Bones - Occipital Bone

Question 1

External surface of the occipital bone

Bony landmarks?

Answer 1

1) External occipital proturberance - posterior of the head - origin site for the trapezius and the nuchal ligament.
2) Occipital condyles - located anteromedially to the foramen magnum - articulates with the superior articular facets of the atlas.
3) Occipital fossae - located posterior to the condyles - accomodates the superior articular facets during head extension.
4) Pharyngeal tubercle - located on the anterior margin of foramen magnum - serves as an attachment point of the pharyngeal raphe.

Question 2

Internal surface of the occipital bone

Bony landmarks?

Foramina?

Surfaces?

Answer 2

1) Internal occipital proturberance - internal aspect of the basal occipital bone - located in the centre of the cruciform eminence (divides the deeply concave internal surface of the occipital bone into four fossae)
2) Groove for the transverse sinus - extends laterally from the cruciate eminence
3) Groove for the superior sinus - extends superiorly from the cruciate eminence.
4) Groove for the sigmoid sinus - located laterally to the foramen magnum
5) Internal occipital crest - descends inferiorly from the centre of the cruciate eminence - separates the left and right cerebellar fossae and provides the attachment for the falx cerebri.
6) Foramen magnum - large opening - a number of structure passes through:
i) Medulla
ii) Meninges
iii) Vertebral arteries
iv) Anterior and posterior spinal arteries
v) Dural veins

Surfaces:

1) Basilar (clivus part) - located anterior to the foramen magnum.
2) Squamous - located posterior to the foramen magnum.