Autonomic and Digestive system in the head and neck pdf - Head and Neck

Basic Anatomy

619

Summary of the Branches

of the Cervical Plexus

and Their Distribution

T A B L E 1 1 . 7

Branches

Distribution

Cutaneous
Lesser occipital

Skin of scalp behind ear

Greater auricular

Skin over parotid salivary gland,

auricle, and angle of jaw

Transverse

cutaneous

Skin over side and front of neck

Supraclavicular

Skin over upper part of chest and

shoulder

Muscular
Segmental

Prevertebral muscles, levator scapulae

Ansa cervicalis

(C1, 2, 3)

Omohyoid, sternohyoid, sternothyroid

C1 fibers via

hypoglossal nerve

Thyrohyoid, geniohyoid

Phrenic nerve

(C3, 4, 5)

Diaphragm (most important muscle of

respiration)

Sensory

Phrenic nerve

(C3, 4, 5)

are summarized in Table 9.4.

The branches of the brachial plexus and their distribution

Branches

axillary sheath.

artery and vein are enclosed in the

(see Fig. 9.20). Here, the brachial plexus and the axillary

Pericardium, mediastinal parietal

pleura, and pleura and peritoneum

covering central diaphragm

Injury to the Brachial Plexus

ing a local anesthetic. The anesthetic solution is massaged

The roots and trunks of the brachial plexus occupy the antero-

inferior angle of the posterior triangle of the neck. Incomplete

lesions can result from stab or bullet wounds, traction, or

pressure injuries. The clinical findings in Erb-Duchenne and

Klumpke’s lesions are fully described on page 429.

Brachial Plexus Nerve Block

It will be remembered that the axillary sheath, formed from the

prevertebral layer of deep cervical fascia, encloses the bra-

chial plexus and the axillary artery. A brachial plexus nerve

block can easily be obtained by closing the distal part of the

sheath in the axilla with finger pressure, inserting a syringe

needle into the proximal part of the sheath, and then inject-

along the sheath, producing a nerve block. The syringe needle

C L I N I C A L N O T E S

(continued)

may be inserted into the axillary sheath in the lower part of the

posterior triangle of the neck or in the axilla.

page 89)

neck and ends in the cardiac plexus in the thorax (see

which descends in the

superior cardiac branch,

The

form the pharyngeal plexus

branches of the glossopharyngeal and vagus nerves to

which unite with the pharyngeal

Pharyngeal branches,

12th cranial nerves

which join the 9th, 10th, and

Cranial nerve branches,

carotid artery.

ies and are distributed along the branches of the external

arteries. These branches form a plexus around the arter

to the common and external carotid

Arterial branches

rami of the cervical nerves

to the upper four anterior

Gray rami communicantes

plexus.

branches around the artery to form the internal carotid

the carotid canal in the temporal bone. It divides into

onic fibers, accompanies the internal carotid artery into

consisting of postgangli

internal carotid nerve,

The

Branches

skull (Fig. 11.60).

The superior cervical ganglion lies immediately below the

rior, middle, and inferior cervical ganglia.

The sympathetic trunk possesses three ganglia: the supe

the prevertebral layer of deep fascia (Fig. 11.49).

embedded in deep fascia between the carotid sheath and

common carotid arteries (i.e., medial to the vagus) and is

sympathetic trunk. It lies directly behind the internal and

where it becomes continuous with the thoracic part of the

to the base of the skull and below to the neck of the 1st rib,

The cervical part of the sympathetic trunk extends upward

Cervical Part of the Sympathetic Trunk

exercise. Rarely, pressure on the first thoracic nerve causes

At the root of the neck, the brachial plexus and the subclavian

Compression of the Brachial Plexus and the

Subclavian Artery

artery enter the posterior triangle through a narrow muscu-

lar–bony triangle. The boundaries of the narrow triangle are

formed in front by the scalenus anterior, behind by the sca-

lenus medius, and below by the 1st rib. In the presence of a

cervical rib (see page XXX), the 1st thoracic nerve and the

subclavian artery are raised and angulated as they pass over

the rib. Partial or complete occlusion of the artery causes

ischemic muscle pain in the arm, which is worsened by

symptoms of pain in the forearm and hand and wasting of the

small muscles of the hand.

