Review: Anatomy of the Skin

Here is what we have learned from Anatomy of the Skin:

• The skin is a vital organ that covers the entire outside of the body, forming a protective barrier against pathogens and injuries from the environment. The skin is the body's largest organ; covering the entire outside of the body, it is about 2 mm thick and weighs approximately six pounds.
• The skin helps regulate body temperature, gathers sensory information from the environment, stores water, fat, and vitamin D, and plays a role in the immune system protecting us from disease.
• The color, thickness and texture of skin vary over the body. There are two general types of skin; thin and hairy, which is more prevalent on the body, and thick and hairless, which is found on parts of the body that are used heavily and endure a large amount friction, like the palms of the hands or the soles of the feet.
• Basically, the skin is comprised of two layers that cover a third fatty layer. These three layers differ in function, thickness, and strength.
• The outer layer is called the epidermis; it is a tough protective layer that is made up of five sublayers that work together to continually rebuild the surface of the skin.
• The second layer of the skin (located under the epidermis) is called the dermis; it contains collagen and elastin, blood vessels, lymph vessels, nerve endings, sweat glands, sebaceous (oil) glands, and hair follicles.
• The innermost layer of the skin is a fatty layer of subcutaneous tissue consisting of a network of fat and collagen cells and is known as the subcutis or hypodermis.
• The basal cell layer of the epidermis contains melanocytes. Melanoma develops when melanocytes undergo malignant transformation.
• The stratum corneum is the outermost layer of the epidermis, and is made up of thin layers of continually shedding, dead keratinocytes. The stratum corneum is also known as the "horny layer," because its cells are toughened like an animal's horn. As the outermost cells age and wear down, they are replaced by new layers of strong, long-wearing cells.
• Regional lymph nodes for melanoma of the skin vary by primary site, and are bilateral or contralateral for the primary sites of head, neck and trunk.