2. The Integumentary System

3. 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

4. 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-?

5. 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)

6. 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

7. 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

9. 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.

10. 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

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

12. 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

13. 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.

14. 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

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

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