This presentation deals with description of the normas: verticalis, occipitalis, lateralis, frontalis and basalis. There is another presentation “Skull – inside and some separate bones” to complete the objectives. Objectives  Identify the features of the major bones forming the cranial cavity according to normas and separate bones.  Describe the major sutures.  Describe the structure of the flat bones forming the skull and their blood supply.  Discuss ossification of the skull and the changes that occur during postnatal development.  Locate important bony surface landmarks.

1. Anatomy of the skull (1) Dr. Akram Jaffar Ph.D.

4. Features of the flat bones of the skull The flat bones of the skull consist of a sandwich of cancellous bone (diploe) (G., diploos = double) between two layers of compact bone so they are extremely strong. As the diploe contains a red bone marrow it is drained by large veins (the diploic veins), which open into the nearest venous sinus. There are no accompanying diploic arteries as the blood supply of the bones of the skull is derived from the meningeal arteries Diploic veins The emissary veins connect the veins of the scalp with the dural venous sinuses inside the skull and are obviously a possible route for the spread of infection. Emissary veins

6. Primary craniosynostosis Premature closure of the sutures of the skull results in skull deformities. When premature closure of the coronal or the lambdoid suture occurs on one side only, the skull is twisted and asymmetrical. The type of deformed skull that forms depends on which sutures close prematurely. Premature closure of the sagittal suture, results in a long, narrow, and wedge-shaped skull.

10. The normas Five views of the exterior of the skull are used in anatomical descriptions, each is spoken of as a norma Norma verticalis Norma frontalis Norma lateralis Norma basalis Norma occipitalis

11. Norma verticalis

19. Parietal foramen Transmits a small emissary vein from the superior sagittal sinus. Pierces each parietal bone near the sagittal suture.

23. Norma occipitalis

32. Mastoid emissary foramen The mastoid foramen is near or in the occipitomastoid suture. The mastoid foramen transmits an emissary vein from the sigmoid sinus

33. Norma lateralis

47. Groove for the middle temporal artery The middle temporal artery , a branch of the superficial temporal artery, pierces the fascia and runs up vertically deep to temporalis. The middle temporal artery produces a vertical groove on the squamous part of the temporal bone

48. Radiographic point This is a convenient place to mention that the auricle of the ear can be seen as a semicircular shadow on the lateral skull x-ray. 6 months

49. Norma frontalis

53. Supraorbital foramen Supraorbital foramen and notch The supratrochlear foramen, usually a notch medial to the supraorbital foramen

54. Infraorbital foramen Double foramen Transmits a nerve and vessels of the same name

55. Mental foramen The mental foramen is in line with the longitudinal axis of the 2 nd premolar tooth Transmits a nerve and vessels of the same name

58. Norma basalis

62. Norma basalis (the base of the skull) ovale spinosum carotid jugular Stylomastoid lacerum The foramen ovale lies in front of spinosum; both in the greater wing of the sphenoid