Integumentary system is the organ system that covers the body . It includes the skin , hair , nails , sweat glands and subcutaneous tissue , the tissue beneath the skin. The integumentary system is one of the body’s major organ systems.
The integumentary system functions to protect the body from chemical and physical injury, from infection, and from ultraviolet (UV) radiation from sunlight. It also helps to regulate body temperature through perspiration . The many nerves in skin enable the body to sense touch, vibration, temperature, and pain, so that the body is aware of its environment. The integumentary system also has some metabolic functions. For example, it excretes (gets rid of) some of the body’s waste products through sweat. Also, one step in the production of vitamin D occurs in the skin.
The skin
is divided into two layers. The outer layer is called the epidermis. It consists of many layers of flattened cells called keratinocytes. These cells form the body’s outermost protection. They create a waterproof seal that prevents the body from losing or gaining too much moisture. Keratinocytes divide rapidly, so that cells lost to cuts, scrapes, and simple friction are quickly replaced. Millions of keratinocytes are shed and replaced each day. The epidermis also contains pigmented (colored) cells called melanocytes. These cells give skin its color and protect the body from the harmful UV radiation.
The deeper layer of skin is the dermis. It is a strong but flexible layer of tissue with many nerves, blood vessels, and glands. The main component of the dermis is collagen , a strong, ropelike protein that gives skin its strength and durability.
Beneath the skin is a thick layer of tissue called the subcutaneous layer or hypodermis. Within this layer, the body stores much of its adipose ( fat ) tissue. When a person gains weight, excess fat accumulates within this layer.
Skin appendages.
The hair, nails, and sweat glands of skin are collectively called skin appendages. Hair and nails consist of keratinocytes that produce keratin , a hard protein that gives nails their firm structure and hair its strength. Hair grows from follicles located deep within the dermis. Millions of hair follicles are located all over the body except on the palms, soles, lips, nipples, and parts of the external genitalia. Melanocytes within hair follicles produce the pigment that gives hair its natural color. Nails are a special growth of the epidermis at the ends of fingers and toes. They act as tools that help people to pick up small objects and to scratch.
Sweat glands are also distributed throughout the body surface. They produce a watery secretion on the surface of skin that helps to cool the body when it gets too hot. Sweat glands are also stimulated by fear, nervousness, and embarrassment.
