Anatomy of the muscles that move the forearm

The muscles that move the forearm include the muscles that flex it and the muscles that extend it. These muscles lie on the forearm. Other muscles impart to the forearm the pronation movement, and still others the supination movement; these muscles do not lie on the forearm.

Extensor muscles - a pair. One of the muscles of this pair extends with an inward bias, for it grows from under the front of the forearm and from the lower edge of the scapula and adjoins the elbow at its inner parts. The second muscle extends the forearm with an outward deviation, since it comes from the back of the forearm and adjoins the outer parts of the elbow. When these muscles combine in their action, they necessarily extend the forearm in a straight position.

There are also a pair of flexor muscles. One of the muscles of this pair - the large one - bends inward, and this is because it grows from the lower edge of the shoulder blade and from the “beak”. At the origin of each muscle there is a special head of the muscle. The muscle slopes toward the inside of the forearm, and its tendon, like a nerve, is adjacent to the front of the upper flint.

The second muscle flexes the forearm with an outward deviation, as it grows from the outside of the humerus at the back. This muscle has two fleshy heads; one of them is behind the humerus, the other is in front of it. Along its length, this muscle goes somewhat deeper inward until it reaches the front of the lower “flint”.

To pull tighter, the muscle that bends the arm, deflecting it outward, is connected to the lower “flint,” and the one that deflects it inward is connected to the upper one. When these muscles act together, they certainly bend the forearm in a straight direction.

Both extensor muscles are covered by the muscle surrounding the humerus; it is more likely that this muscle is part of the latter, the flexor muscle.

As for the muscles that turn the forearm palm up, there are a couple of them. One muscle is located outside, between the flints, and approaches the upper flint without a tendon. The other muscle is thin, oblong, and grows from the top of the head of the humerus, closer to the outside. Most of it passes into the forearm and penetrates further and further until it approaches the wrist joint. It goes to the inner part of the edge of the upper “flint” and connects to it through a membranous tendon.

The muscles that tilt the forearm palm down are also a pair, and they are located on the outside.

One of the muscles of this pair begins from the upper 6 internal end of the head of the humerus and connects to the upper “flint”, and not to the wrist joint.

The other muscle is shorter, its fibers are transverse and its tip is very similar to nerves. It starts from the lower flint and is adjacent to the lower end of the wrist joint.