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STUDY OF SKIN AND SCALP
Historiology of the Skin
The skin’s surface is not made up of just one single layer. It has two defined layers – the epidermis, also called the scarf skin, is the outermost layer of the skin which provides a protective covering for the inner layer and contains no blood vessels but has many small nerve endings.
The dermis, which is the inner layer of the skin, is also known as derma, carium, cutis or true skin. The dermis is highly sensitive and is a vascular layer of connective tissues containing numerous blood vessels, nerves, sweat glands, oil glands, hair follicles and muscles. The dermis itself consists of two layers – the papillary or superficial layer and reticular or deeper layer. The skin receives its nourishment from the blood and lymph. Between half and two-thirds of the total blood supply of the body is distributed to the skin which contains numerous capillaries. The blood and the lymph circulating through the skin contribute to its growth and nourishment. The skin contains the surface endings of many nerve fibres, classified as follows:
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Motor nerve fibres which are distributed to the blood vessels and the arrector pipli muscles
of the hair follicles.
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Sensory nerve fibres which react to heat, cold, touch, pressure and pain.
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Secretory nerve fibre which are distributed to the sweat and oil glands of the skin.
The pliability of the skin depends upon the elasticity of the fibres of the dermis. When a healthy skin expands, it regains its former shape immediately, where as an aged skin, on the other hand, is characterized by its loss of elasticity. The complexion depends primarily upon the melanin or colouring matter deposited in the stratum and the papillary layer of the dermis and partly on the blood supply in the skin.
Cleanliness keeps the skin free from blemishes. The skin contains two types of duct glands which extract materials from the blood to form new substances. The first type is known as the sweat gland which secretes sweat. The other type is the sebaceous or oil gland which secretes sebum – a semi-fluid oily substance flowing through the oil ducts. However, when the sebum becomes hardened and the ducts are blocked, a blackhead is formed.
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