The Skin Integumentary System Chapter 6 Cutaneous Membrane

The Skin & Integumentary System Chapter 6

Cutaneous Membrane (skin) ► body covering ► helps prevent water loss ► helps regulate body temperature ► helps produce vit. D needed for normal bone and tooth development ► 2 layers: epidermis & dermis ► Hypodermis or subcutaneous layer (below the dermis)

Epidermis ► made of keratinized stratified squamous epithelium ► layers (from bottom to top): 1. stratum basale (germinativum)-mitotic, contains melanocytes which produce the brown pigment melanin (protects underlying tissues from UV light) 2. stratum spinosum 3. stratum granulosum 4. stratum lucidum –palm and sole only 5. stratum corneumflat, dead cells filled with the waterproofing protein called keratin

Dermis ► main tissue is dense irregular fibrous connective tissue ► contains blood vessels, nerve fibers, accessory organs

Subcutaneous Layer ► made of adipose tissue and loose connective tissue ► has major blood vessels that supply the skin

► Hair follicles-tubelike depression of epidermis-mitosis occurs at base, and old cells become part of the hair itself (shaft) as they die and become filled with keratin; hair color is due to distribution and amount of melanin; red color is due to iron containing pigment ► Sweat glands-2 types: 1) Eccrine sweat glands-empty onto surface of skin; “odorless”; usu. respond to rise in temp. 2)Apocrine sweat glands-empty into hair follicle; “odor”; usu. respond to emotions

► Sebaceous glands-produce oily secretion (sebum): usu. empty into hair follicles; everywhere except palms and soles ► Arrector pili muscles-bands of smooth muscle attached to base of hair follicles: contraction causes goose bumps ► Nails-dead keratinized cells; produced at nail bed; area of most active growth is lunula

Figure 06. 10

Figure 06. 07

Regulation of Body Temperature ► Skin’s role in promoting heat loss- blood vessels leading to skin dilate; blood vessels leading to internal organs constrict---more blood flows to dermis and heat is lost through skin ► Skin’s role in conserving heat-blood vessels leading to skin constrict; blood vessels leading to internal organs dilate--more blood flows to organs, and less heat is lost through skin

Types of Heat Loss ► radiation-heat escapes from a warm area to cooler area ► conduction-heat moves from body directly into molecules of cooler object in contact with the body surface ► convection-as cool air circulates over skin, heat flows to it

► evaporation-fluid (sweat, water, etc. )on surface of skin evaporates, carrying heat with it High humidity in the air interferes with evaporation because the air already is saturated with water vapor, so less water can enter the air through evaporation from the skin---the body is not able to lose heat as well

► In hot and humid environments, the body can overheat because there is less evaporation, and the air temperature may be close to or greater than body temperature (radiation of heat from the skin decreases) ---person may suffer from heat exhaustion. ► If excessive heat loss occurs, the brain triggers the skeletal muscles to contract slightly, generating some heat----then may shiver, generating even more heat. Also, sweat gland activity decreases.

► In elderly people, sweat glands become replaced by fibrous tissue

Factors affecting skin color ► Genetics-most influential ► Environmental-sunlight, UV light, X-Rays ► Physiological-whether blood is oxygenated or deoxygenated; presence of abnormal pigments, such as carotene (orange) and bilirubin(yellow)

Inflammation ► blood vessels in injured area dilate and become more permeable, causing blood to flow to the area and some of the liquid part of the blood to enter the tissue (tissue becomes reddened, warmed, and swollen)