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Skull Anatomy Flashcards

1
Q

identify pterion

A

The pterion is the H-shaped junction on the lateral skull where four bones meet:

Frontal - Anterosuperior
Parietal - Posterosuperior
Temporal (squamous part) - Inferior
Sphenoid (greater wing) - Anteroinferior

About 3–4 cm above the zygomatic arch

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2
Q

relevance of pterion

A

It is the thinnest part of the skull.

Lies directly over the anterior division of the middle meningeal artery (MMA).

Fracture at the pterion can lacerate the MMA → leads to a life-threatening extradural hematoma (Lucid interval, rapid deterioration)

Surgical access - Used as landmark in craniotomies

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3
Q

layers encountered pterion burr hole

A

SCALP and temporalis muscle

skin
connective tissue
aponeurosis of occipitofrontalis muscle
loose areolar tissue
temporalis muscle
periosteum

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4
Q

identify coronal suture

A

The coronal suture is the joint between the frontal and parietal bones.

It runs transversely across the skull

The coronal suture appears as a thin radiolucent line (dark line on the X-ray image) between the frontal and parietal bones.

The suture is typically straight and smooth on a normal X-ray.

Fractures across the coronal suture (especially in trauma) can involve the dura mater, potentially leading to complications like epidural hematoma.

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5
Q

age cranial sutures ossify by

A

18-24 years

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6
Q

what is it called if cranial sutures are fused at birth?

A

Craniosynostosis is the premature fusion of one or more cranial sutures, leading to abnormal skull shape and potentially raised intracranial pressure (ICP).

sagittal suture is the most common

causes more expansion at other stures and abnormal skull shape

cranial vault remodelling usually performed before 12 months

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7
Q

when does the mastoid bone develop

A

2 years

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8
Q

what are the diploic veins?

A

veins found in the skull that drain the diploic space to the dural venous sinus

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9
Q

tear to which vessel might cause subdural haematoma

A

cerebral and bridging veins

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10
Q

dural venous sinuses

A

These are valveless endothelial-lined channels between layers of dura mater that drain venous blood from the brain, meninges, and skull into the internal jugular vein.

superior sagital sinus
inferior sagital sinus
stright sinus
transverse sinus
sigmoid sinus
cavernous sinus
occipital sinus

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11
Q

clinical relevance of dural venous sinuses

A

Site of thrombosis (e.g. sagittal sinus), infection spread from face (“danger triangle”)

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12
Q

diploic veins

A

These are valveless veins located within the diploë (spongy bone between inner and outer skull tables) that communicate with both scalp veins and dural sinuses.

The diploic and emissary veins provide a route for extracranial infections to reach dural sinuses → potential for cavernous sinus thrombosis.

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13
Q

type of joint temporomandibular

A

bi-arthrodial hinge joint (synovial)

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14
Q

articulating surfaces of TMJ

A

head of mandible
mandibular fossa of the temporal bone
articular tibercle of squamous temporal

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15
Q

movements of TMJ

A

elevation
depression
protrusion
retraction
side to side

opening = depression and protrusion.

DLGM - digastric, lateral pterygoid, geniohyoid, myloghyoid

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16
Q

muscles of mastication

A

masseter
temporalis
lateral and medial pterygoid

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17
Q

muscles opening the mouth

A

DLGM

digastric
lateral pterygoid
geniohyoid
mylohyoid

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18
Q

ethmoidal sinus

A

The ethmoidal sinuses (or ethmoid air cells) are a group of small air-filled cavities within the ethmoid bone, located between the nose and the orbits.

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19
Q

foramen ovale

A

OVALE

otic ganglion
v3 (mandibular nerve, 3rd branch of trigeminal)
Accessory meningeal artery
Lesser petrosal nerve
Emissary veins

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20
Q

lesser petrosal nerve

A

preganglionic parasympathetic

synapses in otic ganglion

stimulate saliva production parotid gland

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21
Q

foramen spinosum

A

middle meningeal artery

meningeal branch of the mandibular nerve

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22
Q

foramen rotundum

A

maxillary nerve

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23
Q

foramen lacerum

A

ICA (passes along superior surface, doesn’t traverse it)

nerve and artery of the pterygoid canal (greater petrosal)

24
Q

optic canal

A

medial to the anterior clinoid process, lies the optic canal CN 2 traverses the optic canal.

