Lecture 5.3: Integumentary

System

Secrete onto skin About 2-5 million throughout the body Lots in palms and soles of feet Secretion: 99% water Electrolytes Urea Cools surface and lowers body temp Blood vessels dilate Reddens skin Negative Feedback System

Merocrine Glands

Figure 5.7

Protect tips Nail body—what you see Nail bed—skin under nail body Nail root—produces nail Pink color due to blood vessels

Nails

Figure 5.8

Bleeding at injury Mast cells trigger inflammatory response Scab forms Phagocytes remove debris Clot forms Epidermal cells form Scab falls off New epidermis underneath

Injury and Repair

Figure 5.9 1

Figure 5.9 2

Figure 5.9 3

Figure 5.9 4

First Degree Killed superficial epidermis Injured deep epidermis Inflamed, tender

Burns

Second Degree Killed superficial and deep epidermis Injured superficial dermis Blisters, very painful

Burns cont…

Third Degree Killed all epidermal and dermal cells Injured hypodermis and organs Charred No sensation

Burns cont…

Skin injuries and infections common Stem cell activity decreases Epidermis thins Immune system less sensitive Increased rate of infection Muscle and bone weaken Due to decreased vitamin D production Sensitive to sun Due to decreased melanin production Skin pales

Aging

Dry, scaly skin Decreased sebum and perspiration Hair thins and changes color Follicles stop Decreased melanocytes Sagging and wrinkling Decreased elastic fibers Ability to lose heat decreases Reduced blood supply Slow skin repair

Aging cont…