Norma Verticalis (The View Of The Skull From Above)

This varies very much with different individuals, and may be nearly circular or a long oval. The T-shaped sutures of the large bones forming the vault is seen: the two parietal bones join in the middle line; and anteriorly, where the parietals join the frontal, and posteriorly, where the parietals join the occipital, are situated the openings called the anterior and posterior fontanelles, found on the head at birth. These are due to the ossification of the several bones not being complete.

Norma Basalis (the view of the base of the skull, without the mandible)

In front is seen the row of upper teeth, between them being the processes of the maxillae forming the roof of the mouth. Behind this is the sphenoid bone which, as it were, bolts together the whole skull underneath. The pterygoid plates, two on each side, hang down for the attachment of muscles, and the great wings of the sphenoid pass out on each side to articulate with the temporal bones. Articulating with the body of the sphenoid bone is the basilar process of the occipital bone, and behind this is seen the opening for the passage of the spinal cord. On each side of the opening are the prominent articular facets for articulation with the first vertebra. There are numerous foramina on the base of the skull for the passage of the cranial nerves.

Frontal bone

The Frontal bone consists of three parts: a frontal part, forming the forehead; an orbital part, forming the upper margins of the eye-sockets; and a nasal part which helps to form the bridge of the nose.

The frontal part is convex in both its diameters, most marked just above the orbital margins.

The orbital part consists of the two rounded margins, separated from one another by the nasal notch. At the inner third of the margin is a deep groove, or may be a foramen, for the passage of the supra-orbital nerve; the margins end in the external angular processes.

Fig. 39. - The External Base of the Skull.

1. Ant. Palatine Fossa

2. Post. Nasal Spine

3. Post. Border of Vomer

4. Facial Surf. of Sup. Maxilla

5. Hamular Process of Int. Pterygoid Plate of Sphenoid

6. Pterygoid Fossa

7. Ext. Pterygoid Plate

8. Zygomatic Process of Malar

9. Zygoma of Temporal

10. Pharyngeal Tubercle (pointer crosses Foram. Lacerum Med.)

11. Eustachian Groove

12. Groove for Chorda Tympani Nerve

13. Petrous Portion of Temporal (Origin of Levator Palati)

14. Carotid Foramen

15. Ext. Auditory Meatus

16. Ext. Auditory Process

17. Basion

18. Mastoid Process

19. Jugular Foramen

20. Ant. Condvlar Foramen

21. Digastric Groove

22. Occipital Groove

23. Post. Condvlar Foramen

24. Sup Curved Line of Occipital

25. Inf. Curved Line

26. Ext. Occipital Crest

27. Ext. Occipital Protuberance

28. Opisthion

29. Foramen Magnum

30, Right Occipital Condyle 31. Foram. Lacerum Medium at +

32. Vaginal Proc. of Tymp. Plate

33. Mastoid Foramen

34. Stylo-Mastoid Foramen

35. Styloid Process

36. Tympanic Plate (Post, part of Glenoid Fossa)

37. Spinous Proc. of Sphenoid

38. Ant. part of Glenoid Fossa 39.Foramen Spinosum

40. Foramen Ovale 41. Foramen Vesalii

42. Preglenoid Tubercle

43. Eminentia Articularis

44. Zygomatic Fossa

45. Infratemporal Crest

46. Temporal Division of Great Wing of Sphenoid

47. Spheno-Maxillary Fissure

48. 1uberosity of Sup. Maxilla

49. Ext. Access. Palat. Foramen

50. Post. Access. Palat. Foramen

51. Post. Palatine Foramen

52. Right Post. Naris (pointer crosses ridge for Tensor Palati)

53. Groove for Descend. Palat. Artery

54. Horiz. Plate of Palate Bone

55. Palat. Proc. of Sup. Maxilla

The nasal part is roughened and projects backwards for the articulations of the nasal bones and other bones which are inside the face.