Osteology of Skull and structures of Eyes/Ears

Question 1

What are the boundaries of each cranial fossa?

Answer 1

A: Front of skull to Lesser Wing of Sphenoid
M: Lesser Wing to Petrous part of Temporal Bone

Question 2

What are the main bones and features of Anterior Cranial Fossa?

Answer 2

Ethmoid bone: Containing Cribriform Plate
Crista Galli (Attach apex to Falx Cerebri)

Question 3

What are the holes in the ACF?

Answer 3

Optic Canal, Cribriform Foramina

Question 4

What are the main bones and features of MCF?

Answer 4

Sella Turcica: Depression on sphenoid body containing pituitary gland
Meckel’s Cave: Site of Trigeminal nerve ganglion splitting into 3

Question 5

Holes of the MCF? (5)

Answer 5

SOF, Foramen Rotundum, Ovale, Spinosum, Lacerum

Question 6

What are the features and bones of Posterior Cranial Fossa?

Answer 6

Tentorium Cerebelli attaches to petrous part of temporal bone and ridge of occipital

Question 7

What are the holes of the PCF?

Answer 7

Hypoglossal Canal, Jugular Foramen, IAM, Foramen Magnum

Question 8

What component is found in each hole of PCF?

Answer 8

FM: Vertebral and Spinal Arteries, SC
HC: CN12, JF: CN9.10.11 and Jugular Vein
IAM: CN 6,7 (7 exits out Stylomastoid foramen)

Question 9

What are the other cranial nerve pathways?

Answer 9

CN1: Cribriform Foramina, CN2: Optic Canal
CN 3,4,5a,6: Superior Orbital Fissure
FR: 5b, FO: 5c, (FS: Middle meningeal)

Question 10

Which muscles do CN3 innervate and their action?

Answer 10

LPS: Elevate upper eyelid
SR: Elevation of eyeball
IR: Depression of eyeball
MR: Adducts eyeball
IO: Elevates, abducts and laterally rotate

Question 11

What does CN4 and CN6 innervate and action?

Answer 11

CN4: SO: Depress, abduct and med rotate
CN6: LR: Abducts eyeball

Question 12

Boundaries of each section of the ear?

Answer 12

External: EAM to Tympanic Membrane
Middle: TM to Lateral wall of Inner Ear
Inner: Middle Ear to IAM