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1 Name the arrowed structure.

2 Name the arrowed structure.

3 Name the arrowed structure.

4 Name the arrowed structure.

5 Name the arrowed structure.

Answers

1 Dorsum sellae.

2 Cerebellar tonsil.

3 Basion.

4 Clivus.

5 Pituitary infundibulum.

Comments:

The sella turcica (also known as the hypophyseal or pituitary fossa) is a hollow in the sphenoid bone which contains the pituitary gland. The anterior boundary of the pituitary fossa is the tuberculum sellae, above which are two small processes called the anterior clinoid processes. The posterior boundary of the pituitary fossa is the dorsum sellae (‘back of the seat’), which is continuous inferiorly with the clivus. Two processes at top of the dorsum sellae are known as the posterior clinoid processes.

The clivus is a backward-sloping structure in the skull base which is formed by part of the sphenoid bone superiorly and part of the occipital bone inferiorly. Posterior to the clivus sits the basilar artery and the pons. The inferior tip of the clivus is an anatomical landmark known as the basion—this is the anterior margin of the foramen magnum.

Exam tip:

 On a T1-weighted MRI, the posterior part of the pituitary gland (neurohypothysis) is brighter than the anterior pituitary (adenohypothysis).