Fxs and Structures of Dermis strong flexible conn tissue cells include fibroblasts cells that synthesize the extracellular matrix and collagen macrophages and occasionally mast cells and white blood cells 2 layers fx and strutures o papillary composed of areolar conn tissue with collagen and elastic fibers and blood vessels Contains capillary loops nutrients for the epidermal layer Meissner s corpuscles sense light touch and vibrations many found on fingertips and nerve endings o reticular 80 of the thickness of dermis Collagen fibers provide strength resiliency Stretch marks due to tears in the collagen of dermis contains several parts o structural protein fibers o sweat glands o hair follicles o sebaceous glands o nail roots o nerve endings scars tattoos GLANDS two main types of sweat glands o eccrine merocrine sweat glands 304 million abundant on palms soles forehead o apocrine sweat glands are confined to axillary and anogenital areas sebaceous oil glands active at puberty o widely distributed most develop from hair follicles become o sebum secreted oily holocrine secretion bactericidal o acne softens hair and skin plugged sebaceous ducts whitehead blackhead o treatments benzoyl peroxide antibacterial salicyclic acid unclogs pores antibiotics kill bacteria Dioxycycline tetracycline erythromycin HAIR fxs o alerting body to presence of foreign particle such as insect or irritant on the skin o guarding the scalp agst physical trauma heat loss sunlight o visual identification hair characteristics help determine sex age identification o insulation anorexia location entire surface except palms soles lips nipples and portions of external genitalia consists of dead keratinized cells containds hard keratin more durable than soft keratin of skin associated with glands and a muscle hair pigments melanins in o gray white hair decreased melanin production hair root hair shaft o lower part of the hair o attached to the integument o upper part of the hair o not attached to the integument one hair is called a pilus types of hair o vellus is the hair at birth peach fuzz o terminal hair is present in specific regions normal adult hair o lanugo hair is fine baby hair last trimester of pregnancy and sometimes on babies but falls off pale fine body hair of children and adult females terminal is coarse long hair of eyebrows scalp axillary and pubic HAIR GROWTH growth phase weeks to yrs followed by regressive stage and resting phase 1 3 mos growth phase varies 6 10 yrs in scalp 3 4 mos In eyebrows hair grows at rate of 3 mm day and lose 10 100 hairs a day phases of growth o active phase of the hair growth cycle anagen o catagen transitional phase of the hair cycle bw growth and resting of the hair follicle o telogen the resting phase of the hair growth cycle hair follicle o extends from the epidermal surface into the dermis o hair begins deep in the dermis the hair papilla contains capillaries and nerves that provide nourishment the hair bulb produces hair matrix hair matrix epithelium is one of the fastest growing cell populations in human body o a hair follicle is a part of the skin that grows hair o internal root sheath the inner layer contacts the cuticle in lower hair root o external root sheath extends from skin surface to hair matrix o glassy membrane basement membrane a dense conn tissue sheath contacts conn tissues of dermis hair anatomy o central medulla o cortex surrounds medulla o cuticle on outside of cortex is most heavily keratinized hair pigments melanin types o pheomelanin is responsible for the yellowish blond to red colors o eumelanin is responsible for the brown to black shades hair follicle receptor root hair plexus o sensory nerve endings around each hair bulb stimulated by bending a hair responds to initial movement arrector pili muscles o smooth muscle attached to follicle o responsible for goose bumps HAIR THINNING AND BALDNESS o is hair thinning in both sexes o true baldness genetically determined and sex influenced condition male pattern baldness is caused by follicular response to testosterone
View Full Document
Unlocking...