
salivatorius
inferior (P)
In formatio reticularis of
medulla oblongata between nucleus ambiguus
and olivary nucleus.
Nucleus ambiguus (M)
Formatio reticularis of
medulla oblongata
Nucleus solitarius (S)
In the region of trigonum
n. vagi, in medulla oblongata.
Ponto-cerebellar
angle
Porus acusticus Organon
spirale,
internus
crista
ampulares,
macula utriculi, macula sacculi
Inferiorly to two Foramen jugu- (S) Cavum tympani,
previous ones in lare
tuba auditiva, tunica
superior part of
mucosa radicis linsulcus
dorsolatguae, pharyngis, toneralis, posteriorly
silla palatina, glomus
to olive
caroticus, glandula
parotidea
(M)
M.
stylopharyngeus.
Muscles of pharynx
The same groove Foramen
(S) Dura mater of the
as n. glossopha- jugulare
posterior cranial fossa,
ryngeus caudally to
skin of internal acoustic
it
meatus. Organs of the
neck, thorax and abdomen (except left part of
large intestine)
Nucleusdorsalisn.vagi (P)
(P) Smooth muscles and
in the same area, dorsally
glands of organs of thoto the previous one
racic and abdominal
cavities (except left part
of large intestine)
Nucleus ambiguus (M).
(M) Tunica muscularis
Formatio reticularis medulpharyngis, m. levator veli
la oblongata, deeper to nupalatini, m. uvulae, m.
cleus dorsalis n. vagi
palatoglossus, m. palatopharyngeus, mm. laryngis
Nucleus ambiguus (M)
Radices craniales Foramen jugu- М.
sternocleidoIn medulla oblongata as a the same groove as lare
mastoideus, m. tracontinuation of the same n. vagus, but more
pezius
name nucleus of X, XI caudally.
pairs
Nucleus spinalis n. accessorii (M). In between anterior
and posterior horns of the
spinal cord
Radices spinales
between anterior
and posterior roots
of the cervical
nerves on the level
С2-C6 segments
XII. n. hypoglosHomologues Nucleus n. hypoglossi Sulcus
Canalis n. hy- Muscles of the tongue
sus (M)
of the anterior (M). In medulla oblongata ventrolateralis of poglossi
roots of spinal in the region of trigonum medulla oblongata
nerves.
nervi hypoglossi
Примечание:
(M) – motor innervation
(S) – sensory innervation
(P) – parasympatetic innervation
11
Fig. 21. Areas of innervations of cranial nerves (scheme).
I PAIR – OLFACTORY NERVES, NERVI OLFACTORII.
OLFACTORY PATH
These are nerves of special sense - they consist of visceral sensory fibers (perceive chemical irritation - odors). Unlike other cranial sensory nerves, the olfactory nerve does not have a
sensory nucleus or ganglion. Therefore, they are called false cranial nerves. The first neuron is
located on the periphery in regio olfactoria of the mucous membrane of the nasal cavity (superior nasal concha and upper part of the nasal septum). The dendrites of the olfactory cells are directed to the free surface of the mucous membrane, where they end with the olfactory vesicles,
and the axons form the olfactory filaments, fili olfactorii, 15-20 on each side, which penetrate
into the cranial cavity through the cribriform plate of the ethmoid bone. In the cranial cavity,
they reach the olfactory bulbs of the lower surface of the frontal lobe of the cerebral hemispheres
and end there. The second neurons are located in the olfactory bulbs, the axons of which form
the olfactory tract, tractus olfactorius. This tract goes along the lower surface of the frontal lobe
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in the groove of the same name and ends in the olfactory triangle, anterior perforated substance
and a septum pellucidum, where the third neurons of the olfactory path are located. Axons of the
third neurons are divided into two bands:
1. The lateral stria, stria lateralis, goes on its side to the cortex of uncus, giving part of
the fibers to the amygdaloid body.
2. The medial stria, stria medialis, goes to another hemisphere. Its fibers pass through the
anterior commissure of the brain, continuing on the opposite side in the form of a diagonal stria
(stria diagonalis, seu bandaletta diagonalis, Broca's diagonal band). As a result, the fibers reach
the same centers as the previous ones (uncus, amygdaloid body), but on the contralateral (opposite) side.
An intermediate stria, stria intermedia, which goes to the mammilary bodies (corpora
mamillaria), is also determined. From neurons of the mammilary bodies begins the mammillothalamic fasciculus, fasciculus mamillothalamicus. This tract is the beginning of the Papetz cycle.
Among the pathologies of the olfactory analyzer are known such as: anosmia - complete
loss of smell (possible unilateral and bilateral anosmia), hyposmia - reduced ability to smell,
dysosmia - perverted perception of smells, phantosmia - perception of nonexistent odors. The
causes of these pathologies can be extremely diverse: congenital disorders, injuries, infection,
inflammatory processes of the brain, toxic processes, neurodegenerative diseases, etc.
II PAIR – OPTIC NERVE, NERVUS OPTICUS.
Like the olfactory nerves, it belongs to the false cranial nerves, has no ganglion and nucleus.
It is a nerve of special sense (light) and consists of fibers, which are a set of axons of
multipolar ganglionic cells of the retina. The optic nerve begins with the optic disc in the area of
the optic part of the retina, its blind spot. Perforating the vascular and fibrous tunics, it leaves the
eyeball medially and inferiorly from its posterior pole. In accordance with the topography there
are four parts of the optic nerve:
- intraocular, perforating choroid and sclera of the eyeball;
- orbital, extending from the eyeball to the optic canal;
- intracanalicular, corresponding to the length of the optic canal;
- intracranial, located in the subarachnoid space of the base of the brain, extending from
the optic canal to the optic chiasm.
In the orbit, the optic canal and in the cranial cavity the optic nerve is surrounded by a
sheath (vagina), the layers of which correspond to the meninges of the brain, and the intravaginal
spaces correspond to the intermeningeal spaces.
The first three neurons are in the retina. The set of photosensitive retinal cells (rods and
cones) are the first neurons of the optic tract; giant and small bipolar cells - the second neuron;
multipolar ganglionic cells - the third neuron. The axons of these cells form the optic nerve. The
nerve passes through the optic canal, canalis opticus, and enters the cranial cavity. In the area of
the prechiasmatic groove 2/3 of all nerve fibers coming from the medial visual fields decussate.
These fibers come from the medial parts of the retina, which receives visual information from
the lateral sides due to the intersection of light beams in the lens. Approximately 1/3 nondecussating fibers go into the optic tract of their side. They come from the lateral parts of the retina, which receives light from the nasal half of the visual field (lens effect). An incomplete decussation of the optic tracts allows the transmission of impulses from each eye to both hemispheres, providing binocular stereoscopic vision and the possibility of synchronous movement of
the eyeballs. After this partial decussation optic tracts are formed and bend around the cerebral
peduncles from the lateral side and appear on the dorsal part of the brainstem. Each optic tract
contains fibers from the same retinal halves of both eyes. So, in the composition of the right optic tract, non-crossed fibers from the lateral half of the right eye and crossed fibers from the medial half of the left eye pass. Therefore, the right optic tract conducts a nerve impulse from the
13
lateral part of the visual field of the left eye and the medial (nasal) part of the visual field of the
right eye.
The fibers of each optic tract follow in 3 directions that pass to the subcortical visual centers:
- lateral geniculate bodies of the diencephalon, corpora geniculate lateralis;
- pulvinar of the thalamus of the diencephalon, pulvinar thalami (then to the cortex);
and part of the fibers, without synapse in geniculate bodies, follows through the brachium
into
- superior colliculi of the tectum of the midbrain, colliculi superioris tecti mesencephalici.
