The Skull

Areas of Anatomy

1) Gross anatomy: part listing of the human body; studied by region or by system

2) Microscopic anatomy: histology

3) Developmental anatomy: embryology

4) Functional anatomy: physiology

5) Radiographic anatomy: study of the human body using x-rays

- Anatomical position: body upright, with palms and hands facing forward, and feet close together

- Body defining planes:

1) Coronal plane: passes from one side to another dividing the body into anterior and posterior parts

2) Sagittal plane: passes from front to back dividing the body into right and left parts. Mid-Sagittal

is when the right and left parts are exactly equal, the dividing line passing in the middle

3) Transverse plane: passes from side to side and front to back horizontally dividing the body into

superior and inferior parts

- Relative anatomical terms:

o Anterior = ventral = front

o Posterior = dorsal = back

o Superior = cephalic = upper

o Inferior = caudal = lower

o Proximal = closer to origin

o Distal = away from origin

o Superficial = close to surface

o Deep = away from surface

- Movement of body parts :

o Extension = returning part to normal position

o Flexion = bending body part ( forward movement of body part)

o Abduction = moving part away from position; laterally

o Adduction = moving part closer to body; medially

o Rotation = along 1 axis, its either external (lateral) or internal (medial)

o Circumduction = combined complex movement

o Protrusion = forward movement of the mandible

o Retraction = moving mandible back to its place

- Basic body tissues and parts:

o Tendons: fibrous connective tissue band which originates from the skeletal muscle and

inserts into the bone.

o Aponeurosis; fibrous connective tissue that forms a flat sheet. it lies between parts of the

body

o Fascia: a covering structure which surrounds and divides large spaces in the body to smaller

compartments

o Borsa: synovial structure that is found between, tendon-tendon, tendon-bone, it produces

synovial fluid for lubrication

Body Systems:

1) Nervous system:

a. Central nervous system: brain and spinal cord

b. Peripheral nervous system: cranial nerves (12 pairs arise from the brain), spinal nerves (31

pairs arise from spinal cord) and autonomic nervous system.

Spinal cord:

o Contains dorsal horn, which is located at the dorsal aspect. It is completely sensory

o Contains ventral horn, located at the ventral aspect. It is completely motor

o Dorsal root arises from dorsal horn while ventral root arises from ventral horn

o Dorsal root passes through dorsal root ganglion, ventral root passes through ventral root

ganglion

o After passing through ganglia they form together spinal nerves

o They then divide into ventral and dorsal rami both being mixed

(Sensory and motor)

2) Mucoskeletal system : has 3 main components

a. Joints: where 2 or more bones come together

i. Bony joints: immovable (pelvis, sutures)

ii. Relatively movable: fibrocartilage

iii. Freely movable: synovial

b. Muscles: smooth, skeletal, cardiac

i. Skeletal: it is for movement, it is named based on

1. Function: extensor, abductor, etc

2. Shape: deltoid

3. Size: maximus, minimus

4. Attachment: temporalis

5. Length: short, long

c. Bones: 2 types

i. Axial skeleton: lies in the center (ex: pelvis)

ii. Appendicular: has similar right and left parts

Note: nerves are either

sensory or motor or both

Sensation

General Special

Pain Vision

Touch Taste

Temprature Hearing

Pressure Smelling

Nervous and endocrine

systems are responsible

for body function.

Bone is classified according to being:

Short

Long (ex: arm & forearm)

Flat (ex: skull)

Irregular (vertebrae)

Pneumatic: contains air cavities

Sesamoid: bone that lie in the tendon (ex: patella)

Synovial Joints

Synovium is the membrane that produces the synovial fluid, it is important for lubrication and

reduction of friction.

It is a weak structure, thus surrounded by fibrous joint capsule to prevent it’s separation during

movement.

Joint stability is achieved by:

1) Joint capsule

2) Shape of the bone forming the joint

3) Ligaments

4) Muscles around the joint

The skull is part of the axial skeleton

It is composed of 22 bones:

- 21 firmly joined together by sutures

- Mandible: a single movable bone which articulates with the skull at the TMJ (a synovial

joint)

The 22 bones are either single or paired (one on each side)

Bones are either facial or cranial

6 Single Bones 8 Paired Bones

Mandible Maxillary

Frontal Nasal

Occipital Zygomatic

Sphenoid Inferior Nasal conchae

Ethmoid Parietal

Vomer Temporal

Lacrimal

Palatine

Note:

The hard palate is formed by

the Maxillary bones (anterior

1/3) and the palatine bones

(posterior 2/3)

It is not necessary

to have all the

structures to

achieve stability

Views of the Skull

Outside views

Superior

Inferior = Basal

Posterior = occipital

Anterior = Frontal

Lateral = Temporal

1) Anterior View: frontal

Bones present in this view are: frontal, nasal, lacrimal, maxillary, mandibular, zygomatic,

vomer, inferior conchae

a. Frontal bone: convex in shape, forms forehead

b. Orbit: opening of the eyes. Has 4 orbital margins

i. Supraorbital margin: formed by frontal bone

ii. Medial orbital margin: formed by fontal (superiorly), maxilla (inferiorly)

iii. Infraorbital: formed by zygoma, and maxilla

iv. Lateral orbital margin: frontal (superiorly), zygomatic (inferiorly)

Landmarks of the orbit:

1) Supraorbital notch/foramen: in the superior orbital margin for transmission of vessels

and nerves. Painful if pressed on

2) Superciliary arch: a bony elevation lying above the supraorbital margin. (eyebrows

lie exactly above the margin)

