Introduction, Organization & Integumentary System

Introduction, Organization & Integumentary System

The skin is the largest organ of the body that accounts for about 15% of the total adult body weight. It has multiple dynamic functions, including protection against outside physical, chemical, and biologic attackers, as well as avoidance of excess water loss from the body and a part in thermoregulation (Kanitakis, 2002).

        The skin has three layers: the epidermis, the dermis, and subcutaneous tissue. The outermost level, the epidermis, is made up of of a specific group of cells known as keratinocytes that function to synthesize keratin, which is a long, threadlike protein with a protective character. The middle layer, the dermis, is made up of a structural protein known as collagen. The dermis resides on the subcutaneous tissue, which contains small portions of fat cells known as lipocytes. The thickness of the layers fluctuates substantially, depending on the physical location on the body.

        The epidermis is separated into five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

Stratum Basale - The stratum basale has the dividing cells. This layer is also known as stratum germinativum.

Stratum Spinosum - The stratum spinosum is comprised of a layer several cells deep. The cells have sharp or spiny parts on them.

Stratum Granulosum - The cells in the stratum granulosum have keratohyaline granules.

Stratum Lucidum - The stratum lucidum only exists in thick skin.

Stratum Corneum - The stratum corneum is the outmost layer. It is also known as the horny layer. The cells in this layer are basically bags of keratin. They contain no nuclei or organelles.

        Sweat glands, hair, nails and sebaceous glands are all epidermal appendages. Several types of skin stem cells have been discovered to include 1. Epidermal stem cells which are responsible for daily regeneration of the diverse layers of the epidermis. These stem cells are located in the basal layer of the epidermis. 2. Hair Follicle stem cells that guarantee constant renewal of the hair follicles and 3. Melanocyte stem cells in which are responsible for renewal of melanocytes, a type of pigment cell. It hasn’t been determined where these stem cells are found in humans.