Skin

"The skin is the largest organ of the body, with a total area of about 20 square feet. The skin protects us from microbes and the elements, helps regulate body temperature, and permits the sensations of touch, heat, and cold.
Skin has three layers: The epidermis, the outermost layer of skin, provides a waterproof barrier and creates our skin tone.
The dermis, beneath the epidermis, contains tough connective tissue, hair follicles, and sweat glands.
The deeper subcutaneous tissue (hypodermis) is made of fat and connective tissue.
The skin’s color is created by special cells called melanocytes, which produce the pigment melanin. Melanocytes are located in the epidermis."

Skin Ulcer

Skin ulcers are open sores that are often accompanied by the sloughing-off of inflamed tissue. Skin ulcers can be caused by a variety of events, such as trauma, exposure to heat or cold, problems with blood circulation, or irritation from exposure to corrosive material. Pressure ulcers, also known as decubitus ulcers or bedsores, are skin ulcers that develop on areas of the body where the blood supply has been reduced because of prolonged pressure; these may occur in people confined to bed or a chair, or in those who must wear a hard brace or plaster cast.