Department of Anatomy

	Sign In Sign-Up

Human Anatomy

Head and Neck

FOR MEDICAL AND DENTAL STUDENTS

Revised by: Dr. Nikravesh

page 68:

Summary

The nose includes the external nose and the nasal cavity. The nasal cavity

extends from the nares in front to the posterior nasal apertures. Above it

is related to the anterior and middle cranial fossae. Below it is separated

from the oral cavity by the hard palate. Laterally it is related to the exterior

in front, and farther back to the orbit, the maxillary and ethmoidal sinuses

and the pterygoid processes. Posteriorly the nasal cavity communicates with

the nasopharynx. The nasal cavity is divided into right and left halves by

the nasal septum.

The functions of the nasal cavity are: (a) to subserve the sense of smell,

(b) to provide an airway for respiration, (c) to filter, warm and moisten the

inspired air, and (d) to cleanse itself of foreign matter that is extracted from

the air.

NASAL CAVITY

Objectives:

1. Identify, on a living subject, the features of the surface anatomy of the

nose.

2. Describe the bony skeletons of the nasal septum and nasal cavity.

3. Give an account of the paranasal air sinuses with particular reference

to their purported functions and drainage.

4. Describe the general and special sensory innervation of the nasal

mucosa.

page 69:

QUESTIONS FOR STUDY:

1. What is epistaxis? What arteries are most commonly involved?

2. Why might a patient with maxillary sinusitis present with a toothache?

3. Why is the maxillary sinus particularly prone to infection?

4. What is an oro-antral fistula? Why might it result from an extraction of

an upper premolar or molar tooth?

5. Why is the pterygopalatine ganglion known as the ganglion of hay

fever?

ORAL CAVITY

Relevant features:

surface features of the dorsum of the tongue;

palatoglossal arch;

muscles of the tongue and their function;

motor and sensory nerve supply of the tongue;

submandibular ganglion;

sublingual gland;

deciduous and permanent teeth;

openings of parotid and submandibular ducts.

page 70:

ORAL CAVITY

1. In the sagittal section of the head study the oral cavity which is the

most cranial part of the alimentary canal. Also examine your own mouth.

Observe that the teeth separate the oral cavity into two parts. The larger

part enclosed within the teeth is the oral cavity proper. The narrow

space placed outside the teeth and limited externally by the lips and

cheek is the vestibule into which the parotid duct opens opposite the

crown of the upper second molar tooth.

2. Observe that the oral cavity proper has a roof and a floor, and that it

continues posteriorly into the pharynx. Note that the oral cavity proper

is bounded laterally and in front by the alveolar arches, the teeth and

the gums. Verify that the roof is formed by the hard palate in front and

the soft palate behind. In the middle of the soft palate identify the

uvula hanging downwards from its posterior edge. Posteriorly observe

the anterior palatoglossal and the posterior palatopharyngeal folds

(arches) passing down from the sides of the soft palate. The

palatoglossal folds, covering the palatoglossus muscles, pass from

the soft palate to the sides of the tongue, and the palatopharyngeal

folds, covering the palatopharyngeal muscles, pass from the soft palate

into the pharynx. The palatoglossal folds mark the posterior limit of

the oral cavity; this is the oropharyngeal isthmus, the entrance to the

pharynx. In between the palatoglossal and palatopharyngeal folds lies

the palatine tonsil. The greater part of the floor of the mouth is formed

by the anterior part of the tongue resting on the mylohyoid muscles.

3. Examine the tongue. Note that it has a root, the pharyngeal part,

through which its extrinsic muscles gain entry into the tongue. That

part of the tongue which projects into the oral cavity is called the oral

part. The tongue has a tip, margins as well as dorsal and ventral surfaces.

On the dorsum of the tongue note the inverted V-shaped sulcus called

the sulcus terminalis. The oral part of the tongue lies in front of the

sulcus while the pharyngeal part lies behind it. Observe a midline fold,

the median glossoepiglottic fold, as it runs from the dorsum of the

tongue to the epiglottis, and a pair of lateral glossoepiglottic folds

running from the lateral borders of the tongue to the sides of the

epiglottis. Between the median and lateral folds observe the shallow

depression called the vallecula, one on each side. Make a transverse

section through the free part of the tongue and observe the closely

packed, vertical, transverse and superior and inferior longitudinal

muscles arranged on either side of a midline vertical septum. These

are the intrinsic muscles of the tongue.

page 71:

4. In the median plane observe a crescentic fold of mucous membrane,

the frenulum linguae, connecting the inferior surface of the anterior

part of the tongue to the floor of the mouth. Note that the

submandibular duct opens on either side of the lower part of the

frenulum in the floor of the mouth. Lateral to the frenulum observe

the bulge in the mucous membrane caused by the sublingual gland.

