Anatomy of the Skull and Face

Question 1

What is the upper and lower part of the cranium called?

Answer 1

The upper part is the vault and the lower part is the floor

Question 2

What joints are between the bones of the skull?

Answer 2

Immobile joints called sutures.

• coronal suture - where the frontal bone and parietal bone unite
• sagittal suture - where the two parietal bones unite
• lambdoidal suture - where the occipital and parietal bones unite
• Pterion - H shaped suture where the frontal, parietal, squamous part of the temporal and greater wing of sphenoid bones meet

Question 3

A fracture of the pterion endangers which structure and why?

Answer 3

The anterior branch of the middle meningeal artery (branch of the maxillary artery), it grooves the bone just deep to the pterion –> extradural haemorrhage

Question 4

Describe the temporal bone

Answer 4

Has several parts
- squamous part is flat, moulded to the brain contour, has 3 parts projecting off it
- zygomatic process anteriorly
- mastoid process posteriorly
- styloid process deep
Then have the petrous part of the temporal bone - wedge shaped, projects into the cavity

Question 5

Describe the sphenoid bone

Answer 5

Has a body and wings

• body has a depression “hypophysial fossa” where the pituitary gland sits
• split between the greater and lesser wings is the “superior orbital fissure”

Question 6

What makes up the anterior cranial fossa?

Answer 6

The horizontal plane of the frontal bone and the lesser wing of sphenoid, contains the frontal lobe

Question 7

What makes up the middle cranial fossa?

Answer 7

Greater wings of sphenoid anteriorly and the petrous part of the temporal bone posteriorly, contains the temporal lobe

Question 8

What makes up the posterior cranial fossa?

Answer 8

Petrous part of the temporal bone to the occipital bone, contains the cerebellum

Question 9

What are the meninges?

Answer 9

3 connective tissue layers - dura, arachnoid and pia mater
Dura mater - outer tough, fibrous layer
Arachnoid mater - intermediate layer, much more delicate, lines the internal surface of the dura
Pia mater - most delicate, very hard to peel away from brain tissue

Question 10

What are the spaces between the meninges?

Answer 10

Extradural space - between the skull and the dura (potential space, can get a [typically arterial] bleed here)
Subdural space - between the dura and arachnoid mater (potential space can get a [typically venous] bleed here)
Subarachnoid space - where the CSF circulates

Question 11

What are the projections of the dura into the cranial cavity and what is their purpose?

Answer 11

Lodge between the major subdivisions, function to restrict rotatory displacement of the brain.

• Falx cerebri lies in the sagittal plane immediately between the sagittal suture, between the L and R hemispheres, attached to the EOP posteriorly
• Tentorium cerebri comes from behind in an almost horizontal plane, grooves in the posterior cranial fossa, separates the cerebellum and cerebrum
• Falx cerebelli lodges between the L and R cerebellar hemispheres
• Diaphragma sellae grooves in the pit in the body of the sphenoid, dural diaphragm

Question 12

What are the dural venous sinuses?

Answer 12

Endothelial lined spaces where the outer and inner layers of dura have split to form a dural partition, contains venous blood from the brain and from bone (diploic veins) and emissary veins (from the scalp)

Question 13

What are the sinuses/the course of venous drainage of the skull?

Answer 13

• Superior sagittal sinus running in the root at the attachment of the falx cerebri
• Inferior sagittal sinus at the free inferior margin, joins with the great cerebral vein
• changes its name to become the straight sinus, running along the line where the falx cerebri and tentorium cerebelli meet

Question 14

What is the confluence of sinuses?

Answer 14

Where the straight sinus and the superior sagittal sinus mix on the internal aspect of the EOP
- from here get the development of the transverse sinus in the root of the tentorium cerebelli

Question 15

What is the course of the transverse sinus?

Answer 15

Tracks along the posterior wall of the posterior cranial fossa, snakes out as an S shape and becomes the sigmoid sinus at the petrous part of the temporal bone, down to the jugular foramen and out here to become the jugular vein

Question 16

What is the cavernous sinus?

