Do you know what is the body’s largest organ is? Are you surprised to find out that it's the skin! Yes you heard it right, it’s the skin! The skin which you might not even consider as an organ! Skin makes up of 12% to 16% of an adult body weight and it covers 12 to 20 square feet.
Skin comprises of 3 layers: epidermis (the external layer), dermis and the Hypo dermis (subcutaneous) layer.
The outer and upper layer is known as the epidermis. The main function of the epidermis is to form a tough barrier against the outside world. It is the part of the skin which we can see, feel and touch. At the base of the epidermis, new skin cells are continuously forming. At the point when the cells are prepared, they begin moving toward the highest point of the epidermis. This procedure takes around 2 weeks to a month. As newer cells keep moving up, older cells close to the top kick the bucket and die and rise to the surface of the skin. These shedding of cells is called dead skin cells.
They just stick around for a little time. Before long, they drop off. Each moment of the day we lose around 30,000 to 40,000 dead skin cells off the surface of our skin. Epidermis is continually making new skin cells that move to the top to replace the old ones. The vast majority of the cells in the epidermis (95%) work to make new skin cells. You may ponder about the other 5% of the skin cells. They make a substance called melanin. Melanin is a pigment that protects against UV radiation and it gives skin color. The darker your skin is, the more melanin you have. The epidermis also contains very important Langerhans cells. They are part of the skin's immune system. These cells help detect foreign substances and defend the body against infection.
Under the epidermis, next layer is called dermis. It is the thickest of the skin layers. It has collagen and elastin. Collagen determines the health of the skin. Collagen health determines the contour of the skin, how wrinkly the skin can be! Collagen and elastin gives skin its flexibility and strength. The dermis contains blood vessels. They provide nutrients to the skin. The blood vessels play a big part in regulating the body temperature. The heat can make the blood vessels to dilate which in turn, allows large amount of blood to flow near the skin surface and thats where the heat can be released. In contrast, cold can make the blood vessels constrict, which is turn, retains the body's heat.
The dermis contains oil glands. These are called sebaceous glands. They secrete sebum into hair follicles. Sebum is the skin's own natural lubricant (oil) which keeps the skin moist and soft. It makes the skin waterproof. When sebum is present, skin won't retain water and get soaked. When sebaceous glands deliver too little sebum, which is basic in elderly, the skin turns out to be dry and more inclined to wrinkling. A lot of sebum, as is normal in adolescents, regularly leads to skin break outs. It also acts as a barrier against foreign substances.
Besides secreting sebum, skin also excretes sweat through sweat glands. Sweat is a result in response to heat and stress. Sweat is made up of water, salt, and other chemicals. As sweat evaporates, it gives a cooling effect, meaning it cools off the body. There are specialized sweat glands called the apocrine sweat glands which are found in the armpits and the genital area. These ones secrete a thick and oily sweat that produces a body odor. It also gets rid of toxins in the body, such as excess salt and waste chemicals.
The nerve endings in the dermis can sense pain, touch, temperature and pressure. Interestingly, some areas of the skin has more nerve endings than others. Our fingertips and toes are the heroes of the nerves and are extremely sensitive to touch.
Do you know there are more than 100,000 follicles on the head alone! The hair follicles are like a sac from which hair grows. It produces different kinds of hair which are found all over the body. Hair plays important part in regulating body temperature. Hair follicles depend on sebaceous glands to bring on the shine. Associated with every follicle in the dermis layer is a little sebaceous gland that discharges sebum onto the hair. This gently coats the hair with oil, giving it some shine.
Another layer under the dermis is called hypodermis or subcutaneous layer. It is a layer of fat which is contained in living cells and they are called fat cells. They are held together by fibrous tissues. Hypodermis layer provides the protective padding. It also contains connective tissue. It also carries blood vessels and nerves. Its function is to help insulate the body from heat and cold, regulating body temperature. The loss of subcutaneous tissue in later years of life prompts to facial drooping and makes wrinkles more obvious.