Introduction, Organization & Integumentary System
Trident University

Introduction:
The integumentary system, otherwise known as, the skin is the largest and one of the most important organs in the human body and is made up of three different layers, the epidermis, the dermis and the sub-cutaneous. It is the organ system that is constantly changing and regenerating itself over a period of four to six weeks as it protects our internal body parts from damage. It also performs necessary functions like, temperature regulation, waste excretion and it is the protective coating over the internal body tissues. The skin also serves as the sensory receptor for pain and pleasurable sensations from pressure and temperature and, when we are exposed to sunlight, our integumentary system also generates necessary vitamin D. (Sanders, 2007) The integumentary system makes up around seven percent of a human being’s total body weight and is composed of the skin, skin derivatives, glands, hair and nails. (Graaff, 2001 )

How Skin cells are formed:
The human skin is composed of several layers. The surface layer, or the one you can see, is the epidermis. The epidermis is composed of multiple layers of cells made up of Keratinocytes and they comprise roughly 85 percent of the cells in the epidermis. These cells make keratin, a hard protein substance which provides structural integrity and also makes up your nails and hair.
New keratinocytes are grown at the lowest level of the epidermis, the mitotic layer, through a process called mitosis. Here the keratinocytes divide to form two identical cells, one of which remains for future mitosis and the other moves upward to the differentiation layer for further changes. (Graaff, 2001 )

Stages of skin cell maturation:
The differentiation layer is the thickest layer of the epidermis and this is where the keratinocytes grow and