The ducts of this gland open here by minute orifices.

5. Remove the mucosa from the remainder of the tongue and follow the

extrinsic muscles of the tongue into its substance:

(a) genioglossus originates from the superior mental spine of the

mandible and radiates backwards and upwards into the whole tongue;

(b) hyoglossus originates from the greater horn and adjacent part of

the body of the hyoid bone and inserts into the posterior half of

the side of the tongue;

downwards and forwards to insert into the side of the tongue; and

(d) palatoglossus originates from the palatine aponeurosis and passes

downwards to insert into the posterior part of the side of the tongue.

Summary

Note that all the intrinsic and extrinsic muscles of the tongue are supplied

by the hypoglossal nerve, except the palatoglossus which is supplied by

the cranial part of the accessory nerve via the vagus nerve and

pharyngeal plexus.

The anterior two-thirds of the tongue receives its sensory supply from

the lingual nerve and taste from the chorda tympani nerve. The posterior

one-third of the tongue receives its sensory and taste supply from the

glossopharyngeal nerve.

Note that the tongue is used in sucking, chewing and swallowing. It is

important in speech and is also an organ of taste.

page 72:

ORAL CAVITY

Objectives:

1. Identify the surface anatomical features of the lips, vestibule, oral cavity,

palate, and tongue.

2. Give an account of the processes of chewing and swallowing.

3. Give an account of the innervation of the salivary glands.

4. Describe the muscles of the tongue and the movements they produce.

5. Describe the sensory, motor and taste innervation of the tongue.

6. Describe the lymphatic drainage of the tongue.

7. Identify the palatine and lingual tonsils on a living subject.

QUESTIONS FOR STUDY:

1. Where would one look for the openings of the submandibular duct in the oral cavity?

2. What is a sialogram? What is a sialolith?

3. To which side would the tongue deviate if the right hypoglossal nerve

were interrupted?

4. How does the lymphatic drainage of the anterior two-thirds of the tongue

differ from that of the posterior one-third? Of what clinical significance

is this difference?

5. In the case of infection of the palatine tonsils, which deep cervical

lymph nodes are likely to be enlarged and tender?

6. Where would one find the valleculae?

page 73:

SOFT PALATE AND PHARYNX

Relevant features:

three parts of the pharynx and their boundaries;

pharyngeal opening of the pharyngotympanic tube and tubal elevation;

palatoglossal and palatopharyngeal arches, and palatine tonsil;

retropharyngeal space;

pharyngeal plexus on the surface of the buccopharyngeal fascia;

superior, middle and inferior constrictor muscles, their attachments and

their innervation;

relationship of glossopharyngeal nerve to superior and middle

constrictors;

levator veli palatini and tensor veli palatini muscles;

pterygoid hamulus and palatine aponeurosis;

greater palatine and nasopalatine nerves.

SOFT PALATE AND PHARYNX

1. In the sagittal section of the head and neck, identify the pharynx. Verify

that the pharynx extends from the base of the skull to the level of the

cricoid cartilage at C6.

Identify the three subdivisions of the pharynx:

(a) The nasopharynx is the part behind the nasal cavities and extends

down to the level of the soft palate. Below this is the oropharynx

lying behind the oral cavity. Most caudally is the laryngopharynx

which lies behind the larynx.

In the lateral wall of the nasopharynx identify the opening of the

pharyngotympanic tube once again. Note that the opening is

bounded by an elevation, the tubal elevation, caused by the underlying

cartilaginous part of the pharyngotympanic tube. Behind the tube lies

the pharyngeal recess. Observe that a fold of mucous membrane,

the salpingopharyngeal fold, runs downwards from the tubal

elevation. This fold contains the salpingopharyngeus muscle.

(b) The oropharynx contains the palatoglossal and palatopharyngeal

arches, with the palatine tonsil in between them. Note that the

medial surface of the tonsil is free while its lateral surface has a

fibrous capsule separating it from the superior constrictor muscle

which forms the lateral wall of the pharynx here. A tonsillar

branch from the facial artery pierces the constrictor muscle to

reach the tonsil. Between the tonsil and the muscle lie the large

veins draining the tonsil.

page 74:

is composed of the inlet of the larynx with a depression on either

side called the piriform fossa (deep to this fossa lies the internal

laryngeal nerve); and the mucous membrane on the posterior

surface of the arytenoid and cricoid cartilages below the level of

the laryngeal inlet. Note that the boundaries of the laryngeal inlet

are the epiglottis anterosuperiorly, the interarytenoid fold of

mucosa posteroinferiorly and the aryepiglottic folds of mucosa

on either side. Again note that on either side the piriform fossa

lies between the aryepiglottic fold medially and the posterior part

of the lamina of the thyroid cartilage laterally.

