Head Lecture Notes

7/21/2019 Head Lecture Notes

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HE HEAD

Introduction to the skull

Superficial face; scalp

Parotid region and deep face

Intracranial cavity and meninges; cranial nerves

Eye and orbit

Nose, nasal cavities and paranasal sinuses

Oral cavity and contents

Ear and temporal bone

Lymphatics of the head and neck

NTRODUCTION TO THE SKULL

Text: Gross Anatomy, K. W. Chung, 6thedition: pp. 352-357

Reference: Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5thedition: pp. 886-905; 6thdition: pp. 822-842

Development of theskull

The base of the skull develops by endochondralossification

The brain and cranial nerves develop before the skull, so when the chondrocranium

develops, its components form around the nerves and form foramina.

The chondrocranium ossifies from a number of centers.

The last piece of cartilage to ossify is between the body of the sphenoid bone and the

occipital bone, just anterior to the foramen magnum: this is the spheno-occipital

synchondrosis. Its epiphyseal plate exists for the growth in length of the base of the

skull and it ossifies at age 25.

he bones of the calvariumossify by intramembranousossification

The bones of the calvarium also ossify from separate centers and they meet to form

sutures (Clemente plate 482 fig. 756; Grant p. 608-609; Netter 3e 2-11; 4e 2-12). The

process is completed at about 3 years.
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he bones of the face are partly basal and partly calvarial bones so they ossify both by

tramembranous and endochondral ossification.

alvalrial bones

he bones of the cranium and the underlying lobes of the brain have the same name

Clemente plate 481 fig. 754; Grant p. 610-615, 722-723; Netter 3e 2-7, 4e 4 &105):

Thefrontal bone (which houses the frontal lobe of the brain) ossifies from 2 centers and

there are right and left frontal bones at birth (Clemente plates 484-485;Grant p. 608-

609; Netter 3e 11, 4e 12). The metopic sutureseparating the 2 frontal bones normally

ossifies, leaving one large frontal bone.

Theparietal bones are separated from each other by the sagittal suture (Clemente plate

482 fig. 756; Grant p. 614-615; Netter 3e 7, 4e 7) and from the frontal bone by the

coronal suture (Clemente plate 482 fig. 756; Grant p. 612-613; Netter 3e 4; 4e 4-7).

t birth, the anterior fontanelle (Clemente plate 485 fig. 762; Grant p. 608-609; Netter 3e1, 4e 12)is a diamond-shaped area between the 2 frontal bones and the 2 parietal bones. It

ulsates and bulges when the baby cries. It closes by 18 months to 2 years and is then known

the bregma (Clemente plate 482 fig. 756; Grant p. 614; Netter 3e 7, 4e 7).

The parietal bones and the occipitalbone meet at the posteriorfontanelle(Clemente

plate 485; Grant p. 609; Netter 3e 11; 4e 12) which becomeslambda, alongthe

lambdoid suturein the adult (Clemente plate 482 fig. 756; Grant p. 614; Netter 3e 7,

4e 7).The side wall of the skull is completed by the squamous part of the temporal bone and

the greater wing of thesphenoid bone, at the pterion (Clemente plate 481;Grant p.

612-613; Netter 3e 4, 4e 4).

This is located 4 cm above the midpoint of the zygomatic arch and is the site of

surgical exploration for the middle meningeal artery (Grant p. 635, Netter 3e

6, 4e 6).

The flat bones of the skull (frontal, parietal, temporal and occipital) are formed by a

sandwich of diplo(cancellous bone containing red bone marrow) between 2 layers ofcompact bone (Clemente plate 486 fig. 765; Grant p. 634; Netter 3e 96, 4e 102).

The bones are drained by diploic veins; there are usually 4 on each side: frontal,

anterior temporal, posterior temporal and occipital (Clemente plate 486 fig. 764; Grant

p. 634; Netter 3e 94, 4e 99 & 102) which open into the nearest convenient venous

sinus.

The flat bones of the skull are also pierced by emissary foraminatransmitting emissary

veinsconnecting veins of the scalp with the dural venous sinuses inside the skull (this is

a possible route for the spread of infection). They may be seen in the parietal bone or inthe temporal bone posterior to the external auditory meatus (Grant 785; Netter 3e 94,

96; 4e 7, 99 & 102).

an X-ray of the skull, it is necessary to differentiate the following normal structures from


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actures (Grant p. 620-621; Netter 3, 5):

the sutures (possible metopic suture),

the diploic veins,

and the middle meningeal artery.

he pineal gland near the center of the brain may contain corpora aranaceae(calcareous

anules) and it can be used to detect displacement of the brain.

Theoccipital bone (Clemente plate 482 fig. 757; Grant p. 614; Netter 3e 8, 4e 6 & 8):

The external occipital protuberanceis located inferior to lambda.

Thesuperior nuchal linesrun lateral from the external occipital protuberance and

the inferior nuchal linesare situated inferiorly.

he cranial fossae (Clemente plates 496-497; Grant p. 618-619;

Netter 9):

om anterior to posterior, 3 fossae form 3 successive steps leading down to the foramen

agnum.

Anterior cranial fossa:

Orbital plate of the frontal bone

Lesser wing of the sphenoid bone

The cribriform plate of the ethmoid with the crista gallitransmits olfactory nervesfrom the upper part of the nasal cavity; this is a possible route for infection or escape

route for CSF in skull fractures.

Optic canalfor transmission of optic nerve.

Anterior clinoid processesprojecting posteriorly to the posterior clinoid processes of

the sphenoid bone.

Middle cranial fossa

is formed by thegreater wing of the sphenoid bone and the temporal bone. It isoccupied by the temporal lobeof the brain.

The greater wings and the body of the sphenoid bone form a butterfly shape.

The most posterior tip of the greater wing contains the foramen spinosum.

Anterior to the foramen spinosum is the foramen ovaleand then the foramen

rotundum. The foramen rotundum leads to the pterygopalatine fossa.

Thesuperior orbital fissureis a gap between the lesser wing and the greater wing of

the sphenoid leading to the orbit, just lateral to and below the optic nerve.

The body of the sphenoid bone contains the hypophyseal fossafor the pituitary gland.This fossa is also called the sella turcicaand it is shaped like a 4-poster bed (clinoid

processes; clinical = patient is in bed).

Its maximum length is 14 mm and its depth is 8 mm. Measurements are important

because pituitary tumors cause ballooning of the sella.


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Theforamen lacerumis located lateroposterior to the sella.

he middle meningeal arteryenters the skull through the foramen spinosum and its groove

n be traced laterally and anteriorly on the squamous portion of the temporal bone before

viding into anterior and posterior (frontal and parietal) branches.

The anterior branch crosses the greater wing at the pterion and then breaks up into

branches that run superiorly and posteriorly.

The posterior branch runs posteriorly supplying bone and meninges.

Posterior cranial fossa

is formed by the temporal bone and the occipital bones.

houses the cerebellum.

he posterior cranial fossa contains:

the foramen magnumfor the lower end of the medulla.The clivus,anterior to the foramen magnum, which leads up to the body of the sphenoid

bone.

The transverse sinus

The sigmoid sinuswhich ends at thejugular foramen.

The hypoglossal canal (anterior condylar) canaland the posterior condylar canal.

The internal auditory meatuson the posterior aspect of petroustemporal bone.

The arcuate eminenceon the petrous portion of the temporal bone, marking the

position of the superior semicircular canal.

he superior sagittal sinus(Grant p. 613; Netter 97-98) is continuous with the right

ansverse sinus whereas the smaller straight sinusis continuous with the left transverse

nus. The right jugular foramen is thus usually larger than the left.

he exterior base of the skull (Clemente plate 498; Grant p. 616-

17; Netter 8).

Recognize the above- mentioned foramina from the exterior.

The spine of the sphenoidbone is near the foramen spinosum.

The jugular foramen is occupied by thejugular bulb (for expansion of the internal

jugular vein) in life.

The styloid process, the mastoid process and the stylomastoid foramenbetween the

2 processes.

Anterior to the jugular foramen and in the petrous portion of the temporal bone lies the

carotid canal.The spine of the sphenoid bone lies medial to the mandibular fossa. The mandibular

fossa articulates with the head of the mandible to form the temporomandibular (TMJ)

joint.

The foramen ovalelies at the base of the lateral pterygoid plate.


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The medial pterygoid plate(with the pterygoid hamulusat its base) and the lateral

pterygoid plate are parts of the sphenoid bone.

The inferior orbital fissureleads anteriorly from the pterygoid region to the orbit.

The hard palateis formed by the palatine process of the maxillaand by the

horizontal plate of the palatine bone. There are 3 foramina in the horizontal plate, the

larger being the greater palatine foramen.

The vomer bonein the posterior opening (the choanae) of the nasal cavity is attached

by a fibrous joint to the undersurface of the body of the sphenoid.

he internal carotid artery (Clemente plate 491 fig. 772, plate 497; Grant p. 644-645;

etter 3e 130, 4e 136):

enters the carotid canal,

runs anteromedially to the foramen lacerum

and then runs superoanteriorly to enter the cranium through the internal orifice of the

foramen lacerum.

It then turns anteriorly and lies on the side of the sella turcica. It now lies in thecavernous sinus.

It then turns superoposteriorly, medial to the anterior clinoid process and breaks up into

3 branches.

HE SKELETON OF THE FACE

he following structures are found in the orbit (Clemente plate 480; Grant p. 650; Netter 3e

4e 2 &4):

thesuperior orbital fissure

the optic canal

The greater and lesser wings of the sphenoid.

Thezygomatic boneand the (hollow) maxilla are in the lateral wall of the orbit.

Theethmoid boneand the small fragile lacrimalbone are in the medial wall .

hesupraorbital, infraorbital andmental foramina(Clemente plate 480; Grant p. 610-11; Netter 2) lie on a vertical line and transmit the ophthalmic,maxillary andmandibular

visions of thetrigeminal(Vth cranial) nerve (Clemente plate 542; Grant p. 630-631;

etter 3e 116, 4e 122).

pdated 10/28/2009

UPERFICIAL FACE AND SCALP

Text: Gross Anatomy, K. W. Chung, 6thedition: pp. 337 344, 347-348


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Reference: Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5thedition: pp. 906-908; 933-957;th edition: pp. 842-865

Dissector:

Clementes Anatomy Dissector, 2nd edition: pp. 303-315

Grants Dissector, P.W. Tank, 14thedition: pp. 199-210

ACIAL MUSCULATURE

main groups of muscle are located on the face:

muscles of facial expressioninnervated by the facial nerve (cranial nerve VII)

and muscles of masticationsupplied by the mandibular division of thetrigeminal

nerve (cranial nerve V).

