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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 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 extrinsic muscle groups are the long flexors and extensors. They are called extrinsic because the muscle belly is located on the forearm. The intrinsic group are the smaller muscles located within the hand itself. The muscles of the hand are innervated by the radial, median, and ulnar nerves from the brachial plexus. [1]
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 lack of palmaris longus muscle does result in decreased pinch strength in fourth and fifth fingers. The absence of palmaris longus muscle is more prevalent in females than males. [5] The palmaris longus muscle can be observed by touching the pads of the fourth finger and thumb and flexing the wrist. The tendon, if present, will be visible ...
Symptoms of radial neuropathy vary depending on the severity of the trauma; however, common symptoms may include wrist drop, numbness on the back of the hand and wrist, and inability to voluntarily straighten the fingers. Loss of wrist extension is due to loss of the ability to move of the posterior compartment of forearm muscles.
Any fracture in the elbow region or upper arm may lead to Volkmann's ischemic contracture, but it is especially associated with supracondylar fracture of the humerus. It is also caused by fractures of the forearm bones if they cause bleeding from the major blood vessels of the forearm. [citation needed]