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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.
This reduction in number gives an inability of the lumbar spine to lordose but gives an anatomy that favours vertical climbing, and hanging ability more suited to feeding locations in high-canopied regions. [34] The bonobo differs by having four lumbar vertebrae. Caudal vertebrae are the bones that make up the tails of vertebrates. [35]
It is composed of 270 bones at the time of birth, [2] but later decreases to 206: 80 bones in the axial skeleton and 126 bones in the appendicular skeleton. 172 of 206 bones are part of a pair and the remaining 34 are unpaired. [3]
Structure. The number of vertebrae in a region can vary but overall the number remains the same. In a human vertebral column, there are normally 33 vertebrae. 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.
[2] [3] In humans, cervical vertebrae are the smallest of the true vertebrae and can be readily distinguished from those of the thoracic or lumbar regions by the presence of a foramen (hole) in each transverse process, through which the vertebral artery, vertebral veins, and inferior cervical ganglion pass. The remainder of this article focuses ...
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).
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The diameter of the spinal cord ranges from 13 mm (1 ⁄ 2 in) in the cervical and lumbar regions to 6.4 mm (1 ⁄ 4 in) in the thoracic area. The spinal cord functions primarily in the transmission of nerve signals from the motor cortex to the body, and from the afferent fibers of the sensory neurons to the sensory cortex.