2. Carefully strip off the mucosa from the superior and inferior aspects of the

soft palate, as well as from the salpingopharyngeal, palatoglossal and

palatopharyngeal folds to expose the muscles (of the same name)

contained within them. Remove also the mucosa on the inner aspect of the

pharynx and note the downward extension of the palatopharyngeus

muscle. Just below the opening of the pharyngotympanic tube, identify

the levator veli palatini muscle and trace it into the soft palate. Trace the

tensor veli palatini muscle as it curves around the pterygoid hamulus

and follow its tendon into the palate where it forms the palatine

aponeurosis, the framework of the soft palate. You saw the tensor from its

lateral side when you were exploring the deep part of the infratemporal fossa.

3. Remove the remains of the cervical part of the vertebral column.

Examine the outer surface of the pharynx formed by the constrictor

muscles of the pharynx.

4. Study the origin of the superior constrictor from the pterygoid hamulus,

the pterygomandibular raphe, the side of the tongue and the posterior

end of the mylohyoid line of the mandible. Verify the attachments of the

pterygomandibular raphe; above it is attached to the pterygoid hamulus

and below to the posterior end of the mylohyoid line. Note that the anterior

part of the raphe gives attachment to the buccinator muscle. Clean the

superior constrictor muscle and observe how the styloglossus muscle

enters the tongue by passing under the constrictor muscle near the

mandible. Note the insertion of the superior constrictor muscle into a

posterior midline raphe which extends to the pharyngeal tubercle of

the occipital bone above. In the interval between the base of the skull

and the superior constrictor, the pharyngotympanic tube and levator veli

palatini muscle enter the pharynx.

page 75:

5. Next observe the origin of the fan shaped middle constrictor from the

stylohyoid ligament, lesser horn of the hyoid, and from the upper

border of the greater horn. Its fibres are inserted posteriorly into the

median raphe. Observe that the upper border of the middle constrictor

overlaps the superior constrictor, and that the glossopharyngeal nerve

and the stylopharyngeus muscle enter the pharynx through this

interval. On the outer surface of the middle constrictor, note the

pharyngeal plexus formed by branches of the glossopharyngeal, vagus,

and sympathetic nerves.

6. Examine the inferior constrictor which arises from the oblique line

of the thyroid cartilage and from the cricoid cartilage. Follow its fibres

backwards to its insertion into the midline raphe posteriorly. Observe

how the upper border of the inferior constrictor overlaps the middle

constrictor muscle, and in this interval identify the internal laryngeal

nerve and the superior laryngeal branch of the superior thyroid

artery as they enter the larynx. Observe how the lower fibres of the

inferior constrictor (cricopharyngeus) become continuous with the

inner circular muscle fibres of the oesophagus. Note that the recurrent

laryngeal nerve and inferior laryngeal branch of the inferior thyroid

artery ascend deep to its lower border before they enter the larynx

while the external laryngeal nerve runs on its superficial surface.

page 76:

Summary

The palate forms the roof of the mouth and the floor of the nasal cavity. It

is divided into a larger anterior hard palate and a smaller posterior soft

palate. The soft palate is elevated in swallowing, phonation (except nasal

consonants) and in the act of blowing.

The pharynx represents the upper end of the digestive tube and is the

common channel for deglution and respiration. It is a fibromuscular tube

and from without inwards it is composed of buccopharyngeal fascia,

muscles, a thin layer of fascia and a mucous membrane.

The pharynx lies behind the nasal cavity, the oral cavity and larynx, and

in front of the cervical part of the vertebral column. It extends from the

base of the skull to the lower border of the cricoid cartilage at the level of

the sixth cervical vertebra, where it is continuous with the oesophagus.

Note that:

(a) all the muscles of the soft palate are supplied by the cranial part of the

accessory nerve via the vagus nerve and pharyngeal plexus, except

the tensor veli palatini which is supplied by the mandibular nerve;

(b) all the muscles of the pharynx are supplied by the cranial part of the

accessory nerve via the vagus nerve and pharyngeal plexus, except

the stylopharyngeus which is supplied by the glossopharyngeal nerve.

SOFT PALATE AND PHARYNX

Objectives:

1. Locate the retropharyngeal space.

2. Locate the three parts of the pharynx

3. Identify the special characteristics of the nasopharynx, oropharynx and

laryngopharynx.

4. Identify the arrangement of the muscles of the pharynx.

5. Discuss the significance of the motor and sensory innervation of the

soft palate and pharynx.