The Autonomic Nervous System in

the Head and Neck

Sympathetic Part

Superior Cervical Ganglion

■

620

CHAPTER 11

the vertebral artery (Fig. 11.57).

the 7th cervical vertebra and the neck of the 1st rib, behind

It lies in the interval between the transverse process of

stellate ganglion.

the first thoracic ganglion to form the

The inferior cervical ganglion in most people is fused with

and ends in the cardiac plexus in the thorax (see page 89)

which descends in the neck

The middle cardiac branch,

artery to the thyroid gland

which pass along the inferior thyroid

Thyroid branches,

5th and 6th cervical nerves

to the anterior rami of the

Gray rami communicantes

Branches

cartilage (Fig. 11.57).

The middle cervical ganglion lies at the level of the cricoid

The Head and Neck

Middle Cervical Ganglion

■

Inferior Cervical Ganglion

dorsal scapular nerve

nerve to subclavius

suprascapular nerve

lateral pectoral nerve

thoracodorsal nerve

musculocutaneous nerve

axillary nerve

radial nerve

median nerve

ulnar nerve

medial cutaneous nerve of the forearm

medial cutaneous nerve of the arm

medial pectoral nerve

upper and lower

subscapular nerves

long thoracic nerve

FIGURE 11.71

Brachial plexus and its branches.

Sympathectomy for Arterial Insufficiency of the Upper

produces not only vasodilatation of the skin vessels, but also

Removal of the stellate ganglion also removes the sym

removed to block the sympathetic pathway to the arm completely.

it is clear that the stellate and the 2nd thoracic ganglia should be

for the treatment of arterial insufficiency. From this information,

Sympathectomy of the upper limb is a relatively common procedure

fibers then join the roots of the brachial plexus as gray rami.

thoracic, stellate, and middle cervical ganglia. Postganglionic

rami, they ascend within the trunk and are relayed in the second

thoracic nerves. On reaching the sympathetic trunk via the white

preganglionic fibers leave the spinal cord in the 2nd to the 8th

The sympathetic innervation of the upper limb is as follows: The

Limb

pathetic nerve supply to the head and neck on that side. This

anhidrosis, nasal congestion, and Horner’s syndrome. For this

reason, the stellate ganglion is usually left intact in sympathecto-

mies of the upper limb.

C L I N I C A L N O T E S

(continued)

Basic Anatomy

621

Horner’s Syndrome

cle and the muscles that radiate from the lips into the face

stance of the lips is made up by the orbicularis oris mus

are lined on the inside by mucous membrane. The sub

(Fig. 11.72). They are covered on the outside by skin and

The lips are two fleshy folds that surround the oral orifice

and they are short in length.

testinal tract. The postganglionic fibers are nonmyelinated,

The last two plexuses are found in the gastroin

mucosal plexus (Meissner’s

(Auerbach’s plexus),

myenteric plexus

pulmonary plexus,

ganglion cells are placed in nerve plexuses, such as the

In certain locations, the

otic.

submandibular,

pterygopalatine,

ciliary,

asympathetic ganglia are the

located close to the viscera they innervate. The cranial par

These preganglionic fibers synapse in peripheral ganglia

within the cranial nerves.

myelinated preganglionic fibers that emerge from the brain

The axons of these connector nerve cells are

of the vagus.

dorsal nucleus

and that of the vagus nerve the

nucleus;

inferior salivary

that of the glossopharyngeal nerve the

superior salivary nuclei;

lacrimatory

nerve the

those of the facial

Edinger-Westphal nucleus;

is called the

The parasympathetic nucleus of the oculomotor nerve

vagus (10th) cranial nerves.

glossopharyngeal (9th),

oculomotor (3rd), facial (7th),

located in the nuclei of the

parasympathetic part of the autonomic nervous system is

The cranial portion of the craniosacral outflow of the

Parasympathetic Part

(Figs. 11.57 and 11.60).