Muscles of facial expression (innervated by the facial nerve)are superficial muscles which

n move skin and fascia in various directions. They are also dilatorsand sphinctersfor the

arious orifices in the face region. The 2 major groups are around the eye and the mouth.

round the eye:

he sphincter is the orbicularis oculi(Clemente plate 462 fig. 728; Grant p. 626, 628-629;

etter 3e 22, 4e 26) which has:

a palpebralpart in the eye lid (closes eye gently)

and an orbital partwhich surrounds the orbit and blends in with the anterior belly of

occipitofrontalis (closing the eye forcibly). The orbital part causes radiating skin

wrinkles from the lateral corner of the eye.

he dilator is the levator palpebrae superioris (Clemente plate 509 fig. 801; Grant p. 654-

55; Netter 3e 77, 4e 84) innervated by the oculomotor nerve (cranial nerve III) and

ostganglionic sympathetic fibers from the superior cervical ganglion.

round the mouth:

he sphincter is the orbicularis oris(Clemente plate 462 fig. 728; Grant p. 630; Netter 3e

2, 4e 26) which closes the lips but can also protrude the lips as in whistling, or kissing.

he dilators are:

Levator labii superioris alaeque nasi ("Grace" muscle; Clemente plate 462 fig. 728;

Grant p. 629; Netter 3e 22, 4e 26)

Levator labii superioris

Levator anguli oris

Zygomaticus minor


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Zygomaticus major

Platysma (risorius; Clemente plate 463 fig. 729; Grant p. 746; Netter 3e 22, 4e 26)

Depressor anguli oris

Depressor labii inferioris

Mentalis

hebuccinator(Clemente plates 466-467; Grant p. 666; Netter 3e 22, 50, 4e 26) is the

ain muscle of the cheek and it keeps the cheeks in contact with the gums so that food does

ot accumulate in the vestibule of the mouth.

Bell's Palsy: lesions of the facial nerve (Cranial nerve VII)

Drainage of tears and dribbling of saliva due to paralysis of the 2 main orbicularis

muscles. Paralysis of buccinator will lead to accumulation of food in the vestibule.

Test by asking patients to screw up the eye (loss of muscle tone causes the normal skin

folds to disappear on the side of the lesion), to smile or to whistle.

Muscles must be supported during recovery or they will stretch under gravity and causea permanent asymmetry of the face.

Muscles of mastication (Grant p. 672-673; Netter 3e 50, 4e 54-55)developed from the first

ranchial archand are innervated by branches from the anterior branch of the mandibular

vision of the trigeminal nerve(Grant p. 828-829, Netter 3e 116, 4e 122):

Themasseter (Clemente plate 466; Grant p. 626-627; Netter 3e 50, 4e 54) muscle

attaches to the zygomatic arch and the outer surface of the mandible near the angle. It is

composed of a superficial and deep part. The masseter closes the jaw and is innervated

by the masseteric nerves passing through the mandibular notch.

Thetemporalis muscleattaches from the lateral side of the skull below the temporal line

to coronoid process and anterior border of the ramus of the mandible almost as far as the

third molar tooth (Grant p. 666-667; Netter 3e 50, 4e 54). The temporalis muscle

closes the jaw and is innervated by the deep temporal nerves.

Thelateral pterygoid muscle (Clemente plate 470;Grant p. 670; Netter 3e 51, 4e 55)

attaches from the lateral surface of the lateral pterygoid plate to the neck of mandible

and the intraarticular disc of the temporomandibular joint. It is the onlymusclein this

group to open the jaw.

Themedial pterygoidis attached from the medial surface of the lateral pterygoid plate

to the deep surface of the mandible (at the angle of the mandible) opposite to the

attachment of the masseter muscle. The angle of the mandible thus lies between these 2

muscles. The medial pterygoid muscle closes the jaw.

Both pterygoid muscles are innervated by the pterygoid nerves.

lood vessels:

he facial artery (Clemente 468, 474; Grant p. 632; Netter 3e 19, 4e 23):

provides the main blood supply.


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passes over the lower border of mandible at the anterior border of the masseter (feel the

pulse).

has a tortuous course to allow for movement of the face, first to the angle of the mouth

and then up at the side of the nose to the medial angle of the eye.

gives off upper and lower labial branches as well as numerous other branches to the face.

Free anastomoses on the same side as well as across the midline.

hefacial veinhas a straighter path and communicates with deeper veins such as veins of the

bit (leading to the cavernous sinus within the skull(Clemente plates 468, 475;Grant p.

33; Netter 3e 19, 81, 4e 23, 85) at the medial angle of the eye and the pterygoid venous

exus. The central face area is thus a "danger area" for an infection on the face to travel into

e skull or into the deep face.

hesuperficial temporal artery(Clemente 468, 474; Grant p. 626-627, 632; Netter 3e 19,

e 23) is a branch of the external carotid artery. Its pulse can be felt in front of the tragus of

e ear. Above the ear it divides into anterior and posterior branches. It anastomoses with the

cial artery.

arotid gland (Grant p. 627; Netter 3e 19, 4e 25, 61)

This major salivary gland becomes inflamed with the mumps. It is enclosed in a split

layer of deep cervical fascia so that swelling of the gland leads to increase in pressure

and pain. The medial thickening in this capsule forms the stylomandibular ligament

(Clemente plate 468, plate 472 fig. 740; Grant p. 674; Netter 3e 12, 14, 4e 16).

The duct (Clemente plate 466; Grant p. 627; Netter 3e 17, 4e 25) leaves the anteriorborder, crosses the masseter muscle, turns around the anterior border of the muscle and

pierces the buccinator muscle to enter the mouth opposite the 2nd upper molar tooth. It

can be rolled under the fingers when the masseter is contracted by clenching the teeth. It

is in line with the tragus of the ear.

The gland occupies the space between the sternocleidomastoid and the back of the

mandible and molds itself to all adjacent structures.

important structures passes through the parotid gland fromuperficial to deep: the facial nerve, the retromandibular vein and

he external carotid artery.

hefacial nerve (Clemente plate 469; Grant p. 627, 830; Netter 3e 21, 4e 25):

from the stylomastoid foramen,

gives off a posterior auricular branch to the occipital belly of occipitofrontalis,

divides within the parotid gland forming an intraglandular network,5 branches emerge from the anterior border of the gland: temporal, zygomatic, buccal,

marginal mandibular and cervical (Palm of hand on parotid gland with 5 fingers spread

onto the face).

*Themarginal mandibularbranch runs below the border of the mandible to supply the


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muscles of the chin. Incision should always be made a finger's width below it.

heretromandibular vein (Clemente plate 477; Grant p. 633; Netter 3e 66, 4e 61)

is formed in the gland by the union of the maxillary and superficial temporal veins,

emerges from the gland near the angle of the mandible

divides into 2 with the anterior branch joining the facial vein and draining into the

internal jugular vein,

the posterior branch joins with the smallposterior auricular veinto form the externaljugular vein (Clemente plate 475; Grant p. 662; Netter 3e 66, 4e 61).

heexternal carotid artery (Clemente plate 477; Grant p. 632; Netter 3e 65, 4e 61 & 69)

divides in the substance of the parotid gland into the maxillary andsuperficial

temporal arteries,

The maxillary artery runs deep to the neck of mandible to enter the infratemporal

region,The superficial temporal artery lies in front of the ear and divides into anterior (frontal -

side of forehead) and posterior (parietal - side of scalp) branches (Clemente plate 474;

Grant p. 626-627; Netter 3e 19, 4e 23).

hescalp is attached to the zygomatic arch laterally (Clemente plate 466; Grant p. 626;

etter 3e 22, 4e 4 & 26).

S = skin

C = connective tissueA = aponeurosis referring to theGalea aponeurotica(epicranial aponeurosis). This

aponeurosis belongs to theoccipitofrontalis muscle locatedantero- and posteriorly. The

posterior attachment of this muscle is to the occipital bone above the superior nuchal

line.

L = space, this is aplane of cleavage for injury and the spread of blood which can travel

as far as the zygomatic arch and into the upper eyelids. The first 3 layers of scalp remain

attached to each other in case of cleavage.

P = periosteum

lood vessels and nerves of the scalp.

nastomoses in the scalp are formed by the following arteries from anterior to posterior

Clemente plates 468, 469; Grant p. 632; Netter 3e 19, 4e 23):

Supratrochlear artery

Supraorbital arterySuperficial temporal artery

Posterior auricular artery

Occipital artery


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he scalp is extremely vascular and bleeds profusely when cut. Due to anastomoses, there is

o single vessel to compress but bleeding may stop by direct pressure on or around the

ound.

missary veins (valveless) may spread infections from the scalp to the intracranial cavity.

ormal blood flow is from inside to outside of the skull.

he following nerves innervate the scalp from anterior to posterior (Clemente plate 469;

rant p. 634; Netter 3e 20, 4e 24):

2 branches from the ophthalmic division of the trigeminal nerve (cranial nerve V): the

supratrochlear and suprorbital nerves

1 branch from the maxillary division of the trigeminal nerve: the zygomaticotemporal

nerve

1 branch from the mandibular division of the trigeminal nerve: the auriculotemporal

nerve

ranches of the trigeminal nerve lie anterior to the external ear or auricle

osterior to the auricle:

The lesser occipital nerve (C2,3)

The greater occipital nerve (C2)

The third occipital nerve (C3)

dated 10/28/2009

THE PAROTID REGION AND THE DEEP

FACE

ext: Gross Anatomy, K. W. Chung, 6thedition: pp. 344-352

eference: Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5thedition: pp. 976-987; 6thdition: pp. 914-928

issector:

lementes Anatomy Dissector, 2nd edition: pp. 316-327

rants Dissector, P.W. Tank, 14thedition: pp. 210-214

he zygomatic bone has processes related to thefrontal, maxillary and temporal bones

Clemente plates 480, 481; Grant p. 610-613; Netter 3e 2, 4e 4)


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ony landmarks on the mandible (Grant p. 664-665; Netter 3e 4, 13, 4e 15):

The body is formed by the fusion of the right and left sides at 2 years (Clemente plate

484 fig. 760).

