Our Skin- An Overview
The skin is the outer covering of the body. It is a remarkable organ, for serving a spectrum of functions and in being the largest organ of the body. It is our shield against the external environment and so protects us from all the harsh physical factors outside, right from the sinful sun rays, microbes and harsh chemicals to minor cuts and injuries. The skin is made up of three layers, each with its own important parts. The layer on the outside is called the epidermis.
Epidermis
Epidermis in itself comprises of 4 more sub-layers. Each sub-layer is built of different types of cells and performs the function designated to them. Epidermis is devoid of blood and lymph vessels, although it does have nerve endings. The maximum thickness of this layer is 1 mm. The cells of the lowermost level are the youngest and rapidly dividing. As they mature, they travel upwards and also age subsequently. The cells on the topmost layer are the dead cells and are ready to shed. The skin sheds a billion cells everyday and this process of ageing with upward movement takes about 2 weeks to a month. The predominant cell types of epidermis are Keratinocytes,
Melanocytes and Langerhans cells. Keratinocytes are the major type. They form "keratin", which is the major protein present in skin, hair and certain other cells. Melanocytes are the pigment "melanin" forming cells. Melanin decides the colour and tone of the skin. Langerhans cells are the immunity guardians since they keep a check on the pathogens and hence are the controllers of immune function.
Dermis
The dermis is the central layer of the skin between epidermis and subcutaneous tissue and constitutes bulk of the skin. It is again made up of 2 layers: superficial papillary and deeper reticular layers. The integration of epidermis with dermis happens via a basement membrane. Dermis provides elasticity, turgor , firmness and moisture to the skin at large. This happens because of presence of essential components like collagen and elastin. While collagen is the structural skeleton, elastin provides with elasticity. The predominant type of cell in dermis is the fibroblasts. They help in the synthesis of collagen, which is the framework of the skin as a whole. Collagen in turn is composed of a certain compound called the "glycosamines" which hold water and maintains the turgor and elasticity of the skin. Dermis is also rich in blood vessels, lymph and nerve endings, apart from few muscle nuclei. While blood vessels provide nutrition in the form of oxygen to the cells of the dermis, the lymph nodes protect it from the external environment. Dermis is also home to hair follicles, sebaceous glands and sweat glands. The sebaceous glands around the hair follicles particularly produce sebum. Sebum is a lubricant that protects the hair and skin. However an excess of sebum leads to oiliness of skin and promotes acne whereas less than normal sebum makes the skin dry. It is in the dermis that wrinkles form. Therefore, the use of creams and topical lotions are not much of help in treating wrinkles because of the large collagen and elastin molecules in the skin that hinder their permeability into the skin. Tattoo ink also stays in this layer and this layer does not shed, it makes it difficult to remove tattoos.
Functions
-Skin is the main external barrier to pollution, chemicals, pathogens and even trauma.
-Regulation of temperature is largely maintained by skin. Acting upon the signals sent by the hypothalamus, the skin adjusts the temperature by releasing heat in form of sweat and by dilation of blood vessels or by pilomotor reflex which prevents the heat from escaping.
-Synthesis centre of vitamin D by the action of sun rays.
-Skin acts as a dry barrier to fluid loss and thus maintains the essential nutrients from being washed away.
It is imperative that proper care be taken of skin. There are billions and billions of microbes like bacteria and yeast that find home in human skin. Most of the bacteria are the friendly sort and maintain equilibrium between the harmful and good ones.
However, antibiotics can alter this sensitive balance and can promote the growth of yeasts which, for most times, cause infections. Regular cleansing of skin is must for; dirty skin facilitates the growth of harmful pathogens and creates a base for acne and other infections. Regular cleansing also ensures removal of the dead layer of the skin, dirt, grime and excess oils.
Human skin is distinctly different in different parts of the body. The skin texture, colour and thickness are different of palms and soles than that of face. It is therefore; wise to know the basic facts about skin. It is only when wrinkles, acne or other ailments appear on skin that one feels the need to understand the structure and function of skin. It is best to know the facts before hand and to take utmost care of the skin because the first and foremost way to look good is by flaunting a radiant and healthy skin.