ansa subclavia

is referred to as the

artery and then turns upward behind it. This anterior bundle

bundle crosses in front of the first part of the subclavian

resented by two or more nerve bundles. The most anterior

cervical ganglion to the inferior or stellate ganglion is rep

The part of the sympathetic trunk connecting the middle

cardiac plexus in the thorax (see page 89)

which descends to join the

inferior cardiac branch,

The

to the subclavian and vertebral arteries

Arterial branches

7th and 8th cervical nerves

to the anterior rami of the

Gray rami communicantes

Branches

The local anesthetic is then injected beneath the prevertebral

A stellate ganglion block is performed by first palpating the large

ment of the ganglion in cancerous growth, which may interrupt

include lesions of the brainstem or cervical part of the spinal cord;

of the sympathetic nerve supply to the orbit. Pathologic causes

the eyeball into the orbital cavity). It is caused by an interruption

(drooping of the upper eyelid), and enophthalmos (depression of

Horner’s syndrome includes constriction of the pupil, ptosis

traumatic injury to the cervical part of the sympathetic trunk; trac-

tion of the stellate ganglion caused by a cervical rib; and involve-

the peripheral part of the sympathetic pathway to the orbit.

Stellate Ganglion Block

anterior tubercle (carotid tubercle) of the transverse process of

the 6th cervical vertebra, which lies about a fingerbreadth lat-

eral to the cricoid cartilage. The carotid sheath and the sterno-

cleidomastoid muscle are pushed laterally and the needle of the

anesthetic syringe is inserted through the skin over the tubercle.

layer of deep cervical fascia. This procedure effectively blocks

the ganglion and its rami communicantes.

■

and

and the

the

and the

car-

diac plexus, the

the

and the

plexus).

The Digestive System in the Head

and Neck

The Mouth

The Lips

-
-

hard palate

soft palate

uvula

palatopharyngeal

fold

palatine tonsil

palatoglossal fold

sulcus terminalis

vallate papillae

foramen cecum

posterior wall
of oral part of
pharynx

mucous
membrane
lining vestibule

buccinator
muscle

opening of
parotid duct

upper second
molar tooth

lingual
vein

lingual
nerve

lingual
artery

opening of
submandibular duct

openings of ducts
of sublingual gland

sublingual fold

frenulum of
tongue

plica fimbriata

FIGURE 11.72

Undersurface of the tongue.

Cavity of the mouth. Cheek on the left side of the face has been cut away to show the buccinator muscle

and the parotid duct. B.

622

CHAPTER 11

opens onto the floor of the mouth on the summit of a small

The submandibular duct of the submandibular gland

(Fig. 11.72).

plica fimbriata

the frenulum, the mucous membrane forms a fringed fold,

midline to the floor of the mouth (Fig. 11.72). Lateral to

connects the undersurface of the tongue in the

tongue

frenulum of the

A fold of mucous membrane called the

from the sides of the tongue to the gum of the mandible.

the tongue and by the reflection of the mucous membrane

The floor is formed largely by the anterior two thirds of

and the soft palate behind (Fig. 11.72).

The roof of the mouth is formed by the hard palate in front

Roof of Mouth

The mouth proper has a roof and a floor.

Mouth Proper

opposite the upper second molar tooth (Fig. 11.72).

opens on a small papilla into the vestibule

salivary gland

duct of the parotid

bule in contact with one another. The

that of the muscles of the lips keeps the walls of the vesti

mucous membrane. The tone of the buccinator muscle and

which is made up by the buccinator muscle and is lined with

The lateral wall of the vestibule is formed by the cheek,

the mucous membrane from the lips and cheeks to the gums.

The vestibule is limited above and below by the reflection of

mouth proper behind the third molar tooth on each side.

the lips. When the jaws are closed, it communicates with the

municates with the exterior through the oral fissure between

and the gums and the teeth internally. This slitlike space com

The vestibule lies between the lips and the cheeks externally

Vestibule

cavity proper.

The mouth is divided into the vestibule and the mouth

formed on each side by the palatoglossal fold (Fig. 11.72).

oropharyngeal isthmus,

entrance into the pharynx, the

The mouth extends from the lips to the pharynx. The

The Mouth Cavity

inner surface of the lips to the gums.