2 rami.

Alveolar process for the teeth.

Coronoid process.

Condylar process with head (in temporomandibular joint) and neck (Clemente plates

481, 542, 543;Grant p. 664-665; Netter 3e 14, 4e 16).

Mandibular notch.

The mandibular foramen and canal lie medial to the mandibular angle. They contain the

inferior alveolar nerve (V3) and vessels.

The lingula serves as attachment point for the sphenomandibular ligament.

hePAROTID BED(Clemente plate 468; Grant p. 662-663; Netter 19) is defined:

Posteriorlyby the mastoid process with the origins of the sternocleidomastoideus andthe posterior belly of the digastric (Clemente plate 476;Grant p. 662; Netter 3e 23, 4e

25);

Mediallyby the styloid process of the temporal bone and the stylohyoid muscle

(Clemente plates 472 fig. 740, plate 476; Grant p. 663; Netter 3e 23, 4e 27).

Styloglossus (Clemente plate 538;Grant p. 788-789; Netter 3e 55, 4e 59) and

stylopharyngeus are also medial to the parotid bed within the lateral pharyngeal space;

Anteriorlyby the sphenomandibular and stylomandibular ligaments (Clemente plate

472;Grant p. 674; Netter 3e 14, 4e 16) as well as the fasciae of the medial pterygoid(Clemente plates 470, 471; Grant p. 668; Netter 3e 51, 4e 55) and masseter muscles

(Clemente plates 468, 469;Grant p. 666-667; Netter 3e 50, 4e 54);

Superiorlyby the zygomatic arch;

Inferiorlyby the posterior belly of the digastric.

Thedeep cervical fascia(Clemente plate 446;Grant p. 747; Netter 3e 31, 4e 24, 35)

nvelops the parotid gland and is weakest between the styloid process and spine of the

henoid:

Infections may spread from the parotid fascia into the lateral pharyngeal space which

communicates with the retropharyngeal space (Clemente plate 549; Grant p. 747;

Netter 3e 31, 4e 35) between the pharynx and prevertebral musculature.

Infections may track inferiorly through the neck and into the thorax, along the course of

the carotid sheath, between visceral and prevertebral fasciae.

heparotid glandis innervated by the lesser petrosal branch (secretomotor) of theIXth

lossopharyngeal) nerve (Clemente plate 527 fig. 836; Grant p. 835; Netter 3e 119, 4e25).

eganglionic parasympathetic fibers from the tympanic plexus in the middle ear (Clemente

ate 527; Grant p. 835; Netter 3e 89, 119, 4e 125, 134):


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enter the middle cranial fossa by a hiatus on the anterior aspect of the petrous bone,

run through the periosteal dura

and exit the middle cranial fossa through the foramen ovale with V3.

The preganglionic fibers synapse in the otic ganglionon the medial aspect of V3.

The postganglionic fibers join with the auriculotemporal nerve to run to the parotid

gland.

The auriculotemporal nervethus carries secretomotor fibers of IXth and sensory fibers

of V3 for pain in the gland.

hesympathetic innervationis from the superior cervical ganglion via the arteries and it

ontrols the fluid content of the saliva.

he INFRATEMPORAL REGION(Clemente plates 478, 479; 481 fig. 755; Grant p.

64-665; Netter 3e 8, 4e 8, 10, 14) is:

inferior to the temporal fossa and zygomatic arch

and deep to the ramus of the mandible.It stretches from the parotid fascia posterior to the mandibular ramus to the tuberosity of

the maxilla.

he lateral wallis formed by the medial aspect of ramus of the mandible

he anterior wallis formed by the:

Body and tuberosity of the maxilla, deep to zygoma and zygomatic process of the

maxilla.The pterygomaxillary fissureor sphenopalatine foramen(Clemente plate 481 fig.

755; Grant p. 665; Netter 3e 12, 4e 14) may be seen in the medial aspect of this

anterior wall, opening into the more medial pterygopalatine fossa.

The inferior orbital fissure may also be seen.

Inferior to the pterygomaxillary fissure is the hamulusserving as attachment point for

the pterygomandibular raph. It serves as the common site of origin for the buccinator

and the superior constrictor muscle and runs from the hamulus to the upper 1/5 of the

mylohyoid line.

he medial wall is formed by the:

lateral pterygoid plate,

superior constrictor muscle,

levator and tensor palati muscles.

he roof of the infratemporal fossais formed by:

the greater wing of the sphenoid anteriorly

and the squamous portion of the temporal bone posteriorly.

he infratemporal crestis on the anterior aspect of the undersurface of the greater wing of


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e sphenoid and serves as an attachment site for the upper head of the lateral pterygoid.

osterior to this infratemporal crest are:

Theforamen ovalefor transmission of V3 and the lesser petrosal nerve (from IXth)

from the middle cranial fossa to the infratemporal fossa (Clemente plates 498, 499;

Grant p. 669; Netter 8, 10);

Theforamen spinosumfor transmission of the middle meningeal artery from the

infratemporal fossa to the middle cranial fossa.

ontents of the infratemporal fossa

he key structure for orientation is the lateral pterygoid muscle (Clemente plate 478;

rant p. 668; Netter 3e 51, 4e 55).

his muscle has 2 heads (Clemente plate 470;Grantp. 668, 672; Netter 3e 51, 4e 55):

from the infratemporal crest to the capsule of the interarticulating disc of the TMJ

and from the lateral aspect of the lateral pterygoid plate to the neck of the mandible.

Protrusive actions of the lateral pterygoid muscle are used to test V3: deviation is

OWARDSthe side of the lesion.

he maxillary arterylies lateral to the lateral pterygoid muscle (Clemente plates 478, 479;

rant p. 668-670; Netter 3e 36, 4e 40).

From the external carotid artery in the parotid gland, the artery enters the posterioraspect of the infratemporal fossa by passing deep to the neck of the mandibular condyle.

It crosses the lateral side of the lateral pterygoid muscle and enters the pterygomaxillary

fissure.

It is divided into a first or mandibular part, second or pterygoid part and third or

pterygopalatine part.

The mandibular and pterygoid parts are associated with the infratemporal fossa

and the pterygopalatine part is associated with the deep face and the nasal region.

he mandibular divisionof the maxillary artery has 5 branches, all entering a canal:

Themiddle meningeal artery is the principal artery to periosteal dura of the cranial

cavity.

Theinferior alveolar arteryruns into the mandibular foramen and supplies the teeth

and the mandible. The angle of the mandible is poorly supplied and may suffer from

alveolar osteitis (dry socket).

Thedeep auricular arterysupplies the auditory meatus

Theanterior tympanic arteryaccompanies the chorda tympani through thepetrotympanic fissure to reach the middle ear.

Theaccessory meningeal branch(inconsistent) enters the foramen ovale and supplies

the trigeminal ganglion and the surrounding dura.


14/49

he pterygoid portionof the maxillary artery has 5 branches supplying muscles of

astication in the infratemporal fossa:

2 deep temporal branches,

a masseteric branch,

a pterygoid branch,

and a buccal branch.

hepterygoid plexus of veins(Clemente plate 477; Grant p. 613; Netter 3e 66, 4e 70)llows the maxillary artery in the infratemporal fossa, lying mostly lateral to the artery.

This is a route for infection: the veins have connections with the cavernous sinusvia the

deepfacial, inferior ophthalmic and emissary veins in the sphenoid bone.

Veins of the head have NOvalves.

ranches of V3 (Mandibular division of the trigeminal nerve)

Anterior division (Clemente plates 478, 479; Grant p. 667-669, 671; Netter 3e 42, 67, 4e

6, 71):

Masseteric branches

Posterior and anterior temporal branches to the temporalis muscle

The nerve to the medial pterygoid

The nerve to the lateral pterygoid

Thebuccal nerve

hebuccal nerve of V3 :

passes between the 2 heads of the lateral pterygoid muscle.

continues into the cheek on the lateral surface of the buccinator muscle.

is the terminal branch of the anterior division

is sensory to the mucosa of the inside of the cheek and the lower gums around the molar

teeth.does not supply the motor innervation of the buccinator.

. Posterior division:

uriculotemporal nerve:

leaves V3 just inferior to the foramen ovale and projects posteriorly in the infratemporal

fossa parallel to the roof.

The initial segment encircles the middle meningeal artery as the artery ascends to enter

the foramen spinosum and receives postganglionic parasympathetic fibers from the otic

ganglion which are secretomotor to the parotid gland.

Passes medial to the head of the mandibular condyle and sends a sensory branch to the

TMJ.


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Enters the deep portion of the parotid gland giving sensory branches as well as

parasympathetic postganglionic fibers from the otic ganglion.

Its terminal portion accompanies the superficial temporal artery and innervates the upper

half of pinna of the ear and part of the temporal region (Pain and general sensation).

nferior alveolar (dental) nerve (Clemente plate 542 fig. 866; Grant p. 828-829; Netter 3e

7, 4e 71)

From the foramen ovale to the mandibular foramen on the medial aspect of the ramus ofthe mandible, lying between the medial and lateral pterygoid muscles and just posterior

to the lingual nerve (Clemente plate 478; Grant p. 669, 671; Netter 3e 67, 4e 71) .

The branch to mylohyoid and to the anterior belly of the digastric is the onlybranch in

the infratemporal fossa. It first lies in the mylohyoid groove, and then on the inferior

aspect of the mylohyoid to reach the anterior belly of the digastric muscle (Clemente

plate 479; Grant p. 681; Netter 3e 67, 4e 71).

