Skin may be the most familiar of the organ, and it is located in the body surface, the total area of an average of about 1.6m, about 16% by weight of the total weight, so called "the body's largest organ," it is no different righteousness. The thickness of the surface of our skin is not the same, not the thickest skinned, but the hands and soles of the feet, the eyelids are the thinnest.
In order to introduce the following.
Epidermis
90% of the epidermis keratinocytes (basal cells) and 10% of the dendritic cells. 1) epidermal keratinocytes located innermost, also known as the basal layer, and then began to grow outward deformation. First, cells become polygonal, cytoplasmic grow thorns, so called prickle cell, where the parts called acanthosis. Then out into a flat or diamond-shaped cells, the cytoplasm appears large particles, called granulosa cells, where the parts called granular layer. Then the outside, flat-nuclear cells, cell death become keratinocytes, called the site where the horny layer. Start from the base cell division to cell death (stratum corneum) is generally about 28 days. 2) dendritic cells comprising: a) melanocytes, has the effect of melanin synthesis, located in the basal cell layer. b) Langerhans cells, a kind of immune cell function, located in the upper layer of the spine. c) undifferentiated cells, which can be converted into melanoma cells, may be converted into Langerhans cells. d) Merkel cells, which are likely to feel the tactile cells.
Skin damage repair, cell division is complete shape, it does not leave scars.
Summary: skin epidermal keratinocytes gradually mainly outgrowth of the last cell death become keratin to protect the skin, keratin has strong water absorption, generally for 15 to 20% moisture, make the skin moist and soft. There is also the epidermal melanocytes, it will secrete melanin granules according to the strength of ultraviolet radiation. Sometimes, the melanoma cell metabolism bad, there will be two poles, the stain and white.
Dermis
The thickness of the dermis skin layer was about 15 times. Dermis layer of connective tissue is composed of collagen fibers, reticular fibers and elastic fibers. Therein contains nerves, blood vessels, lymphatics, piloerection muscle, hair follicles, sebaceous glands, sweat glands and size. There fibroblasts, tissue cells, mast cells. Dermal layer also contains 60% water, sticky polysaccharides, proteins and inorganic salts. If less than 60% moisture, the skin will dry and wrinkled.
Dermal layer of collagen fibers, reticular fibers, elastic fibers are produced by fibroblasts made, so eat and do not eat collagen does not matter. If skin damage hurt the dermis, fibroblasts will make a lot of fibrous tissue repair is the basis of fibrous tissue, scar.
Summary: dermis where there is a will like a spider spinning cells, the body's collagen is synthesized by such cells, called spit silk fibers. This cell's name is called - fibroblasts. Its shapes, but all projections (spinning), the middle of a big nucleus. It is not only present in the dermal layer of skin, but also present in the bones, tendons, blood vessels and internal organs. Fibroblasts and collagen production will be used to produce three kinds of collagen fibers, collagen fibers (white fibers), elastic fiber (yellow fibers) and reticular fibers. Collagen fibers are made and collagen proteins, it has a strong toughness and tensile strength, but poor by the elastic fibers of collagen type , it is poor toughness and good these two fibers interwoven together, they make the dermis both toughness and elasticity of. But with age, elasticity will diminish and disappear. Reticular fibers but also by the type collagen, which constitutes reticulum become extracellular bracket. Thus, we also know that collagen material it is only really play a supportive role in the dermal layer of collagen fibers, elastic fibers and reticular fibers made of collagen as raw material. Like reinforced concrete, you move to the piece of steel, it is useless, you only have to build the steel reinforced building. Human fibroblasts also very busy. It gilded wire and capillaries together granulation tissue damage to human body parts were filled. But the mechanic to repair things and not the same as the original. Repair skin repair the liver, leaving when SARS, repair lung, leaving lifelong refractory pulmonary fibrosis.
Subcutaneous layer
This is the thickest layer of the skin, it contains a lot of fat cells, as well as loose connective tissue, blood vessels, nerves, lymph vessels, sweat glands and hair follicles deep. Play a moisturizing cold buffer force, the role of providing energy.
Summary: subcutaneous tissue layer, some people are happy people worry. Because this is where fat accumulation, both will have a "curvy", will have a "curve is not the United States" and tells the people how not to bother it.
Skin appendages
The size of the sweat glands, hair, sebaceous glands and finger (toe). a) apocrine. Apocrine found in the armpits, areola, around the navel, around the anus and genitals. Secreted protein, carbohydrate and fat milky liquid. Therefore, these secretions in the bacterial decomposition will produce a special smell "body odor." b) eccrine. Eccrine born with systemic distribution, discharge water, salt, a small amount of urea, uric acid and other metabolic wastes. As the role of urea, there is a long time without a bath sour smell. c) hair. The major components of hair keratin. It is one of the characteristics of mammals. It can be cold, shading, anti-friction. d) the sebaceous glands ingredients include: triglycerides, fatty acids, cholesterol, carbohydrates and inorganic salts. Slightly acidic, moist skin play a role.
Summary: skin appendages, skin absorption, skin appendages is three: the sebaceous glands, hair follicles and sweat glands. The subsidiary is also in the protection of the skin, such as the secretion of the sebaceous glands secrete sebum plus sweat, skin cells generated lipids mixed with oxygen in the air, oxidation occurs, it will be able to form a layer on the skin surface of a weak acid film, called sebum film. Our body temperature regulation, also depend on these appendages.
In addition to these, the skin is still our sensory systems. We can perceive pain, pressure, cold, heat, but also the perception wet, rough, hard, soft, smooth, better perception of object shape, two-point discrimination, location and so on. Blind rely more skin to literacy learning. Our skin is also involved in immune function and metabolic function, so that the skin is really important to us.
After puberty, with age, our skin starts to age. Sebaceous glands, sweat glands began to shrink, reducing the secretion of sebum, the skin loses luster. Epidermal keratinocytes layer begins to thicken, granular layer and prickle cell layer thinning, sometimes vacuolar degeneration, reduced cell regeneration. Dermis also began to shrink. Connective tissue reduction, elastic fibers lose their elasticity, dermis relaxation. Meanwhile, the subcutaneous tissue loses moisture, subcutaneous fat cells shrink, stretch plus subcutaneous muscle tissue, wrinkles began to appear on the face.
62 (Author: iced tea 62)
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