The main subcortical center of vision is the lateral geniculate bodies, where most of the
fibers of the optic path end. Here its fourth neurons are located. The axons of these neurons in a
compact bundle pass through the posterior third of the posterior limb of the internal capsule, then
form optic radiation, radiation optica, and end on neurons of the cortical center of vision on the
medial surface of the occipital lobe on the sides of the calcarine sulcus.
A small number of fibers of the optic tracts are directed to the neurons of the posterior
nuclei of the thalamus. The axons of the neurons of these nuclei transmit visual information to
the integration center of the diencephalon - the medial nucleus of the thalamus, which has connections with the motor nuclei of the extrapyramidal and limbic systems. These structures regulate muscle tone, carry out emotional-behavioral reactions, and alter the functioning of internal
organs in response to visual irritations.
A part of the fibers goes to the superior colliculi, providing an unconditionally reflex reaction of the eyeball and the implementation of the pupil reflex in response to light irritations.
The axons of the nucleus of the superior colliculi are directed to the motor nuclei of the III, IV,
VI pairs of cranial nerves, to the accessory nucleus of the oculomotor nerve (the nucleus of K.
Westphal, L. Edinger), to the nuclei of the reticular formation, to the nucleus of Cajal’s and to
the integration center of the midbrain, which is also located in the superior colliculi.
The connections of the neurons of the superior colliculi with the motor nuclei of III, IV,
VI pairs of cranial nerves provide a motor reaction of the eyeball muscles to light stimuli (binocular vision) and connections with the neurons of the Cajal’s nucleus allows coordinated movement of the eyeballs and head (maintaining body balance). From the cells of the integration center of the midbrain begins the tecto-spinal and tecto-nuclear tracts, which carry out unconditional
reflex motor reactions of the muscles of the trunk, limbs, head and eyeballs to sudden strong
light irritations. From the cells of the reticular formation, the reticulopetal and reticulospinal
tracts begin, which regulating muscle tone in conjunction with exogenous irritations. The cells of
the accessory nucleus of the oculomotor nerve send axons to the ciliary ganglion, which provides
parasympathetic innervation of the sphincter pupillae muscle and ciliary muscle, which provides
accommodation for the eye. The chain of neurons providing these reactions is called the pathway
of pupil reflex.
The pathway of the pupil light reflex
It provides an involuntary response of the pupil to light. It consists of two parts: sensory
and motor. The sensory one is part of the optic nerve and contains four neurons (the first three
are in the retina, the fourth is in the superior colliculi of the quadrigeminal plate). The processes
of the fourth neurons are directed to the parasympathetic nucleus of Yakubovich, where the fifth
neuron of the pupil light reflex pathway is located and its motor part begins, which is part of the
oculomotor nerve. Together with the oculomotor nerve, the processes of the fifth neuron enter
the orbit through the superior orbital fissure. Here the parasympathetic fibers are separated,
forming the so-called parasympathetic root of the ciliary ganglion, radix parasympathica ganglion ciliare, enter this parasympathetic ganglion and end on its cells, which are the sixth neurons
of the pupil light reflex pathway. Axons of sixth neurons are sent to the eyeball and innervate the
ciliary muscle, m. сiliaris and sphincter pupillae muscle, m. sphincter pupillae.
14
The examination of visual fields is very important for neurological practice. The loss of
half of the visual fields is called hemianopsia. In case of complete blockage of the optic nerve,
blindness occurs in this eye - amaurosis. With partial damage to the fibers of the optic nerve,
there are limitations of the visual fields in the form of a sector or island - scotoma of the affected
eye. In case of total destroying of optic chiasm, there is complete bilateral blindness, anopsia.
With partial damage to the optic chiasm (pituitary tumors, hydrocephalus), when pressure affects
the fibers coming from the inner halves of the retina of both eyes, bitemporal hemianopsia occurs, i.e. the right eye falls out in one eye, and the left field of vision in the other. If the outer
corners of the optic chiasm are damaged (due to carotid aneurysm), the lesion will affect the
temporal halves of both retinas. In case of damage to the optic tract, lateral geniculate bodies,
thalamus, and occipital lobe, hemianopsia is observed, i.e. loss of opposite visual fields. When
examining the fundus of the eyeball, attention should be paid to the change in the nipple of the
optic nerve with an increase in intracranial pressure (congestive nipple), its atrophy in pituitary
tumors. Hypertension is characterized by the phenomenon of narrowing of arteries and dilation
of veins.
III PAIR – OCULOMOTOR NERVE, NERVUS OCULOMOTORIUS
This is a mixed nerve somatic animal and autonomic parasympathetic fibers. It has 2 nuclei: motor, nucleus nervi oculomotorii, and parasympathetic, accessory nucleus (Yakubovich or
Edinger-Westphal), nucleus accessorius. The nuclei are located in the tegmentum of the midbrain at the level of the superior colliculi of the quadrigeminal plate. The nerve exits from the
brain in the interpeduncular (Tarin’s fossa), fossa interpeduncularis. After leaving the brain, the
nerve enters the cavernous sinus, sinus cavernosus, and exits the skull through the superior orbital fissure, fissura orbitalis superior, entering the orbit. Here it is divided into 2 branches: superior and inferior, ramus superior et inferior. The superior branch goes along the upper wall of
the orbit and innervates levator palpebrae superioris muscle and the superior rectus muscle of the
eyeball, m. levator palpebre superior et m. rectus superior. The inferior one goes along the lower
wall of the orbit, gives off the parasympathetic root of the ciliary ganglion. These parasympathetic fibers after synapse in the ciliary ganglion (see the pathway of the pupil light reflex) innervate the smooth muscles of the eyeball. The remaining fibers of the inferior branch are divided
into three bundles and innervate the medial and inferior rectus muscles of the eyeball and the inferior oblique muscle of the eyeball.
With complete damage to the oculomotor nerve, the following pathology is observed:
1. Due to a violation of the innervation of the levator palpebrae superioris muscle, the eye
is covered with a drooped eyelid - ptosis.
2. The eyeball is turned outward and slightly downward (due to the preserved action on
the eye muscles of the branches IV and V of the pairs of cranial nerves).
3. The pupil is dilated (due to preserved action of the dilator pupillae muscle).
4. Deterioration of vision at short distances due to paralysis of accommodation (ciliary
muscle is affected).
5. The inability to move the eyeball up and inward due to damage to the superior and medial rectus muscles of the eyeball.
IV PAIR – TROCHLEAR NERVE, NERVUS TROCHLEARIS
Motor nerve. It has one motor nucleus, nucl. nervi trochlearis, which lies in the lining of
the midbrain at the level of the inferior colliculi of the quadrigeminal plate. It exits the midbrain
from the dorsal surface after the decussation of its fibers in the superior medullary velum, velum
medullare superius. The nerve pass laterally to the cerebral peduncles, appear on the inferior surface of the brain, perforate the dura mater, passes into the cavernous sinus along with the oculomotor and ophtalmic nerves. It exits the skull through the superior orbital fissure, fissura orbitalis superior. It goes along the upper wall of the orbit and innervates the superior oblique muscle
of the eyeball, m. obliquus superior.
15
Injury to trochlear nerve causes convergent strabismus and diplopia (double vision when
looking down).
V PAIR – TRIGEMINAL NERVE, NERVUS TRIGEMINUS.
PARASYMPATHIC GANGLIONS OF THE HEAD
Mixed nerve, contains motor and sensory fibers.