QUESTIONS FOR STUDY:

1. What important nerve may be injured by a foreign body lodged in the

piriform fossa? What danger would a patient face if this nerve were

injured?

2. How can an enlargement of the pharyngeal tonsil (adenoid) be related

to an infection of the middle ear?

3. What cranial nerves are involved in the pharyngeal (gag) reflex?

page 77:

THE LARYNX

Relevant features:

skeleton of the larynx;

joints and ligaments of the larynx;

cricothyroid muscles and their function;

posterior cricoarytenoid muscles and their function;

vocalis muscles and their function;

inlet of the larynx formed by the epiglottis and aryepiglottic and

interarytenoid folds;

vestibule of the larynx;

vestibular folds and rima vestibuli;

ventricle of the larynx;

vocal fold and vocal ligament and the rima glottidis and vocalis muscle;

infraglottic cavity of the larynx;

submucous and mucous membrane layers;

internal and external branches of the superior laryngeal nerve; and

recurrent laryngeal nerve.

LARYNX

1. Identify the larynx in the sagittal section of your head and neck

specimen. For reference use also prepared specimens and models of

the larynx. Verify that the larynx extends from the hyoid bone and

root of the tongue to the level of the cricoid cartilage (at C6) below

which it continues as the trachea. It lies in front of the pharynx

opposite the third, fourth, fifth and sixth cervical vertebrae. The larynx

consists of a cartilaginous framework formed chiefly by the thyroid,

cricoid, artytenoid and epiglottic cartilages, which are covered with

mucous membrane. Look at models of the laryngeal cartilages and

try to obtain a three dimensional comprehension of the manner of

articulation of these cartilages. Note that the thyroid cartilage consists

of the two quadrilateral laminae joined together in front by the

laryngeal prominence and the angle of the thyroid cartilage. You

saw that the laminae were covered by the thyroid gland and the

infrahyoid muscles. The cricoid cartilage articulates with the inferior

cornua of the thyroid cartilage. Posteriorly, the upper surface of

the lamina of the cricoid cartilage articulates with the two arytenoid

cartilages. Identify the apex and the vocal and muscular processes

of each arytenoid cartilage. The vocal folds pass forwards from the

vocal processes to the inner aspect of the thyroid cartilage just on

either side of the midline.

page 78:

2. Next look at the interior of the larynx. First examine the inlet of the

larynx. Below the inlet identify the two horizontal folds on the lateral

wall, the vestibular fold superiorly and the vocal fold inferiorly.

The space between the inlet of the larynx and the vestibular folds is

the vestibule, and that between the vestibular folds and the vocal

folds is known as the ventricle. The space below the vocal folds is

the infraglottic cavity. Verify that the ventricle leads upwards into a

recess lateral to the vestibular folds. Note that the space between the

right and left vestibular folds is the rima vestibuli and that between

the two vocal folds is the rima glottidis. It is important to realise

that the space between the two vocal folds is narrower than that

between the vestibular folds.

3. Now examine the posterior surface of the larynx. Dissect out the

laryngeal muscles by removing the mucosa of the posterior wall. As

you remove the mucosa, try to identify the branches of the recurrent

and internal laryngeal (sensory) nerves. The muscles of the larynx are:

(a) the posterior cricoarytenoid muscle arising from the posterior

surface of the lamina of the cricoid cartilage and curving upwards

and laterally to be inserted into the muscular process of the

arytenoid of the same side;

(b) the lateral cricoarytenoid muscle placed anteriorly and laterally

in the interval between the cricoid and thyroid cartilages; it runs

from the upper border of the arch of the cricoid and passes

upwards and backwards to gain insertion into the muscular process

of the arytenoid on the same side;

one arytenoid to the other;

(d) the oblique arytenoid muscle passes upwards from one muscular

process to the opposite apex of the arytenoid. The two muscles

form an ‘X’ placed on the back of the arytenoids. Some of these

muscle fibres can be traced into the aryepiglottic folds to become

continuous with the aryepiglottic muscles which are attached to

the side of the epiglottis;

page 79:

(e) re-identify the cricothyroid muscle on the external surface of the

larynx and confirm its attachments to the arch of the cricoid and

to the lower border of the thyroid cartilage;

(f) carefully remove the lamina of the thyroid cartilage and identify

the underlying thyroarytenoid muscle. Define its attachments to

the arytenoid behind and to the inner aspect of the thyroid lamina

in front. Note that some fibres continue as the thyroepiglottic muscle superiorly; and

(g) medial to the thyroarytenoid muscle identify the fibres of the vocalis

muscle attached posteriorly to the vocal process of the arytenoid

and anteriorly to the back of the thyroid cartilage near the midline.

