The Integumentary System

The Integumentary system consists of the skin, hair, nails, and various glands. It is the most visible organ system of the body The Integumentary system has two major components: The cutaneous membrane (skin) is an organ composed of the superficial epithelium, (epidermis) and the underlying connective tissues of the dermis The accessory structures include hair, nails and a variety of exocrine glands

MAJOR FUNCTIONS: Protection- covers/ protects underlying tissues and organs from impacts, chemicals, and infections, prevents the loss of body fluids. Temperature maintenance-HOW? Synthesis and storage of nutrients- the epidermis synthesizes vitamin D3 , a steroid building block for a hormone that aids calcium uptake. The dermis stores large reserves of lipids in adipose tissue. Sensory reception- receptors detect touch, pressure, pain, and temperature stimuli Excretion and secretion-?

Epidermis Thick skin- palms of hands and soles of feet, contains five layers. (about as thick as a paper towel) Thin skin- covers the rest of the body and has only four layers. (about as thick as a plastic sandwich bag)

Layers of the Epidermis Stratum Germinativum- deepest epidermal layer, cells firmly attach to the basement membrane. Forms epidermal ridges which extend into dermis Dermal projections called dermal papillae extend upward between adjacent ridges, obtain nutrients by dermal blood vessels Intermediate Strata- combines three layers to form the outer protective barrier of the skin 1) Stratum Spinosum (spiny layer)- daughter cells continue to divide and add to the thickness of the epithelium

2) Stratum Granulosum (grainy layer) consists of cells displaced from the Statum Spinosum. Site of keratin production: extremely durable and water-resistant- skin and hair, calluses, nails (hooves), horns 3) Stratum Lucidum (clear layer in palm/sole)- covers the stratum granulosum and cells are flattened, densely pack and filled with keratin Lastly = Stratum Corneum- flattened, dead outer layer

Skin Color Pigmentation- the epidermis contains variable amounts of two pigments: carotene and melanin Carotene is an orange-yellow pigment that normally accumulates in epidermal cells Melanin is a brown, yellow-brown, or black pigment produced by melanocytes Melanocytes manufacture and store melanin within intracellular vesicles, they slowly increase activity with sunlight Ultraviolet light is beneficial because it stimulates synthesis of vitamin D3 in the epidermis However excessive amounts and long term exposure damages the skin and can cause skin cancer.

3 Factors Determining Skin Color 1) Genetic- all people have the same # of melanocytes What differs? Amount of melanin produced and size/ distribution of melanin. Production controlled by several genes Albinism- lack of pigment in skin, hair, iris. Avg. 1 in 20,000 people, 1 in 200 for Hopi

2) Environmental factors- Tanning! Light ( UV rays) stimulate melanocytes

3) Physiological Dilation/ constriction of blood vessels- flush/pale Presence of carotene- accumulates in adipose tissue Jaundice- if newborn infants, signals immature liver. Adults, signals liver failure

Skin Cancer Skin cancer is the most common type of cancer The most common type is basal cell carcinoma which originates in the stratum germinativum The less common are squamous cell carcinomas which involve more superficial layers of the epidermis Melanomas are the most dangerous, usually starting as moles and can appear anywhere on the body.

Dermis Papillary layer- loose connective tissue that supports and nourishes the epidermis, contains capillaries and nerves Reticular layer- interwoven meshwork of dense, irregular connective tissue, elastic and collagen fibers are present The elastic fibers provide flexibility and prevent damage

Next: Accessory structures: nails, hair, glands Injury repair Aging

Student Lectures (That sounds like work!!) 1) The Dermis 121-122 2) Subcutaneous layer 122 3) Structure of hair 122 4) Function of hair/ hair color 122-123 5) Sebaceous glands 124 6) Apocrine sweat glands/ nails 124-126 7) Merocrine sweat glands 124-125 8) Burns ( include table 5-1) 128 9) Injury repair 126-127 10) Aging 128 11) Questions pg 121/123/126 12) Interconnectedness 132