Anatomy of the Skull and Face Flashcards
(35 cards)
What is the upper and lower part of the cranium called?
The upper part is the vault and the lower part is the floor
What joints are between the bones of the skull?
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
A fracture of the pterion endangers which structure and why?
The anterior branch of the middle meningeal artery (branch of the maxillary artery), it grooves the bone just deep to the pterion –> extradural haemorrhage
Describe the temporal bone
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
Describe the sphenoid bone
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”
What makes up the anterior cranial fossa?
The horizontal plane of the frontal bone and the lesser wing of sphenoid, contains the frontal lobe
What makes up the middle cranial fossa?
Greater wings of sphenoid anteriorly and the petrous part of the temporal bone posteriorly, contains the temporal lobe
What makes up the posterior cranial fossa?
Petrous part of the temporal bone to the occipital bone, contains the cerebellum
What are the meninges?
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
What are the spaces between the meninges?
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
What are the projections of the dura into the cranial cavity and what is their purpose?
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
What are the dural venous sinuses?
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)
What are the sinuses/the course of venous drainage of the skull?
- 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
What is the confluence of sinuses?
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
What is the course of the transverse sinus?
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
What is the cavernous sinus?
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
What is the arterial supply to the bones and dura of the skull?
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
What is the structure of the scalp by layers?
S - skin
C - dense connective tissue (neurovascular plane)
A - aponeurosis (between frontalis and occipitalis)
L - loose connective tissue (crosshatched, allows movement
P - pericranium
Why do scalp wounds gape? How do you close them?
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
What is the venous drainage of the scalp?
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
What are the principles of the muscles of facial expression?
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
What is the developmental origin and nerve supply of the muscles of facial expression?
They arise from the 2nd pharyngeal arch and are supplied by the facial nerve (CNVII)
What is the innervation to the scalp and face anterior to the ears?
Cutaneous supply by CNV
- ophthalmic division to tip of nose
- maxillary division to top lip
- mandibular division
What is the innervation to the scalp behind the ears?
Dorsal rami of cervical spinal nerves (C2 back of the head, C3 cervical collar, C4 is shoulder tip)
