THE INTEGUMENTARY SYSTEM C14L3 HUMAN SKIN

Integumentary System skin hair nails

Skin Stats … Approx. 28 hundred sq. inches (about 18 sq. feet) of skin cover the body Average thickness is 1/8 inch Weighs 6-9 pounds (6% of the body weight) Skin is the largest organ of the human body

A piece of skin the size of a quarter contains: 1 yard of blood vessels 4 yards of nerves 25 nerve endings 100 sweat glands more than 3 million cells

FUNCTIONS OF THE SKIN Protection Sensory Response Temperature Regulator Excretion Manufacture Absorption

Protection (a mechanical shield) Your skin is one of your body’s major defenses. The skin does not permit significant amounts of substances like water in or out of the body. It keeps your body from drying out. Bacteria, viruses, and many common chemicals that you constantly touch would be very harmful if they penetrated into the body. Skin is an effective barrier to most of them.

Protection (a mechanical shield) Perspiration and oils secreted by the skin provide a form of chemical protection which is acidic and sometimes has enzymes that inhibit the growth of certain microorganisms.

Sensory Response Nerve receptors for pressure, temperature, and pain are in the skin. Communication between your body and the outside world. The more sensory receptors there are in an area of skin, the more sensitive it is.

Temperature Regulator The amount of blood being carried to the surface of the skin is regulated to control the amount of thermal energy released. Blood vessels in skin dilate when you need to cool off and constrict when you need to conserve heat. Also evaporation of sweat cools the body.

EXCRETION (Secretion) A small amount of body wastes is excreted with sweat. sweat glands – move moisture to the surface to cool, also give off certain wastes to help keep the body clean oil glands (sebaceous) – coat the skin with oils to keep it from drying out.

VITAMIN MANUFACTURE The skin produces small amounts of vitamin D if exposed to sunlight. Vitamin D helps it absorb calcium and phosphorous to promote bone growth. As little as minutes of sunlight 2-3 days a week will produce sufficient vitamin D.

ABSORPTION The skin can absorb some chemicals, a few drugs, and a small amount of oxygen.

Layers of the Skin Epidermis (1) Dermis (2) Hypodermis (3) 1 2 3

Epidermis the outermost layer of the skin has dead cells at the surface and living cells underneath contains nerve endings (example: pain receptors) the older cells of the epidermis fill with a waxy substance called keratin and die approximately every 25 days (faster for some people and in some areas of the body) a completely new epidermis covers the body

Epidermis The epidermis produces melanin, which is a pigment that protects the body by absorbing some of the Sun’s damaging ultraviolet rays.

Dermis the inner, much thicker layer of the skin; giving skin strength, nourishment, and flexibility. contains: connective tissues blood vessels nerve endings sweat glands hair follicles oil glands

Hypodermis layer consists of loosely arranged fat cells and fibers the fat cells help to cushion and insulate you body and store energy

Skin

Skin Color dark pigment - melanin yellowish pigment - carotene Pink color of a person's skin is his blood showing through. Other colors are the results of pigments.

Melanin Melanin is produced by special cells (melanocytes) in the skin.

Freckles Freckles are clumps of cells that contain more melanin that the rest of the skin.