The structure of the structure of the lower and upper extremities is the same. In the process of development, the hand ceased to serve man as a support. Now he can make complex various movements with her. Thus, the bone and articular structure of the upper limbs reflects their function as parts of the body that provide free movement. In this case, freedom of movement is determined by the permissible degree of freedom in the joints.
The upper limb of a person is divided into three segments: shoulder, forearm and hand. The bones are connected by ligaments and joints, forming links that work like levers.
The structure of the forearm includes bones (ulnar and radial), upper and lower cylindrical joints, as well as muscles of the posterior and anterior groups.
The ulna is located medially (on the little finger side), the radius is laterally (on the side of the thumb). They are connected using the upper and lower cylindrical joints. Their combined action provides rotational movements of the forearm in and out. Moreover, mobility is peculiar only to the radius. It moves (like the movement of the leg of a compass) around the ulnar bone, which remains motionless. Sinking below the ulna , the radius bone articulates with the skeleton of the wrist.
The human forearm has muscles of the posterior and anterior groups. The front ones consist of flexors for the fingers and hand and muscles that rotate inward. In the back group are extensors of the fingers and hands and muscles that rotate outwards.
It should be noted that all the diverse and complex movements in the segments of the upper limbs are carried out by a complex of simple movements of different joints.
The human forearm can bend, rotate inward or outward, and unbend. In this case, movements are made around the transverse and vertical axis in the elbow joint. Movements are made by four functional muscle groups.
The bending movements are carried out: a round pronator involving the forearm muscles starting from the humerus (internal epicondyle), the biceps muscle of the shoulder, brachioradius muscle, and shoulder muscle.
Extension movements are carried out by the triceps muscle. It is part of the shoulder and consists of the ulnar muscle, the muscles of the forearm, starting from the epicondyle, located laterally in the humerus.
Movement (rotation) inward (pronation) is carried out by a round and square pronator. In this case, the brachioradial muscle is involved (with the opposite pronation of the position).
Movement (rotation) outward (supination) in the forearm of a person is carried out by the arch support muscle and the biceps muscle. Rotational movements are made from the proned position (from the inside to the outside).
The muscles included in the human forearm also participate in the movements of the hand and wrist.
Flexion is performed by the radial and ulnar flexors of the wrist, the long palmar muscle, the superficial, deep and long flexors of the fingers. It should be noted that three finger flexors produce simultaneous movement.
The wrist can bend, rotate inward or outward and unbend. It should be noted that articular mobility is limited. An exception is the carpal-metacarpal joint of the thumb.
The free movements of all segments of the upper limbs are determined by the permissible degree of freedom in each joint. It should be noted that the development of the muscles of the forearm, in particular, those involved in the movements of the hand and fingers, are crucial in the proper development of the child. Therefore, at an early age, it is necessary to work with them so that the movements of the fingers correspond to the age of the child. It is proved that properly developed hand motility prevents complications in the development of the speech apparatus.