The first neuron of the sensory part is located in the trigeminal (semilunar, Gasserian)
ganglion, ganglion trigeminale seu semilunare, located on the anterior surface of the temporal
bone pyramid, in the trigeminal impression. Here, the dura mater splits into two layers, forming
the Meckel’s cave, in which the trigeminal ganglion is located. The peripheral processes of the
cells located in the ganglion go to the periphery, forming three branches of the trigeminal nerve,
and the central ones, forming a sensory root, radix sensoria, enter the brainstem, where they end
on three sensory nuclei: spinal nucleus of trigeminal nerve, n. spinalis nervi trigemini (projected
onto the rhomboid fossa, descending to the spinal cord), mesencephalic nucleus of trigeminal
nerve, n. mesencephalicus nervi trigemini, which rises up into the midbrain, and the principal
sensory (pontine) nucleus, n. principalis nervi trigemini. The motor part of the trigeminal nerve
starts from one motor nucleus, n. motorius nervi trigemini, the processes of which, leaving the
brain, form the motor root, radix motoria, which passes under the Gasserian ganglion and join
the third branch of the trigeminal nerve. Thus, the first branch of the trigeminal nerve is the ophtalmic nerve, n. ophthalmicus, is fully sensory, the second branch is maxillary, n. maxillaris, also
sensory, and the third - the mandibular nerve, n. mandibularis contains both sensory and motor
fibers.
A feature of the trigeminal nerve is the presence of the autonomic cranial ganglions along
its branches. Cells of these ganglions receive the preganglionic parasympathetic fibers from the
nuclei of the III, VII and IX pairs of cranial nerves. Postganglionic fibers attach to the branches
of the trigeminal nerve and reach the working organ. Each branch of the trigeminal nerve gives
the meningeal branch, r. meningeus, to the dura mater of the brain.
Ophtalmic nerve, nervus ophthalmicus
The first branch of the trigeminal nerve. It carries out the sensory innervation of the eyeball, lacrimal gland, lacrimal sac, mucous membrane of the ethmoid labyrinth, frontal and sphenoid sinuses, skin and conjunctiva of the upper eyelid, glabella, nose, forehead. Therefore, its
innervation zone is located above the palpebral fissure.
Sensory nerve. It starts from the Gasserian ganglion, passes through the lateral wall of the
cavernous sinus. Exiting the cavernous sinus, it gives a branch to the cerebellum, r. tentorii, goes
into the orbit through the superior orbital fissure and divides into 3 nerves:
1. Nasociliary nerve, n. nasociliaris.
2. Frontal nerve, n. frontalis.
3. Lacrimal nerve, n. lacrimalis.
1. Nasociliary nerve, n. nasociliaris, goes along the medial wall of the orbit to the medial
corner of the eyeball and gives off 5 branches:
- sensory root of ciliary ganglion, radix sensoria ganglii ciliaris - goes to the ciliary ganglion;
- long ciliary nerves, nn. ciliares longi - innervate the tunics of the eyeball;
- posterior ethmoidal nerve, n. ethmoidalis posterior, - enters the nasal cavity through the
foramen with the same name and innervates the mucous membrane of the nasal cavity and sphenoid sinus;
- anterior ethmoidal nerve, n. ethmoidalis anterior, - goes into the cranial cavity through
the foramen with the same name, and then through the cribriform plate, penetrates the nasal cavity, gives a branch to the frontal sinus and innervates the anterior sections of the lateral wall and
nasal septum, up to the tip of the nose;
16
- infratrochlear nerve, n. infratrochlearis, - is the terminal branch of the nasociliary nerve.
It goes to the medial corner of the eye, where it anastomoses with the supratrochlear nerve.
2. The frontal nerve, n. frontalis, goes along the superior wall of the orbit and divides into
three nerves:
- supratrochlear nerve, n. supratrochlearis, - anastomoses with the infratrochlear nerve
and they innervate the skin and conjunctiva of the medial corner of the eye, the lacrimal sac, the
skin of the dorsum of the nose and forehead;
- supraorbital nerve, n. supraorbitalis, - innervates the skin of the forehead and scalp;
- the frontal branch, r. frontalis - goes to the frontal region and innervates the skin of this
area.
3. The lacrimal nerve, n. lacrimalis, goes along the lateral wall of the orbit, where an
anastomosis from the zygomatic nerve, ramus communicans cum nervo zygomatico, approaches
it. This anastomosis consists of vegetative fibers coming from the pterygopalatine ganglion. The
nerve becomes mixed (contains sensory, sympathetic and parasympathetic fibers). The lacrimal
branches, rr. lаcrimale, with all vegetative fibers and part of the sensory ones innervate the lacrimal gland, and the lacrimal nerve, in which only the sensory fibers remained, innervates the
skin and conjunctiva of the lateral angle of the eye.
Along the first branch of the trigeminal nerve is the ciliary ganglion, ganglion ciliare,
which is in the orbital cavity.
Ciliary ganglion, ganglion ciliare
The parasympathetic vegetative ganglion is located in the orbit laterally to the optic
nerve. Three types of fibers are suitable for it:
1. Parasympathetic root, radix parasympathica, parasympathetic fibers that come from
the nucleus of Yakubovich as part of the oculomotor nerve.
2. Sensory root, radix sensoria, - sensory fibers coming from the nasociliary nerve.
3. Sympathetic root, radix sympathica, - sympathetic fibers coming from the cavernous
plexus.
Since the ganglion is parasympathetic and contains only parasympathetic cells, parasympathetic fibers are interrupted (i.e., the transmission of a nerve impulse through synaptic connections to the nerve cells of the ganglion), while sensory and sympathetic fibers transit. Three types
of fibers form 3-6 short ciliary nerves, nn. ciliares breves:
- parasympathetic - innervate the sphincter pupillae muscle, m. sphincter pupillae;
- sympathetic - dilator pupillae muscle, m. dilatator pupillae;
- sensory - innervate the nucleus of the eyeball.
Maxillary nerve, nervus maxillaris
The second branch of the trigeminal nerve innervates the gums and teeth of maxilla, nose,
lower eyelid, upper lip, cheek and temporal region, mucous membrane of the palate, upper lip,
nasal cavity, maxillary sinus, cheek. Therefore, it innervates the middle part of the face between
the palpebral fissure and the angle of the mouth.
Sensory nerve begins in the Gasserian ganglion. It leaves the skull through foramen rotundum. Before exiting the skull, the meningeal branch, ramus meningeus, which innervates the
dura matter of the middle cranial fossa, departs from it. Leaving the skull, the nerve enters the
pterygopalatine fossa, fossa pterygopalatina, where it is divided into three branches:
1. Ganglionic branches, rr. ganglionares.
2. Zygomatic nerve, n. zygomaticus.
3. Infraorbital nerve, n. infraorbitalis.
1. Ganglionic branches, rr. ganglionares, pass to the pterygopalatine ganglion, ganglion
pterygopalatinum. Using these branches, a mutual exchange of fibers between the nerve and the
ganglion is carried out, that’s why all branches of the nerve and the ganglion will include sensory, sympathetic and parasympathetic components.
17
2. Zygomatic nerve, n. zygomaticus, leaves the pterygopalatine fossa through the inferior
orbital fissure, enters the orbit, goes along its lateral wall, where it gives the connecting branch to
the lacrimal nerve ramus communicans cum nervo lacrimalo. Then, through the zygomaticoorbital foramen, foramen zygomaticoorbitale, goes inside the zygomatic bone, where it is divided
into two branches:
- zygomaticofacial, r. zygomaticofacialis, which, through the foramen with the same
name, leaves the zygomatic bone and innervates the skin of the lateral surface of the face;
- zygomaticotemporal, r. zygomaticotemporalis, which goes through the foramen with the
same name and innervates the skin of the temporal region.