optic nerve and 3 layers of dura
ophthalmic artery
sympathetic nerves

25
why is meningeal infection seen as papilloedema
3 layers of dura around optic nerve pass through optic canal
26
superior orbital fissure
lateral to the optic canal (anterior to the clnioid process) sphenoid bone lacrimal branch of ophthalmic (CNV1) frontal branch of opthalmic nerve nasociliary branch of ophthalmic nerve ophthalmic vein trochlear (CN4) occulomotor (CN3) abducens (CN6)
27
carotid canal
sympathetic plexus internal carotid deep petrosal emissary vein doesn't pass straight upwards, takes a 90degree turn within petrous temporal bone to open into foramen lacerum
28
jugular foramen
inferior petrosal sinus glossopharyngeal, vagus, accessory nerves (CN. IV,X,XI) sigmoid sinus - IJV
29
stylomastoid foramen
stylomastoid artery facial nerve
30
foramen magnum
vertebral arteries spinal arteries medulla dens ligament
31
cranial fossa in the sphenoid bone
foramen ovale foramen spinosum rotundum lacerum optic canal SOF
32
cranial fossa in temporal bone
carotid canal jugular foramen stylomastoid foramen internal acoustic meatus
33
cranial fossa in occipital bone
foramen magnum hypoglossal canal
34
tegmen tympani
separate the inner ear from the cranial cavity
35
what is the cranial nerve track on the clivus
abducens
36
cribiform plate
Within the ethmoid bone, lie the foramina of the cribriform plate. They contain CN 1, the olfactory nerve bundles.
37
name of the juvenile structure that makes the clivus
spheno-occipital synchrodosis
38
benign tumours of the posterior cranial fossa
hemangioblastoma acoustic neuroma ependyoma ependymoblastoma
39
muscles attached to the styloidprocess
styloglossus stylohyoid stylopharyngeus
40
lytic skull lesions
lytic mets multiple myeloma paget's sarcoidosis osteomyelitis haemangioma
41
boundaries middle cranial fossa
anterior - lesser wing cranial fossa, anterior clinoid process posterior - petrous part temporal bone, dorsum sellae lateral - squamous part temporal bone
42
contents middel cranial fossa
temporal lobe
43
boundaries posterior cranial fossa
anterior - apex of the petrous part of the temporal bone posterior - occipital bone lateral - squamous and mastoid parts of temporal bone
44
bones forming posterior cranial fossa
occipital and temporal bones
45
cavernous sinuses
2 cavernous sinuse lying laterally either side of the sella turnica
46
where do the cavernous sinuses drain blood from
superior opthalmic veins facial vein emissary veins from pterygoid plxeus sphenoparietal sinuses
47
where does the blood drain to from the cavernous sinus
superioer and inferior petrosal sinuses IJV intercavernous sinus
48
clinical significance of cavernous sinus
cavernous sinus thrombosis - due to infections from the dangerous area of the face(drained by the ophthamlic and facial veins) may spread to the cavernous sinus as the draining veins are valveless
49
signs of cavernous sinus thrombosis
painful swelling of the eye 3,4,5,6 nerve palsy gradual vision loss abducens most vulnerable due to central location CSS typically presents unilaterally, with: Ophthalmoplegia: Due to CN III, IV, and VI involvement Ptosis (CN III) Diplopia Horner’s syndrome (partial): Miosis, ptosis — from sympathetic fiber involvement Facial sensory loss: CN V1 (forehead, upper eyelid) CN V2 (cheek, upper lip) Proptosis / chemosis / conjunctival injection: From venous congestion Possible visual loss (if optic chiasm or orbital apex is involved)
50
causes of cavernous sinus syndrome
caverous sinus tumours most common cause - Pituitary adenoma, meningioma, metastases, lymphoma
51
what is the major vein draining the brain parenchyma
great cerebral vein
52
describe the blood flow from the superior sagittal sinus to the IJV
Superior Sagittal Sinus ↓ Confluence of Sinuses ↓ Transverse Sinus (→ typically right) ↓ Sigmoid Sinus ↓ Internal Jugular Vein Superior Sagittal Sinus (SSS) Runs along the attached margin of the falx cerebri, draining blood from the cerebral hemispheres.Flows posteriorly. Confluence of Sinuses Located at the internal occipital protuberance. Receives blood from: Superior sagittal sinus Straight sinus Occipital sinus Not all blood mixes here equally — there's often flow preference (SSS → right transverse sinus, straight sinus → left). Transverse Sinus (usually right side for SSS) Runs laterally in the attached margin of the tentorium cerebelli. Becomes the sigmoid sinus. Sigmoid Sinus S-shaped curve descending through the posterior cranial fossa. Exits the skull via the jugular foramen. Internal Jugular Vein (IJV) Formed as the sigmoid sinus exits the cranium. Continues down the neck, eventually joining the subclavian vein to form the brachiocephalic vein → SVC.
53
location of straight sinus
tentorium cerebelli
54
blood supply to the temporalis muscles
maxillary artery
55

MRCS (26 decks)

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