The integumentary system includes the skin, hair, nails, and glands. It protects the body, regulates temperature, and detects stimuli. Blood cell production occurs in the bone marrow (skeletal system), not the integumentary system.
Keratin is a tough, fibrous protein found in the outer layers of the skin (epidermis). It protects against abrasion and water loss. Collagen and elastin are found in the dermis for support and flexibility, while melanin provides pigment.
The dermis is the middle layer of the skin that contains connective tissue, blood vessels, nerves, sweat glands, and sebaceous (oil) glands. The epidermis is avascular, and the hypodermis primarily consists of fat and connective tissue.
Melanocytes, located in the basal layer of the epidermis, produce melanin, a pigment responsible for skin color and protection against UV radiation. They do not produce keratin or have a direct role in temperature regulation or bacterial defense.
Eccrine sweat glands are distributed throughout the body and play a key role in regulating body temperature through sweat production. Sebaceous glands produce oil, apocrine glands are involved in scent and are active in specific areas, and ceruminous glands produce earwax.
