vertebra

…one between each pair of vertebrae below the first cervical vertebra, or atlas, and above the second sacral vertrebra (just above the tailbone). The lumbar (lower back) disks are thickest, the thoracic (chest or upper back) are thinnest, and the cervical are of intermediate size. These differences are associated with…

Each vertebra, in higher vertebrates, consists of a ventral body, or centrum, surmounted by a Y-shaped neural arch. The arch extends a spinous process (projection) downward and backward that may be felt as a series of bumps down the back, and two transverse processes, one to…

…centrums, or bodies, of the vertebrae and the intervertebral disks—the tough, resilient pads between the vertebral bodies—while in back and on the sides the cord is enclosed and protected by the portion of each vertebra called the neural arch. Between the neural arches are sheets of elastic connective tissue, the…

…one or more of the vertebrae. Spondylitis takes several forms; the most widely occurring forms are ankylosing spondylitis, hypertrophic spondylitis, and tuberculous spondylitis.

…slipping of one of the vertebrae on the subjacent vertebra or on the sacrum, the triangular bone at the base of the spinal column. The most common vertebrae involved are the lumbar (lower back). The condition is often associated with degenerative joint disease or with abnormalities of the vertebral column,…

The vertebrae constituting the spinal column are generalized with centrums (i.e., ventral, or lower, sections connecting with the adjacent vertebrae) that are rather poorly developed. The notochord (i.e., a resilient, flexible cord of specialized cells passing through the vertebral column) is usually persistent in adults. An…

The number of vertebrae varies from 39 to 63, with remarkable variation (11 to 25) within the neck (cervical) series. The principal type of vertebral articulation is heterocoelous (saddle shaped). Each of the 3 to 10 (usually 5 to 8) chest (thoracic) vertebrae normally bears a pair of…

…the gill arches of primitive vertebrates, collectively termed the visceral skeleton. Visceral elements in the mammalian skeleton include the jaws, the hyoid apparatus supporting the tongue, and the auditory ossicles of the middle ear. The postcranial axial skeleton in mammals generally has remained rather conservative during the course of evolution.…

In mammals the vertebral centra articulate by means of intervertebral disks of fibrocartilage. Bony disks (epiphyses) formed on the generally flat ends of the centra are characteristic of mammals. Regional differentiation in the mammalian backbone is marked. The number of vertebrae in each group, excepting the caudal vertebrae,…

The vertebral column of snakes is highly elongated and has more vertebrae than any other living animal—up to 600 in the Australian python (Morelia oenpelliensis). Since there are no limb girdles associated with the skeleton, there are no good delimiters of regions, but snakes…