3. Infraorbital nerve, n. infraorbitalis, through the inferior orbital fissure enters the orbital
cavity, goes along its inferior wall, enters the infraorbital groove and canal and through the infraorbital foramen, foramen infraorbitalis, enters the face, where it divides into its terminal
branches. Inside the pterygopalatine fossa, the posterior superior alveolar branches, rr. alveolares superiores posteriores through the foramens with the same name enter the maxilla and participate in the formation of the superior dental plexus, plexus dentalis superior, from which the
dental branches innervate molars. In the region of the infraorbital groove and canal, the superior
middle and anterior alveolar branches, rr. alveolares superior medius et anteriores, also participate in formation of superior dental plexus which giving tooth branches, rr. dentales superiores
to premolars, incisors and canines and superior gingival branches, rr. gingivales superius. Plexuses located in the alveolar process of the maxilla exchange fibers, which explains the irradiation
of pain in dental diseases. When entering the face through the infraorbital foramen in the canine
fossa, the nerve forms a "small goose foot", pes anserinus minor, consisting of branches that innervate:
- skin of the lower eyelid, rami palpebrales inferiores;
- skin of the lateral surface of the nose, rami nasales externi;
- skin and mucous membranes of the upper lip and gums, rami labiales superiores;
- the mucous membrane of the anterior sections of the nasal cavity, rr. nasales inferiores.
Pterygopalatine ganglion, g. pterygopalatinum
This is a parasympathetic (paraorganic, third order) ganglion, located in the adipose tissue of the pterygopalatine fossa. Three types of fibers are suitable for it:
1. Sensory root, radix sensoria, - ganglionic branches, rr. ganglionares, from the maxillary nerve.
2. Parasympathetic root, radix parasympathiсa, is a greater petrosal nerve, n. petrosus
major, which extends from the intermediate nerve (VII pair) along the anterior surface of the
temporal bone pyramid to the foramen lacerum.
3. Sympathetic root, radix sympathiсa, is a deep petrosal nerve, n. petrosus profundus,
which begins from the internal carotid plexus, plexus caroticus internus, formed by neurons of
the superior cervical ganglion of the sympathetic trunk. Sympathetic and parasympathetic roots
i.e. the greater and deep petrosal nerves are connected in the region of foramen lacerum, forming
a pterygoid, or Vidian nerve, n. canalis pterygoidei, which enters the pterygopalatine fossa
through the channel of the same name and reaches the pterygopalatine ganglion. Since it is a parasympathetic ganglion, only parasympathetic fibers are interrupted in it, while sensory and sympathetic ones transit.
From the ganglion arise:
- medial and lateral superior posterior nasal branches, rr. nasales posteriores superiores
mediales et laterales, which penetrate the sphenopalatine foramen and pass to the mucous membrane of the posterior sections of the superior and middle nasal meatuses;
- inferior posterior nasal branches, rr. nasales posteriores inferiores, traveling through
the greater palatine canal to the mucous membrane of the floor of the nasal cavity;
18
- nasopalatine nerve, n. nasopalatinus, (Scapra’s nerve), passing first through the sphenopalatine foramen to the mucous membrane of the nasal septum, and then through the incisive canal, canalis incisivus, to the mucous membrane of the hard and soft palate;
- greater and lesser palatine nerves, nn. palatini major et minor; from the pterygopalatine
fossa go through the canals with the same name enters the oral cavity, where innervates the mucous membrane of the hard and soft palate.
Mandibular nerve, nervus mandibularis
The third branch of the trigeminal nerve innervates the gums and teeth of the lower jaw,
the mucous membrane of the tongue, cheek and lower lip, skin of chin, submandibular and sublingual salivary glands, temporo-mandibular joint, mastication muscles, some muscles of the
neck, palate and middle ear. Therefore, the sensory fibers of this nerve innervate the lower part
of the face (below the angle of the mouth).
This is a mixed nerve that contains both sensory and motor fibers. Sensory fibers start
from the Gasserian ganglion, and motor fibers start from the motor nucleus, nucleus motorius. It
leaves the skull through the foramen ovale, and enters the infratemporal fossa, fossa infratemporalis. Immediately after exiting the skull, the spinosus nerve (or meningeal branch), n. spinosus departs from it, which returns through foramen spinosum to the cranial cavity and innervates the dura mater of the middle cranial fossa. In the infratemporal fossa, the nerve is divided
into two branches:
1. The anterior, ramus anterior, mainly motor, to the mastication muscles.
2. The posterior, ramus posterior, mostly sensory.
From the anterior branch arise:
1.1. The masseteric nerve to the masetter muscle, n. massetericus.
1.2. Deep temporal nerves, nn. temporales profundi, to the temporal muscle.
1.3. Lateral pterygoid nerve, n. pterygoideus lateralis, to the muscle of the same name.
These three nerves are motor, and the fourth:
1.4. The buccal nerve, n. buccalis, is a sensory, innervating skin and mucosa of cheek.
From the posterior branch:
2.1. Medial pterygoid nerve, n. pterygoideus medialis, motor, innervate the muscle with
the same name, and also give branches to tensor veli palatine muscle and tensor tympani muscle,
m. tensor veli palatini et m. tensor tympani.
2.2. Lingual nerve, n. lingualis, sensory, passes between the pterygoid muscles, then goes
down and anteriorly along the inner surface of the lower jaw, enters the tongue and ends there.
The chorda tympani, which is a branch of the VII pair of cranial nerves, carries parasympathetic
fibers and fibers of taste sense, attaches to the lingual nerve. In addition, sympathetic fibers from
the external carotid plexus, plexus caroticus externus, (its continuation is the facial plexus, plexus facialis) are suitable for the lingual nerve. Thus, the nerve becomes mixed and contains 4
types of fibers: general sensory, special sensory (taste), parasympathetic and sympathetic fibers.
From the lingual nerve depart:
- sublingual nerve, n. sublingualis, contain three types of fibers, except taste. Firstly pass
to the sublingual ganglion, ganglion sublinguale. After the ganglion all three types of fibers are
sent to the sublingual salivary gland.
- submandibular branches, rr. submandibulare, contain three types of fibers, except taste.
Firstly sent to the node with the same name, ganglion submandibulare, and then to the submandibular salivary gland.
- lingual branches, rr. linguales, contain all 4 types of fibers. Fibers of general sense innervate the anterior two-thirds of the tongue, fibers of taste sense innervate all the papillae of the
tongue except the vallate, and vegetative fibers innervate the small salivary glands of the tongue.
- branches to isthmus of fauces, rr. isthmi faucimi, to the mucous membrane of the palato-glossal arch and to the palatine tonsils.
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Submandibular, g. submandibulare, and sublingual ganglions, g. sublingvale
Located next to the glands of the same name, parasympathetic in structure, containing peripheral parasympathetic neurons whose axons (postganglionic fibers) end in the salivary glands
of the tongue, submandibular and sublingual glands. Preganglionic parasympathetic fibers extend from the superior salivary nucleus of the facial nerve. They pass as a component of chorda
tympani, lingual and submandibular nerves of the mandibular nerve and are interrupted on the
neurons of the ganglions. General sensory fibers are called ganglionic branches, rami ganglionares. After passing through ganglions, they provide general sensation to these glands. Sympathetic fibers enter the ganglions from the plexus of the lingual artery, pl. sympathicus a. lingualis, transit through ganglions and bring trophic innervation.
2.3. Inferior alveolar nerve, n. alveolaris inferior, a mixed nerve, contains sensory and
motor fibers. It goes along the inner surface of the lower jaw and in the region of mandibular
foramen is divided into sensory and motor parts.
Sensory fibers enter the mandibular canal and exit through the mental foramen. Inside the
canal nerve gives inferior alveolar branches, rr. alveolares inferiores, which enter the alveolar
process of the lower jaw, form the plexus, plexus dentalis inferior, from which the branches to
lower tooth arise, rr. dentales inferiores, and the inferior gingival branches, rr. gingivales inferiores. The terminal branch of the sensory part, n. mentalis, innervates the skin of the chin and
mucous membrane of the lower lip.
Motor fibers form the mylohyoid nerve, n. mylohyoideus, which goes along the inner surface of the lower jaw in the groove of the same name and innervates the muscle of the same
name and the anterior belly of the digastric muscle, m. digastricus.
2.4. Auriculotemporal nerve, n. auriculotemporalis, sensory, goes in front of external
acoustic meatus up to the temporal region. The branches from the otic ganglion attaches to it.