—connect the

labial frenulae

of mucous membrane—the

midline on the outer surface of the upper lip. Median folds

is the shallow vertical groove seen in the

philtrum

The

nerves, connective tissue, and many small salivary glands.

(Fig. 11.73). Also included are the labial blood vessels and

The Head and Neck

Floor of Mouth

the

papilla on either side of the frenulum of the tongue (Fig. 11.72).

sublingual fold.

ing a low fold of mucous membrane, the

The sublingual gland projects up into the mouth, produc-

Numerous ducts of the gland open on the summit of the fold.

The greater palatine and nasopalatine nerves

Roof:

Sensory Innervation of the Mouth

attached to the alveolar periosteum.

The mucous membrane of the gingiva, or gum, is strongly

being bitten between the teeth when the jaws are closed.

that prevent redundant folds of mucous membrane from

the buccinator muscle by elastic fibers in the submucosa

In the vestibule, the mucous membrane is tethered to

Mucous Membrane of the Mouth

(Fig.

lary division of the trigeminal

11.74) from the maxil

nerve

levator labii
superioris

levator labii
superioris
alaeque nasi

infraorbital
nerve (V2)

buccal
nerve (V3)

mental
nerve (V3)

levator anguli oris

zygomaticus minor

zygomaticus major

risorius

orbicularis oris

platysma

depressor anguli oris

depressor labii inferioris

mentalis

FIGURE 11.73

Arrangement of the facial muscles around the

lips; the sensory nerve supply of the lips is shown.

glossopharyngeal

nerve (all sensations)

glossopharyngeal nerve (IX)

nasopalatine

nerve (V2)

greater

palatine

nerve (V2)

lesser

palatine

nerve (V2)

lingual nerve (V3)

(common sensation)

chorda tympani (VII)

(taste)

FIGURE 11.74

greater petrosal branch of the facial nerve.

run with branches of the maxillary nerve (V2) and join the

mucous membrane of the hard and soft palate; taste fibers

Sensory nerve supply to the

Sensory nerve supply to the mucous

membrane of the tongue. B.

Basic Anatomy

innervated by the buccal branch of the facial nerve)

sion of the trigeminal nerve (the buccinator muscle is

The buccal nerve, a branch of the mandibular divi

Cheek:

of the facial nerve.

taste fibers travel in the chorda tympani nerve, a branch

of the mandibular division of the trigeminal nerve. The

The lingual nerve (common sensation), a branch

Floor:

623

bered. The close relation of the submandibular duct to the floor

medical professional is called on to examine. Needless to say,

Clinical Significance of the Examination of the

Mouth

The mouth is one of the important areas of the body that the

the physician must be able to recognize all the structures vis-

ible in the mouth and be familiar with the normal variations

in the color of the mucous membrane covering underlying

structures. The sensory nerve supply and lymph drainage of

the mouth cavity should be known. The close relation of the

lingual nerve to the lower third molar tooth should be remem-

of the mouth may enable one to palpate a calculus in cases of

periodic swelling of the submandibular salivary gland.

C L I N I C A L N O T E S

Development of the Mouth

topharyngeal folds, and most of the soft palate are entodermal

the teeth are ectodermal structures. The secretory epithelium

pears during the third week of development (Fig. 11.75). If this

The cavity of the mouth is formed from two sources: a depres-

sion from the exterior, called the stomodeum, which is lined

with ectoderm, and a part immediately posterior to this,

derived from the cephalic end of the foregut and lined with

entoderm. These two parts at first are separated by the buc-
copharyngeal membrane, but this breaks down and disap-

membrane were to persist into adult life, it would occupy an

imaginary plane extending obliquely from the region of the

body of the sphenoid, through the soft palate, and down to the

inner surface of the mandible inferior to the incisor teeth. This

means that the structures that are situated in the mouth ante-

rior to this plane are derived from ectoderm. Thus, the epithe-

lium of the hard palate, sides of the mouth, lips, and enamel of

and cells lining the ducts of the parotid salivary gland also are

derived from ectoderm. On the other hand, the epithelium of

the tongue, the floor of the mouth, the palatoglossal and pala-

in origin. The secretory and duct epithelia of the sublingual

and submandibular salivary glands also are believed to be of

entodermal origin.

