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The fibres of striated muscle have a cylindrical shape with blunt ends, whereas those in smooth muscle are spindle-like with tapered ends. Striated muscle tissue has more mitochondria than smooth muscle. Both smooth muscle cells and cardiac muscle cells have a single nucleus, and skeletal muscle cells have many nuclei. [6]
There are generally twelve muscles in the posterior compartment of the forearm, which can be further divided into superficial, intermediate, and deep. Most of the muscles in the superficial and the intermediate layers share a common origin which is the outer part of the elbow, the lateral epicondyle of humerus.
The muscles of the hand are the skeletal muscles responsible for the movement of the hand and fingers. The muscles of the hand can be subdivided into two groups: the extrinsic and intrinsic muscle groups. The extrinsic muscle groups are the long flexors and extensors. They are called extrinsic because the muscle belly is located on the forearm ...
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.
The distal part of the upper limb between the elbow and the radiocarpal joint (wrist joint) is known as the forearm or "lower" arm, and the extremity beyond the wrist is the hand. By anatomical definitions, the bones , ligaments and skeletal muscles of the shoulder girdle , as well as the axilla between them, are considered parts of the upper ...
The anconeus is a small muscle that stabilizes the elbow joint during movement. Some embryologists consider it as the fourth head of the triceps brachia as the upper and lower limbs have similar embryological origins, and the lower limb contains the quadriceps femoris muscle which has four heads, and is the lower limb equivalent of the triceps.
In anatomy, extension is a movement of a joint that increases the angle between two bones or body surfaces at a joint. 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.
The latter involves compression at the wrist of the superficial sensory branch of the radial nerve which does not innervate hand muscles. [citation needed] Robert Wartenberg (1887-1956) was a neurologist born in Belarus who worked in Germany until 1935 when he emigrated to the United States. He was widely published and described a number of ...