Otic ganglion, g.oticum
It is located on the base of the skull near the foramen ovale. Parasympathetic ganglion
(paraorganic, III order, terminal). Three types of fibers are suitable for it:
1. Sensory - connecting branches from the mandibular nerve, rr. communicans cum g.
oticum.
2. Parasympathetic fibers - a lesser petrosal nerve, n. petrosus minor, which is a branch of
IX pair.
3. Sympathetic fibers come from the plexus of the middle meningeal artery, pехus a. meningeus medius, which is part of the external carotid plexus.
Parasympathetic fibers in the node are interrupted, while sensory and sympathetic fibers
transit. All three types of fibers join the auriculotemporal nerve.
The nerve gives groups of branches:
- articular, rami articulares - sensory, innervate the temporo-mandibular joint;
- nerves of the external acoustic meatus, nn. meatus acustici externi – sensory, innervates
the skin of the external acoustic meatus;
- anteriorauricular nerves, nn. auriculares anteriores – sensory, innervate skin and cartilage of the anterior auricle;
- superficial temporal branches, rr. temporalis superficiales – sensory, to the skin of the
temporal region;
- branches of the tympanic membrane, rr. membranae tympani, to the eardrum;
- parotid branches, rr. parotidei - contain three types of fibers and innervate the parotid
salivary gland, glandula parotis.
Damage to one of the branches of the trigeminal nerve causes disturbance of all types of
sensation in the innervation zone. The reflexes associated with this nerve either depressed or lost.
In case of damage to the motor root of this nerve, paralysis of the masticatory muscles develops.
With one-sided damage, the lower jaw deviates toward the damage when opening the mouth,
bilateral paralysis makes it impossible to chew and leads to sagging of the lower jaw. Damaging
of the nucleus of the spinal tract of the trigeminal nerve leads to dissociated anesthesia or hyper20
esthesia (only pain and temperature sensitivity are disturbed). Lesions of the trigeminal nerve are
usually accompanied by disorders of sweating, vasomotor phenomena, disorders of tissue nutrition, which are especially dangerous in the cornea (neurotrophic keratitis), dysfunction of large
glands of the oral cavity.
VEGETATIVE (PARASYMPATHETIC) CRANIAL GANGLIONS
Name of ganglion
Ganglion ciliare
Ganglion pterygopalatinum
Parasympathetic center
of brainstem; nerves with
preganglionic parasympathetic fibers
Orbita, laterally
Nucl. accesorius
n.opticus
n.оculomotorii, radix
oculоmоtorius from n.
oculomotоrius
Fossa pterygоpala- Nucl. salivatorius superitina along n.
or, nucl. lacrimalis, n.
maxillaris
petrosus from n. facialis
Localization of
ganglion
Ganglion submandibulare
Glandula submandibularis superiorly
Ganglion sublinguale
Glandula submandibularis superiorly
Ganglion oticum
Basis cranii externa under foramen
ovale along n.
mandibularis
Nerves with postganglionic parasympatheric fibers
Target organ
Nn. ciliares breves
M. sphincter
pupillae, m. ciliaris
Nn. palatini, nn.
nasales
posteriores,n.
zygomaticus
Nucl. salivatorius
Rr. submandibulasuperior, chorda tympani res
from n. facialis
Nucl. salivatorius
Rr. sublinguales
superior, chorda tympani
from n. facialis
Nucl. salivatorius inferior, N. auriculotemn. petrosus minor from n. poralis
glosopharyngeus
Mucosa of
palate, nasal
cavity, lacrimal
gland
Glandula submandibularis
Glandula sublingualis
Glandula parotidea
VI PAIR - ABDUCENT NERVE, NERVUS ABDUCENS
This is a motor nerve. It has one motor nucleus, nucleus nervi abducentis, which is located in the pons and is projected in the upper triangle of the rhomboid fossa (in the region of the
facial colliculus, colliculus facialis). It comes out of the brain between the pons and the pyramid
of the medulla oblongata. Then the nerve passes anteriorly through the medial wall of the cavernous sinus (together with the internal carotid artery). Enters the orbit through the superior orbital fissure and innervates the lateral rectus muscle of the eyeball, m. rectus lateralis. When a
nerve is damaged, a convergent strabismus, the inability to turn the eyeball outward, diplopia
when looking towards the damaged muscle are noted.
VII PAIR - FACIAL NERVE, NERVUS FACIALIS
The mixed nerve contains sensory, motor and parasympathetic fibers. Motor fibers are
axons of the motor nucleus, nucl. nervi facialis located in the depths of the pons under the facial
colliculus. Sensory fibers are a collection of peripheral processes of pseudounipolar cells of the
sensory geniculate ganglion, ganglion geniculi. The central processes end on the neurons of the
nucleus of solitary tract, nucl. tractus solitarius. The preganglionic parasympathetic fibers of the
facial nerve begin from the parasympathetic nucleus of pontine tegmentum - the superior salivary, nucl. salivatorius superior. Sensory and secretory fibers are combined under the name of
the intermediate nerve, n. intermedius, and the motor part of the fibers is proper facial nerve, n.
facialis proprius.
Proper facial nerve, nervus facialis proprius
The motor, has one motor nucleus, which is located in the pons and is projected in the
upper triangle of the rhomboid fossa, the fibers go into the colliculus facialis, form a loop and
exit the brain between the pons and the medulla oblongata in the pontocerebellar angle. Then the
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nerve goes to the back of the pyramid and through porus acoustics internus enters meatus acousticus internus and facial canal. In the facial canal, the nerve runs horizontally, going outwards,
then turns at a right angle backwards, after that it descends vertically, exiting the skull through
stylomastoid foramen. Upon leaving the skull, the nerve bends forward, enters the parotid gland,
in the thickness of which forms the parotid plexus, plexus parotideus, and divides into terminal
branches. On its way, the nerve gives 9 branches:
1. Stapedius nerve, n. stapedius, departs in the facial canal and innervates the stapedius
muscle.
2. Posterior auricular nerve, n. auricularis posterior, after leaving the facial canal innervates the muscles of the auricle and the occipital belly of the cranial muscle, venter occipitalis m.
epicranii.
3. Digastric branch, ramus digastricus, innervates the posterior belly of m. digastricus.
4. Stylohyoid branch, ramus stylohyoideus, to the muscle of the same name.
The terminal five branches form pes anserinus major, and innervate all the muscles of facial expression and platysma. These nerves go anterior to the auricle of the tragus, radially splitting into the terminal branches. Therefore, vertical sections on the face are not recommended.
5. Temporal branches, rami temporales, innervate mm. auricularis anterior, orbicularis
oculi, epicranius (venter frontalis), corrugator supercilii, procerus.
6. Zygomatic branches, rami zygomatici, innervate m.m. zygomatici et orbicularis oculi.
7. Buccal branches, rami buccales, innervate mm. risorius, buccalis, levator labii superioris, orbicularis oris, levator anguli oris et nasales.
8. Marginal branch, ramus marginalis mandibulae, - goes along the edge of the lower jaw
to the chin, innervates mm. depressor labii inferiores, mentalis, depressor anguli oris.
9. Cervical branch, ramus coli, runs down behind the angle of the lower jaw and innervates platysma, forming with the transverse nerve of the neck from the cervical plexus a superficial cervical loop, ansa cervicalis superficialis.
Intermediate nerve, n. intermedius
The nerve is mixed, contains parasympathetic fibers and sensory (special sense (taste))
fibers. It has two nuclei projected onto the rhomboid fossa:
- parasympathetic superior salivary nucleus, nucleus salivatorius superior;
- the sensory nucleus of solitary tract, nucleus tractus solitarii, common to the VII, IX
and X pairs.