E M B R Y O L O G I C N O T E S

mandibular

process

olfactory pit

maxillary

process

buccopharyngeal

membrane

brain

buccopharyngeal

membrane

stomodeum

region of

developing neck

pericardial cavity

notochord

second pharyngeal

arch

pharynx

four pharyngeal pouches

FIGURE 11.75

fibrous septum.

right and left halves by a median

dible and the hyoid bone below. The tongue is divided into

the styloid process and the soft palate above and to the man

membrane (Fig. 11.77). The muscles attach the tongue to

The tongue is a mass of striated muscle covered with mucous

The Tongue

upper jaw.

30. The teeth of the lower jaw appear before those of the

third molar, which may happen between the ages of 17 and

to erupt at 6 years of age. The last tooth to erupt is the

molars, and 6 molars in each jaw (Fig. 11.76). They begin

There are 32 permanent teeth: 4 incisors, 2 canines, 4 pre

Permanent Teeth

those of the upper jaw.

2 years. The teeth of the lower jaw usually appear before

6 months after birth and have all erupted by the end of

and four molars in each jaw. They begin to erupt about

There are 20 deciduous teeth: four incisors, two canines,

Deciduous Teeth

The Teeth

developing embryo showing the buccopharyngeal membrane breaking down.

The face of the

Sagittal section of the embryo showing the position of the buccopharyngeal membrane. B.

624

CHAPTER 11

sulcus terminalis

by a V-shaped sulcus, the

tongue can be divided into anterior and posterior parts

The mucous membrane of the upper surface of the

Mucous Membrane of the Tongue

The Head and Neck

(Fig. 11.77).

Three types of papillae are present on the upper

(see page 659).

marks the site of the upper end of the thyroglossal duct

The foramen cecum is an embryologic remnant and

oral part, and the posterior third, or pharyngeal part.

to divide the tongue into the anterior two thirds, or

by a small pit, the foramen cecum. The sulcus serves

The apex of the sulcus projects backward and is marked

surface of the anterior two thirds of the tongue: the

and the

fungiform papillae,

filiform papillae, the
vallate papillae.

The mucous membrane on the inferior surface of

lingual tonsil.

nodules, the

(Fig. 11.77), caused by the presence of underlying lymph

the tongue is devoid of papillae but has an irregular surface

The mucous membrane covering the posterior third of

the tongue is reflected from the tongue to the floor of the

Deep cervical lymph nodes

Posterior third:

cervical lymph nodes

Submandibular and deep

Sides of the anterior two thirds:

Submental lymph nodes

Tip:

Lymph Drainage

The veins drain into the internal jugular vein.

and the ascending pharyngeal artery supply the tongue.

The lingual artery, the tonsillar branch of the facial artery,

muscles are summarized in Table 11.8.

The origin, insertion, nerve supply, and action of the tongue

Hypoglossal nerve

Nerve supply:

and the palatoglossus.

They are the genioglossus, the hyoglossus, the styloglossus,

These muscles are attached to bones and the soft palate.

Alter the shape of the tongue

Action:

Hypoglossal nerve

Nerve supply:

and vertical fibers.

attached to bone. They consist of longitudinal, transverse,

These muscles are confined to the tongue and are not

intrinsic and extrinsic.