3) Glabella: hairless region between the supraciliary arches. Clinical significance: 1-

skin turgidity can be measured in patients suspected of dehydration. 2- glabellar

reflex, in which a person’s forehead is taped several time and the subject blinks, if the

blinking persists, which is called Myerson’s sign, being an early symptom of

Parkinson’s disease, dementia and neurological disorders

4) Nasion: root of the nose, depressed area between the 2 orbits

5) Infra-orbital foramen: located in the anterior surface of the maxilla on the same line

vertically with the supra-orbital foramen

6) Anterior nasal apertures: (nasal openings), their boundaries are the 2 nasal bones

superiorly, maxillary bone laterally, maxillary bone inferiorly

7) Zygoma: 2 bones below the orbit

8) Inferior and middle nasal conchae (superior are hidden and not seen in frontal view)

Superior and middle nasal conchae are part of the ethmoid but the inferior nasal

concha is a separate bone

9) Alveolar processes

a. Of the maxilla, have sockets that carry the maxillary teeth

b. Of the mandible, containing sockets for the mandibular teeth

2) Lateral View: also called the temporal view

Landmarks of the lateral view:

a. Anterior nasal spine: union of 2 maxillary bones at the lower border or the anterior nasal

apertures

b. Nasal septum: divides nasal cavity vertically into 2 cavities

nasal septum is divided into 3 parts: anteriorly nasal cartilage, inferiorly vomer,

superiorly perpendicular plate of the ethmoid.

c. Lateral orbital margin

d. Temporal lines: they are either superior and inferior or one single line

e. Zygomatic arch: formed by the zygomatic process of temporal bone and the temporal

process of the zygomatic bone

f. Temporal fossa:

i. Region limited by temporal lines superiorly and zygomatic arch inferiorly

ii. Formed by: frontal, parietal, greater wing of sphenoid and temporal bones

iii. Gives rise to temporalis muscle

iv. Pterion:

1. H-shaped region

2. Lies above anterior branch of middle meningeal artery

3. Very thin bone, easily fractured leading to injury of underlying artery

which will result in intercranial, epidural or extradural hematoma. May

compress the brain tissue

g. External acoustic meatus: auditory tube, posterior to the TMJ

h. Mastoid process:

i. Conical bony projection behind ear, pulpable area

ii. Contain air filled cells, function in?????

iii. Provides attachment to muscles and ligaments???????

i. Styloid process: deep, not pulpable, attaches muscles and ligaments (styloid apparatus)

j. Paranasal air sinuses: air filled cavities which open into the nose

i. Frontal

ii. Maxillary

iii. Sphenoid

iv. Ethmoid

3) Superior View: calvaria

Bones present are: frontal bone, right and left parietal bones, occipital bone

Landmarks:

a. Coronal suture: between frontal bone and the 2 parietal bones

b. Sagittal suture: between the 2 parietal bones

c. Lambdoid suture: between the 2 parietal and the occipital bones

d. Bregma : meeting point of coronal and sagittal sutures

e. Lambda: meeting point of lambdoid and sagittal sutures

f. Parietal foramen: in the parietal bones, for transmission of emissary veins (veins which

connect venous blood from the outside to the inside)

Neonatal skull:

- Sutures are not well joined together

Sagittal suture looks like an arrow

Metopic suture: lies between the 2 frontal bones and ossifies by the age of 5

Anterior fontanelle: unossified “bregma”, ossifies by the age of 18 month to form

bregma

Posterior fontanelle: unossified “lambda”, ossifies by the age of 9 month to form

lambda

They function to assess the intercranial pressure by palpation (bulge if high

and depress if low pressure)

4) Posterior view:

- Landmarks of the posterior view:

Sagittal Suture

Lambdoid Suture

External Occipital protuberance: a projection in the squamous part of the occipital

bone

Nuchal lines: superior and inferior extending from the lateral part of the external

occipital protuberance

Temporal Bone

Parietal Bone

Occipital Bone

Maxillary Bone

Mandibular Bone

5) Inferior view:

12 pairs of cranial nerves which pass through the openings in the inferior view

I. Olfactory

II. Optic

III. Occulomotor

IV. Trochlear

V. Abducent

VI. Trigeminal

i. V1 ophthalmic

ii. V2 Maxillary

iii. V3 Mandibular

VII. Facial

VIII. Vestibulochoclear

IX. Glossopharyngeal

X. Vagus

XI. Accessory

XII. Hypoglossal

Landmarks of the inferior view:

1) U-Shaped maxilla

Muscles of mastication:

1) Temporalis

2) Masseter

3) Medial pterygoid

4) Lateral pterygoid

2) Hard palate: separates oral from nasal cavity, anterior 2/3 formed by maxilla, posterior 1/3 formed by

the horizontal plate of the palatine bone

3) Palatine process of the maxilla

4) Sphenoid bone

a) Greater wing

b) Lesser wing

c) Medial and lateral pterygoid processes

d) Body of the sphenoid

5) Pterygoid fossa: lies between the medial and lateral pterygoid processes and gives attachment to

pterygoid muscles

6) Infratemporal fossa: exposed by removal of the zygomatic arch and the mandible, it’s boundaries are:

a) Anteriorly: maxilla

b) Posteriorly: styloid process

c) Laterally: zygomatic arch or ramus of the mandible

d) Medially: lateral pterygoid plate

7) Posterior nasal openings: nasal choanae, communicates the nasal cavity to the oropharynx it’s

boundaries are:

a) Superiorly: body of the sphenoid

b) Inferiorly: horizontal plates of the palatine bone

c) Medially: vomer

d) Laterally: medial pterygoid processes

8) Temporal bone:

a) Zygomatic process

b) Squamous part

c) Petrous part

d) Styloid process

e) Mastoid process

f) Tympanic plate

6) Cranial base of the skull:

- Contains several openings and foramina through which the nerves and blood vessels pass

- Occipital condyle: bony mass on each side of foramen magnum and articulates with atlas (C1)

to form atlantooccipital joint

Opening position

Structures passing through

Cribriform plate Part of the Ethmoid bone Olfactory bulb/fibers (from olfactory

nerve I)