The portion of the inferior alveolar nerve in the ramus of the mandible is entirely

sensory to lower teeth, lower gums and the mucosa of the lower lips.It exits the mandible as the mental nerve(Clemente plate 542; Grant p. 630, 671;

Netter 3e 67, 4e 71) to innervate the mucosa and gum adjacent to the lower lip.

ingual nerve (Clemente plate 479; Grant p. 668-669; Netter 3e 67, 4e 71)

lies anterior to the inferior alveolar nerve and remains medial to mandible.

receives the chorda tympaniin the infratemporal fossa. The chorda tympani reaches the

infratemporal fossa via the petrotympanic fissure (Clemente plate 527 fig. 835, plate565 fig. 919;Grant p. 625; Netter 3e 42, 4e 46). The chorda tympani contains

preganglionic parasympathetic secretomotor fibers of VII from the tympanic plexus and

special sensory fibers for taste from the anterior 2/3 of the tongue. The taste fibers have

their cell bodies in the geniculate ganglion of VII.

Terminal distribution of the lingual nerve and associated fibers which mediate general

sensation (pain, touch temperature and pressure) is to the floor of the mouth and the

anterior 2/3 of the tongue.

Mandibular block technique:

Injection of anesthetic is performed in the fascial compartment defined by the fascial

covering of the medial pterygoid and the medial aspect of the ramus of the mandible

(Clemente plate 477; Grant p. 678; Netter 3e 51, 4e 55).

The anesthetic diffuses to the lingual and inferior alveolar nerves.

emporomandibular joint (TMJ; Clemente plate 473; Grant p. 674-675; Netter 3e 14, 4e

6)

Head of mandible

Mandibular fossa and articular tubercle of the temporal bone

Synovial joint with intraarticular disc dividing joint into a lowercompartment (hinge


16/49

rotation for mandibular head) and uppercompartment (sliding joint for protrusion).

Minor supportive elements of the TMJ:

Lateral temporomandibular ligament(thickening of the joint capsule; Clemente

plate 472; Grant p. 674-675; Netter 3e 14, 4e 16)

Stylomandibular ligament (between parotid and submandibular glands;

Sphenomandibular ligament

Major supportive elements of the TMJ: MUSCLES OF MASTICATION

ovements of the mandible:

Elevation

Depression

Protrusion

Retraction

dated 10/28/2009

NTRACRANIAL CAVITY AND MENINGES;

CRANIAL NERVES


eference: Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5thedition: pp. 908-933, 1124-1154;th edition: pp. 865-878, 1054-1082.

issector:



he cranial cavity is a rigid box containing brain, important blood vessels and CSF. It

ommunicates with the vertebral canal through the foramen magnum (Clemente plate 498;

rant p. 642; Netter 3e 5, 4e 5) and with tissues outside the cranium via foramina. Because

is a rigid box, extensive bleeding or a growing tumor inside the cranium has little room for

xpansion and an early rise in intracranial pressure will occur.

tructure of intracranial blood vessels:

To avoid collapse of the veins during a rise in pressure (systole), the veins have rigid

walls composed of dura and are called venous sinuses (Clemente plates 488, 489;


17/49

Grant p. 639; Netter 3e 100, 4e 102-104).

Intracranial arteries have thin walls because when the arteries are distended during

systole, the effect is counteracted by a rise in intracranial pressure. However, the arteries

are prone to localized distension (aneurysm) and when the vessel breaks, this may lead

to a fatal hemorrhage.

Meninges

Dura mater (pachymeninx)

Arachnoid

The subarachnoid space continues through the foramen magnum, around the spinal cord.

Pia mater (closely adherent to the brain)

Arachnoid and pia mater are also called leptomeninges.

Dura mater:

layers (Clemente plate 486 fig. 765; Grant p. 636; Netter 3e 96, 4e 102):

An outer fibrous layer

and an inner serous layer, which parts from the fibrous layer to form the venous sinuses.

he dura is supplied by small arteries and the middle meningeal artery (Clemente plate

87;Grant p. 635; Netter 3e 95, 4e 100). The vein runs with the artery.

tracranial partitions of the dura mater:

Thefalx cerebri(Clemente plate 488; Grant p. 638; Netter 3e 97, 4e 103) with the

superior sagittal sinus, starts at the crista galli.

The tentorium cerebelliincompletely roofs over the posterior cranial fossa.

At this level, the midbrain runs superiorly through the opening to join with the

diencephalon (Grant p. 640; Netter 3e 98, 100, 4e 104, 106). The sharp edges of dura

may have fatal consequences when the brain is displaced by force or a space-occupyinglesion.

he flow of the cerebrospinal fluid in the venous sinuses is from the superior sagittal sinus to

eright transverse sinus tothesigmoid sinus totheinternal jugular vein (Clemente plates

88, 489; Grant p. 639; Netter 3e 97, 98, 4e 103-104 ).

he arachnoid villi drain CSF from the subarachnoid space to the venous sinuses. With age,

e arachnoid villi become clumped together to form the arachnoid granulations (Clemente

ate 486 fig. 765, plate 487; Grant p. 637; Netter 3e 94 - 96, 4e 100, 102).

heinferior sagittal sinusis in the free edge of the falx cerebri and receives part of the

ainage of the great cerebral vein (of Galen)and becomes the straight sinus (Grant p.

39; Netter 3e 97, 4e 103-104). This passes to the left and forms the left transverse sinus,


18/49

ft sigmoid sinus and left internal jugular vein.

Because the flow from the larger superior sagittal sinus tends to go to the right transverse

nus, the right jugular foramen is usually bigger than the left (Clemente plate 498; Grant p.

15; Netter 3e 7, 4e 104). But, at other times, the ends of the superior sagittal sinus and the

raight sinus join together to form the confluence of the sinuses and the jugular foramina will

e even in size.

hecavernous sinuses, are found on either side of the sella turcica (pituitary gland;lemente plates 489, 494; Grant p. 639; Netter 3e 98, 4e 104):

Anteriorly, the superior andinferior opthalmic veinsopen into them.

Posteriorly, minor venous sinuses (superior and inferior petrosal sinuses) also open

into them. The inferior petrosal sinus communicates at its other end with the internal

jugular vein at the jugular foramen.

The cavernous sinuses are joined across the midline by intercavernous sinuseslying

anterior and posterior to the pituitary gland. The pituitary fossa is roofed in by thediaphragma sellaethrough which runs the pituitary stalk (Clemente plate 492 fig. 773;

Grant p. 640; Netter 3e 98, 4e 104). Superoanteriorly, lies the optic chiasma.

Veins from the lower parts of the brain also drain into the cavernous sinuses.

The cavernous sinus contains cranial nerves III, IV, V, and VI, and the internal

carotid artery (Clemente plate 490 fig. 770; Grant p. 644; Netter 3e 98, 4e 104).

lood supply of the brain

fter passing through the cavernous sinus, the internal carotid artery turns superiorly

Clemente plate 458, plate 493;Grant p. 643-649; Netter 3e 130, 132, 133, 4e 136, 138,

40):

it then gives out the opthalmic artery (which runs into the optic canal with the optic

nerve),

and terminates as the anterior andmiddle cerebral arteries and theposterior

communicating artery.Before it breaks up into terminal branches, it gives out small branches to the pituitary

gland and adjacent structures.

hevertebral artery (Grant 647; Netter 4e 138-139)goes through the foramen magnum

nd gives off:

the anterior spinal artery

the posterior spinal artery,

the posterior inferior cerebellar arteryand finally joins with the opposite artery to form the basilar artery.

he basilar artery lies ventral to the pons of the brainstem, on the clivus. The basilar artery

nds out :


19/49

branches to the brainstem,

theanterior inferior cerebellar artery

and terminates as the superior cerebellar andposterior cerebralarteries.

erminal branches of the internal carotid and the vertebral arteries form the circle of

Willis.

Cranial nerves within the craniumhe cranial nerves all leave the brain on its ventral surface except for the IVth cranial

rochlear) nerves (Clemente plate 495; Grant p. 642, 644; Netter 3e 112 4e 114-115).

t cranial(olfactory) nerve: The cell bodies from the olfactory epithelium lie in the

factory mucosa and their axons travel upwards to reach the olfactory bulb through the

ibrifrom plate (Clemente plate 524 fig. 830; Grant p. 813, 818; Netter 3e 113, 4e 119).

nd cranial (optic) nerves(Clemente plate 495; Grant p. 819-820; Netter 3e 114, 4e 120)

evelop as optic stalks which are prolongations of the brain, surrounded by the meninges: The

rebrospinal fluid may extend as far as the back of the eyeball (Grant p. 647; Netter 83, 4e

7) and rise in intracranial pressure will affect the optic nerve and the optic disk (Clemente

ate 520 fig. 822; Grant p. 651; Netter 3e 86, 4e 90).

Nerve fibers of the optic nerve will not regenerate if cut.

Optic nerves leave the eyeballs posteriorly, enter the cranium through the optic canal and

form the optic chiasma.

ote (Grant p. 820; Netter 3e 114, 4e 120):

the pattern of nerve fibers in the optic nerve, chiasma and optic tract.

The difference betweenblindness, bitemporal hemianopia andhomonymous

hemianopia.

Ird, IVth and VIth cranial nerves innervate the muscles of the eyeball (LR6, SO4)3

Clemente plate 510-512; Grant p. 821; Netter 3e 115, 4e 121)

VIth cranial (abducens) nerve for the abductor muscle.

IVth (trochlear)nerve for the superior oblique muscle.

IIIrd cranial (oculomotor) nerve for all other muscles including the levator palpebrae

superioris.

he IIIrd cranial nerve:

passes between the superior cerebellar and posterior cerebral arteries (Clemente plate

493; Grant p. 644, 646; Netter 3e 136, 4e 143)

pierces the dura posterior to the clinoid process

travels high up in the lateral wall of the cavernous sinus (Clemente plate 490 fig. 770,


20/49

plate 492 fig. 773; Grant p. 644; Netter 3e 98, 4e 104)

enters the orbit via the superior orbital fissure

divides into upper and lower branches (Clemente plates 511, 513; Grant p. 822-823;

Netter 3e 115, 4e 121).

he IVth cranial nerve

passes around the midbrain from its dorsal aspect (Clemente plate 495; Grant p. 644;

Netter 3e 108, 4e 114),pierces the dura posterior to the IIIrd cranial nerve (Clemente plate 492 fig. 773; Grant

p. 644; Netter 3e 98, 4e 104),

lies in the lateral wall of the cavernous sinus below the IIIrd cranial nerve (Clemente

plate 490 fig. 770; Grant p. 644; Netter 3e 98, 4e 104).