The fibers go along with the facial nerve and enter the facial canal. In the area of geniculum canalis facialis, there is a peripheral sensory ganglion, ganglion geniculi, which consists of
pseudounipolar cells, the peripheral processes of which go to the organs, and the central ones go
to the brain, to the nucleus of solitary tract. After this ganglion two nerves are formed:
1. The greater petrosal nerve, n. petrosus major, - consists of parasympathetic preganglionic fibers. It leaves the canal of the temporal bone through hiatus canalis nervi petrosi majoris
on the anterior surface of the pyramid, lies in the groove of the same name, reaches foramen
lacerum, where it joins deep petrosal nerve, n. petrosus profundus, forming the Vidian nerve or
nerve of pterygoid canal, n. canalis pterygoidei. Through the pterygoid canal this nerve enters
the pterygopalatine fossa and reaches the ganglion of the same name, where it preganglionic fibers interconnect. From the ganglion, vegetative fibers reach n. maxillaris, then pass to n. zygomaticus, and as a component of the communicating branches depart to the lacrimal nerve and in
the form of rr. lacrimales are sent to the lacrimal gland, which they innervate.
2. The chorda tympani, consists of sensory gustatory and parasympathetic preganglionic
fibers. It passes in the facial canal, then enters the tympanic cavity through its posterior wall,
passes between the malleus and the incus, and exits the tympanic cavity through a petrotympanic
(Glaserian) fissure, fissure petrotympanica. Then it goes down between the pterygoid muscles
and joins the lingual nerve. Parasympathetic fibers of the chorda tympani, after interconnection
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in the ganglions of the same name, innervate the salivary glands of the oral cavity, and the taste
fibers - the papillae of the tongue, except the vallate ones.
Damag to the motor nucleus or root of the facial nerve causes peripheral paralysis of the
muscles of facial expression, loss of superciliary and corneal reflexes. Nerve damage at the level
of the ponto-cerebellar angle is combined with damage to the vestibulo-cochlear nerve and is accompanied by taste impairment in the anterior 2/3 of the tongue, dry eyes and oral mucosa, and
loss of hearing on the side of the lesion. If the nerve is affected in the facial canal below to the
origin of the VIII pair, but above the origin of the greater petrosal nerve, then along with paralysis, dry eye, taste disorder, and salivation are observed. In case of nerve damage below the origin
of a greater petrosal nerve, lacrimation appears due to a violation of the tone of the lacrimal sac.
The damaging of the facial nerve after it leaves the skull is characterized only by paralysis of the
facial muscles and lacrimation.
VIII PAIR - VESTIBULO-COCHLEAR NERVE. NERVUS VESTIBULOCOCHLEARIS.
AUDITORY AND VESTIBULAR PATHWAYS.
Nerve of special sense, consists of two parts - cochlear and vestibular, forming the corresponding nerves, cochlear (auditory), n. cochlearis, and the vestibular (statokinetic) n. vestibularis.
Cochlear nerve, n. cochlearis
The first neuron of the cochlear nerve is located in the spiral ganglion, ganglion spirale
(Cortii), which is placed in the spiral canal of the cochlea, canalis spiralis cochleae. Its peripheral processes go to the receptors of the organ of Corti, and central ones form the cochlear nerve.
Through the floor of the internal acoustic meatus, which is adjacent to the base of the modulus,
the nerve enters the internal acoustic meatus, passes through it and enters the cranial cavity
through the porus acousticus internus. The nerve goes back and in the ponto-cerebellar angle,
laterally to the VII pair, enters the brain, where it reaches the cochlear nuclei projecting in the
lateral corner of the rhomboid fossa. There are two nuclei of the cochlear nerve: nucleus cochlearis ventralis et dorsalis, which are the the II neurons of the auditory pathway. The fibers of the
dorsal nucleus make a complete decussation, forming striae medullares ventriculi quarti, and
then go as part of the lateral lemniscus, lemniscus lateralis. Fibers coming from the ventral nucleus are interrupted in the nucleus of the trapezoid body of pons on its own and mainly the opposite side. For these fibers, the nucleus of the trapezoid body will be the III neuron of the auditory pathway and its processes attach to the lateral lemniscus of the opposite side. The lateral
lemniscus is a continuation of the trapezoid body and its fibers go to the subcortical centers of
hearing - the medial geniculate bodies, corpus geniculatum mediale, and the inferior colliculi of
the midbrain, colliculus inferior tecti mesencephali. The third subcortical center is the median
nucleus of the thalamus, associated with the subcortical sensory center of the extrapyramidal system. Fibers from the nuclei of the medial geniculate bodies pass through the posterior limb of the
internal capsule, forming acoustic radiations, radiatio acustica, go to the cortical end of the auditory analyzer, which is located in the middle part of the superior temporal gyrus, gyrus temporalis superior, in the depths of the Silvian sulcus, in the secondary gyri of Heschl (transverse
temporal gyri). Axons of the inferior colliculi form the tecto-nuclear and tecto-spinal tracts,
which travel to the motor nuclei of cranial nerves and anterior horns of the spinal cord.
Vestibular nerve, nervus vestibularis
A nerve of special sense, conducts impulses that give information about the position and
movement of the body in space. The first neuron is located in the vestibular ganglion, which is
located in the floor of the internal acoustic meatus. Dendrites pass through foramens in the floor
of the acoustic meatus and in the bony labyrinth. After this they follow the receptors located in
the ampullary crests of the semicircular canals and in the spots of the utriculus and sacculus on
the vestible of the labyrinth of the internal ear, forming the anterior, posterior, and lateral ampul23
lar nerves, nn. ampullares anterior, posterior et lateralis, saccular nerve, n. saccularis, utricular
nerve, n. utricularis. Axons of the cells of the vestibular ganglion form the vestibular nerve,
which goes along the internal acoustic meatus, through the porus acusticus internus penetrates
the cranial cavity, enters the brain with n. cochlearis, laterally to n. facialis and ends on four nuclei projecting in the lateral corner of the rhomboid fossa, recessus lateralis or area vestibularis.
The nuclei are called:
1. The superior vestibular nucleus, nucl. vestibularis superior (Bekhterev).
2. Lateral vestibular nucleus, nucl. vestibularis lateralis (Deiters).
3. The medial vestibular nucleus nucleus, nucl. vestibularis medialis (Schwalbe).
4. The inferior vestibular nucleus, nucl. vestibularis inferior (Roller).
These cells are the second neurons of the vestibular nerve. Ascending fibers end on the
cells of the upper nucleus, descending - on the other three. Axons of the cells of the vestibular
nuclei form several bundles that are sent to the spinal cord (tr. vestibulo-spinalis), to the cerebellum (tr. vestibulo-cerebellaris), to the posterior and medial longitudinal fasciculi (fasciculus longitudinalis posterior et medialis), as well as to the thalamus (tr. vestibulo-thalamicus), followed
by a continuation to the cortical end of vestibular analyzer. The processes of the second neurons
go via the inferior cerebellar peduncles to nucl. fastigii of cerebellum, which will be the third
neuron of the vestibular tract, which ends in the cortex of the cerebellar vermis. The other part of
the fibers of lateral and medial nuclei pass through the thalamus and the posterior limb of the internal capsule and ends the cortical end of the vestibular analyzer, which is located in the middle
and inferior temporal gyrus, gyrus temporalis medius et inferior. The inferior nucleus fibers
forms tractus vestibulospinalis, which runs in the anterior funiculi of the spinal cord till the lowest segments of the spinal cord, and terminates on motor nuclei.
As a result of a partial decusstaion of the auditory tract in the brainstem, a unilateral damage to the auditory pathway above the brainstem does not cause hearing impairment, since the
function is completely compensated by the opposite hemisphere. The defeat of the auditory tract
below the brainstem is accompanied by either a decrease in hearing - hypacusia, or its complete
loss - anacusia.
