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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.
A fully grown adult features 26 bones in the spine, whereas a child can have 33. Cervical vertebrae (7 bones) Thoracic vertebrae (12 bones) Lumbar vertebrae (5 bones) Sacrum (5 bones at birth, fused into one after adolescence) Coccyx (set of 4 bones at birth)
Each vertebra (pl.: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal segment and the particular species.
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).
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 upon ...
Together the lumbar and thoracic curves bring the body's center of gravity directly over the feet. [7] Specifically, the S-shaped curve in the spine brings the center of gravity closer to the hips by bringing the torso back. Balance of the whole vertebral column over the hip joints is a major contribution for efficient bipedalism. [17]
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.
The number of rows in the table for the relevant Terminologia Anatomica muscle. For example, TA splits the nasalis muscle into transverse and alar parts, so their TA column entries are 2. For Origin, Insertion and Action please name a specific Rib, Thoracic vertebrae or Cervical vertebrae, by using C1-7, T1-12 or R1-12.