Optic canal At root of lesser wing Optic nerve II

Ophthalmic artery

Supraorbital

fissure

Communicates the orbital canal and middle

cranial fossa, between lesser and greater

wings of sphenoid

Oculomotor nerve III

Trochlear nerve IV

Ophthalmic nerve V1

Abducent VI

Superior and inferior ophthalmic veins

Foramen

Rotundum

In greater wing of sphenoid, communicates

middle cranial fossa with pterygopalatine

fossa

Maxillary nerve V2

Foramen Ovale In greater wing of sphenoid , communicates

middle cranial to Infratemporal fossa

Mandibular nerve V3

Foramen

lacerum

Between body of the sphenoid and Petrous

part of temporal bone

Greater Petrosal nerve

(a branch of the facial nerve VII, which

then leaves through the stylomastoid

foramen)

Foramen

spinosum

In greater wing of the sphenoid,

communicates middle cranial fossa to

Infratemporal fossa

Anterior branch of the middle

meningeal artery

Carotid canal In Petrosal part of temporal bone, opens

into posterior wall of foramen lacerum

Internal carotid artery

Sympathetic nerve plexus

Internal acoustic

meatus

Intracranially, in the posterior surface of the

Petrous part of the temporal bone

Facial nerve VII

Vestibulocochlear nerve VIII

Stylomastoid

foramen

Between styloid and mastoid processes of

the temporal bone

Facial nerve VII (pure motor branch)

Jugular foramen Between occipital bone and Petrous part of

temporal bone

Glossopharyngeal IX

Vagus nerve X

Accessory nerve XI

Internal jugular veins

Sigmoid sinus

Posterior meningeal artery

Inferior Petrosal venous sinus

Condylar canal Anterior to occipital condyle Emissary veins

Hypoglossal

canal

Posterior to condyle Hypoglossal nerve XII

Foramen

magnum

Occipital bone Spinal root and its covering meninges

Spinal root accessories

Vertebral artery

The spinal root arises from the spinal cord

then enters the skull through foramen

magnum to join with the cranial root and

leave jugular foramen as accessory nerve

Vertebral

arteries supply

posterior part of

the brain

Cranial Fossae

1) Anterior cranial fossa:

Boundaries: from Squamous part of the frontal bone to the lesser wing of the sphenoid

Contents: frontal lobes of brain

Floor is formed by:

Cribriform plate of the Ethmoid bone , it lies between the nasal cavity and the

anterior cranial fossa (part of floor of ACF and roof or nasal cavity)

Crista galli: upward bony projection (from cribriform plate) which attaches to falx

cerebri

Orbital plate of frontal bone

2) Middle cranial fossa:

Boundaries: lesser wing of sphenoid anteriorly to petrous part of temporal bone

posteriorly

It is composed of 2 lateral portions, a central portion formed by superior surface of the

body of the sphenoid

Great petrosal

The central portion includes sella turcica (also called the hypophyseal fossa or pituitary

fossa). Tuberculum sellae: anterior limit of sella turcice. Dorsum sellae: posterior limit of

sella turcica

Floor:

Greater wing and body of sphenoid

Squamous part of temporal bone

Part of Petrous part of temporal bone

3) Posterior cranial fossa:

- Boundaries: upper border of Petrous part of temporal bone anteriorly and Squamous part of

occipital bone Posteriorly

- Contains: the cerebellum

- Landmarks:

Internal occipital protuberance: projection in the inner surface opposite to the

external occipital protuberance

Sigmoid sulcus: S-shaped sulcus, contains the sigmoid venous sinus

Sulcus for Transverse Sinus: contains the transverse venous sinus

Meninges

They are 3 membranes which surround the brain and spinal cord.

I. Pia mater: delicate layer directly attached to the brain and spinal cord

a. Subarachnoid space: space that lies between the Arachnoid mater and the Pia mater.

Contains CSF (cerebrospinal fluid) which act as a cushion to protect the brain and spinal

cord

II. Arachnoid mater: transparent layer, which lies over the Pia mater. It shows trabeculations

(arachnoid granulation villi), which function in the drainage of the CSF and the venous blood in

the venous sinuses

a. Subdural Space: contains blood vessels

III. Dura mater: tough layer which lies over the Arachnoid mater

Cranial dura: consists of periosteal layer (endosteal layer) which is the lining of the skull

bone, and the real dura mater, which is the tough fibrous layer

a. Epidural Space: lies between dura mater and bone. Contains blood vessels

IAM Stylomastoid

foramen Foramen lacerum

Facial nerve

Before the facial nerve enters the internal

acoustic meatus, it gives a branch to the

greater petrosal nerve, which then leaves

through foramen lacerum. The facial nerve

leaves the Stylomastoid foramen as pure

motor

Facial

Dura Mater

The Dura mater is separated into 2 layers called the dural folds or projections, they separate different

brain hemispheres.

I. Falx Cerebri:

a. separates the 2 cerebral hemispheres

b. Double layer of dura which separate the 2 cerebral hemispheres

c. Attached anteriorly to crista galli

d. It has 2 borders:

i. Upper: superior Sagittal sinus lies in it

ii. Lower border: inferior Sagittal sinus lies in it

II. Falx Cerebelli:

a. separates the 2 cerebellar hamispheres

III. Tentorium Cerebelli:

a. separates the cerebellum from the occipital lobes of the cerebrum

b. Forms a tent over the posterior cranial fossa

IV. Diaphragm Selli:

a. Very small dural projection that form the roof of sella turcica

b. Has an opening in the middle for the stalk of the pituitary gland

Dural Venous Sinuses

Venous channels which lie between the 2 layers of the Dura mater. They lack valves and smooth muscles

in their walls, as blood flows with gravity.

