The anatomy of the human hand is quite complicated. So, arteries, veins, nerves and muscles branch and constantly intersect with each other, and the network of tendons and ligaments respond to each command of the brain. In addition, they easily bend and contract. The structure of the arm involves a large load on the muscles, since during the day a person makes a large number of various movements, and the shape of the arm depends on their condition.
All this complex construction of the hand is covered with skin, which serves as its protection against bacteria, toxic substances and radiation. It should be noted that it is waterproof, has the ability to maintain a certain body temperature and collect sensory information that comes from the outside, so this structure of the hand allows you to accurately manipulate those objects with which this hand is in contact.
The lower layer of skin on the back of the hand is thin, so the hands freeze more often than other organs. The dermis on the back has a small amount of sweat and sebaceous glands, which is why the skin dries faster. This layer of skin also contains nerves, lymphatic and blood vessels, as well as elastin and collagen, which make it strong and elastic. However, ultraviolet light, which penetrates through the dermis, has a negative effect on these two proteins, so the skin of the hands loses its elasticity and wrinkles form on it faster.
The structure of a person’s hand has some peculiarity. So, in the lower layer of the epidermis are cells that produce melanin. Thanks to it, the skin absorbs ultraviolet light, thereby preventing its penetration into the dermis. If the sun's rays have a prolonged effect on the skin of the hands, this leads to the formation of age spots.
The structure of the human hand , including the wrist, can be considered as a separate chapter. They consist of twenty-seven bones that perform their functions perfectly, and tendons that attach muscles to the bones.
If we consider the skeleton of the brush, then we can distinguish eight bones that form the wrist, five bones that form the metacarpus (wrist), and fourteen bones that form the phalanges of the fingers.
The bones of the wrist are two rows of four bones in each. The first row includes scaphoid and lunate bones, as well as trihedral and pea-shaped. The second row - bone-trapezoid, capitate and hook-shaped bones.
The bones of the hand consist of the base, head (knuckle) and body. The bones of the fingers consist of three phalanges, except for the thumb (it has two phalanges).
Examining the structure of the hand , it should be noted that the muscles that control the wrist and hand are quite a lot. They are divided into front (responsible for flexion), rear (responsible for extension) and internal muscles (help to move fingers).
The hand performs the following functions: grasping, clear coordinated movements, tingling.
Thus, the hand is attached to the body with the help of bones, muscles and joints and consists of three parts: forearm, shoulder and hand. Bending at the elbow provides the hands with great mobility and functionality, so we can make a variety of movements.
It should be noted that at the ends of the fingers are sensory cells, thanks to which a person cognizes the world with the help of touches, which is why they are sensitive to pain. To protect them, there are nails, which are a horny plate consisting of keratin other than keratin of the skin. So, it is more porous, harder and less swells when water gets on it.
The structure of the hand allows a person to know the world around him by touching and manipulating objects, which makes him different from other representatives of mammals.