Essentials of Human Anatomy & Physiology Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Chapter 36-3 The Integumentary System

The Integumentary System Composed of the skin, sweat and oil glands, hair, and nails. Accounts for 7% of the body’s weight. Major role is protection from pathogens and dehydration. Varies in thickness from 1.5 to 4.0 mm. Composed of 3 distinct layers. Epidermis, Dermis, and hypodermis or superficial fascia

Epidermis Outermost layer. Composed mostly of keratinized stratified squamous epithelium. Contains 4 distinct cell types and 4 to 5 distinct layers.

Cell Types of the Epidermis Keratinocytes—produce keratin, a fibrous protein that give the epidermis its protective properties.Those on the surface of the skin are dead. Millions rub off per day. Friction may lead to a thickening of the cells known as a callus.

Cell Types of the Epidermis Melanocytes—synthesize melanin. Located at the deepest layer of the epidermis. The melanin is transferred to the keratocytes. Protects against UV damage.

Cell Types of the Epidermis Langerhans’ cells—arise from the bone marrow. Act as macrophages that activate the immune system. Merkel cells—present at the junction of the epidermis and dermis. Associated with sensory receptors.

The Dermis Made mostly of connective tissue. The hide of the human body. Contains the hair follicles, sweat glands, oil glands, lymphatic vessels, and many sensory receptors. Skin color—determined by melanin, carotene, and hemoglobin. Freckles, Moles and Paleness Photosensitivity, Bruises, Bronzing, Jaundice

Skin Appendages Sweat Glands—more than 2.5 million per person. Ceruminous glands—secrete earwax. Mammary glands—secrete milk. Sebaceous Glands—oil glands. Found everywhere except the palms and soles. Secrete sebum.Usually secreted into hair follicles. Bactericidal + other functions.

Hair Parts of the hair –Shaft Medulla Cortex Cuticle –Root –Hair follicle Hair bulb Root hair plexus Hair papilla

Nails Modification of the epidermis Composed of keratin. Composed of a free edge, body, and a root. Nail bed—epidermis under the nail. Nail matrix—growth occurs here. Lunula cuticle

Functions of the Integument Chemical barriers—acid mantle, human defense Biological Barriers—Langerhan’s cells and macrophages. Physical barrier –Some substances can cross the skin. Lipid soluble substances. Oleoresins—poison ivy. Organic solvents. Salts of heavy metals

Functions of the Integument Temperature Regulation –Sweat glands –Vasodilation and vasoconstriction Cutaneous Sensation –Meissner’s corpuscles, Pacinian corpuscles –Root hair plexuses –Pain and heat/cold receptors Metabolic Functions –Vitamin D synthesis Blood Reservoir –Shunts more blood into the circulation when needed. Excretion

Skin disorders Basal cell carcinoma—30% of caucasians get this type of skin cancer. Does not metastasize. Squamous Cell carcinoma—arises from the keratinocytes in the stratum spinosum. May metastasize. Melanoma—arises in the melanocytes. Rapidly metastasizes.