Answer 16

A pair of sinuses, one on each side of the lateral aspect of the body of sphenoid

• receive blood from the cerebral, ophthalmic and emissary veins of the face –> very important venous connections
• structures that are heading for the superior orbital fissure pass through or in the lateral wall of the cavernous sinus

Question 17

What is the arterial supply to the bones and dura of the skull?

Answer 17

Many small meningeal arteries

• most important is the middle meningeal, branch of the maxillary artery (external carotid)
• enters the skull through foramen spinosum, spans out and splits into anterior and posterior branches that groove the internal surface

Question 18

What is the structure of the scalp by layers?

Answer 18

S - skin
C - dense connective tissue (neurovascular plane)
A - aponeurosis (between frontalis and occipitalis)
L - loose connective tissue (crosshatched, allows movement
P - pericranium

Question 19

Why do scalp wounds gape? How do you close them?

Answer 19

Frontalis and occipitalis pull in opposite directions

• arteries are attached to the fibrous septa - holds these open and doesn’t allow clotting to take place
• bandage around the head, compress the input

Question 20

What is the venous drainage of the scalp?

Answer 20

Emissary veins come from the connective tissue layer and join the diploic veins to drain through the venous sinuses
- IMPORTANT to treat an infected scalp wound because otherwise infection can travel –> meningitis, encephalitis

Question 21

What are the principles of the muscles of facial expression?

Answer 21

All arise from bone or fascia and all attach to the skin of the face. All surround a facial orifice, and are divided into muscles that encircle those orifices and act as sphincters or radiate out from those orifices to act as dilators

Question 22

What is the developmental origin and nerve supply of the muscles of facial expression?

Answer 22

They arise from the 2nd pharyngeal arch and are supplied by the facial nerve (CNVII)

Question 23

What is the innervation to the scalp and face anterior to the ears?

Answer 23

Cutaneous supply by CNV

• ophthalmic division to tip of nose
• maxillary division to top lip
• mandibular division

Question 24

What is the innervation to the scalp behind the ears?

Answer 24

Dorsal rami of cervical spinal nerves (C2 back of the head, C3 cervical collar, C4 is shoulder tip)

Question 25

What is different about C1?

Answer 25

It has NO cutaneous distribution

Question 26

What is the vascular supply to the face and scalp?

Answer 26

Anastomosis between branches of the internal and external carotid

• internal carotid –> ophthalmic artery, supplies the central area of the forehead
• external carotid –> facial artery

Question 27

What is the course of the facial artery?

Answer 27

Arises in the neck, crosses the inferior border of the mandible and winds onto the face
- has a tortuous course, heading for the medial angle of the eye

Question 28

What is the vascular supply to the lateral and posterior part of the scalp?

Answer 28

Lateral - superficial temporal artery which passes over the zygomatic arch
Behind the ear - posterior auricular artery
Occipital region - occipital artery

Question 29

What is the venous drainage of the face?

Answer 29

Facial vein accompanies the facial artery

- runs posterior and slightly more superficial than the artery, and is straighter

Question 30

What is the parotid gland and where is it located?

Answer 30

A serous salivary gland, sits below the zygomatic arch, above the angle of the mandible, in front of the ear, behind one of the muscles of mastication and superficial to the styloid process. It is wrapped in parotid fascia –> infection can cause painful swelling

Question 31

What is the course of the parotid duct?

Answer 31

It emerges from the front of the gland onto masseter and disappears at the anterior border of masseter
- pierces buccinator and enters the oral cavity at the upper second molar

Question 32

What is the organisation within the parotid gland?

Answer 32

From superficial to deep:

1. Facial nerve
2. Retromandibular vein
3. External carotid artery

Question 33

What is the course of the facial nerve in the face?

Answer 33

Exits the stylomastoid foramen, gives a branch to occipitalis then enters the posteromedial surface of the parotid

• within the substance of the parotid forms a pexiform arrangement (pes anserinus)
• see 5 terminal branches emerging from the anterior surface (TZBMC)

Question 34

What is the retromandibular vein?

Answer 34

Formed within the parotid gland by the superficial temporal and maxillary veins joining

Question 35

What happens to the external carotid artery in the parotid?

Answer 35

Within the parotid it divides into its two terminal branches

- superficial temporal and maxillary