4. Squamous part Basilar part two Condylar parts

5. The squamous part the most posterior part of the vault and the base of the skull and the middle of the posterior edge of the foramen magnum

6. The external occipital crest passes from the posterior edge of the foramen magnum to the external occipital protuberance

7. The external occipital protuberance a roughened elevation and located at the middle of superior nuchal line

8. superior nuchal line inferior nuchal line

9. un upper and lower pair of fossa separated from each other by the groove for the transverse sinus

10. The internal occipital protuberance at the middle of the transverse sinus upwards the sagittal groove downwards the internal occipital crest.

11. anteriorly with the parietal bone at the lambdoid suture and laterally articulates with the mastoid process

12. The basilar part the anterior edge of the foramen magnum and extended upwards in the base of the skull to meet the body of the sphenoid bone

13. Laterally it articulates with the petrous part of the temporal bone.

14. The inferior surface of the basilar part has a small prominence called pharyngeal tubercle.

15. The two condylar parts the most of the lateral edge of the foramen magnum

16. The occipital condyle on its inferior surface

17. The condyles are elliptical in shape and diverge as they pass backwards The lower surface of each condyle is everted and convex from before backwards and from side-to-side

18. the superior aspect of the lateral mass of the 1st cervical vertebra (the atlas)

19. The hypoglossal canal the hypoglossal nerve is above the anterior part of the condyle

20. The jugular process The anterior edge of that part of bone lateral to the condyle

21. the jugular foramen jugular process formed the posterior boundary

22. The jugular tubercle On the upper surface between the anterior part of the jugular foramen and the hypoglossal canal Laterally the condylar part fused with the posterior part of the temporal bone.

23. Laterally the condylar part fused with the posterior part of the temporal bone.

24. The condylar part is deeply grooved on its upper surface by the termination of the sigmoid sinus.