About Skin
Skin is a living barrier between the body and the outside world. It limits water loss, blocks many harmful substances and microbes, senses touch and temperature, helps regulate body heat, makes vitamin D when exposed to appropriate sunlight, and repairs itself after minor injury.
Epidermis
The epidermis is the outer layer of skin.
Learn MoreDermis
The dermis is a deeper supportive layer containing collagen, nerves, glands, follicles, and blood vessels.
Learn MoreBelow the Skin
A fatty layer beneath the skin helps cushion the body and store energy.
Learn MoreSweat
Sweat helps cool the body when it evaporates.
Learn MoreMelanin
Melanin helps determine skin, hair, and eye color and absorbs ultraviolet radiation.
Learn MoreHair and Nails
Hair and nails are specialized structures made largely from keratin.
Learn MoreHealing
Skin begins repairing damage soon after an injury.
Learn MoreSkin Microbiome
Healthy skin naturally supports communities of microorganisms.
Learn MoreEpidermis
Most epidermal cells are keratinocytes that produce the tough protein keratin. New cells form in deeper layers and gradually move outward, where dead surface cells are continually shed.
Dermis
Collagen and elastic fibers give skin strength and flexibility. Sensory nerve endings detect pressure, pain, temperature, and other signals.
Below the Skin
This subcutaneous tissue is not technically part of the skin itself, but it anchors skin to deeper structures and contains larger blood vessels and nerves.
Sweat
Sweat glands release mostly water and salts onto the skin surface. Evaporation removes heat. The nervous system increases sweating when body temperature rises.
Melanin
Specialized cells called melanocytes produce melanin. People have broadly similar numbers of melanocytes, but the amount, type, size, and distribution of pigment differ.
Hair and Nails
Hair follicles extend into the skin and produce hair shafts. Nails grow from a specialized region near the base of each nail and protect the ends of fingers and toes.
Healing
Clotting limits bleeding, immune cells clean the area, new tissue fills the gap, and surface cells grow across the wound. Larger injuries can produce scar tissue.
Skin Microbiome
Different body areas create dry, moist, or oily habitats. Normal microbes interact with skin chemistry and immune defenses. Having microbes on skin is a normal part of being human.