Single Sinuses Paired Sinuses

Superior Sagittal Venous Sinus Transverse Venous Sinus

Inferior Sagittal Venous Sinus Sigmoid Venous Sinus

Straight Sinus Cavernous Venous Sinus

Superior Petrosal Sinus

Inferior Petrosal Venous Sinus

Single Sinuses

I. Superior Sagittal venous sinus:

a. In the upper border of the falx cerebri

b. Runs upwards and backwards ending at the internal occipital protuberance

II. Inferior sagittal venous sinus:

a. In the lower border of the falx cerebri

b. Joins with the great cerebral vein to form the straight sinus, which runs upwards and

medially

III. Straight Sinus:

a. Formed by the union of the great cerebral vein and the inferior petrosal venous sinus

b. Runs at the meeting point of the tentorium cerebella and falx cerebri

c. Ends at the internal occipital protuberance

Paired Sinuses

I. Transverse Sinus:

a. Right transverse sinus: continuation of the superior Sagittal sinus

b. Left transverse sinus: continuation of the straight sinus

c. Passes lateral to the internal occipital protuberance on both sides

II. Sigmoid Sinus:

a. Continuation of the transverse sinus

b. Ends at the jugular foramen forming the jugular bulb which then continues as internal

jugular vein

III. Cavernous Sinus:

a. Cave like, lies in body of the sphenoid

b. It has a special importance as some important structures pass through it

i. Vessels: internal carotid artery

ii. Nerves: Occulomotor III, Trochlear IV, Abducens VI, V1 & V2 of trigeminal V

c. Infection in the dangerous zone (angle between mouth and eye) can easily transmit it into

the brain by the following pathway:

Facial Vein pterygoid venous plexus

inferior ophthalmic vein cavernous sinus

Cavernous sinus receives blood from superior

and inferior ophthalmic vein. Before entering

the sinus, the inferior ophthalmic vein

communicates with the pterygoid plexus

Any problem in the cavernous

sinus affects movement of

eyeball, sensation of the face,

blood supply to the brain

IV. Superior petrosal sinus:

a. Arises from the upper posterior part of the cavernous sinus

b. Runs in the upper border of the petrous part of the temporal bone, to joining the sigmoid

venous sinus

V. Inferior petrosal sinus

a. Arises from lower part of cavernous sinus

b. Joins internal jugular vein, from outside the skull after passing through the jugular

foramen

c. It’s the only venous sinus that leaves the skull with the venous blood

Individual Bones of the Skull

1) Maxilla: a paired bone which has 4 processes and 4 surfaces

- 4 surfaces :

Superior: it separates the orbital cavity from the maxillary air sinuses

Anterior: facial

Posterior: forms anterior limit of infratemporal fossa

Medial (nasal): forms lateral wall of the nasal cavity

- 4 processes:

Frontal: joins the frontal bone to form the medial orbital margin

Zygomatic: joins the zygoma to form the infra orbital margin

Alveolar: Contains sockets for upper teeth

Palatine: joins palatine bone to form the hard palate

- Articulations of the maxilla: frontal, nasal, zygomatic, inferior nasal concha, palatine bone,

ethmoid, maxilla

- Maxillary nasal sinuses are located in the medial (nasal) process. It is one of the biggest

sinuses and functions in resonance of voice and lightening of weight of skull

2) Mandible: A single bone, horseshoe shaped, which is composed of a body and 2 rami

- The body: composed of 2 surfaces (inner and outer) and 2 borders (superior and inferior)

Outer surface:

Mental protuberance: lies in the midline

Mental tubercle: lies on both sides of the protuberance

Mental foramina: located below the apices of the premolar-molar. Can be

used to determine the age of a person as it is closer to the inferior border in

infants and closer to the superior border in elderly people, in adults it lies in

the middle. (the change in position is relative as the bone is not completely

grown in infants and is resorbed in elderly)

Oblique line: also called the external oblique ridge, extends from mental

foramen to the anterior border of the ramus

Inner surface:

Superior and inferior mental spines (genial tubercles): 4 projections which

lie in the midline which give attachment to:

Superior: genioglossus muscle

Inferior: geniohyoid muscle

Mylohyoid line: gives attachment to mylohyoid muscles which are 2 muscles

join to form the floor of the mouth

Sublingual fossa: a depression which lies above the mylohyoid line. Contains

the sublingual salivary glands

Submandibular fossa: a depression which lies below the mylohyoid line.

Contains the submandibular salivary gland

Digastric fossa: located below the genial tubercle

- The Ramus: each has 2 surfaces(medial and lateral),2 processes (anterior/coronoid and

posterior/condylar) and 2 borders (anterior and posterior)

- Ramus meets the body to form the angle of the ramus

Surfaces:

Lateral: smooth except where it gives attachment to the massetter muscle

Medial surface:

Mandibular foramen: opens to the mandibular canal which ends at

the mental foramen, transmitting the inferior alveolar nerve and

blood vessels. Mental nerve is the continuation of the inferior The ramus is sandwiched by the

massetter muscle from outside

and medial pterygoid from the

inside

alveolar nerve, supplies lower teeth and lip, thus anesthesia is given

in it.

Lingula: bony projection, lies anterior to mandibular foramen.

Provides attachment to ligaments.

Rough region in the lower part of inner surface, gives attachment to

the medial pterygoid muscle.

Processes:

Coronoid/anterior: gives attachment to temporalis

Condyle/posterior:

Head: articulates with mandibular fossa of temporal bone forming

TMJ

Neck : provides attachment to capsule of TMJ

3) Sphenoid Bone: a single bone has the shape of a butterfly.

