The skin, which is also called the cutis , is an organ formed by a continuous tissue, belonging to the integumentary system. In turn, it is made up of cells and various tissues, in particular epithelial and connective tissues, and these are made up of cells of various types. It also has several layers so that its functions will also be diverse. Let us know then what are the layers of the skin: Main characteristics and functions.
The layers of the skin: Main characteristics and functions
The skin represents approximately 15% of the body weight (approximately 10 kg) and has an area of approximately 1.5 – 2 cm2. Its thickness varies from approximately 0.2 mm on the eyelids to 3 mm on the scalp, palm and back of the hands.
After the skeletal muscles, the skin is the largest organ by extension of our body.
As already mentioned , the skin is made up of several layers. From the outside to the inside they are :
- Epidermis
- Dermis
- Hypodermis
Below we describe its main characteristics:
Epidermis
The epidermis is the most superficial layer of the skin. Its thickness varies from 30 microns (in the area of the mammary areola) to 2 mm in the palms of the hands.
The epidermis can be divided into five main layers (strata):
- Basal or germinative;
- Thorny;
- Grainy;
- Lucid;
- Horny.
Dermis
The dermis is the layer of skin under the epidermis. This layer of skin contains connective tissues and houses the body’s hair follicles, sweat and sebaceous glands, and blood vessels. The dermis also contains nerve endings that are responsible for sending messages to the brain when, for example, you burn your hand on a hot stove or feel itchy on the back of your neck. Blood vessels located in the dermis help supply the skin with fresh blood that carries the oxygen and nutrients it needs to be healthy.
Within its connective tissues, the dermis produces two important proteins: collagen and elastin , responsible for the shape, structure, firmness and elasticity of your skin.
Hypodermis
The hypodermis is made up of subcutaneous fats (under the skin), connective tissues, blood vessels, and nerve cells. It is the layer of skin where fat is deposited and stored. The blood vessels in the hypodermis are larger and connect to the rest of your body. Stored fat helps regulate body tissue and protects internal body organs from bumps, blows, and falls.
The tissue of the hypodermis produces an important cell: adipocytes that store fat used for energy, cushioning and insulation.
The main functions of the skin
This very large organ has two main characteristics:
- She is able to repair herself after an injury;
- It is very elastic . As a result, it can adapt perfectly to the changes in body volume and shape that occur physiologically in each individual as they grow.
Among the main functions performed by the skin, we remember in particular
- Protection : the skin protects us from trauma, UV radiation, chemicals and microorganisms that are harmful to our body.
- Thermoregulation : with the help of the sweat glands, the skin regulates blood flow through vasodilation or vasoconstriction, in order to avoid excessive heat loss.
- Fluid maintenance: it is essential that our body, after a serious trauma, such as a burn, does not release too much fluid and electrolytes. The consequences, if the skin did not perform this task, it would be deadly.
- Metabolic : the synthesis of vitamin D occurs in the skin.
- Nutrient reserve : the skin is the seat of the essential lipid reserve for our body.
- Immune : the skin coordinates the response of the immune system to fight pathogens and tumors.
- Sensory : its outermost layer, the epidermis, is capable of transmitting tactile, thermal and painful stimuli; the innermost layer, the hypodermis, can also perceive vibrational and thermal signals.
- A defense against pathogens : Our skin uses some defense mechanisms to avoid colonization by pathogens. The stratum corneum, already described in the previous paragraph, has such a resistant and dense structure that it creates a real barrier that prevents essential fluids from leaving the body and, at the same time, bacteria and microbes penetrate the skin and attack the body. In addition, the stratum corneum is continually renewed every fourteen days . This process leads to flaking and the consequent expulsion of microbes.
