Editing Anatomy and Physiology (section)

== Integumentary System ==

The skin has three layers: the '''epidermis''' (avascular, nourished by diffusion, contains melanocytes and keratinocytes), the '''dermis''' (blood vessels, nerve endings, hair follicles, sweat and sebaceous glands, collagen), and the '''subcutaneous (hypodermis)''' layer of fat and connective tissue.

Functions: protection and barrier defense, temperature regulation through vasodilation, vasoconstriction, and sweating, sensation, vitamin D synthesis, and fluid and electrolyte conservation.

'''Nursing application:'''
* Pressure injury staging follows anatomy. Stage 1 is intact skin with nonblanchable erythema, stage 2 is partial thickness loss into the dermis, stage 3 is full thickness with visible subcutaneous fat, and stage 4 exposes muscle, tendon, or bone. Unstageable injuries are obscured by slough or eschar; deep tissue injury appears as persistent nonblanchable deep red, maroon, or purple discoloration.
* Because the epidermis is avascular and the dermis holds the vessels, capillary refill and blanching tell you about dermal perfusion.
* Burns destroy the barrier function, so the immediate threats are massive fluid shift and hypovolemia first, and infection later.
* Older adults have thinner dermis, less subcutaneous fat, and reduced elasticity, which increases skin tear and pressure injury risk and makes skin turgor an unreliable hydration indicator. Check turgor over the sternum or forehead in older adults instead of the back of the hand.