The Integumentary System

This lesson introduces the anatomy of the integumentary system, including the system’s function. This lesson also describes the effects of aging and cancer on the integumentary system.

The Skin’s Many Layers

The integumentary system is a body system comprised of the skin and accessory structures, including the hair, sebaceous and sweat glands, and nails. This system protects the body, maintains homeostasis, and provides sensory information about the external environment.

The largest organ in the integumentary system is the skin. Often not thought of as an organ, the skin is made of four different tissues that work together to perform a variety of functions such as preventing toxic substances from entering the body and regulating body temperature.

As shown in the image, the skin consists of several layers. These layers are divided into three regions: epidermis, dermis, and subcutaneous tissue. The epidermis is the outermost layer composed of keratin and stratified squamous epithelium tissue. Keratin is made of keratinocytes, which toughen and waterproof skin. Other cell types that make up the epidermis are melanocytes, which give skin its color, merkel cells, and Langerhans cells.

The epidermis can have either four or five layers depending on where it is located on the body. As shown in the following image, these layers consist of the stratum basale (innermost layer), stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.

For Example

The soles of the feet have five layers because they are exposed to a lot of friction as a person walks. The epidermis on the leg consists of only four layers.

Nerve endings and blood vessels are not found in the epidermis. Epidermal cells are found deep in the stratum basale and constantly undergo mitosis to make new cells. As new cells are made, they travel to the outer skin surface, producing the protein keratin. Epidermal cells fill with keratin and die upon reaching the skin’s surface. When this happens, the leftover keratin from the dead cells help form the stratum corneum, which is the waterproof layer. These dead epidermal cells are gradually shed from the skin and replaced with new cells.

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