However, the IVth cranial nerve enters the superior portion of the orbital fissure to reach

the upper border of the superior oblique (Clemente plate 510; Grant p. 821; Netter 3e

98, 4e 86).

he VIth cranial nerve

leaves the brain at the lower border of the pons in the posterior cranial fossa (Clemente

plate 495; Grant p. 646, 812-813; Netter 3e 108, 115, 4e 104).

pierces the dura on the clivus,

runs over the ridge of the petrous portion of the temporal bone

enters the cavernous sinus (Clemente plate 490; Grant p. 644; Netter 3e 98, 4e 104).

It lies lateral to the internal carotid artery before entering the orbit via the lower part ofthe superior orbital fissure (Clemente plate 513;Grant p. 821; Netter 3e 115, 4e 83,

121).

heVth cranial (trigeminal) nerve (Clemente plate 514; Grant p. 644-645, 824-829; Netter

e 116, 4e 122)

starts in the posterior cranial fossa,

crosses the petrous temporal bone, carrying with it a diverticulum of dura (cavum

trigeminale or Meckel's cave) from the posterior cranial fossa,enlarges to form the ganglion in the middle cranial fossa over the roof of the carotid

canal.

nteriorly, its 3 branches (ophthalmic, maxillary and mandibular) pierce the dura in the

vernous sinus.

The ophthalmic division pierces the dura and enters the orbit via the superior orbital

fissure and divides into frontal, lacrimal and nasociliary divisions (Clemente plates 510,512; Grant p. 825; Netter 3e 81, 4e 86).

The maxillary nerve leaves the cranium via the foramen rotundum (Clemente plate 510;

Grant p. 826; Netter 3e 98, 4e 122).

The mandibular nerve leaves the cranium via the foramen ovale accompanied by the


21/49

lesser petrosal nerve (Clemente plate 511; Grant p. 828-829; Netter 3e 41, 4e 46).

heVIIth cranial (facial) nerveand the VIIIth cranial (vestibulocochlear) nerve run into the

ternal auditory meatus (Clemente plate 494; Grant p. 642, 813; Netter 3e 98, 4e 104).

arasympathetic fibers which will form the chorda tympani andthe greater petrosal nerve

avel in the nervus intermediuslying between VII and VIII (Clemente plate 574; Grant p.

13; Netter 3e 98, 118, 4e 104, 123).

heVIIIth cranial (vestibulocochlear) nerveenters the internal auditory meatus and dividesto vestibular and cochlear branches (Grant 832; Netter 124).

heIXth cranial (glossopharyngeal) nervearises from the medulla of the brain and

mmediately enters the jugular foramen to exit the cranium (Clemente plates 494, 495; Grant

642; Netter 98, 119, 125).

heXth cranial (vagus) nervepasses through the jugular foramen accompanied by the

anial portion of the XIth cranial nerve.

heXIth cranial (accessory) nerve:

Thespinal portionarises from the side of the upper 5 segments of the spinal cord and

enters the cranium via the foramen magnum.

It joins with the cranial portion and X to pass through the jugular foramen and

immediately leaves to supply sternocleidomastoideus and trapezius.

Thecranial portionjoins with X to be distributed with its branches.

heXIIth cranial (hypoglossal) nerve(Clemente plate 495; Grant p. 839; Netter 3e 122, 4e

28) is a purely motor nerve arising from the side of the medulla to pass through the

ypoglossal (anterior condylar) canal (Clemente plate 494; Grant p. 813; Netter 3e 7, 4e 8,

04).

pdated 10/28/2009

EYE AND ORBIT

Text: Gross Anatomy, K. W. Chung, 6thedition: pp. 375-387

Reference: Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5thedition: pp.

57-977; 6th edition: pp. 889-914

Dissector:

Clementes Anatomy Dissector, 2nd edition: pp. 366-379


22/49

Grants Dissector, P.W. Tank, 14thedition: pp. 227-233

ony landmarks:

Themargin of the orbitis formed by the frontal, zygomatic and maxillary bones

(Clemente plate 480; Grant p. 650; Netter 2).

Themedial wall of the orbitis formed by the lacrimal and ethmoid bones.The lateral wall of the orbit is formed by the zygomatic bone.

Thefloor of the orbit is formed by the maxillary bone

The roof of the orbitis formed by the orbital plate of the frontal bone.

Deep in the orbit,the greater and lesser wings of the sphenoid bone are separated by the

superior orbital fissure.

The inferior orbital fissure is a gap between the maxillary bone and the greater wing of

the sphenoid bone.

The optic canal lies in the root of the lesser wing of the sphenoid bone.

he medial walls of the orbit are parallel, whereas the lateral walls diverge (Clemente plate

09 fig. 802; Grant p. 652-653; Netter 3e 79, 4e 83): the long axis of the orbit is at an

ngle to the long axis of the eyeball.

he fibromuscular cone:

All the recti muscles of the eyeball originate from a fibrous ring that includes the lower

part of the inferior orbital fissure and the optic canal (Clemente plate 517 fig. 815;Grant p. 656; Netter 3e 79, 4e 83-84).

From this fibrous ring, the recti muscles spread out to attach around the periphery of the

eyeball (Clemente plate 516; Grant p. 658; Netter 3e 80, 4e 84).TThe

The superior oblique muscle arises from the body of the sphenoid bone, superomedial to the opticcanal and to the tendinous attachment of the rectus superior. Distally, it ends in a tendon whichloops through the trochlea and attaches to the superolateral posterior quadrant of the eyeball,between the superior and lateral recti muscles.The inferior oblique muscle arises from the orbital surface of the maxilla, lateral to the nasolacrimal

groove. It ascends laterally between the inferior rectus and the orbital floor, and then between theeyeball and the lateral rectus. It attaches to the inferolateral posterior quadrant of the eyeballbetween the inferior rectus and superior oblique.

A fascial sheath is continuous around and between the muscles, forming a fibromuscular

cone.

The interior of the cone is filled with fat and contains the optic nerve (Clemente plate

517 fig. 816; Grant p. 655; Netter 3e 79, 4e 83).

he levator palpebrae superiorismuscle (Clemente plate 509 fig. 801; Grant p. 654-655;

etter 3e 77, 80, 4e 84):

Superior to the cone, outside of it, lies the levator palpebrae superioris muscle attaching

anteriorly to the upper eyelid.

From the back of the orbit, above the fibrous ring, it lies under the roof of the orbit.


23/49

It is supplied both by the IIIrd cranial nerve and sympathetic nerves (loss of either

innervation will lead to ptosis).

Muscles of the eyeball (Clemente plate 516; Grant p. 658-659; Netter 3e 80, 4e 84):

helateral rectus(LR)on the lateral wall of the orbit, is an abductor (Clemente plate 515

g. 809; Grant p. 653; Netter 3e 79, 4e 84) and turns the pupil laterally.

hemedial rectus (MR)lies along the medial wall of the orbit and turns the pupil medially.eft and right medial recti muscles contract simultaneously to cause convergence of the gaze

or focusing on a near object).

hesuperior rectus(SR) turns the pupil superiorly and medially (Clemente plate 514 fig.

08; Grant p. 659; Netter 3e 80, 4e 84).

heinferior rectus(IR) turns the pupil inferiorly and medially.

hesuperior oblique(SO) runs along the medial wall to reach the trochlea (Clemente plate

15 fig. 810; Grant p. 657; Netter 3e 81, 4e 84). It then loops posteriorly through a fascial

ing before being attached to the eyeball. Its action are incyclotorsion (primary), depression

econdary) and abduction (tertiary).

heinferior oblique(IO) arises from the floor of the orbit and travels laterally below the

yeball, attaching to the eyeball laterally (Clemente plate 515 fig. 810; Grant p. 654, 656;

etter 3e 80, 4e 84). Its actions are excyclotorsion (primary), elevation (secondary) and

bduction (tertiary).

he secondary actions of the superior and inferior oblique muscles are best demonstrated with

e eye adducted.

ovements of the eyeball:

Looking straight up: SR and IO

Looking straight down: IR and SO

Looking left: left LR and right MR

he movements of the eyeball are finely coordinated and may be easily disturbed (influence of

cohol).

LOOD VESSELS

heophthalmic arteryarises from the internal carotid artery (Clemente plate 513; Grant p.

57; Netter 3e 81, 4e 85).

he ophthalmic artery gives out the central artery of the retina which:

is an end artery.

enters the optic nerve


24/49

travels near its center towards the eyeball (Clemente plate 520, plate 521 fig. 824;

Grant p. 657, 660-661; Netter 3e 83, 4e 90).

divides within the eye into superior temporal andinferior temporalbranches. These in

turn give rise to nasal (medial) andtemporal (lateral) branches accompanied by

corresponding veins. These can be observed with an ophthalmoscope (Clemente plate


the orbit, the ophthalmic artery crosses to the medial side, above the optic nerve (Clemente

ate 512, 513; Grant p. 657; Netter 3e 81, 4e 85). It then travels anteriorly along the medial

all of the orbit and ends by dividing into dorsal nasal andsupratrochlear arteries,

merging onto the face .

ther branches of the ophthalmic artery in the orbit are:

Thelacrimal artery, which follows the lateral wall of the orbit, supplies the lacrimal

gland and ends on the face by supplying the eyelids.

Thelong (2) andshort (many) posterior ciliary arteries(Clemente plate 518 fig. 817;Grant p. 661; Netter 3e 86, 4e 91) which enter the eyeball to supply the choroid.

The short arteries supply the back of the eyeball.

The long arteries enter the back of the eyeball but will break up into branches only

at the corneoscleral junction.

The long and/or short posterior ciliary arteries may give out an anterior ciliary

arteryto the front of the eyeball.

Thesupraorbital arterylies below the roof of the orbit and runs out superiorly to

supply the scalp (Clemente plate 512, plates 504-505; Grant p. 632, 652, 657; Netter3e 19, 81, 4e 85).

