Integument System Anatomy & Physiology Chapter 6

Fig Skin and Its Tissues: Functions of Skin – 1.Protective Covering 2.Helps regulate body temp. 3.Retards water loss. 4.Houses sensory receptors 5.Synthesizes some biochemicals 6.Excretes some wastes.

Fig. 6.01a Epidermis – Outer layer. Cells are stratified squamous epithelium. Dermis – Inner layer. Contains connective tissue (collogen & elastin) epithelial tissue, nervous tissue & blood. Subcutaneous Layer – not a skin layer, lies between dermis and muscle – mostly adipose tissue (fat).

Fig Layers of the Epidermis: *Basement Membrane – anchors Dermis to Epidermis *Stratum basale (germinativum) – produces new skin cells and pushes them up toward surface. *Stratum Spinosum *Stratum granulosum *Stratum lucidum *Stratum corneum – outermost layer. Keratinization = older cells filling with keratin protein, becoming tougher and more waterproof.

Fig Melanocytes – specialized cells that produce melanin. Melanin – pigment that absorbs UV light to prevent mutations to DNA in skin cells and damage to connective tissue. Cytocrine secretion – extensions of melanocytes deposit melanin granules in nearby cells.

Fig. 6.03a Skin Color: caused by differences in melanin produced (amount, size of granules, and distribution). Other Factors: UV exposure, blood flow, oxygen levels, diet (beta-carotene), jaundice.

Fig Accessory Organs of the SkinNails: Lunula – white, half-moon region. Actively dividing epithelial cells that become keratinized. Nail Plate – keratinized scales that form the nail. Nail Bed – surface of skin, under the nail plate.

Fig. 6.05Hair: Hair Follicle – tubelike depression of epidermal cells. Cells divide and grow from hair root. As older cells are pushed up, they become keratinized and die. Hair Color – caused by melanocytes depositing varied amounts of melanin into cells. Red – caused by trichosiderin, another pigment. Arrector pili muscle – smooth muscle attached to hair follicle. Contracts when cold or emotional to give goosebumps!

Fig. 6.06

Sweat Glands – coiled tubes that serve as exocrine glands releasing sweat. Eccrine Glands – release water, salt, urea and uric acid (Sweat). For reducing body temperature and excretory functions. Apocrine Glands – in groin and armpits, release sweat and some pheromones. Modified Sweat Glands – Ceruminous glands – ear wax. Mammary glands - milk

Fig Sebaceous glands – specialized glands that secrete oil and cell debris (sebum) into the hair follicles. Sebum – oily mixture that is secreted. Keeps hair and epidermis soft, pliable and waterproof!

Fig. 6.01b

6.3 Regulation of Body Temperature Cooling the body/increasing heat loss: 1. Sweat – evaporation from epidermis removes heat from body. 2. Vasodialation – increase blood flow to surface of skin. Increases heat loss to air. Warming the body & preventing heat loss. 1.Adipose tissue – insulates against heat loss. 2.Vasoconstriction – blood flow reduced to surface of skin. 3.Involuntary contraction of muscles – increases heat production by muscles. 4.Shivering – large groups of muscles contracting producing more heat.

Fig. f6.a Skin Cancers Know your skin cancer ABC’s: (When it doubt – have a doctor check it out!) A = Asymmetry B = irregular Borders C C = non-uniform Color D = Diameter larger than a pencil eraser E = Elevated

Fig. f6.aa Squamous cell carcinoma – Arise from nonpigmented epithelial cells within the deep layer of epidermis. Cutaneous carcinomas – most common and treatable types of skin cancers. - appear in people, around 40+, who are regularly exposed to sun and who are light-skinned.

Fig. f6.ab Basal Cell Carcinoma – arises from cancerous cells in the Stratum Basale/Stratum Germanativum. Also a type of Cutaneous carcinoma (common and highly treatable). Caused from prolonged exposure to UV light.

Fig. f6.ac Malignant Melanoma – caused by cancerous melanocytes. Caused by short exposures to intense sunlight by people who normally stay indoors. Occurs at any age! Treatable if growth is horizontal. Vertical growth into deeper tissue can spread and be fatal.

Table Healing of Wounds Damage to skin causes increased blood flow to area to expedite new cell growth. Scab – clotting of blood to prevent fluid loss and infection. Scar – caused by rapid production of collagen-based connective tissue to heal wounds (produced by fibroblasts).

Topic of Interest: Types of Burns 1 st degree – injury to the epidermis alone. Heals within about 1 week. 2 nd degree – injury to the epidermis and some dermis. 3 rd degree – injury to the epidermis, the dermis and the accessory organs. May require transplant or skin substitute depending on size of burn.