What is Skin
The skin is the outer covering of the body, also known as the epidermis, of an animal. It is the largest organ of the human body made up of multiple layers of epithelial tissues, and guards the underlying muscles, bones, ligaments, and internal organs.
The human skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system. The skin has multiple layers of ectodermal tissue and guards the underlying muscles, bones, ligaments and internal organs. Human skin is similar to that of most other mammals, except that it is not protected by fur.
Unclean skin favors the development of pathogenic organisms - the dead cells that continually slough off of the epidermis mix with the secretions of the sweat and sebaceous glands and the dust found on the skin to form a filthy layer on its surface. If not washed away, the slurry of sweat and sebaceous secretions mixed with dirt and dead skin is decomposed by bacterial flora, producing a foul smell. Functions of the skin are disturbed when it is excessively dirty; it becomes more easily damaged, the release of antibacterial compounds decreases, and dirty skin is more prone to develop infections.
Because it interfaces with the environment, skin plays a very important role in protecting (the body) against pathogens. Its other functions are insulation, temperature regulation, sensation, synthesis of vitamin D, and the protection of vitamin B foliates. Severely damaged skin will try to heal by forming scar tissue. This is often discolored and de-pigmented.
The Skin is composed of three primary layers:
Epidermis
Provides waterproofing and serves as a barrier to infection. The epidermis contains no blood vessels, and cells in the deepest layers are nourished by diffusion from blood capillaries extending to the upper layers of the dermis. The main type of cells which make up the epidermis are Merkel cells, keratinocytes, with melanocytes and Langerhans cells also present.
Dermis
Serves as a location for the appendages of skin. The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechano-receptor/nerve endings that provide the sense of touch and heat. It contains the hair follicles, sweat glands, sebaceous glands, apocrine glands, lymphatic vessels and blood vessels.
Hypodermis
(subcutaneous adipose layer). The hypodermis is not part of the skin, and lies below the dermis. Its purpose is to attach the skin to underlying bone and muscle as well as supplying it with blood vessels and nerves. It consists of loose connective tissue and elastin. The main cell types are fibroblasts, macrophages and adipocytes (the hypodermis contains 50% of body fat).
Dermatosis (plural dermatoses)
Defined as "any disease of the skin," and, while thousands of skin disorders have been described, only a small number account for most visits to the doctor.
As skin ages, it becomes thinner and more easily damaged. Intensifying this effect is the decreasing ability of skin to heal itself as a person ages. Skin aging is caused by the fall in elasticity. Aging skin also receives less blood flow and lower gland activity.
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