The muscles of the tongue are divided into two types:

Muscles of the Tongue

(Fig. 11.72).

plica fimbriata

vein, the mucous membrane forms a fringed fold called the

seen through the mucous membrane. Lateral to the lingual

lateral side of the frenulum, the deep lingual vein can be

frenulum of the tongue.

mucous membrane, the

tongue is connected to the floor of the mouth by a fold of

mouth. In the midline anteriorly, the undersurface of the

On the

Intrinsic Muscles

Extrinsic Muscles

Blood Supply

crown

enamel

dentine

pulp in
pulp cavity

gingiva

odontoblasts

periodontal
ligament

periodontal
ligament
alveolar
bone

root canal

cementum

neck

root

permanent tooth

FIGURE 11.76

Sagittal section through the lower jaw and

developing permanent tooth.

gum showing an erupted temporary incisor tooth and a

palatopharyngeal
fold

epiglottis median glossoepiglottic

fold arrow leading into

piriform fossa

vallecula

tonsil

lymphoid
tissue

sulcus
terminalis

fungiform
papillae

vallate papillae

palatoglossal
fold

foramen cecum

FIGURE 11.77

Dorsal surface of the tongue showing the

arrows

fossa on each side (

valleculae, the epiglottis, and the entrance into the piriform

Basic Anatomy

625

Muscles of Tongue

T A B L E 1 1 . 8

Intrinsic muscles

Shape changes:

and palatoglossus muscles on both sides acting together

Styloglossus

Retraction and elevation of the posterior third:

together

Hyoglossus muscles on both sides acting

Depression:

sides acting together

Styloglossus and hyoglossus muscles on both

Retraction:

together (Fig. 11.78)

The genioglossus muscles on both sides acting

Protrusion:

Movements of the Tongue

tion and taste)

Glossopharyngeal nerve (general sensa

Posterior third:

chorda tympani branch of the facial nerve (taste)

lar division of trigeminal nerve (general sensation) and

Lingual nerve branch of mandibu

Anterior two thirds:

Sensory Innervation

Vertical

Transverse

Muscle

Origin

Insertion

Nerve Supply

Action

Intrinsic Muscles
Longitudinal

Median septum and

submucosa

Mucous membrane

Hypoglossal nerve

Alters shape of tongue

Extrinsic Muscles
Genioglossus

Superior genial spine of

mandible

Blends with other muscles

of tongue

Hypoglossal nerve

Protrudes apex of tongue

through mouth

Hyoglossus

Body and greater cornu

of hyoid bone

Blends with other muscles

of tongue

Hypoglossal nerve

Depresses tongue

Styloglossus

Styloid process of tem-

poral bone

Blends with other muscles

of tongue

Hypoglossal nerve

Draws tongue upward and

backward

Palatoglossus

Palatine aponeurosis

Side of tongue

Pharyngeal plexus

Pulls roots of tongue upward

and backward, narrows

oropharyngeal isthmus

Development of the Tongue

At about the fourth week, a median swelling called the

end of each first pharyngeal arch), appears on each side of the

floor of the pharynx (Fig. 11.79). A little later, another swelling,

appears in the entodermal ventral wall or

tuberculum impar

called the lateral lingual swelling (derived from the anterior

tuberculum impar. The lateral lingual swellings now enlarge,

grow medially, and fuse with each other and the tuberculum

impar. The lingual swellings thus form the anterior two thirds

of the body of the tongue, and since they are derived from the

first pharyngeal arches, the mucous membrane on each side

will be innervated by the lingual nerve, a branch of the man-

dibular division of the 5th cranial nerve (common sensation).

The chorda tympani from the seventh cranial nerve (taste)

also supplies this area.

Meanwhile, a second median swelling, called the

innervated by the 9th cranial nerve (common sensation and

the tongue is formed from the third pharyngeal arches and is

pears. Thus, the mucous membrane of the posterior third of

arch on each side overgrow the other arches and extend

arches are entering this region. The anterior ends of the third

anterior ends of the second, third, and fourth pharyngeal

culum impar and becomes V shaped. At about this time, the

appears in the floor of the pharynx behind the tuberculum

copula,

impar. The copula extends forward on each side of the tuber-

into the copula, fusing in the midline. The copula now disap-

taste).

E M B R Y O L O G I C N O T E S

(continued)

Laceration of the Tongue

truded from the mouth. It can also occur when a patient acci

A wound of the tongue is often caused by the patient’s teeth

following a blow on the chin when the tongue is partly pro-

dentally bites the tongue while eating, during recovery from

an anesthetic, or during an epileptic attack. Bleeding is halted

by grasping the tongue between the finger and thumb pos-

terior to the laceration, thus occluding the branches of the

lingual artery.

