General Facts About Skin
Human skin consists of 3 main layers; upper epidermis, middle dermis & lower sub-cutaneous tissue
Skin is the largest organ in the body, accounting for 15-20% of total body weight & covers a surface area of 2 m2.
The epidermis is mainly composed of keratinocytes and is 0.4-1.5mm in thickness. It is formed by division of cells in the basal layer which move outwards forming upper layers. The cellular progression from the basal layer to the skin surface takes about 30 days.
Other cells in the epidermis are the melanocytes, Langerhans' cells and Merkel cells.
Melanocytes are cells that distribute packages of melanin pigment which gives skin its colour. The number of melanocytes does not differ much between white and black skin. Rather it is the nature of the melanin and the size of the cells containing it that account for the different appearances.
The dermis is a supporting matrix with a remarkable capacity for retaining water. The thickness of the dermis varies from less than 0.5 mm to more than 5 mm. There are two principal types of protein, collagen and elastic tissue, out of which collagen comprises 80-85% of the dry weight.
Skin also contains many supporting structures like hair follicles, pilosebaseous unit which secrete oily substance called sebum.
Functions of Skin :
The main function of skin is to act as a barrier to external environment which can be
Regulation of body temperature achieved through dilation or constriction of blood vessels or secretion of sweat by sweat glands
As sensory organ, helping in perception of different sensations
Subcutaneous fat has important roles in cushioning trauma as well as providing insulation and a calorie reserve.