It is composed of:

- Body

- 2 greater wings

- 2 lesser wings

- 2 pterygoid processes

Body:

o Has 2 surfaces:

Superior: forms sella turcica/pituitary fossa/

Inferior: forms upper margin of coanae and upper border of pharynx

o Sphenoid air sinuses:

Upper border: sella turcica

Lower border: roof of pharynx

Visible in the anterior view

Greater wing of sphenoid:

o Has 4 surfaces:

Cranial surface

Lateral surface: temporal

Inferior : infratemporal , roof of infratemporal fossa

orbital

Between the lesser and greater wings lies the superior orbital fissure

Pterygoid plates/processes:

Medial and lateral processes/plates in between them lies the pterygoid fossa

The pterygoid fossa provides attachment to the medial and lateral pterygoid

muscles

The pterygoid fossa can be seen only in the posterior view

Optical canal is located at the roof of lesser wing and above superior orbital

fissure, while rotundum is below superior orbital fissure

Above the pterygoid plate lies the pterygoid canal (transmits the pterygoid

nerve)

Ovale, rotundum and spinosum are present on the greater wing but are not

visible in the anterior or posterior view.

Articulations of the sphenoid bone:

o Palatine bone, ethmoid, nasal bone, temporal , vomer, frontal, parietal, occipital,

zygoma, maxilla

4) Ethmoid: single bone, lies between the 2 orbits

- it is also located in:

o upper part of nasal cavity

o roof of nasal cavity

o perpendicular plate of the ethmoid, forms part of the nasal septum

o lateral wall of ethmoid forms the medial wall of the orbit

o medial wall of the ethmoid forms the lateral wall of the nasal cavity

- the labyrinth contains air filled cavities (ethmoidal air cells), each has

o medial/ nasal plate

has 2 projections: superior and middle nasal conchae

o lateral/orbital plate

- cribriform plate separates the nasal cavity from the anterior cranial fossa

To differentiate between

medial and lateral views of

the nasal cavity: in the medial

view the septum is present

5) Frontal Bone: single bone, developed from 2 halves, which are separated by the metopic suture

(ossifies at the age of 5 years)

- It is composed of 2 processes:

o Maxillary: articulates with the maxilla to form medial orbital margin

o Zygomatic: articulates with the zygoma to form lateral orbital margin

- In the upper orbital margin lies the supraorbital foramen/notch

- Supraciliary arch: lies above the supraorbital margin (below the eyebrow)

- Glabella: hairless area between the supraciliary arches

- Frontal nasal sinuses: 2, which drain the nasal cavity

o They are lined by the same epithelium of the nasal cavity

o They function in:

Weight reduction

Sound resonance

- Squamous part:

o Forms the vault and forehead

o Forms the floor of the anterior cranial fossa

o Forms the roof of the orbital cavity

- Foramen cecum: lies anterior to crista galli, for transmission of emissary veins

6) Temporal Bone: paired bone, on the lateral sides of the skull, composed of 5 parts

Squamous, petrous, mastoid, styloid, tympanic

- Squamous:

o Vertical flat part

o Forms part of the floor of the temporal fossa

o Has the zygomatic process which articulates with the zygoma to form

the zygomatic arch

o Mandibular fossa: inferior to zygomatic process. Site of articulation with

the condyle

- Tympanic plate:

o Anterior limit of external acoustic meatus

- Mastoid process:

o Conical, palpable bony projection, lies behind the ear

o Contains air filled cavities (mastoid air cells)

o For resonance of sound

o Gives attachment to sternocleidomastoid muscle and posterior belly of

Digastric muscle

o Gives attachment to ligaments

- Styloid process:

o Deeply seated, non-palpable

o This downwardly projected bony process

o Gives attachment to:

Chorda tympani

exits between the

tegmen tympani

and anterior edge

of tympanic plate

Stylohyoid muscle

Stylopharyngeal muscle

Styloglossus muscle

Stylohyoid ligament

o Stylomastoid foramen lies between the styloid and mastoid processes

- Petrous part:

o Sometimes called petromastoid (closely related to mastoid)

o Hard rock like bony part containing important structures

Ear cavity (through internal acoustic meatus)

Carotid canal (transmits internal carotid artery and sympathetic

plexus)

Facial nerve

Vestibulocochlear nerve

7) Occipital bone: single flat bone, forms posterior part of the skull and part of the base of the skull

- Squamous part: The curved, expanded plate behind the foramen magnum

o Superior and inferior nuchal lines which project laterally from the

external occipital protuberance

o Internal occipital crest: projection which lies posterior to the foramen

magnum (internally)

o Internal occipital protuberance (internally)

o Has transverse groove for transverse sinus (internally)

- Basilar part: the thick part in front of the foramen magnum,

o Projects anteriorly, forming part of the roof of the pharynx (pharyngeal

tubercle)

- Articulates with part of the sphenoid

8) Nasal bone: a paired bone

- Join in the midline

forming part of the

roof of the nasal cavity

9) Zygomatic bone: paired bone, forms the

prominence of the cheek

- Articulates with frontal, maxillary, greater wings of sphenoid and temporal bone

10) Lacrimal bone: paired bone

- Forms part of the medial wall of the orbit

- Nasolacrimal duct: a canal that connects the orbit to the nasal cavity (for the

drainage of tears)

11) Palatine bone: paired bone, L-shaped

- 2 plates:

o Horizontal: forms the posterior third of the hard palate and the

projecting nasal crest forms part of the nasal septum

o Perpendicular plate: forms lateral wall of the nasal cavity

12) Inferior nasal conchae: paired bones

- Attached to lateral wall of the nasal cavity

- A fragile bone

- Increases surface area of nasal cavity

- Lined by mucous membrane

13) Vomer: single bone, a thin deep plate

- Articulates with

o Maxilla

o Ethmoid

o Sphenoid

o Septal cartilage

(inferiorly)

Face

Nasal septum: vomer,

septal cartilage,

perpendicular plate of

the ethmoid

The face extends from the hair to the lower border of the mandible and from the ear to the ear