It lies along the lateral side of the vocal ligament.

4. Remove the muscles to examine the ligaments connecting the laryngeal

cartilages. Identify first the thyrohyoid membrane passing from the

upper border of the thyroid cartilage, behind the hyoid bone to be

attached to the superior border of the body of the hyoid, this part of

the membrane is the median thyrohyoid ligament. Observe the lateral

thickening of the membrane which forms the lateral thyrohyoid

ligament.

5. Next identify the cricovocal membrane which is attached to the upper

border of the cricoid arch and sweeps upwards and medially to a free

edge, the vocal ligament, which is attached anteriorly to the back of the

thyroid cartilage near the median plane and posteriorly to the vocal process

of the arytenoid cartilage. This ligament is the core of the vocal fold.

6. Note that the cricothyroid and cricoarytenoid joints are all synovial

with loose capsules, thus permitting gliding and rotatory movements.

7. Finally dissect the root of the epiglottis and define its attachment to

the posterior surface of the thyroid cartilage below its notch.

8. Revise the attachments and actions of the laryngeal muscles as

sphincter, adductor and abductor groups.

page 80:

Summary

The larynx connects the lower anterior part of the pharynx with the trachea.

It is an air passage, an organ of phonation and has a sphincter mechanism.

The larynx has a skeleton consisting of supporting parts, linked at joints

and moved by muscles. Fascia, both well-defined and ill-defined, is present.

And the larynx is covered by a mucous membrane on the inner aspect. The

nerve supply and lymphatic vessels are of considerable clinical significance.

The muscles of the larynx consist of three functional groups: (a) those

concerned with sphincteric action, (b) those that are adductors, and (c) the

abductor group (this refers to the paired posterior cricoarytenoid muscles).

During quiet respiration the vocal folds are in mid-position between

abduction and adduction, while in deep and forced respiration the vocal

folds are widely abducted.

Voiced speech requires adduction of the vocal folds and sufficient forceful

expiration. Adduction and abduction of the vocal folds in speech is due to

expiratory air exerting sufficient pressure to separate the vocal folds.

Tension, length and thickness of the vocal folds affect the pitch of the

voice and are varied by the laryngeal muscles.

Note the motor and sensory innervation of the larynx:

(a) All the muscles of the larynx are supplied by the recurrent laryngeal

nerve with the exception of the cricothyroid muscle which is supplied

by the external laryngeal nerve.

(b) The mucous membrane of the larynx is supplied by the internal

laryngeal nerve down to the level of the vocal folds, below that level

the supply comes from the recurrent laryngeal nerve.

page 81:

THE LARYNX

Objectives:

1. Describe the skeleton and joints of the larynx.

2. Give an account of the major intrinsic muscles of the larynx that (a) act

as sphincters to guard the entrance of the trachea; and (b) change the

position and length of the vocal folds.

3. Give an account of the motor supply of the muscles of the larynx.

4. Give an account of the sensory innervation of the mucosal lining of the

larynx.

5. Describe the arrangement of the submucous layer in relation to oedema of the larynx.

6. Describe how the larynx moves during swallowing.

QUESTIONS FOR STUDY:

1. In what position would you find the vocal folds during: (a) quiet

respiration; (b) forced inspiration; and (c) production of a high note?

2. What are the differences between the vestibular and vocal folds?

3. What effects on breathing and speech would result from: (a)

complete interruption of the external laryngeal nerve; (b) complete

unilateral interruption of the recurrent laryngeal nerve; and

4. A type of laryngotomy known as a cricothyroidectomy or coniotomy

is an emergency procedure performed in order to relieve acute

obstruction of the airway. How is it performed? What structures are at risk?

5. What is glottis (laryngeal) oedema?

6. What part of the thyroid gland may need to be moved or cut during a

tracheotomy?

page 82:

THE EAR

Relevant features:

external, middle and internal ear;

external acoustic meatus;

tympanic membrane;

walls, roof, and floor of tympanic cavity;

mastoid cells and mastoid antrum;

auditory ossicles;

bony part of pharyngotympanic tube, and tensor tympani muscle and its canal;

fenestra vestibuli;

pyramidal eminence and stapedius muscle;

promontory and branches of tympanic plexus;

fenestra cochleae;

prominences of facial and semicircular canals;

chorda tympani nerve;

internal jugular vein and internal carotid artery related to floor of tympanic cavity;

internal acoustic meatus;

facial nerve in facial canal and vestibulocochlear nerve;

geniculate ganglion and origin of greater petrosal nerve;

orientation of the three semicircular canals; cochlea; and

greater and lesser petrosal nerves.

