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The muscle fibres of the diaphragm radiate outward from the central tendon. While the diaphragm is one muscle, it is composed of two distinct muscle regions: the costal, which serves as the driver in the work of breathing, and crural diaphragm, which serves as an "anchor;" attaching the muscle to the lower ribs and lumbar vertebrae.
The brachioradialis, flexor of the elbow, is unusual in that it is located in the posterior compartment, but it is actually a muscle of flexor / anterior compartment of the forearm. The anconeus , assisting in extension of the elbow joint, is by some considered part of the posterior compartment of the arm.
Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed (bent) elbow. Straightening of the arm would require extension at the elbow joint. If the head is tilted all the way back, the neck is said to be extended.
When the arms are in a fixed overhead position, the latissimus dorsi pulls the trunk upward and forward. [8] It has a synergistic role in extension (posterior fibers) and lateral flexion (anterior fibers) of the lumbar spine, and assists as a muscle of both forced expiration (anterior fibers) and an accessory muscle of inspiration (posterior ...
Most of the large number of muscles in the forearm are divided into the wrist, hand, and finger extensors on the dorsal side (back of hand) and the ditto flexors in the superficial layers on the ventral side (side of palm). These muscles are attached to either the lateral or medial epicondyle of the humerus. They thus act on the elbow, but ...
The hypaxial muscles are located on the ventral side of the body, often below the horizontal septum in many species (primarily fish and amphibians). In all species, the hypaxial muscles are innervated by the ventral ramus (branch) of the spinal nerves, while the epaxial muscles are innervated by the dorsal ramus.
The origin of a muscle is the bone, typically proximal, which has greater mass and is more stable during a contraction than a muscle's insertion. [14] For example, with the latissimus dorsi muscle, the origin site is the torso, and the insertion is the arm. When this muscle contracts, normally the arm moves due to having less mass than the torso.
Stress positions place the human body in such a way that a great amount of weight is placed on just one or two muscles and joints. Forcing prisoners to adopt such positions is a method of ill-treatment used for extracting information or as a punishment, possibly amounting to torture. Such positions also are sometimes used as a punishment for ...