The body's front line of defense against pathogens. Composed of two layers. It consists of an outer ectodermal epidermis that is more or less cornified and penetrated by the openings of sweat and sebaceous glands and an inner mesodermal dermis that is composed largely of connective tissue and is richly supplied with blood vessels and nerves.
The epidermis (outer layer of the skin) is mostly made up of flat, scale-like cells called squamous cells. Under the squamous cells are round cells called basal cells. The deepest part of the epidermis also contains melanocytes. These cells produce melanin, which gives the skin its color.
The dermis (inner layer of skin) contains blood and lymph vessels, hair follicles, and glands. These glands produce sweat, which helps regulate body temperature, and sebum, an oily substance that helps keep the skin from drying out. Sweat and sebum reach the skin's surface through tiny openings called pores.