The Integumentary System Integumentary System Organ - two or more kinds of tissues grouped toghether and performing specialized functions. Skin is an organ composed of sheetlike membranes of epithelium and connective tissue. Types of Membranes 1. Serous membrane a. Line body cavities that lack openings to the outside. b. Secrete serous fluid for lubrication. c. Found in the inner lining of the thorax and abdomen. Types of Membranes 2. Mucous Membranes a. Line cavities and tubes that open to the outside of the body. b. Secrete mucus c. Found in oral and nasal cavities and tubes of digestive, respiratory, urinary and reproductive systems. Types of Membranes 3. Synovial membranes a. Form inner linings of the joint cavities between the ends of bones at freely moving joints (synovial joints) b. Secrete thick, colorless synovial fluid 4. Cutaneous membrane - the external body covering, SKIN The Functions of Skin 1. Protective covering 2. Regulates body temperature 3. Slows water loss 4. Contains sensory receptors 5. Synthesizes biochemicals 6. Excretes wastes Skin and Its Tissues Epidermis 1. Stratum basale - deepest layer of the epidermis, cells undergo mitosis. 2. Keratinization occurs as cells are pushed towards the surface. 3. Stratum corneum - outermost layer of dead cells. Epidermis 4. Epidermis protects underlying tissues against water loss, mechanical injury, and effects of harmful chemicals. 5. Melanin protects from UV light. 6. Melanocytes transfer melanin to epidermal cells. Epidermis Dead cells As cells are pushed up they become keratinized Basal cells undergoing mitosis Skin Color 1. All people have about the same concentration of melanocytes. 2. Skin color is due to the amount of melanin and the size of pigment granules in the epidermis. 3. Skin color is influences by environmental and physiological factors as well as genes. Skin Color 4. Albinism - genetic disorder characterized by no melanin, resulting in white skin and hair. Dermis 1. Binds the epidermis to the underlying tissues 2. Contains blood vessels that supply all skin cells with nutrients and regulate body temperature. Dermis 3. Contains nerve fibers a. May carry impulses to muscles and glands of the skin. b. May be associated with sensory receptors in the skin. 4. Contains hair follicles, sebaceous glands, and sweat glands. Subcutaneous Layer 1. Loose connective and adipose tissue 2. Conserves body heat. 3. Contains blood vessels that supply the skin and adipose tissue. Accessory Organs of the Skin 1. Hair follicles a. Hair develops from epidermal cells at the base of a tubelike hair follicle. b. Cells are keratinized and pushed towards the surface as new cells are formed. Accessory Organs of the Skin Hair Follicles cont…. c. Smooth muscle cells attached to each follicle. d. Hair color is determine by genes that determine how much melanin is produced. Accessory Organs of the Skin 2. Sebacceous Glands a. Attached to hair follicles. b. Secrete sebum (oily secretion) which keeps hair soft and water proof c. Acne - infection of sebacceous glands Accessory Organs of the Skin 3. Nails a. Protective covers on ends of fingers and toes. b. Keratinized epidermal cells produce nails. c. Keratin of nails is harder than that produced by the skin’s epidermal cells Accessory Organs of the Skin 4. Sweat Glands a. Consists of a coiled tube. b. Sweat - mostly water, also contains salts and waste products. c. Eccrine sweat glands respond to elevated body temperature, while apocrine sweat glands respond to emotional stress. Regulation of Body Temperature Regulation of body temperature is vital because heat affects the rates of metabolic reactions. Normal body temperature is 37ºC (98.6ºF) Regulation of Body Temperature 1. Increase in body temperature causes dermal blood vessels to dilate and sweat glands to secrete sweat. 2. Decrease in body temperature causes dermal blood vessels to constrict and sweat glands become inactive. Regulation of Body Temperature 3. Excessive heat loss stimulates skeletal muscles to contract involuntarily. 4. Fever results from an elevated temperature set point. Healing of Wounds 1. Inflammation - affected area becomes red, warm, swollen and tender. 2. Dividing epithelial cells fill in shallow cuts. 3. Clots close deeper cuts, sometimes leaving a scar where connective tissue replaces skin. 4. Granulations form as part of the healing process.
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