Cranium and face
The skull has 22 bones. Eight form the cranium, the case around the brain, and fourteen form the face. All but one are locked together along seams called sutures. The mandible, the lower jaw, is the only one that moves. A man's cranium holds about 1.4 litres.
The skull from the front, with the bones of the face coloured, Gray's Anatomy, 1918, figure 190Wikimedia Commons, Henry Vandyke Carter, Public domain (Gray190.png)
The cranium's floor is pierced by holes for nerves and vessels. The largest, the foramen magnum, lets the spinal cord through to the brain.
Inside each temporal bone lie the three smallest bones of the body, the malleus, incus and stapes of the middle ear. They carry sound from the eardrum to the inner ear. The stapes is about 3 mm long. This model lacks them.
The three ossicles of the middle ear: the malleus, the incus and the stapesWikimedia Commons, Marc Giacone and Angelito7, CC BY-SA 3.0 (Auditory ossicles-en.svg)
Sources
- Susan Standring (ed.), Gray's Anatomy, 42nd ed. (2020), chapters on the skull and on the ear.
- Arthur Guyton and John Hall, Textbook of Medical Physiology, 13th ed. (2016), ch. 53.
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