skull

—skull-less, adj. —skull-like, adj.

/skul/, n.

1. the bony framework of the head, enclosing the brain and supporting the face; the skeleton of the head.

2. the head as the center of knowledge and understanding; mind: to get literature's great ideas through our skulls.

3. Armor. the part of a helmet that covers the top of the head.

4. out of one's skull, Slang. crazy; demented.

[1175-1225; ME scolle < ON skalli]

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Skeletal framework of the head.

With the exception of the lower jaw, its bones meet in immovable joints (sutures) to form a unit that encloses and protects the brain and sense organs and gives shape to the face. The cranium, the upper part enclosing the brain, comprising the frontal, parietal, occipital, temporal, sphenoid, and ethmoid bones, is globular and relatively large compared to the facial portion. Its base has an opening through which the spinal cord connects to the brain. The skull sits on the top vertebra (atlas), which permits back-and-forth motion. For side-to-side motion, the atlas turns on the next vertebra (axis). See also craniosynostosis, fontanel.

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▪ anatomy

 skeletal framework of the head of vertebrates, composed of bones or cartilage, which form a unit that protects the brain and some sense organs. The upper jaw, but not the lower, is part of the skull. The human cranium, the part that contains the brain, is globular and relatively large in comparison with the face. In most other animals the facial portion of the skull, including the upper teeth and the nose, is larger than the cranium. In humans the skull is supported by the highest vertebra, called the atlas, permitting nodding motion. The atlas turns on the next-lower vertebra, the axis, to allow for side-to-side motion.

 In humans the base of the cranium is the occipital bone (occipital), which has a central opening (foramen magnum) to admit the spinal cord. The parietal (parietal bone) and temporal bones form the sides and uppermost portion of the dome of the cranium, and the frontal bone forms the forehead; the cranial floor consists of the sphenoid and ethmoid bones. The facial area includes the zygomatic (zygomatic bone), or malar, bones (cheekbones), which join with the temporal and maxillary bones to form the zygomatic arch below the eye socket; the palatine bone; and the maxillary, or upper jaw, bones. The nasal cavity is formed by the vomer and the nasal, lachrymal, and turbinate (nasal concha) bones. In infants the sutures (joints) between the various skull elements are loose, but with age they fuse together. Many mammals, such as the dog, have a sagittal crest down the centre of the skull; this provides an extra attachment site for the temporal muscles, which close the jaws.

 

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