Theanterior andposterior ethmoidal arteriesenter canals in the ethmoid bone to

supply the ethmoidal air cells and the posterior ethmoidal artery continues into the nasal

cavity.

eins accompany all the arteries but they drain into the superior andinferior ophthalmic

eins(Clemente plates 475, 494; plate 514 fig. 807; Grant p. 656; Netter 3e 81, 4e 85),

hich communicate with the cavernous sinus and the pterygoid plexus of veins.

ERVES

Motor innervation

he IVth cranial nerve enters the orbit above the fibrous ring (Clemente plate 510; Grant p.

56; Netter 3e 79, 4e 83) and therefore lies outside of the muscular cone, crosses to the

edial side and enters the upper border of the superior oblique muscle (Clemente plate 511;rant p. 652-653; Netter 3e 82, 4e 86).

he VIth cranial nerve enters within the fibrous ring (Clemente plates 510-513; Grant p.

56; Netter 3e 79, 4e 85) and immediately turns laterally to enter the lateral rectus.


25/49

he IIIrd cranial nerve divides into 2 divisions lying above and below the nasociliary nerve

ithin the cone:

The superior branch travels upward to reach the superior rectus and the levator palpebrae

superioris muscles (Clemente plate 511; Grant p. 822; Netter 3e 115, 4e 121).

The inferior branch (Clemente plate 513; Grant p. 822; Netter 3e 115, 4e 121) breaks

up to supply the medial rectus, the inferior rectus and the inferior oblique muscles.

The nerve to the inferior oblique carries parasympathetic fibers from the

Edinger-Westphal nucleusin the midbrain. They travel in a branch to the ciliary

ganglionwhere they synapse. The short ciliary nervestravel to the back of the

eyeball. They supply the ciliaris muscle and thesphincter pupillae (Grant p.

650, 805; Clemente plate 823; Netter 3e 82, 83-85, 4e 86, 121).

ensory innervation

ensory nerves are all branches of the ophthalmic division of thetrigeminal (Vth cranial)

erve: the frontal andlacrimal nervesenter the orbit above the fibrous ring and the

asociliarywithin it.

he frontal nerve(Clemente plate 510; Grant p. 652; Netter 3e 82, 4e 86) is directly below

e roof of the orbit, lying on the levator palpebrae superioris. It divides into the supraorbital

nd supratrochlear nervesleaving the orbit at its upper border and supplies the scalp

Clemente plates 504-505; Grant p. 634; Netter 3e 20, 4e 24).

helacrimal nervetravels along the lateral wall of the orbit to supply the skin of the eyelidsClemente plate 507 fig. 797; Grant p. 652-653; Netter 3e 82, 4e 86) and it also carries

arasympathetic secretomotor fibers to the lacrimal gland (Clemente plate 507 fig. 797;

rant p. 825; Netter 3e 116, 4e 122).

henasociliary nervehas similar branches to the ophthalmic artery, except that:

short ciliary nerves are derived from the ciliary ganglion, notthe nasociliary nerve

and the lacrimal nerve is a separatebranch from the ophthalmic division.

he nasociliary nerve gives off 2 long ciliary nerves entering the back of the eyeball, which

rry sympathetic fibers to the dilator pupillae (Clemente plate 512; Grant p. 823; Netter

e 82, 4e 121) and sensory fibers to the cornea (Grant p. 823). Along the medial wall of the

bit, the nasociliary nerve gives out a posterior ethmoidal nerveand ends by turning into

e anterior ethmoidal nerve, giving off a small infratrochlear nerve (Clemente plate 513;

rant p. 653; Netter 3e 82, 4e 86).

pdated 10/28/2009

NOSE, NASAL CAVITIES AND PARANASAL


26/49

INUSES


eference: Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5thedition: pp. 1010-1022.

issector:



utaneous innervation

The nerve supply to the skin of the nose is by V1 (infratrochlear nerve) and V2

(infraorbital nerve; Clemente plate 504; Grant p. 630; Netter 3e 20, 4e 24).

The innervation of the tip of the nose is by the external nasal nerve, an anterior

ethmoidal branch ofthe nasociliary nerve (V1) running from the root of the nose to the

tip of the nose.

Loss of sensation to the tip of the nose may be due to an intracranial,

intraorbital or ethmoidal air sinus disorder affecting V1 pathway from

the trigeminal ganglion.

ony landmarks

The pairednasal bonesarticulate with the frontal bone and frontal processes of the

maxillary bones (Clemente plate 522 fig. 825; Grant p. 690; Netter 3e 32, 4e 36).

Thecentral septal cartilageconnects with the superior lateral cartilagesarticulating

with the nasal bones (Clemente plate 524 fig. 829; Grant p. 690; Netter 32, 4e 36).

Alar cartilagesare supported by the septal cartilage.

NASAL CAVITIES

The nares(nostrils) open into the right and left nasal cavities separated by the septum.

Thechoanaeare the posterior apertures leading to the nasopharynx (Clemente plate

552;Grant p. 616, 790-791; Netter 3e 33, 4e 37).

oor of nasal cavity:

palatine processes of the maxilla

and horizontal plates of the palatine bone.

oof of nasal cavity is composed of (Clemente plate 523; Grant p. 691; Netter 3e 34-35, 4e


27/49

8-39):

Anterior part: slope of the nasal bones

Intermediate part: cribriform plate of ethmoid bone

Posterior part: anterior and inferior aspects of the body of the sphenoid bone.

asal septum (Clemente plate 524 fig. 829; Grant p. 691; Netter 3e 35, 4e 39):

The perpendicular plate of the ethmoid bone and the vomer bone may articulate witheach other posteriorly.

The septal cartilage intervenes between bony elements of the septum, forming support

for the midline ridge of the nose, tip and columella (between nares from tip of the nose

to anterior nasal spine of the maxilla).

Deviation of the nasal septum is most frequent between the vomer and the septal

cartilage.

ateral wall (Clemente plate 525; Grant p. 691; Netter 3e 34, 4e 38)

Superior, middle and inferior nasal conchaeand their corresponding meatuses.

Sphenoethmoid recesslies superior to the superior concha.

Vestibule,just inside each naris, is lined by skin.

Atrium,inferior to nasal bones, is lined by mucoperiosteum.

he inferior concha

is a separate bone articulating with maxilla, lacrimal and palatine bones on the lateralwall of the nasal cavity (Clemente plate 523; Grant p. 691; Netter 3e 34, 4e 38).

Its meatus contains the opening of the nasolacrimal ductdraining tears from medial

aspect of the orbit into the nasal cavity (Clemente plate 507 fig. 798; Grant p. 695;

Netter 3e 34, 78, 4e 37-38, 82 ).

he posterior extent of the nasal cavity is adjacent to the opening of the auditory tube in the

asopharynx (Clemente plate 525; Grant p. 695; Netter 3e 33, 4e 37).

he middle concha is a process of the ethmoid bone (Clemente plate 523; Grant p. 691;

etter 3e 33, 4e 38)and it overlies the middle meatus.

aranasal air sinuses open into this meatus: the hiatus semilunaris (Clemente plate 522 fig.

26; Grant p. 695; Netter 3e 33, 4e 37)opens on the wall of the middle meatus between the

nciform process of the ethmoid bone and the ethmoid bulla.

Frontal sinusdrains into the superior aspect of the hiatus semilunaris (Clemente plate

522 fig. 826; Grant p. 695; Netter 3e 33, 4e 37).Anterior andmiddle ethmoidal air sinusesdrain through openings of the ethmoidal

bulla on superoposterior aspect of the hiatus semilunaris.

Maxillary air sinushas its ostium directly inferior to the ethmoid bulla within the hiatus

semilunaris.


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he superior concha is also a process of the ethmoid bone (Clemente plate 523; Grant p.

91; Netter 3e 34, 4e 38).

It overlies the superior meatus receiving the opening of the posterior ethmoidal air cells

(Clemente plate 525 fig. 832; Grant p. 695; Netter 3e 32, 33, 4e 38).

uperior to the superior concha is the spheno-ethmoidal recess where the sphenoid air cells

ain into nasal cavity.

NERVE SUPPLY TO THE NASAL CAVITY

he mucosa of upper nasal cavity is innervated by the olfactory (I) and trigeminal (V1;

nterior ethmoidal) nerves (Clemente plate 524 fig. 830; Grant p. 692; Netter 3e 38-39, 4e

2-43).

The anterior ethmoidal nerve carries general sensation (pain, temperature, touch

and pressure).

ost of the general sensation of the lateral wall and nasal septum is mediated by V2, which is

sociated with the pterygopalatine ganglion (Clemente plate 526; Grant p. 692; Netter 3e

9, 4e 43).

The pterygopalatine ganglion receives the preganglionic parasympathetic fibers of the

superficial(greater) petrosal nerve (VII; Clemente plate 527; Grant p. 692, 700, 831;

Netter 3e 39, 117, 4e 43, 123).

The postganglionic parasympathetic neurons send secretomotor fibers to glands above

the floor of the mouth.

erminal branches of the infraorbital nerve (Grant p. 692; Netter 3e 38, 4e 42)also enter the

estibule of the nose from the skin covering the nares.

small branch from the anterior superior alveolar nerve also innervates the anterior nasal

ucosa of the inferior meatus (Grant p. 692; Netter 3e 38, 4e 42).

he mucosa on the lateral wall of the nose is innervated by branches of the descending greater

alatine nerve from the inferior pole of the pterygopalatine ganglion.

uperior and inferior posterior lateral nasal nerves run in the mucoperiosteum covering the

onchae and the meatus.

he nasal septum mucosa is innervated by the nasopalatine nerve (Clemente plate 524 fig.

30; Grant p. 692; Netter 3e 39, 4e 43).

It enters the nasal cavity from the pterygopalatine fossa through the sphenopalatine

foramen

and descends on the median nasal septum.

The terminal branch leaves the nasal cavity via the incisive foramen (Clemente plate


29/49


he sympathetic innervation of the nasal cavities comes from the superior cervical ganglion.

hese postganglionic fibers reach the nose via the nerve of the internal carotid artery

Clemente plate 527; Grant p. 701; Netter 3e 40, 4e 44) and the deep petrosal nerve of the

erygoid canal. In the pterygopalatine fossa, they join with terminal branches of the maxillary

tery and are vasomotor to blood vessels in the nasal cavity and palate.