With damage to the vestibular nerve, there are disorders of orientation in space, balance,
coordination of movements since communication with the cerebellum is broken, nystagmus with the nuclei of the oculomotor nerves, dizziness, vomiting - the influence of the vagus nerve.
These disorders can be the result of diseases of the inner ear, pathology in the ponto-cerebellar
angle, brainstem, cerebellum and cerebral cortex. It should be noted that as a result of training,
addiction to vestibular irritations occurs.
IX PAIR - GLOSSOPHARYNGEAL NERVE, NERVUS GLOSSOPHARYNGEUS
Mixed nerve, contains motor, sensory and parasympathetic fibers. It has three nuclei located in the medulla oblongata and projecting into the rhomboid fossa in the region of the vagus
nerve triangle:
- motor, nucleus ambiguus, nucleus ambiguus, common with X and XI pairs;
- parasympathetic, inferior salivatory nucleus, nucleus salivatorius inferior;
- sensory, nucleus of solitary tract, nucleus tractus solitarii, common with VII and X
pairs of cranial nerves.
The nerve exits the brain in the upper part of the posterior lateral sulcus of the medulla
oblongata. The nerve exits from the skull through the jugular foramen. There is a superior sensory ganglion of glossopharyngeal nerve here. Then the nerve goes to the inferior surface of the
temporal pyramid, where there is an inferior sensory ganglion in the fossula petrosa. After that,
the trunk of the glossopharyngeal nerve is located behind the internal carotid artery, curving in
an arc, goes along the lateral edge of the stylopharyngeal muscle to the root and dorsum of the
tongue, where it ends. Thus, sensory nerve fibers are represented by peripheral processes of
pseudounipolar cells of the superior and inferior ganglions, the central processes of which end on
24
the nucleus of solitary tract. The motor fibers are axons of the cells of the nucleus ambiguus, and
parasympathetic fibers come from the inferior salivatory nucleus.
On its way, the nerve gives off branches:
1. Tympanic nerve, n. tympanicus - leaves under the inferior ganglion, consists of sensory and parasympathetic fibers, goes through the canaliculus tympanicus into the tympanic
cavity, where it forms the tympanic plexus, plexus tympanicus, which together with the sympathetic fibers, from the internal carotid plexus, nn. caroticotympanici, innervates the mucosa of
the tympanic cavity and auditory tube. From this plexus, a parasympathetic lesser petrosal nerve,
n. petrosus minor, emerging from the tympanic cavity through hiatus canalis nervi petrosi minoris. From the skull, this nerve exits through fissura sphenopetrosa, and reaches the otic ganglion. Postganglionic branches as a component of auriculo-temporal nerve of the fifth pair are
directed to the parotid gland. The whole path, including the tympanic nerve, tympanic plexus and
the lesser petrosal nerve, is called the Jacobson anastomosis.
2. Pharyngeal branches, rr. pharyngei - together with the laryngeal-pharyngeal branches
from the superior cervical ganglion of the sympathetic trunk and the same branches of the vagus
nerve, participate in the formation of the plexus pharyngeus.
3. Tonsillar branches, rr. tonsillares - innervate the mucous membrane of the palatine
tonsil and palatine arches.
4. Branch to stylopharyngeal muscle, r. stylopharyngeus - motor, innervates the muscle
of the same name.
5. Lingual branches, rr. linguales - their sensory part innervates the mucous membrane
of the posterior third of the tongue, taste fibers innervate the vallate papillae, and parasympathetic fibers - the small salivary glands of the tongue.
6. Sinus branch, r. sinus carotici (Hering's nerve), innervates the carotid sinus and carotid body (glomus caroticus) of the sinocarotid zone in the area of bifurcation of the common carotid artery.
7. Communicating branch with the auricular branch of the vagus nerve, r. communicans
cum r. auricularis n. vagi, is involved in the innervation of the skin of the external acoustic meatus.
So, the glossopharyngeal nerve provides the general and taste sensory innervation to
mucous of the posterior third of the tongue, sensory to mucous of the pharynx, palatine arches,
tonsils, tympanic cavity, auditory tube, external acoustic meatus, sinocarotid zone. The motor
innervation is to stylopharyngeal muscle and the parasympathetic (secretory) – to parotid gland.
With the defeat of this nerve, the following symptom complex is observed:
1. Loss of taste on the side of the same name on the back third of the tongue - ageusia.
2. Minor swallowing disorder, as of greater importance in the innervation of the pharynx is the vagus nerve.
3. Anesthesia of the mucous membrane of the upper half of the pharynx.
Unilateral deactivation of the function of the parotid gland does not lead to dry mouth
due to the compensating effect of the remaining salivary glands.
X PAIR – VAGUS NERVE, NERVUS VAGUS
The longest of cranial nerves. The nerve is mixed, consists of motor, sensory and parasympathetic fibers. It has three nuclei projecting in the lower triangle of the rhomboid fossa, i.e.
in the medulla oblongata:
- motor ambiguus nucleus, nucl. ambiguus, common for IX, X and XI pairs of cranial
nerves;
- sensory nucleus of solitary tract, nucl. tractus solitarii, common for VII, IX and X pairs;
- parasympathetic posterior (dorsal) nucleus, nucl. dorsalis nervi vagi.
From the brain, the nerve exits through the posterior lateral groove of the medulla oblongata with 5-6 roots, which are then combined into one trunk and through the foramen jugulare
leaves the cranial cavity. In the jugular foramen there is a thickening - a superior sensory gangli25
on, g. superius. 1-1.5 cm inferiorly is the inferior sensory ganglion, g. inferius. Both ganglions
consist of sensory cells, the processes of which make up the sensory portion of the nerve. The
central processes are directed to the brain (to the sensory nuclei), and peripheral - to the periphery, as part of the branches of the vagus nerve. Then the nerve goes to the neck as part of the
neurovascular bundle, consisting of the carotid artery, internal jugular vein and vagus nerve. All
of them are covered with a connective tissue membrane and are located first on the side of the
larynx, then on the side of the thyroid gland and trachea. When passing into the thoracic cavity,
the right vagus nerve passes in front of the right subclavian artery, and the left along the anterior
surface of the aortic arch. Both nerves in the thoracic cavity deviate posteriorly, go along the
posterior surface of the root of the lung, and in the posterior mediastinum reach the esophagus.
The right vagus nerve goes along the posterior surface of the esophagus and forms the posterior
esophageal plexus there, and the left goes to the anterior surface and forms the anterior esophageal plexus, respectively. These plexuses stretch along the esophagus and pass through the diaphragm to form the anterior and posterior vagal trunks, truncus vagalis anterius et posterius. In
the abdominal cavity, the anterior trunk goes along the anterior surface of the cardiac part of the
stomach and breaks up into separate branches, some of them go to the liver, the rest form the anterior gastric plexus, plexus gastricus anterius. The posterior trunk goes along the posterior surface of the stomach, gives a small number of branches to its walls, and the rest of the most
branches goes to the coeliac (solar) plexus, plexus coeliacus seu solaris, and is involved in its
formation. The gastric branches of vagus nerve innervate the muscles, glands, and gastric mucosa. From the coeliac plexus, vegetative fibers travel through the blood vessels to all organs of the
abdominal cavity, with the exception of the lower parts of the colon (descending colon and sigmoid) and pelvic organs and innervate them. Along the large vessels, a whole series of plexuses
are formed.
Topographically, the entire trunk of the vagus nerve is divided into 4 parts:
1. Cranial - between the superior and inferior sensory ganglions.
2. Cervical - between the inferior sensory ganglion and the origin of the recurrent laryngeal nerve.
3. Thoracic - from the origin of the recurrent laryngeal nerve to the diaphragm.
4. Abdominal - from the diaphragm to the entrance to the lesser pelvis.
Branches of the vagus nerve.
Cranial part:
1. Meningeal branch, r. meningeus, originating from the superior ganglion, goes through
the jugular foramen into the cranial cavity and innervates the dura mater of the posterior cranial
fossa.
