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At the base of the skull, the backbone begins. The skull is supported by the topmost cervical (neck) vertebra. The curious thing about a backbone is that the word has come to suggest something solid, straight, and unbending.
The back, however, just isn't like that: it consists of 26 knobby, hollowed-out bones- vertebrae, rather improbably held together by muscles, ligaments, and tendons. Is is not straight when we stand, but has definite backward and forward curvatures; and even some of its most important structures (the disk between the vertebrae) aren't made of bone, but of cartilage.
All in all, however, the backbone is fairly well designed structure in term of several different functions it serves- but with some built-in weaknesses.
The next post will further explain about The Vertebrae.
The hardest substance in the human body is the enamel that covers the exposed surface of a tooth. Below the gum, the tooth's outside surface is composed of somewhat softer cementum. Beneath enamel and cementum is a bonelike substance, call dentin, which covers the soft interior of the tooth, called pulp. Pulp is serviced by blood vessels and nerves through the root or roots of the tooth. The passageway of nerves and blood vessels that lead up through the tooth from the gum sockets is called a root canal. Tooth and gum are stuck to each other by a tough, adhesive tissue called periodontal (or peridental- "surrounding the tooth") membrane.
The bones of the skull have as their most important function the protection of the brain and sense organs. There are also, of course, the jawbones that support the teeth and gums and which enables us to bite and chew our food.
Most of the skull appears to consist of a single bone- a hard, unbroken dome. Actually, the brain cage or cranium consists of eight individual platelike bones which have fused together in the process of growth. At birth, these bones are separated, causing the soft spots of fontanelles we can readily feel on a baby's head. As the baby's brain enlarges, the bones grows along their edges to fill in the fontanelles, finally knitting together in what are called suture lines, somewhat resembling inexpertly mended clothes seams. Along the suture lines, the skull bones continue to grow until the individual's mature skull size is reached.
Most of the skull appears to consist of a single bone- a hard, unbroken dome. Actually, the brain cage or cranium consists of eight individual platelike bones which have fused together in the process of growth. At birth, these bones are separated, causing the soft spots of fontanelles we can readily feel on a baby's head. As the baby's brain enlarges, the bones grows along their edges to fill in the fontanelles, finally knitting together in what are called suture lines, somewhat resembling inexpertly mended clothes seams. Along the suture lines, the skull bones continue to grow until the individual's mature skull size is reached.
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