Contents of the face:

- Skin: includes hair follicles, sweat glands and sebaceous glands

- Connective tissue: has superficial fascia only, no deep fascia

- Muscles: mastication and facial expression muscles

- Blood Vessels: arteries and veins

- Glands: parotid and submandibular glands

- Nerves: trigeminal and facial nerves

Muscles of facial expression:

- Responsible for expression

- Control size of facial openings (each has sphincter/closes

o Mouth

o Nose

o eyes

- Arise from facial skeleton and are inserted into skin

- Arise from 2nd branchial arch

- Supplied by facial nerve

Muscles of the Eyes:

Name of Muscle Sphincter/Dilator Function

Orbicularis oculi Peripheral/orbital part Central/palpebral part

sphincter

Whole muscle: helps move tears towards midline of face

Orbital part: forceful closure Palpebral part:gentle closure

Frontalis Dilator Elevates eyebrows, and wrinkles forehead, opens the

eye

Levator palpebrae superioris

Dilator Elevates upper eyelid, only muscle supplied by the

occulomotor nerve

Muscles of the nostrils:

Name of Muscle Sphincter/dilator Function

Dilator naris Dilator Dilates opening of nose

Compressor naris Sphincter Closes opening of nose

Muscles of the Mouth:

Name of muscle Sphincter/dilator function

Orbicularis oris Sphincter Arises from the maxilla and mandible, brings the 2 lips together (whistling action)

Zygomaticus major and minor Dilator Elevates the angel of the mouth

Levator labii superioris Dilator Elevates the upper lip upwards

Levator anguli oris Dilator Lies between the zygomaticus major and minor, elevates angel

of mouth

Depressor labii inferioris Dilator Moves lip downwards

Depressor anguli oris Dilator Moves angel of mouth downwards

Mentalis Dilator Depressing of chin

Resorius Dilator Moves angle of mouth horizontally

Platysma Dilator Depression of lower lip, tightening of the skin of the neck

Muscles of the Cheek:

External Carotid Artery

Common Carotid Artery

Internal Carotid

Facial Artery Superficial

Temporal

Artery

Maxillary

Artery

Infraorbital

Artery

Mental Artery

Ophthalmic

Artery

Supratrochlear

Artery

Supraorbital

Artery

Superficial

Temporal

Vein

Facial Vein Retromandibular

Vein

External and

Internal Jugular

Veins

Buccinator Muscle: lie between massetter and angel of mouth

- Anterior fibers mix with orbicularis oris muscle

- Pierced by the duct of the parotid gland

- Function

o Blowing

o Pushing food out of the vestibule into the oral cavity proper

Blood Supply of the Face

1) Arterial blood supply:

2) Venous drainage:

Nerve Supply of the face

Sensory for the skin

Motor for the muscles

Trigeminal Nerve

V

Ophthalmic

division V1

Maxillary Division

V2 Mandibular

Division V3

Skin of the face from the

angle of the eye upwards.

Upper eyelid skin, anterior

and lateral parts of the

nose, forehead

From angle of the eye to the

angle of the mouth. Lower

eyelid, skin of cheeks, upper

lip

Angle of the mouth

downwards. Parotid

region, lower lip, chin,

lateral side of the scalp

Sensory Supply:

Motor Supply:

All muscles of facial expression are supplied by the facial nerve (VII) except the levator palpebrae

superioris muscle which is supplied by the occulomotor nerve (III)

Facial Nerve gives 5 motor branches:

- Temporal

- Zygomatic

- Buccal

- Mandibular

- cervical

Facial Palsy: damage to the facial nerve

It leads to:

paralysis to ½ of the face

inability to whistle

inability to close eyes leading

To dry and ulcerated cornea

inability to blow

angle of mouth droops causing saliva to come out

face will shift towards normal side

Parotid Region

It is the area in the side of the face inferior and anterior to the ear

salivary glands in the parotid region are:

o parotid: the largest salivary gland

o submandibular

o sublingual

o scattered small salivary glands in the submucosa of the cheeks

saliva is either

o serous (water like)

o mucous (thicker)

o it helps in digestion, turning food into a bolus thus making swallowing easier and also

helps in speech

1) parotid salivary glands:

- 1 on each side: wedge shaped, exocrine gland

- It has 3 surfaces:

o Anteromedial surface: faces the massetter muscle, medial pterygoid

muscle and ramus of mandible

o Posteromedial surface: faces the mastoid process and

sternocleidomastoid muscle

o Lateral surface: faces the skin and great auricular nerve

- Surrounded by parotid capsule which is a continuation of the investing layer of

the deep fascia

- Stansen’s duct: the opening of the parotid gland. Starts from the anterior border

of the gland and then passes through the massetter and turns medially to pierce

the buccinator muscle then pens into the vestibule opposite to the upper second

molar

- Structures that pass within the

parotid gland:

o Facial nerve

o Retromandibular vein

o External carotid

artery

o Auriculotemporal

nerve

Facial Nerve: enters the parotid gland without

supplying it from the posteromedial surface, dividing

it into a deep lobe and a superficial lobe. It ends

within the parotid gland giving five terminal motor

branches (temporal, zygomatic, Buccal mandibular, cervical)

Structures passing into the parotid gland:

1) Veins

- Superficial vein and maxillary vein join into the gland to form the

retromandibular vein.