2. Auricular branch, r. auricularis, departs from the superior ganglion, enters the jugular
foramen and penetrates into the tympanic cavity through the canaliculus mastoideus, then leaves
it through the tympanomastoid fissure, reaches the posterior wall of the external acoustic meatus
and innervates it (which is why with irritation of the skin of the external acoustic meatus appears
cough) and the skin of the external surface of the auricle.
Cervical part:
1. Inferior anastomosis, r. communicans inferior, - connects the inferior sensory ganglion
of the vagus nerve with the superior cervical sympathetic ganglion.
2. Communicating branch with the XII pair, r. communicans cum n. hypoglosso.
3. Superior laryngeal nerve, n. laryngeus superior, - goes to the lateral wall of the larynx
and is divided into two branches - external and internal. The external branch is predominantly
motor and innervates m. cricothyroideus et m. constrictor pharyngis inferior. The internal branch
is sensory, enters the laryngeal cavity through the thyrohyoid membrane and innervates the laryngeal mucosa above the glottis, epiglottis and root of the tongue.
4. Pharyngeal branches, rr. pharyngei, - go to the posterior pharyngeal wall and in the region of the m. constrictor pharyngis medius, are involved in the formation of the pharyngeal
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plexus, plexus pharyngeus. From it fibers go to the muscles of the pharynx, mucosa and muscles
of the soft palate except m. tensor veli palatini, which is innervated by V pair.
5. Superior cervical cardiac branches, rr. Cardiac cervicales superiores, - contain sensory
and parasympathetic fibers, pass to the heart along the wall of the common carotid artery, where
they become part of the deep cardiac plexus, plexus cardiacus profundus.
6. Recurrent laryngeal nerve, n. laringeus recurrens, the right one arise from the vagus
nerve at the level of the inferior margin of the right subclavian artery and rises up its posterior
surface, and the left one starts at the level of the inferior margin of the aortic arch and goes back
up to its posterior surface. Then both nerves go in the groove between the trachea and esophagus
and reach the larynx. The recurrent laryngeal nerve contains sensory, motor and parasympathetic
fibers and gives the following branches:
- inferior cervical cardiac branches, rr. cardiaci cervicales inferiores, go to the superficial
cardiac plexus, connecting with the branches of the sympathetic trunk;
- tracheal branches, rr. tracheales - innervate the trachea (mucous membrane, glands,
smooth muscles);
- esophageal branches, rr. oesophagei - innervate the mucous membrane of the esophagus, glands and muscles;
- inferior laryngeal nerve, n. laryngeus inferior, the final branch of the recurrent laryngeal
nerve, in the larynx region breaks up into branches that innervate: all the muscles of the larynx,
except for the cricothyroid, the mucous membrane of the larynx below the glottis, as well as the
thyroid, parathyroid glands, thymus and lymph nodes of the neck.
Thoracic part:
1. Bronchial branches, rr. bronchiales, form the bronchial and then pulmonary plexus,
plexus pulmonalis, innervate the smooth muscles and glands of the bronchi and carry out the
sensory innervation of the bronchi and lungs.
2. Tracheal branches, rr. tracheales, - innervate the trachea.
3. Esophageal branches, rr.oesophagei, - form the anterior and posterior esophageal plexuses.
4. Pericardial branches, rr. pericardici, - are sent to the pericardium and innervate it.
5. Thoracic heart branches, rr. cardiaci thoracici, are involved in the formation of cardiac
plexuses.
Abdominal part:
1. Anterior vagal trunk, truncus vagalis anterior, it gives off the anterior gastric branches,
rr. gastrici anteriores, and hepatic branches, rr. hepatici.
2. Posterior vagal trunk, truncus vagalis posterior, it gives off the posterior gastric
branches, rr. gastrici posteriores, coeliac branches, rr. coeliaci.
As part of the branches of the coeliac plexus (see above - the course of the vagus nerve),
the fibers of the vagus nerves reach the abdominal organs (liver, spleen, pancreas, kidneys, small
and large intestine to the descending colon), for innervation of smooth muscles, glands and mucous membranes.
In case of unilateral damage to the vagus nerve, overhang of the soft palate is observed on
the damage side, its immobility or lag in this half when pronouncing the sound “A”. The uvula is
deviated in a healthy direction. The voice becomes hoarse due to unilateral paralysis of the vocal
fold.
With bilateral damage to the vagus nerve, a nasal tone of the voice is observed, pouring
of liquid food through the nose due to paralysis of the soft palate. Even a complete aphonia is
possible - whispering, soundless speech. Epiglottis paralysis leads to choking during eating,
coughing. Possible tachycardia and respiratory depression. Complete bilateral damage to the vagus nerves leads to death due to cardiac arrest and breathing.
XI PAIR - ACESSORY NERVE, NERVUS ACCESSORIUS
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It is a motor nerve, has two motor nuclei, one cranial - nucl. ambiguus (common with IX
and X pairs), is located in the medulla oblongata, the second is the spinal nucleus, nucl. spinalis
nervi accessorii, which is located in the spinal cord in the six upper segments, closer to the anterior horns. Two roots come from the nuclei:
1. Cranial roots, radices craniales, - exit the brain in the lower third of the posterior lateral groove of the medulla oblongata.
2. Spinal roots, radices spinales, - exit the spinal cord between the anterior and posterior
roots, rise upwards, through the foramen magnum enter the cranial cavity and, joining the cranial
roots, form the trunk of the accessory nerve.
The accessory nerve leaves the skull through the foramen jugulare, and is immediately
divided into two branches:
1. The internal branch, ramus internus, (mainly fibers from the cranial nucleus) approaches the vagus nerve and goes into its composition.
2. The external branch, ramus externus, - goes down, at the level of the angle of the mandible, fits under m. sternocleidomastoideus, gives branches to it, then goes to m. trapezius, and
innervates it.
With nerve damage, peripheral paralysis of the trapezius and sternocleidomastoid muscles is observed.
XII PAIR - HYPOGLOSSAL NERVE, NERVUS HYPOGLOSSUS
The motor nerve has one motor nucleus, n. nervi hypoglossi, which projects in the inferior corner of the rhomboid fossa in the triangle of the hypoglossal nerve, trigonum nervi hypoglossi. From the brain, the nerve exits between the pyramid and olive of the medulla oblongata in
the anterior lateral groove by 10-15 roots. From the skull, the nerve exits through the hypoglossal canal, canalis nervi hypoglossi. It goes down to the neck, located between the internal carotid
artery and the internal jugular vein, then turns forward and upward, goes along the floor of the
oral cavity, enters the thickness of the tongue, where it ends. On its way, the nerve gives the following branches:
1. The superior root, radix superior, departs from the nerve at the point of its bend, connects to the inferior root, radix inferior, extending from the cervical plexus (motor branch),
forming a loop of the hypoglossal nerve, ansa nervi hypoglossi or a deep cervical loop, ansa cervicalis profundus. From the loop branches go to the muscles located below the hyoid bone: m.
sternohyoideus, m. omohyoideus, m. sternothyroideus, m.thyrohyoideus.
2. Lingual branches, rr. lingualis, are the terminal branches of the hypoglossal nerve and
innervate all the muscles of the tongue.
When a nerve is damaged, peripheral paresis or paralysis of the corresponding half of the
tongue develops with atrophy and thinning of the muscles. In the case of a nuclear lesion - fibrillar twitching of the muscles of the tongue can be observed. Unilateral nerve damage does not
cause noticeable functional disorders due to compensatory mechanisms (interweaving of fibers)
of the opposite side. However, a bilateral lesion leads to impaired speech, which becomes entangled, indistinct - dysarthria. With a complete bilateral lesion of the nerve, speech becomes impossible, the tongue is motionless, does not protrude from the mouth - anarthria.
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