LOOD SUPPLY OF THE NASAL CAVITY

he sphenopalatine artery

arises from the maxillary artery in the pterygopalatine fossa (Clemente plate 526;

Grant p. 693; Netter 3e 36-37, 4e 40-41).

It enters the nasal cavity with the nasopalatine nerve and supplies upper 2/3 of the nasal

septum.

It then anastomoses with the greater palatine arteryascending through the incisiveforamen.

The site of anastomosis is a frequent area of hemorrhage (epistaxis or

nosebleed).

he lateral walls of the nasal cavity are supplied by blood vessels accompanying the terminal

anches of the anterior ethmoidal nerve and the greater palatine nerve and they have the same

ame (Clemente plate 526; Grant p. 693; Netter 3e 37, 4e 41) .

he venous drainage of the nose parallels the arterial supply and forms a network overlying

e inferior and middle conchae.

he erectile tissue overlying the conchae humidifies and warms the inspired air in the upper

spiratory passage.

ARANASAL AIR SINUSES

The sphenoid (Clemente plate 522 fig. 826; Grant p. 694; Netter 3e 44, 4e 48-49),

ethmoid (Clemente plate 528; Grant p. 696; Netter 3e 44-45, 4e 48-49), frontal

(Clemente plate 529; Grant p. 696; Netter 3e 44, 4e 48-49) and maxillary are paired

but asymmetrical.

They are lined with respiratory epithelium which becomes converted to stratified

squamous epithelium with chronic respiratory irritation. This may lead to chronic

sinusitis.

inus drainage

phenoid air sinuses drain into the sphenoethmoidal recess (Clemente plate 525 fig. 832;

rant p. 696; Netter 3e 45, 4e 37). A surgical approach to the pituitary may be done through


30/49

ese air sinuses and the nasal cavities.

hmoidal air sinuses (anterior, middle and posterior).

Anterior and middle drain into middle meatus by openings of the ethmoidal bulla

(Clemente plate 522 fig. 826; Grant p. 695; Netter 3e 34, 4e 37).

Posterior ethmoidal air cells drain into the superior meatus.

ontal sinus drains via the infundibulum into the superior extension of the hiatus semilunarisClemente plate 525 fig. 832; Grant p. 695; Netter 3e 45, 4e 37) .

axillary sinus drains into the middle meatus through the hiatus semilunaris. The air sinus

as a floor at the level of the hard palate (Clemente plate 529; Grant p. 698; Netter 3e 45,

e 49)and since the ostium is more superiorly located (Clemente plate 525 fig. 832; Grant

696, 698; Netter 3e 45, 4e 49), there is often drainage problems. The nerve supply is by the

osterior and middle superior alveolar nerves (V2; Clemente plate 527 fig. 836; Grant p.

00; Netter 3e 41, 4e 45).

astoid air sinuses (Clemente plate 527 fig. 836; Grant p. 710; Netter 3e 89, 4e 94) drain

to the nasal cavity via the middle ear and auditory tube.

pdated 11/28/2009

THE ORAL CAVITY AND CONTENTS


eference: Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5thedition: pp. 987-1010; 6thdition: pp. 928-951

issector:



he VESTIBULE

is bounded by lips and cheeks,

is lined with non-keratinized stratified squamous epithelium.the parotid papillais in the superior vestibule, opposite the 2nd upper molar tooth

(Netter 3e 47, 4e 51).

is vascularized by the superior and inferior labial arteriesfrom the facial artery

(Clemente plate 474; Grant p. 632; Netter 3e 32, 4e 36) . These arteries anastomose


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freely with their contralateral counterparts. Because of these profuse anastomoses, lip

bleeding is controlled by grasping the injured lip between the fingers to stop the blood

flow.

Nerve supply of the vestibule:

The orbicularis oris and buccinator muscles are innervated by cranial nerve VII (facial

nerve;Clemente plate 469; Grant p. 629; Netter 3e 21, 4e 25

).The skin and mucosa of the upper lip, cheek and vestibule are innervated by the

anterior, middle and posterior superior alveolar nerves from V2 (Clemente plate

527; Grant p. 700; Netter 3e 42, 4e 45).

The skin and mucosa of lower lip and adjacent anterior vestibule are innervated by the

mental nerve (V3; Clemente plate 476; Grant p. 630-631, 671; Netter 3e 42, 4e 46) .

The mucosa of the inferior vestibule adjacent to the cheek is innervated by the long

buccal (buccinator; Grant p. 630, 668; Netter 4e 46) nerve from the anterior

division of V3.

ORAL CAVITY

The roof is formed by the hard and soft palates with the midline uvula (Clemente plate

530 fig. 843; Grant p. 682; Netter 3e 48, 52; 4e 51).

The posterior border is formed by the pillars of the fauces (Clemente plate 530; Grant

p. 676; Netter 3e 54, 4e 51, 58)

The floor is formed by the tongue divided into anterior 2/3 and posterior 1/3 by the

palatoglossal arch, the V-shaped sulcus terminalisand circumvallate papillae(lying

anterior to the sulcus; Clemente plate 539; Grant p. 676; Netter 3e 54, 4e 58).

The lingual frenulum(Clemente plate 532 fig. 847; Grant p. 680; Netter 3e 47, 4e

51) is found on the undersurface of the tongue with openings of the ducts of the

submandibular gland (Clemente plate 533 fig. 850; Grant p. 680; Netter 3e 47, 4e

51).

In examination of the tongue, grasp the tip of tongue with gauze and pull the

tongue out of the mouth. Examine the lateral aspects of the anterior 2/3 of the

tongue. This is a common site for cancer of the tongue.

LOOR OF THE MOUTH (SUBLINGUAL REGION)

he sublingual gland (Clemente plate 532 fig. 847, plate 543; Grant p. 680-681;

etter 3e 57, 4e 61):

lies on the lingual aspect of the body of the mandible, deep to the plica sublingualis

(sublingual fold), which is the posterolateral continuation of the lingual frenulum.

It has a row of 15 or 16 ("middle-teens") ducts that empty into the floor of the mouth on

the plica sublingualis.


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The duct of the submandibular gland and the lingual nerve lie on the medial surface of

the sublingual gland.

The mylohyoid muscle lies inferior to the sublingual gland.

The sublingual gland is innervated by postganglionic parasympathetic fibers reaching the

gland via its sensory nerve, the lingual nerve (V3).Preganglionic parasympathetic fibers

run with the chorda tympani (VII)synapsing in the submandibular ganglion (Clemente


he lingual nerve

provides thegeneral sensory(pain, touch and temperature) modality to the anterior 2/3

of the tongue and the floor of the mouth (Clemente plate 532 fig. 848; Grant p. 680-

681, 829; Netter 3e 55, 4e 59).

also carries chorda tympani which has special taste fibers and secretomotor fibers of VII.

enters the floor of the mouth on the medial mandible next to the 3rd molar tooth

(Clemente plate 533 fig. 850; Grant p. 680-681; Netter 3e 42, 4e 46). It is thusvulnerable in extraction of the wisdom teeth.

Preganglionic parasympathetic fibers leave the lingual nerve to synapse in the

submandibular ganglion (Clemente plate 535 fig. 855; Grant p. 680, 840; Netter 3e

42, 4e 133). Postganglionic parasympathetic fibers rejoin the lingual nerve to reach the

sublingual salivary gland. The submandibular ganglion is thus suspended from the main

trunk of the lingual nerve.

he lingual nerve is:

superiorto the mylohyoid muscle in the floor of the mouth (Clemente plate 479;

Grant p. 681; Netter 3e 42, 4e 46).

lateralto the submandibular duct (Clemente plate 479; Grant p. 680-681, 780; Netter

3e 42, 4e 46),

and medialto the sublingual gland (Clemente plate 479; Grant p. 680; Netter 3e 56,

4e 60).

Subsequently, it passes inferior and then medialto the submandibular duct to ascend

into the body of the tongue (Clemente plate 533 fig. 850; Grant p. 680-681; Netter 3e

55, 4e 59).

he chorda tympani provides taste fibers which supply the anterior 2/3 of the tongue. The cell

odies are in the geniculate ganglion in the middle ear (Clemente plate 573; Grant p. 709,

31; Netter 3e 117, 4e 135).

he hypoglossal nerve enters the floor of the mouth on the lateral aspect of the hyoglossus

uscle, above the hyoid bone and the mylohyoid muscle (Clemente plate 535 fig. 855;rant p. 681, 780; Netter 3e 55, 4e 59). Cranial nerve XII lies inferior to the lingual nerve

nd is purely motor to the muscles of the tongue.

Test cranial nerve XII by protrusion of the tongue. Deviation is toward the side of


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the lesion.

he tongue

allows for mastication, swallowing, speech and taste.

The anterior 2/3 (body or oral part) is derived from the ectodermal stomodeum.

The posterior 1/3 (pharyngeal part or root) is derived from the endodermal foregut.

These 2 parts are separated by the sulcus terminalis posterior to the circumvallatepapillae (Clemente plate 539; Grant p. 676; Netter 3e 52, 4e 58).

The sulcus terminalis is oriented posteriorly and the foramen cecumcan be found at the

tip of the V-shaped sulcus terminalis. This is the point of origin of the thyroid gland.

Lingual tonsilsare located posterior to the sulcus terminalis.

Mucous membrane of the tongue:

The papillae (filiform, fungiform, circumvallate and foliate)are innervated by cranialnerve VII via the chorda tympani (anterior 2/3) and by IX (posterior 1/3; (Clemente


The taste buds in the epiglottis and the pharyngeal walls are innervated by X.

The taste buds in the palate are innervated by cranial nerve VII via the greater petrosal

nerve. Branches from the latter are distributed by the greater and lesser palatine nerves

(Clemente plate 532 fig. 849; Grant p. 683, 831; Netter 3e 48, 4e 52).

uscles of the tongue

The 3 extrinsic muscles of the tongue change the position of the tongue.