- The retromandibular vein then divides into anterior and posterior divisions

- The anterior division joins the facial vein to form the common facial vein which

extends as the internal jugular vein

- The posterior division joins the great auricular vein to form the external jugular

vein

2) Arteries:

- External carotid enters the gland and ends in it by giving superficial temporal

artery and maxillary artery

Nerve Supply of the gland

1) Sensory:

a. by auriculotemporal nerve which is branch of V3

b. carries pain sensation from the capsule of the parotid gland

2) Autonomic:

a. Sympathetic:

i. By sympathetic plexus surrounding external carotid artery

ii. Decreases salivation and secretions (dry mouth)

b. Parasympathetic

i. By glossopharyngeal carried by the lesser petrosal nerve

ii. The salivary nuclei located in the brain is responsible for the production of saliva

iii. The preganglionic parasympathetic, stops to relay in otic ganglia, located in the

infratemporal fossa

iv. Post ganglionic fibers runs to the parotid gland with the auriculotemporal nerve

Parotid

gland

Superficial

temporal Retromandibular

Maxillary

Facial

Posterior

division

Common

Facial

Internal jugular

External jugular

Ant. division

Great

auricular

Lesser Petrosal Auriculotemporal

Blood Supply of the gland:

- Arterial blood supply: through external carotid artery and terminal branches of

superficial temporal artery and maxillary artery

- Venous drainage: through maxillary vein and superficial temporal vein of the

retromandibular

Lymph nodes:

- Drainage is by the parotid lymph nodes and the deep cervical lymph nodes

Mumps: viral infection of the parotid gland

Parotitis: bacterial infection of the parotid gland

Damage to the

gland can lead to

damage to the

facial nerve

Otic Ganglia

Post ganglionic

Parasympathetic

Secretomotor Fibers

Pre ganglionic

Parasympathetic

Secretomotor Fibers

The Orbit

2 cavities, pyramidal in shape, located in the anterior view of the skull

Each orbit has:

- Base: directed forwards

- Apex: directed backwards

- 4 orbital margins

- 4 walls

I. Roof: separates the orbital cavity from the anterior cranial fossa. Formed from lesser

wing of sphenoid and orbital plate of frontal bone

II. Floor: separates orbit from maxillary air sinuses. Formed from maxilla and zygoma

III. Lateral wall: separates orbit from temporal fossa, formed from zygomatic bone and

greater wing of the sphenoid

IV. Medial wall: separates orbital and nasal cavities, formed from lacrimal, labyrinth of

ethmoid bone and part of palatine bone

- Openinings in the orbit:

1. Superior orbital fissure: communicates with the middle cranial fossa

2. Optic canal: communicates with the anterior cranial fossa/middle cranial fossa

3. Infra-orbital fissure: communicates with the pterygopalatine fossa

4. Supraorbital notch: communicates with the anterior surface of forehead

5. Infraorbital notch: communicates with the face

6. Nasolacrimal duct: connects the nasal cavity to the orbit

- Contents of the orbit

I. Eyeball

II. Muscles

III. Nerves

IV. Blood vessels

V. Fat

VI. Lacrimal apparatus

VII. Ciliary ganglion

I. Eyeball: spherical in shape, camera of the body, consists of 3 layers

a. Outer layer: a fibrous coat that protects the eye. Formed from sclera and cornea

i. Sclera:

1. provides attachment to the muscles

2. white in color

3. protects the eyeball

ii. cornea:

1. transparent part

b. Middle layer: also called the vascular coat.

i. Choroid: becomes enlarged anteriorly to form the Ciliary body

ii. iris: a forward extension of the Ciliary body which gives the color of the eye

(pigmented coat)

iii. pupil: an opening in the middle

iv. 2 muscles of the eye for visual adaptation (affected by the amount of light)

1. Constrictor pupilae: is stimulated by high light intensity and is under

parasympathetic control

2. Dilator pupilae: is stimulated by absence of light, under sympathetic

control

v. Lens: connected to Ciliary body by suspensory ligaments

vi. Ciliary muscles: group of involuntary muscles in Ciliary body

1. Change thickness of lens by changing length of suspensory ligaments

2. Allows for visual accommodation (ability to see far and near)

c. Inner layer: nervous coat called the retina

i. Has many photsensory receptors (rods and cons)

1. Rods: for dark light

2. Cons: for daylight, colors and moving objects

ii. Optic nerve: originates from the retina from the rods and cons

iii. Fibers travel posteriorly from the rods and cons to form the optic nerve

iv. Fundus: site of attachment of the optic nerve to the eyeball. It has no rod and

cons, thus it’s a blind spot

- Chambers of the eyeball: divided because of presence of lens

d. Anterior chamber: contains aqueous humor (an aqueous watery fluid)

e. Posterior chamber: contains vitreous humor (jelly like fluid) it gives the round shape of

the eyes

- Eyelids:

f. Conjunctiva:

i. the lining of the eyelids

ii. a transparent membrane inner surface which turns to line the eyeball

iii. inflammation can occur leading to red itchy eyes (conjunctivitis)

II. Fat:

a. Allows eye to move freely within the bony orbit

b. Supports the eyeball

III. Muscles

There are 2 groups of muscles in the eye

1. Intraocular: muscles inside the eyeball

a. Constrictor

b. Dilator

c. Ciliary muscles

2. Extraocular: muscles inside the orbit (outside the eyeball)

a. Recti (meaning straight)

i. Superior rectus

ii. Inferior rectus

iii. Medial rectus

iv. Lateral rectus

b. Oblique

Nerve

Supply:

LR6 SO4 3

i. Superior oblique

ii. Inferior oblique

c. Levator palpebrae superioris

Movements of the Eyes

Right eye Left eye Movement

Superior Rectus3

Superior rectus3

Inferior Rectus3

Inferior Rectus3

Lateral Rectus6

Medial Rectus3

Medial Rectus3

Lateral Rectus6

Inferior Oblique3

Superior Rectus3

Superior Rectus3

Inferior Oblique3

Superior Oblique4

Inferior Rectus3

Inferior Rectus3

Superior Oblique4

Testing the function of the nerves through eye

movements:

- Abducens VI: look lateral by left eye

- Trochlear IV: look down and lateral by

right eye

- Occulomotor III: look at any other

direction

Problems With the eye:

