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The muscles of the thumb are nine skeletal muscles located in the hand and forearm. The muscles allow for flexion, extension, adduction, abduction and opposition of the thumb. The muscles acting on the thumb can be divided into two groups: The extrinsic hand muscles, with their muscle bellies located in the forearm, and the intrinsic hand ...
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.
It joins with the scapula above at the shoulder joint (or glenohumeral joint) and with the ulna and radius below at the elbow joint. Notice: When the arm is spun so that the thumb point to the outside of the body, meaning the palm of the hand looks forward then it is said the hand is supinated. But when the thumb remains in the inside and the ...
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]
This muscle is the most superficial of the thenar group. Flexor pollicis brevis , which lies next to the abductor, will flex the thumb, curling it up in the palm. (The flexor pollicis longus , which is inserted into the distal phalanx of the thumb, is not considered part of the thenar eminence.)
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 ...
These three muscles act as flexors at the elbow joint. [5] The extensor carpi radialis brevis and longus are both weak flexors at the elbow joint. Brevis moves the arm from ulnar abduction to its mid-position and flexes dorsally. Longus is a weak pronator in the flexed arm and a supinator in the outstretched arm.
Muscles of the posterior forearm. All the labelled muscles (that is, all the visible muscles except the ones on the dorsal hand and one at top left) are innervated by the radial nerve, and represent all muscles innervated by the radial nerve except for the supinator. Muscular branches of the radial nerve: Triceps brachii; Anconeus; Brachioradialis