Anatomy of the skull

Question 1

Hw many bones make up the cranium

Answer 1

8 bones
x1 frontal
x2 parietal
x2 temporal
x1 sphenoid
x1 ethmoid
x1 occipital

Question 2

How many bones make up the facial bones

Answer 2

14 bones
x2 lacrimal
x2 zygomatic
x2 maxillae
x2 nasal
x1 vomer
x2 palatine bones
x2 infrior conchae
x1 mandibular
(only to bones are singular)

Question 3

What are the boundaris of the orbit

Answer 3

Superiorly - frontal boe
Medially - processes of maxilla and frontal bone
Laterally - zygomatic
Inferiorly - maxillae

Question 4

how mny formaina are present in in the maxilla, zygomatic and mandibular bones

Answer 4

maxilla - x2 nferaorbital foramen

zygomatic - x2 each - zygomaticofacial and zygomaticotemporal nerves pass through them

mandible - x2 mental foramen

Question 5

Whereis the infraorbital fissure located

Answer 5

between the greater wing of the sphenoid and the maxilla

Question 6

What are the communications fo the pterygopalatine fossa?

Answer 6

Superiorly - skull (middle craniak fssa) via foramen rotundum

Laterally - infratemporal fossa via the pterygopalatine fissure

medially - sphenopalatine foramen into the nasal cavaity

anteriorly - orbit via the inferaorbital fissure

Question 7

Where are foramen rotundum, foramen ovale and foramen spinosum located and what do they transmit?

Answer 7

F.rotundum - base of greater wing of sphenoid. Allows communcation with the PTG fossa. Transmit maxillary nerve from trigeminal ganglion to PTG fossa

F.ovale - posterio-lateral to F.rotundum in the middle crainal fossa in teh greater wing of sphenoid. Transmits the mandibular nerve (CN V3 - large and small route), accessory meningeal artery and the superficial/lesser petrosal nerve

F. spinosum - lateral to F.ovale in greater wing of sphenoid. Transmits middle meningeal artery and meningeal branches of CN V3

Question 8

Where is F.lacerum located and what does it transmit

Answer 8

petrous part of the temporal bone. Carotid canal open into its side and transmits the internal carotid artery and the greater petrosal nerve (facial nerve branch)

Question 9

What are the boundaries of the anterior, middle and posterior crainal fossa

Answer 9

Anterior - frontal bone (ant), lesser wing of sphenoid (post)

Middle - lesser wing of sphenoid (ant), petrous temporal bone (post), squamous temp bone/greater sphenoid) (lat). Sphenoid bone (med)

Posterior - petrous part of temporal bone (ant), squamous part of occipital bone (post), tentoriu cerebelli (roof)

Question 10

The superior orbital fissure transmits which nerves and other structure?

Answer 10

• oculomotor (CNIII)
• trochlear (CNIV)
• Frontal&lacrimal (CN V1 branches)
• abducent

+ superior orbital vein

Question 11

Where is the groove for the trigeminal ganglion located?

Answer 11

Petrous part of teh temporal bone, lateral to F.lacerum.

Question 12

What structures pass through the lateral wall of the cavernous sinus? and which structures pass directly through?

Answer 12

Lateral wall - CN III, IV V1 and V2

Directly: CN IV and ICA

Question 13

What five structures does the jugular foramen transmit?

Answer 13

Anterior to posterior:
inferior petrosal sinus
Nerves: CN IX, X, XI
large sigmoid sinus

Question 14

What does the internal acoustic meatus transmit?

Answer 14

CN VIII (vestibulocochlear nerve) and motor and sensory roots of the facial nerve

Question 15

What are the two layers of dura

Answer 15

endosteal layer - periosteum of bone. Continuous with sutual ligaments. does not extend through F.magnum

meningeal layer - continuous with epineurium of nerves. does extend through F. magnum. Layer gives rie to four septa to limit rotational movement of the brain

Question 16

What are the attachments of the four septa produced by the meningeal layer of the dura mata

Answer 16

falx cerebri - crista galli (ant), tentorium cerebelli. superior and inferior sagital sinus. Straight sinus runs along attachment to t.cerebelli.

tenroium cerebelli - tentorial notch. Fixed border at and posterior cliniod processes (ant), petrous temp bone (lat). free border runs froward to attach at anterior clinoid processes. Where it crosses the fixed border- CN 3/4 pass forward to enter cavernous sinus. Straight sinus runs along attachment to f.cerebri. Superior petrosal sinus runs along attachment to petrous temp bone. Transverse sinus along attachment to occipital bone

falx cerebelli - internal occipital crest (post), runs between cerebella hemispheres. Occipital sinus runs along its posterior margin

diagragma sellae - rood of sella turcia

Question 17

Sensory stimulation of nerve endings of teh trigeminal nerve above and below the level of the tentorium cerebelli proced what kind of referred pain

Answer 17

superior to the tentorium cereblli - referred pain to the head and face on the same side

inferior to the tentorium cerebelli - back of the neck and scalp along the distribution of the greater occipital nerve

Question 18

What s the course of the middle meningeal artery?

Answer 18

arised form maxiallary artery in the inferotemporal fossa –> along teh squamous part of teh temporal bone –> enters F.spinosum to lie betwen meningeal and endosteal layer of dura. splits into anterior and posterior branch - anterior branch following anterio-inferior along teh parietal bone and posterior curving backwards to supply endosteal layer of dura

Question 19

subconjunctival haemorrhage in trauma - why woudl you be concerns

Answer 19

Fractures i the orbitl plate of the frontal bone result in haemorrhage beneath the conjunctiva and into the orbital cavity causing exophthalmous

Question 20

Which fossa of the skull is most likely to fracture

Answer 20

Middle cranial fosa - weakest due to all the foramia passing through it

Question 21

When is the chondrocranimum formed

Answer 21

3-4 month of brenatal life

chondrocranium is when the cartilaginous part of the neurocranium is unified to form the base of the skull

other section of neurocranium is the membranous part which forms the large flatetr bones eg. frontal, temporal etc.

Question 22

When do the anterior and posterior fontonelles close

Answer 22

Anterior - by 18 months

Posterior - by one year

Question 23

What is hypertelorism

Answer 23

when the eyes are widely separated because of overgrowth of the lesser wing of the sphenoid

Question 24

Describe the following congenital abnormalities

Cranuoschisis

Parietal foramina

craniosyntosis

Plagiocephaly

Answer 24

cranioschisis - vault of the skull open. associated with anencephaly

parietal foramina - dominant inheritance causing foramina to develop in parietal bone

craniosyntosis - premature future of cranial sutures causing abnormal head shape Can lead to increased CSF pressure and learning disabilities

Plagiocephaly - asymmetric head because of irregular fusion of the cranial bones. Normal child development, abnormal shape not caused by complications of delivery

Question 25

What is the problem with a striaght posterioanterior x-ray of the skull from an eye perspective

Answer 25

petrous part of temporal bone is superimposed on lower half of teh orbit

Question 26

Why type of x-ray would you order to view the: frontal and ethmoidal sinuses

Answer 26

posteronterior