THE EAR

Introduction

1. In order to study the auditory and vestibular apparatus, the temporal

bone and the adjacent parts of the sphenoid and occipital bones have

to be removed and decalcified.

2. Remove the temporal bone from your specimen by making two

saw-cuts:

(a) make an anterior cut in the frontal plane through the articular

tubercle of the temporal bone to the foramen spinosum and on to

the median plane;

(b) next make a posterior cut from behind the mastoid process

obliquely forwards to the anterolateral margin of the foramen

magnum; and then

3. Next decalcify the temporal fragment by immersing it in a 10 per cent

solution of concentrated nitric acid for 7 to 14 days. The solution should

be changed twice weekly. To test for completion of decalcification, stick

a needle into the bone. It should sink in when pressure is applied. When

decalcification is complete, wash the specimen in running water for

24 hours and store it in a 50 per cent solution of alcohol in water. This

process makes dissection easier.

Since decalcification takes about two weeks, you may be supplied

with a decalcified temporal bone taken from a cadaver dissected previously.

page 83:

Dissection of the ear

1. The ear is divided into three parts: the external ear, which consists of

the auricle and the external acoustic meatus; the middle ear or

tympanic cavity, which is a narrow air-filled chamber lying between

the external and internal ear; and the internal ear, which comprises a

complex system of canals in the petrous part of the temporal bone,

called the bony labyrinth. Within this labyrinth and surrounded by

perilymph lie membranous tubes and sacs, the membranous

labyrinth, which are filled with endolymph, and in which are located

the receptors for the sensations of hearing and balance.

2. Examine the skull and identify the following landmarks: the external

acoustic meatus and suprameatal triangle externally; and the

internal acoustic meatus and arcuate eminence on the temporal bone

in the cranial cavity.

3. Examine a prosected specimen or a model of the ear and identify the

external, middle and inner ears. Study the features of the external ear

in the living. Note that it consists of the auricle and the external acoustic

meatus. In the auricle, identify the concha, the lobule, tragus,

antitragus and the intertragic notch. Note that the concha of the

auricle leads into the external acoustic meatus. Verify that the auricle

has to be pulled upwards, backwards and laterally, to straighten the

external acoustic meatus to enable one to look into the ear.

4. In your decalcified specimen, remove the skin of the auricle and confirm

that the auricle has a framework of elastic cartilage which makes it very

pliable. Next try to identify the parts of the external acoustic meatus.

Note how tightly the skin is bound down to the wall of the meatus. The

outer third of the meatus is cartilaginous while the rest is bony and

the junction between the two is the narrowest part. At the medial end of

the external acoustic meatus identify the tympanic membrane.

5. Examine the posterior cranial fossa and identify the internal acoustic

meatus. With a scalpel and a pair of forceps gently remove the roof of

the internal acoustic meatus. Trace the facial and vestibulocochlear

nerves laterally. The facial nerve is uppermost and can be traced

towards the medial wall of the middle ear where it swells into the

geniculate ganglion. The ganglion contains the cell bodies of the

sensory (taste) fibres that join the facial nerve in the chorda tympani.

Lever the facial nerve upwards and identify the divisions of the

vestibulocochlear nerve, and if possible the labyrinthine artery. Very

gently remove the bone between the hiatus for the greater petrosal

nerve and the geniculate ganglion; this will expose the course of the

nerve and also the coils of the cochlea.

page 84:

6. Next with a pair of forceps carefully remove the tegmen tympani which

forms the roof of the middle ear. As you do this the small auditory

ossicles will come into view. The most easily recognised ossicle is the

head of the malleus which lies in the epitympanic recess (upper part)

of the tympanic cavity. Anteromedially, the tympanic cavity is

continuous with the bony part of the pharyngotympanic tube.

Try to pass a probe through the pharyngeal opening of the

pharyngotympanic tube into the tympanic cavity. Identify a small

muscle, the tensor tympani, which comes out of a canal just above the

pharyngotympanic tube and passes backwards to be attached to the

malleus below its head.

Note that the malleus articulates with the incus and this in turn

articulates with the stapes. The base of the stapes is applied to the

medial wall of the tympanic cavity. The joints between the three ossicles

are synovial joints.

7. First examine the lateral wall of the tympanic cavity. Note the tympanic

membrane to which the malleus is attached. Above the insertion of the

tensor tympani you should see a thread-like structure crossing the

medial side of the malleus in an anteroposterior direction. This is the

chorda tympani which you saw joining the lingual nerve. The chorda

tympani arises from the facial nerve.

