Occipital

Question 1

Squamous Portion

Answer 1

This is the largest portion. It consists of the large plate bone posterior and superior to the foramen magnum.

Question 2

Condylar (Lateral) Portion

Answer 2

This lies to either side of the foramen magnum, articulating with the temporals.

Question 3

Basilar Portion

Answer 3

This is the thick, square projection anterior to the foramen magnum. This articulates with the petrous portions of both temporals and with the sphenoid suture.

Question 4

External Occipital Protuberance

Answer 4

Lies on the ectocranial midline where the occipital and nachal planes meet. Highly variable in appearance, it’s heavier and more prominent in male individuals.

Question 5

Lambdoid Suture

Answer 5

Passes between the two parietals and the occipital.

Question 6

Superior Nuchal Line

Answer 6

These lie to either side of the midline on the ectocranial surface of the squamous portion. The nuchal and occipital planes merge at these superiorly convex lines.

Question 7

Inferior Nuchal Line

Answer 7

Parallel to the superior nuchal lines but are located about midway on the ectocranial nuchal plane.

Question 8

External Occipital Crest

Answer 8

This is a highly variable median line or crest that passes between the right and left nuchal musculature.

Question 9

Transverse Sulcus

Answer 9

Form the transverse arms of the cruciform eminence. The one on the right is usually larger and communicates directly with the sagittal sulcus.

Question 10

Cruciform Eminence

Answer 10

This defends the endocranial surface of the occipital squama into four fossae. It’s so need due to its cross shape.

Question 11

Sagittal Sulcus

Answer 11

Passes superiorly from the internal occipital protuberance. It is a deep endocranial groove marking the posterior extention of the sagittal sinus.

Question 12

Internal Occipital Crest

Answer 12

The inferior arm of the cruciform eminence.

Question 13

Cerebral Fossae

Answer 13

These are triangular depressions below the lambdoid suture on the endocranial suture of the occipital bone.

Question 14

Cerebellar Fossae

Answer 14

This occupies the inferior part of the endocranial surface of the occipital squama.

Question 15

Condyloid Fossae

Answer 15

Endocranial depressions immediately posterior to the condyles.

Question 16

Occipital Condyles

Answer 16

These are raised oval structures on either side of the foramen magnum, their inferior surfaces are convex.