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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.
The most distinctive characteristic of this bone is the strong odontoid process (dens) that rises perpendicularly from the upper surface of the body and articulates with C1. The body is deeper in front than behind, and prolonged downward anteriorly so as to overlap the upper and front part of the third vertebra.
A typical vertebra has a body (vertebral body), also known as the centrumwhich consists of a large anterior middle portion, and a posterior vertebral arch, [2] also called a neural arch. [3] The body is composed of cancellous bone, which is the spongy type of osseous tissue, whose microanatomy has been specifically studied within the pedicle ...
The supraspinous ligament becomes taut when the spine is fully flexed. [4] The supraspinous ligament, along with the posterior longitudinal ligament, interspinous ligaments and ligamentum flavum, help to limit hyperflexion of the vertebral column.
This system describes how bones are connected to other bones and muscle fibers via connective tissue such as tendons and ligaments. The bones provide stability to the body. Muscles keep bones in place and also play a role in the movement of bones. To allow motion, different bones are connected by joints.
In anatomy, Luschka's joints (also called uncovertebral joints, neurocentral joints) [1] are formed between uncinate process or "uncus" below and uncovertebral articulation above. [2] They are located in the cervical region of the vertebral column from C3 to C7. [ 3 ]
The spinal cord is an estimated 45 centimetres (18 inches) long in males and about 43 cm (17 in) in females. [citation needed] It is ovoid-shaped and is enlarged in the cervical and lumbar regions. The cervical enlargement, stretching from the C4 to T1 vertebrae, is where sensory input comes from and motor output goes to the arms and trunk.
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] Many small accessory bones, such as sesamoid bones, are not included in this.