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Dermis and Hypodermis Dermis Lies deep (beneath the epidermis) Provides strength and elasticity to the skin Creates framework to support the accessory structures Made of 2 layers Papillary Layer Made of areolar tissue Contains capillaries and sensory neurons that serve the epidermis above The top of this layer has dermal papillae that connect to the dermal ridges of the stratum germinativum Reticular Layer Made of a mesh of dense irregular connective tissue w/ lots of collagen and elastin protein fibers Contains hair follicles, sweat glands, oil glands, blood vessels and nerves The collagen and elastic fibers allow the skin to stretch and change shape Skin Damage Aging, hormones, and UV radiation can all damage and reduce the amount of elasticity of the skin causing wrinkles and sagging Hypodermis/Subcutaneous Fibers of the reticular layer extend into the subcutaneous layer so there isn’t a distinct line between the two Made of areolar and adipose tissue Stabilizes skin while allowing movement Areas of subcutaneous fat change during a person’s life Location of injections Accessory Structures/ Hair follicles and hair Human body has appox. 5 million hairs and 98% of them are on the general body not on the head Hair bulb- bottom of hair surrounded by epithelial cells Hair shaft- the part of hair we see Hair color- determined by the amount of pigment Function of Hair Protect scalp from UV radiation, insulate the skull Prevent entry of foreign particles Sensitivity (nerves at base of each hair) Insulation (erector pili muscles in the skin cause hair to stand on end) Glands in the Skin Sebaceous Glands- secrete sebum, which prevents bacterial growth, lubricates and protects hair and skin, ex. of a Holocrine gland Blocked sebaceous glands cause acne Sweat glands- 2-5 million sweat glands, cools body temperature Merocrine- palms, soles, secrete onto surface of skin Apocrine- in armpits, groin, secrete their products into a hair follicle Injury and Repair Step 1- bleeding triggers inflammation Step 2- Scab forms, phagocytic cells remove debris, cells from the stratum germanativum migrate to the area Step 3- Fibroblasts create a meshwork to connect tissue Step 4- Fibroblast continue creating scar tissue