- Convergent Squint/diplopia/strabismus:

double vision created when both eyes move

medially

- Divergent Squint; when one eye moves

normally and the other eye moves laterally

IV. Nerves:

a. Optic nerve II:

i. pure sensory nerve for vision

ii. arises from the retina and goes into the brain

iii. Nasal part of retina views pictures coming from lateral/ temporal side

iv. Lateral part of retina views vision from medial side, these are called visual field

The remaining

cranial nerves arise

from the brain stem

v. The two fibers join to form the optic nerve

vi. Nasal fibers of the optic nerves cross the midline forming the optic chiasma, it

contains nasal fibers of both eyes

vii. Optic tract: the continuation of the nasal fibers of the opposite side eye and the

temporal fibers of the eye on the same side

viii. The optic tract ends in the visual cortex of the occipital lobe of the brain

Damage to the optic nerve: one eye is blind

Damage to chiasma: bitemporal hemianopia (blindness of the fields from the lateral side)

Damage to optic tract: contralateral hemianopia (blindness of the temporal of one eye and nasal of

the other eye)

Decussation:

crossing of fibers to

the opposite side

Optic chiasma is

closely related to

the pituitary gland,

thus any damage to

the pituitary gland

affects the chiasma

If someone

receives a hit in the

back of the brain, it

can affect vision

(visual cortex)

Nerves passing through the optic cavity:

1. V1 of the trigeminal

a. Pure sensory nerve

b. Enters the orbit through superior orbital fissure

c. Branches:

i. Lacrimal: sensory, supplies lacrimal gland, conjunctive and the skin of the upper eyelid

ii. Frontal: ends by giving 2 terminal branches

1. Supraorbital : supply upper eyelid, scalp, skin of the forehead, and frontal air sinuses

2. Supratrochlear : supply upper eyelid, scalp, skin of the forehead, and frontal air sinuses

iii. Nasociliary:has 2 parts:

a. Visceral secretomotor: receives post ganglionic parasympathetic fibers from ciliay ganglia to

supply the Ciliary body (muscles of the iris=constrictor pupilae) and lacrimal gland

b. Sensory: supplies nasal cavity, skin of the nose, skin of upper eyelid and ethmoidal air cells

2. Occulomotor nerve: arises from the brain stem and enters the orbit through the superior orbital fissure.

Has 2 components:

1. Motor: to all muscles of the orbit except the superior oblique and the lateral rectus

2. Parasympathetic: preganglionic fibers which pass through the ciliary ganglia to supply the

ciliary muscles (constrictor pupilae). It’s also responsible for visual accommodation

a. To test the function of the Trochlear:

ii. Defect in eyeball movement

iii. Drooping

iv. Light reflex

3. Trochlear: arises from the brain stem.

a. Enters orbit through superior orbital fissure

b. Pure motor nerve

c. Supplies only superior oblique

4. Abducens arises from the brain stem.

a. Enters orbit through superior orbital fissure

b. Pure motor nerve

c. Supplies only lateral rectus

5. V2 of the trigeminal: pure sensory

a. Leaves skull through foramen Rotundum, to go to pterygopalatine fossa

b. Enters the orbit and become Infraorbital nerve, which runs in the floor of the orbit and leaves the

orbit through the Infraorbital foramen

c. Supplies

I. the skin of the face form angle of the eye to the angle of the mouth

II. nasal cavity

III. maxillary air sinus

IV. upper teeth

V. part of the pharynx

d. Branches:

I. Posterior superior alveolar nerve.

II. Middle superior alveolar nerve

Damage to the occulomotor

causes: 3D

Diplopia

Drooping of upper eyelid= ptosis

Dilated pupil

The pterygopalatine

ganglia is suspended

by V2, but is

functionally related

to the facial nerve

III. Anterior superior alveolar nerve

V. Ciliary Ganglia: small pin head sizes parasympathetic ganglia

a. Functionally related to occulomotor nerve

b. Receives preganglionic fibers

c. Postganglionic fibers pass through the nasociliary nerve

VI. Blood Vessels

a. Arteries: ophthalmic artery,

i. a branch of internal carotid artery

ii. enters the orbit through optic canal, and ends by giving terminal branches

1. supraorbital

2. Supratrochlear

iii. Before entering the orbit it gives central retinal artery which runs in the center of

the optic nerve

iv. Damage can result in blindness, as it supplies the retina

b. Vein:

i. Superior ophthalmic vein: formed by union of supra orbital, Supratrochlear and

angular veins

ii. Inferior ophthalmic vein: forms by small veins in the orbit joined together and

drain into the cavernous sinus

iii. Both leave the obit

VII. Lacrimal Apparatus: contains

a. Lacrimal gland

b. Canaliculi

c. Lacrimal sac

d. Nasolacrimal duct

- Lacrimal gland:

I. an exocrine gland,

II. produces and secretes tears

III. located in upper lateral side of the orbit

IV. has 2 parts

large orbital part

small palpebral part

V. receives its parasympathetic fibers from facial nerve, carried by greater petrosal nerve

VI. tears flow on the anterior surface of the eyeball

VII. blinking distributes the tears to moisten the eyeball

VIII. All tears will accumulate in the medial angle

IX. Superior and inferior punctums: openings in the medial surface of the eye (corner) which

pass the tears on to the canaliculi

- Canaliculi: small ducts which drain the tears to the lacrimal sac, closely related to the medial wall

of the orbit

- Nasolacrimal duct: connects the lacrimal sac to the wall of the nasal cavity, thus making a pathway

for draining the tears (passes through lacrimal bone)

- Tears are then absorbed by the nasal mucosa

- Nasal mucosa inflammation: blocked opening = teary eyes

- Crying: excessive tear production, therefore inability of mucosa to absorb it all, leading to runny

nose

The end