8. Next examine the medial wall of the tympanic cavity. Again identify

the stapes in the medial wall. Its base fits into a window, the fenestra

vestibuli, which is covered by a membrane and lies above the

promontory and below the canal for the facial nerve. The promontory

forms a bulge of the medial wall due to the basal turn of the cochlea. If

you use a magnifying glass you may be able to see the thread-like

tendon of the stapedius muscle, which is attached to the stapes near

its articulation with the incus. Posteriorly, the tendon emerges from

the top of a very small projection of bone called the pyramidal

eminence. In one of the depressions below and behind the promontory

is another small window, the fenestra cochleae, which is closed by a

membrane. However, it is not easy to identify this window.

page 85:

9. The tympanic cavity opens posteriorly through the aditus to the

antrum into the mastoid antrum.

10. Now turn your attention to the bony labyrinth in the petrous part of the

temporal bone. With the help of models and your atlas note the

following: the bony labyrinth consisting of the vestibule, the cochlea

and the three bony semicircular canals. These form the internal ear.

The vestibule lies between the medial wall of the middle ear and the

internal acoustic meatus. In its lateral wall is the fenestra vestibuli,

which is closed by the periosteal lining, and into which the base of the

stapes fits. The vestibule communicates in front with the cochlea and

behind with the semicircular canals.

The cochlea is a tapering spiral tube which makes about two and

one-half turns around a central bony pillar, the modiolus. The first

turn of the cochlea is responsible for the elevation on the medial wall

of the tympanic cavity called the promontory.

Note the three semicircular canals. The anterior semicircular canal

and the posterior semicircular canal are both vertical, the former at

right-angles to, and the latter parallel with the long axis of the petrous

part of the temporal bone. The anterior semicircular canal lies beneath

an elevation, the arcuate eminence, on the upper surface of the petrous

part of the temporal bone, about 1 cm behind the internal acoustic

meatus. The lateral semicircular canal lies horizontal in the angle

between the other two canals.

11. Now return to the divisions of the vestibulocochlear nerve and attempt

to trace the cochlear division into the modiolus and the vestibular

division laterally into the vestibule.

12. You will not be able to study the more detailed anatomy of the

membranous labyrinth on your specimen. For this, special preparations

suitable for microscopic examination are required.

13. Strip off all the muscles attached to the mastoid process and cut it open

with a scalpel to expose the mastoid air cells contained within it.

Remove the air cells and look for the mastoid antrum. Again, note that

the antrum communicates with the tympanic cavity through the aditus to the antrum.

page 86:

Summary

It is important to understand the functions of the auditory ossicles and their

muscles. Sound waves pass from the external acoustic meatus and cause

the tympanic membrane to vibrate. These vibrations are transmitted by the

ossicles to the fenestra vestibuli and thence to the internal ear. Tensor tympani

and stapedius muscles contract reflexly to dampen down excessive

movements of the ossicles due to sounds of high intensity (sound mufflers)

and allow soft sounds to be separated from irrelevant loud ones.

The main sensory and motor innervation of the external ear and middle ear is as follows:

(a) Auricle:

sensory - outer surface (lateral surface): mainly auriculotemporal nerve;

inner surface (cranial surface): mainly great auricular nerve;

concha: may be supplied by a sensory branch from

the facial nerve and vagus nerve;

motor - facial nerve.

(b) Tympanic membrane:

sensory - outer surface: auriculotemporal and vagus nerves;

inner surface: glossopharyngeal nerve.

sensory - glossopharyngeal nerve.

(d) Tensor tympani muscle: motor fibres from the mandibular nerve.

(e) Stapedius muscle: motor fibres from the facial nerve.

page 87:

THE EAR

Objectives:

1. Identify, on a living subject, the features of the surface anatomy of the

external ear.

2. Describe the cutaneous sensory innervation of the external ear, tympanic

membrane, and tympanic cavity.

3. Give an account of the walls, roof, and floor of the tympanic cavity.

4. Give a full account of the facial nerve.

5. Describe how sound is transmitted from the external ear to the fenestra

vestibuli.

QUESTIONS FOR STUDY:

1. What nerve may be seen on the inner aspect of the tympanic membrane

during an otoscopic examination?

2. What spaces communicate with the tympanic cavity? What is the

clinical significance of these communications?

3. What is otitis media?

4. What functional components are represented in: (a) the greater petrosal

nerve; and (b) the chorda tympani?

5. What is the function of the tensor tympani and stapedius muscles?

What is their innervation?

6. What kinds of cell bodies are found in the geniculate ganglion?

Additional Objectives for the Head and Neck

page 88:

MUSCLES AND FASCIAE OF THE HEAD AND NECK

Objectives:

1. Describe the relations of scalenus anterior, scalenus medius, posterior

belly of digastric, sternocleidomastoid, hyoglossus, lateral pterygoid,

obliquus capitis inferior and lateral rectus of the eyeball.