C L I N I C A L N O T E S

626

CHAPTER 11

The Head and Neck

The anterior two thirds of the tongue is separated from the

soft palate.

foramen. The glossopharyngeal nerve also supplies the

enters the front of the hard palate through the incisive

nasopalatine nerve, also a branch of the maxillary nerve,

the greater and lesser palatine foramina (Fig. 11.74). The

division of the trigeminal nerve enter the palate through

The greater and lesser palatine nerves from the maxillary

Nerve Supply of the Palate

nerve supply, and actions are summarized in Table 11.9.

The muscles of the soft palate, their origins, insertions,

a tense sheet.

that the soft palate may be moved upward or downward as

cles of the two sides contract, the soft palate is tightened so

expands to form the palatine aponeurosis. When the mus

The tendon, together with the tendon of the opposite side,

don, which turns medially around the pterygoid hamulus.

as they descend from their origin to form a narrow ten

The muscle fibers of the tensor veli palatini converge

nerve as it passes downward and forward in the carotid tri

ing hindbrain and later migrate inferiorly and anteriorly around

the mucous membrane just anterior to the sulcus terminalis,

of the tongue becomes free. Some of the entodermal cells remain

lying mesenchyme. Later, these cells degenerate so that this part

arches. Around the edge of the anterior two thirds of the tongue,

ryngeal arches and the anterior ends of the third pharyngeal

posterior third by a groove, the sulcus terminalis, which repre-

sents the interval between the lingual swellings of the first pha-

the entodermal cells proliferate and grow inferiorly into the under-

in the midline and help form the frenulum of the tongue.

Remember that the circumvallate papillae are situated on

and that their taste buds are innervated by the ninth cranial

nerve. It is presumed that during development the mucous

membrane of the posterior third of the tongue becomes pulled

anteriorly slightly, so that fibers of the ninth cranial nerve cross

the succus terminalis to supply these taste buds (Fig. 11.79).

The muscles of the tongue are derived from the occipital

myotomes, which at first are closely related to the develop-

the pharynx and enter the tongue. The migrating myotomes

carry with them their innervation, the 12th cranial nerve, and

this explains the long curving course taken by the 12th cranial

angle of the neck (see page 616).

right hypoglossal nerve

cut right hypoglossal
nerve

intact
hypoglossal
nerve

right half
of tongue
atrophied

genioglossus muscle

FIGURE 11.78

Diagrammatic representation of the action of

geus, and the musculus uvulae (Fig. 11.81).

levator veli palatini, the palatoglossus, the palatopharyn

The muscles of the soft palate are the tensor veli palatini, the

Muscles of the Soft Palate

don of the tensor veli palatini muscle.

posterior border of the hard palate. It is the expanded ten

The palatine aponeurosis is a fibrous sheet attached to the

Palatine Aponeurosis

faces of the soft palate.

The mucous membrane covers the upper and lower sur

Mucous Membrane

tine aponeurosis, and muscles.

The soft palate is composed of mucous membrane, pala

lateral wall of the pharynx.

The soft palate is continuous at the sides with the

uvula.

der presents in the midline a conical projection called the

border of the hard palate (Fig. 11.81). Its free posterior bor

The soft palate is a mobile fold attached to the posterior

(Fig. 11.80). It is continuous behind with the soft palate.

maxillae and the horizontal plates of the palatine bones

The hard palate is formed by the palatine processes of the

front and the soft palate behind.

nasal cavity. It is divided into two parts: the hard palate in

The palate forms the roof of the mouth and the floor of the

The origin and insertion and direction of

the nerve lesion.

asked to protrude the tongue, the tip points to the side of

When the patient is

The right hypoglossal nerve (which innervates

the tip of the tongue is protruded in the

The right and left muscles contract equally together

the right and left genioglossus muscles of the tongue.

and as a result (B)

midline. C.

the genioglossus muscle and the intrinsic tongue muscles

on the same side) is cut and as a result the right side of the

tongue is atrophied and wrinkled. D.

pull of the genioglossus muscle.

The Palate

Hard Palate

Soft Palate