Parts of the arm: features of anatomy

The upper limb of man played an important role in the evolutionary development of it as a biological species. In this article we will consider the parts of the human hand and animals, the features of their structure and functioning.

General outline of the structure of the upper limb

The upper limb consists of two parts. The first includes a belt consisting of a clavicle and scapula. To them the second component is attached - the skeleton of free limbs. It includes one unpaired humerus bone. It is movably connected with the ulnar and radial, forming the forearm. The following parts of the hand are brushes. They consist of the bones of the wrist, the pastern and the phalanges of the fingers.

The upper part of the hand

This department includes paired collarbones and scapula. These bones of the upper limb belt provide a mobile connection of the skeleton of the trunk and the free part of the arm. The clavicle on one side is connected to the flat sternum, and on the other side to the scapula. This bone has a slightly curved shape and is well probed all over. Its main functional feature in the body is the location of the shoulder joint at a certain distance from the chest. This greatly increases the amplitude of the movements of the upper limbs.

Lower arm

Bones of the skeleton of the free extremity are connected movably and form several joints: sternoclavicular, humeral, ulnar, radiocarpal. All these structures have a unified structure plan. In any joint, the head of one bone enters the recess of the other. To ensure that the contact surfaces do not experience severe friction, they are covered with hyaline cartilage. Each similar structure is in the joint bag, to which ligaments and muscles are attached.

Some parts of the human hand have their own characteristics. For example, the thumb of the brush is opposed to all the rest. This is due to a person's ability to work consciously.

The structure of the arm in all animals is similar to chordates. It consists of three sections: the shoulder, forearm and hand. Their morphological features and differences are related to the habitat of animals. Thus, in birds, in connection with their ability to fly, the upper limbs turned into wings. Moles and shrews procure their food by making moves in the soil. Therefore, they have wide digging limbs. Representatives of the order of bats of mammals are adapted to an active flight due to the presence of a skin fold and elongated fingers. Ungulates are named after the presence of protective horn formations on their limbs.

The mechanism of the upper limb

All parts of the human hand and animals move due to the presence of muscles. They are attached to the bones with the help of ligaments. The muscles that move the limbs into motion are grouped into two groups. The first flex the limb. For example, the biceps muscle, or biceps, leads the arm to the trunk. Extensors perform reverse actions. In humans, this function is performed by the triceps. The deltoid muscle acts in opposite directions. Her fibers, located on the front surface of the forearm, bend the hand. And those that are located on the reverse side, on the contrary.

In the skin of the hands are receptors of various kinds. These are special sensitive formations that connect the body with the environment. They are able to transform various kinds of influences into nerve impulses. In this form, information enters the appropriate parts of the cerebral cortex. Conductive pathways in this case are nerve fibers. In the brain, information is analyzed and in the opposite direction goes to the working organ. There are several types of receptors in the skin of the hands. Mechanical perceive pressure and touch. Cold and warmth the body perceives with the help of thermoreceptors. But most of all the skin of the hands and fingers is sensitive to the perception of pain. They are formed by nociceptors.

Due to the structural features, the upper limbs perform many important functions. This is the ability to fly, harvest food, build shelters. The most perfect features are the hand of a person, which determines his work activity and is the basis of many evolutionary transformations.