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The number of vertebrae in a region can vary but overall the number remains the same. In a human spinal column, there are normally 33 vertebrae. [3] The upper 24 pre-sacral vertebrae are articulating and separated from each other by intervertebral discs, and the lower nine are fused in adults, five in the sacrum and four in the coccyx, or tailbone.
Various bones of the human skeletal system. The axial skeleton , comprising the spine, chest and head, contains 80 bones. The appendicular skeleton , comprising the arms and legs, including the shoulder and pelvic girdles, contains 126 bones, bringing the total for the entire skeleton to 206 bones.
The number of thoracic vertebrae varies considerably across the species. [31] Most marsupials have thirteen, but koalas only have eleven. [32] The usual number is twelve to fifteen in mammals, (twelve in the human), though there are from eighteen to twenty in the horse, tapir, rhinoceros and elephant.
In human anatomy, the five vertebrae are between the rib cage and the pelvis.They are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse process (since it is only found in the cervical region) and by the absence of facets on the sides of the body (as found only in the thoracic region).
The axial skeleton (80 bones) is formed by the vertebral column (32–34 bones; the number of the vertebrae differs from human to human as the lower 2 parts, sacral and coccygeal bone may vary in length), a part of the rib cage (12 pairs of ribs and the sternum), and the skull (22 bones and 7 associated bones).
The upper surface of each usually has a shallow sulcus for the eighth spinal nerve, and its extremity seldom presents more than a trace of bifurcation. The transverse foramen may be as large as that in the other cervical vertebrae, but it is generally smaller on one or both sides; occasionally, it is double, and sometimes it is absent.
The sacrum (pl.: sacra or sacrums [1]), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1–S5) between ages 18 and 30. [2] The sacrum situates at the upper, back part of the pelvic cavity, between the two wings of the pelvis. It forms joints with four other bones.
Sectional organization of spinal cord. The spinal cord is the main pathway for information connecting the brain and peripheral nervous system. [3] [4] Much shorter than its protecting spinal column, the human spinal cord originates in the brainstem, passes through the foramen magnum, and continues through to the conus medullaris near the second lumbar vertebra before terminating in a fibrous ...