The genioglossusattaches to the superior genial tubercles and protrudes the tongue

(Clemente plate 540; Grant p. 679-680; Netter 3e 59; 4e 63).

The hyoglossusdepresses the tongue.

and the styloglossusretracts the tongue.

The intrinsic (longitudinal, transverse and vertical) muscles change the shape of the tongue.

he lingual artery:

is a branch from the external carotid artery and supplies the tongue.

courses anteriorly on the middle constrictor (Clemente plate 460 fig. 724; Grant p.

763, 781; Netter 3e 53, 4e 59, 69) parallel with cranial nerve XII.

The hyoglossusmuscle intervenes between cranial nerve XII (lateral) and the lingual

artery (medial). The lingual artery is the only major structure medial to the hyoglossus

muscle (Clemente plate 535 fig. 855; Grant p. 679-680, 780-781; Netter 3e 55, 4e 59).Dorsal lingual branchesfrom the lingual artery are given to the dorsum of the tongue

and deep lingual arteriesare given to the body of the tongue.

Other terminal branches supply the genioglossus muscle and the sublingual gland.

Lymphatics follow arteries and drain to both right and left jugular lymphatic trunks of


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the neck (Clemente plate 455; Grant p. 676, 716; Netter 3e 68, 4e 73).

EETH

each adult jaw (Clemente plates 544, 545; Grant p. 685-689; Netter 3e 52-53, 4e 56-57):

4 incisors

2 canines

4 premolars

6 molars

erve supply of teeth and gums (Clemente plate 542 fig. 866; Grant p. 687; Netter 3e 41,

2, 4e 45-46):

2 supply the teeth and gums of the maxillary arch.

The molarteeth are supplied by the posterior superior alveolar nervefrom the

pterygopalatine fossa.

The bicuspids (premolars) are innervated by the middle superior alveolar nerve from

the infraorbital nerve.

The canines and incisorsare innervated by the anterior superior alveolar nerve from

the infraorbital nerve

The gums on the palatal surface are innervated by the nasopalatine nerve(incisors) and

greater palatine nerve(bicuspids and molars; Clemente plate 527; Grant p. 683;

Netter 3e 39, 4e 52).

3 supplies teeth and gums of mandibular arch.

Theinferior alveolar (dental) nerveinnervates all the teeth in the mandible.

The gums of the molars and bicuspids are innervated by the long buccal nerve

The gums of the incisors are innervated by the mental nerve.

The lingual gums are innervated by the lingual nerve.

dated 10/28/2009

THE EAR AND THE TEMPORAL BONE


eference: Clinically Oriented Anatomy, K.L. Moore, A.F. Dalley, 5th

edition: pp. 1022-1037; 6thdition: pp. 966-980

issector:



35/49


he EXTERNAL EAR

formed by the:

Auricle (Clemente plate 564; Grant p. 703; Netter 3e 87-88, 4e 92-93): is made of

elastic cartilage and is continuous with the cartilage of the external acoustic meatus andthe lobule (which is formed by loose connective tissue).

External acoustic meatus (Clemente plate 566 fig. 921; Grant p. 703; Netter 3e 87,

4e 92)

he innervation of the skin of the ear:

Thesuperiorportion is innervated by V3via the auriculotemporal nerve (Clemente

plate 468; Grant p. 627, 703; Netter 3e 20, 4e 24);Theinferiorportion including lobule is innervated by fibers of the great auricular

nervefrom the cervical plexus (C 2, 3);

Theexternal acoustic meatusand the skin surrounding the opening (concha) are

innervated by the vagus nerve (X) forgeneral sensation (Clemente plate 468; Grant

p. 703; Netter 3e 20, 4e 24).

Neurological examination of the skin of ear can determine the status of the

upper spinal cord (great auricular nerve, C 2, 3), the medulla (vagus X) andthe pons (trigeminal V).

he external acoustic meatus (Clemente plate 566 fig. 921; Grant p. 703, 705; Netter 3e

7, 4e 92):

extends from the concha to the tympanic membrane.

Lateral cartilaginous 1/3 (lined with hair, sebaceous glands and ceruminous glands)

Medial bony 2/3 (thin stratified squamous epithelium, also lining external surface of

tympanic membrane).

The auricular branch of the vagus (X)provides the sensoryinnervation (Clemente

plate 479; Grant p. 703; Netter 3e 20, 120, 4e 24, 126).

he MIDDLE EAR or TYMPANUM

ound waves create vibrations on the tympanic membrane moving the 3 bony ossicles

malleus, incus andstapes) which in turn vibrate the oval window (fenestra vestibuli) on the

edial wall of the middle ear: this is an amplification system (Clemente plate 566; Grant p.

04; Netter 3e 88, 4e 93, 95).

he middle ear is a modified bony sinus in the petrous portion of the temporal bone. It

ommunicates with the mastoid air cells through theaditusto the mastoid


36/49

ntrum(Clemente plate 569; Grant p. 710, 713; Netter 3e 89, 4e 94) and with the

asopharynx throughthe auditory tube (pharyngotympanic tube; Clemente plate 566;

rant p. 704-705; Netter 3e 87, 4e 92, 94).

he tympanic cavity and its walls:

The roof is a thin layer of petrous temporal bone (Clemente plate 566; Grant p. 708-

709; Netter 3e 87, 4e 92) separating the middle cranial fossa from the middle ear.

The space below the roof is the epitympanic recess(Clemente plate 566; Grant

p. 708; Netter 3e 88-89, 4e 92-93) for the articular joint of the head of themalleus

andbody of theincus.

The floor of the tympanic cavity rests upon the superior jugular bulb (Clemente plate569 fig. 928, plate 573 fig. 935; Grant p. 710-711; Netter 3e 87, 4e 92).

Where the internal carotid artery (moving anteriorly) diverges from the internal

jugular vein (moving posteriorly), the cranial nerves IX and X send branches into

the bony tympanic floor (Clemente plate 571 fig. 932; Grant p. 710; Netter 3e

89, 4e 94, 125).

Roof and floor converge anteriorly to form the auditory tubewhich is divided by

the processus cochlearis(Clemente plate 569; Grant p. 711; Netter 3e 88-89, 4e

92-94) into:a superior compartment containing the tensor tympani muscle.The tensor

tympani inserts into the handle of the malleus.

and a lower compartment which joins with the cartilaginous portion of the

auditory tube.

The lateral wall of the tympanic cavity is closed by the tympanic membrane.

The ascending carotid artery is associated with the anterior wall of the tympanic cavity,

separated by a thin layer of bone (Clemente plate 571, fig. 932; Grant p. 710; Netter3e 89, 4e 94).

Pulsations may be heard by the patient in some clinical disorders.

The posterior wall of the tympanic cavity contains a tunnel, the aditus, connecting to the

mastoid antrum.

Fluid from the mastoid air cells drain via the aditus into the tympanic cavity and

then into the auditory tube and the nasopharynx.

Fluid may collect within the tympanic cavity if the auditory tube is obstructed dueto an upper respiratory airway infection.

The VIIth cranial nerveenters the posterior wall below the aditus(Clemente

plate 569 fig. 928; Grant p. 708, 710; Netter 3e 89, 4e 94) and exits from the

base of the temporal bone via the stylomastoid foramen (Clemente plate 571 fig.

932; Grant p. 616, 712-713; Netter 3e 89, 4e 94).

The chorda tympaniarises from the facial nerve within the posterior wall of the

middle ear, courses over the eardrum along the lateral wall (Clemente plate 569;

Grant p. 708, 711; Netter 3e 89, 4e 94), and exits via the petrotympanic fissureinto the infratemporal fossa.

The pyramidis also located in the posterior wall. The apex of the pyramid has an

orifice through which the tendon of the stapediuspasses to insert onthe neck of

the stapes (Clemente plate 570; Grant p. 708; Netter 3e 89, 4e 93-94).


37/49


38/49

Malleushas a head, neck, manubrium with lateral process and an inferior tip.

The anterior process of the malleus is attached to a stabilizing ligament

(Clemente plate 568 fig. 926; Grant p. 708; Netter 3e 88-89, 4e 93-94) .

Incus: The body of the incus articulates with the malleus at the malleoincudal

(incudomalleolar) joint (Clemente plate 568 fig. 926; Grant p. 707; Netter

3e 88, 4e 93-94).

Short crus(process) attaches via a ligament to the posterior

wall of the epitympanic recess (Clemente plate 568 fig. 925;Grant p. 709; Netter 3e 89, 4e 94).

Long crusis vertically oriented and descends into the

tympanic cavity. It has a lenticular process,which

articulates with the head of the stapes.

Stapeshas a head, neck, posterior and anterior limbs and footplate

attached to the oval window by an annular ligament.

he role of the middle ear is to transfer vibratory sounds from the air to a fluid

erilymph):

Vibratory surface of eardrum is 55 mm2 .

Footplate is 3.2 mm2 .

Hydraulic ratio between membrane and footplate is 17:1.

Muscles of the ossicles: the contraction of either of these muscles attenuate sound by

ecreasing the movement of ossicles.

Thetensor tympani(Clemente plates 569, 570; Grant p. 708; ; Netter 3e 88-89, 4e 93-

4) in the auditory canal runs around the processus cochleariformis to attach to the handle of

e malleus: the contraction tenses the eardrum by pulling medially. It is innervated by a

anch of V3as it exits foramen ovale.

Thestapediusin the pyramid of the posterior wall, inserts into the neck of the stapes. The

ontraction pulls the foot plate away from the oval window to dampen the sound. It is

nervated by VII.

he INNER EAR

a bony labyrinth(Clemente plates 574-575; Grant p. 704-705, 714; Netter 3e 90-91, 4e

5) containing a membranous labyrinth.

he bony labyrinth consists of:

the cochlea,the vestibule

and the semicircular canals.

1) Thecochleais shaped like a snail shell with 2.5 turns. Vibrations from the


39/49

perilymph of the vestibule is communicated to the fluids of the cochlea stimulating

the hearing receptorsof the inner ear.

2) Thevestibulelies between the cochlea and semicircular canals, communicating

with both chambers. It communicates with the tympanic cavity via the oval

window (fenestra vestibuli).

3) The 3 semicircular canals: anterior (superior), posterior and later

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