2. Analyse the movements and stability of the eyeball.

3. Describe the attachments of the deep cervical fascia pointing out the

continuity between the superficial layer, the carotid sheath and the

pretracheal layers.

4. Explain why:

(a) swellings of the thyroid gland move with swallowing; and

(b) swellings of the parotid gland are painful.

5. Review the attachments of the prevertebral fascia and explain:

(a) the formation of the axillary sheath;

(b) why it is an important landmark to the surgeon; and

or tracks down into the posterior mediastinum.

page 89:

NERVES OF THE HEAD AND NECK

Objectives:

1. Describe the effects of lesions affecting the cranial nerves as well as

the methods employed for testing their integrity.

2. Review the origin, course and distribution of the phrenic nerve.

3. Briefly describe the distribution of the branches of the superior, middle

and cervicothoracic sympathetic ganglia.

4. Describe the location of the ciliary, pterygopalatine, submandibular

and otic ganglia, and their connections.

5. Explain the anatomical basis of:

(a) Horner’s syndrome;

( pain from teeth being referred to the ear;

(d) headache;

BLOOD VESSELS AND LYMPHATICS OF THE HEAD AND NECK

Objectives:

1. Review the areas of distribution of the branches of the external carotid artery.

2. Describe the structures supplied by the branches of the internal carotid

artery.

3. Describe the sites of anastomoses between the external and internal carotid arteries.

4. Describe the area of distribution and course of the four parts of the

vertebral artery giving the developmental reason for this arrangement.

5. Explain alternate routes of venous drainage when the internal jugular vein is ligated.

6. Explain: (a) the collateral circulation when the subclavian artery is

ligated; (b) the importance of the tubercle on the transverse process of

the sixth cervical vertebra (Chassaignac’s tubercle); and (c) the

importance of the relationship of the subclavian artery to the first rib.

page 90:

Objectives:

1. Describe the location of: (a) the pericervical collar of lymph nodes; (b)

the anterior cervical nodes; (c) the superficial and deep cervical nodes;

and (d) the retropharyngeal nodes. Indicate their territory of drainage.

2. Describe the formation and termination of the right lymphatic and thoracic ducts.

VISCERA OF THE NECK

Objectives:

1. Describe the course and relations of the cervical part of the trachea.

2. Describe the course and relations of the cervical part of the oesophagus.

3. Enumerate the structures encountered during a tracheostomy, from superficial to deep.

4. Indicate the clinical importance of the close relationship of:

(a) the facial nerve and its branches to the parotid gland;

(b) the inferior thyroid veins to the front of the trachea;

(d) the thoracic duct to the left internal jugular vein; and

(e) the cervical pleura to the structures in the root of the neck.

5. Describe the developmental basis for the occurrence of:

(a) lingual and retrosternal thyroids;

(b) branchial cysts and fistulae;

(d) hare lip and cleft palate - unilateral and bilateral.

page 91:

References:

1- Google search result: A Guide to Dissection of the Human Body For Medical Education, 2008.

2 - Warwick W. Gray,s Anatomy, 39th Edition, Churchill Livingstone, London, 2007.

3 - Cornelius R. Textbook of Anatomy, 5th Edition, Lippincott Company, London, 1997.

4 - Elaine N M. Human Anatomy and Physiology, 4th Edition, Benjamin/Cummings Science. Publishing, California, 1998.

5 - Hamilton W J. Textbook of Human Anatomy, 2nd Edition, MacMilan Press Ltd, 1976.

6 - Harold E. Clinical Anatomy, 6th Edition, Blackwell, London, 1977.

7 - Josef J. A Textbook of Regional Anatomy, 2nd Edition, Macmilan Press Ltd, 1982.

8 - Linder H. H. Clinical Anatomy, 1st Edition, Aplleton and Lange Press. New jersy, 1989.

9 - Moffat D. B. Lecture Note on Anatomy, 1st Edition, Blackwell Scientific Publitions, Axford, London, 1988.

10 - Moore K. L. Clinically Oriented Anatomy, 3rd Edition, Williams and Wilkins, Baltimore, 1987.

11- O, Rahilly R. Anatomy, 4th Edition, Sunders Company, Philadelphia, 1986.

12 - Prives M. Lysenkov N. and Bushkovich V. Human Anatomy, Vol. 1, 1st Edition, Mir, Moscow, 1985.

13 - Snell R. Clinical Neuroanatomy for Medical students, 2nd Edition, Littel, Brown and Company, Boston, 1986.

Revised by: Dr. Mohammad Reza Nikravesh, May 2008.

Back