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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.
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.
Only skeletal and smooth muscles are part of the musculoskeletal system and only the muscles can move the body. Cardiac muscles are found in the heart and are used only to circulate blood; like the smooth muscles, these muscles are not under conscious control. Skeletal muscles are attached to bones and arranged in opposing groups around joints. [8]
The bone or other structure the muscle is attached to that remains immobile during the action. The term "bone" is omitted from bone names. Insertion The attachment point of the muscle, on a bone or otherwise, that moves during the action. Artery The artery which supplies the muscle with blood. The term "artery" is included to avoid confusing ...
The body is composed of cancellous bone, which is the spongy type of osseous tissue, whose microanatomy has been specifically studied within the pedicle bones. [4] This cancellous bone is in turn, covered by a thin coating of cortical bone (or compact bone), the hard and dense type of osseous tissue.
Movement is powered by skeletal muscles, which are attached to the skeleton at various sites on bones. Muscles, bones, and joints provide the principal mechanics for movement, all coordinated by the nervous system. It is believed that the reduction of human bone density in prehistoric times reduced the agility and dexterity of human movement.
The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal cord is hollow and contains a structure called the central canal, which contains cerebrospinal fluid.
The human back, also called the dorsum (pl.: dorsa), is the large posterior area of the human body, rising from the top of the buttocks to the back of the neck. [1] It is the surface of the body opposite from the chest and the abdomen. The vertebral column runs the length of the back and creates a central area of recession.