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Integument

Skin and its appendages

QuestionAnswer
Keratinocytes - most common cell type in the epidermis - arise from deepest layer of epidermis - present in all epidermal layers - produce keratin: tough fibrous protein that gives the epidermis its protective properties - dead at skin's surface
Layers of the epidermis (top to bottom) - stratum corneum - stratum lucidum (only in thick skin) - stratum granulosum - stratum spinosum - stratum basale
Stratum basale - deepest layer of the epidermis - single row of stem cells that make up the youngest keratinocytes - active cell division - attached to underlying dermis - rely on capillaries in dermis for nutrients
Tactile epithelial cells - found in stratum basale - associated with sensory nerve endings
Melanocytes - make melanin and transport it to nearby keratocytes - respond to UV radiation by increasing production of melanin and transporting to nearby keratocytes--> suntan
Melanin - shields the cell nuclei from incoming UV radiation - more melanin in each melanocyte --> darker skin - most abundant skin pigment
Stratum spinosum - several layers of keratinocytes connected by desmosomes - mitosis occurs, but less than in stratum basale - relies on capillaries in underlying dermis for nutrients - thick bundles of intermediate filaments that contain tension resisting pre-keratin
Dendritic cells - found in the stratum spinosum - part of the immune system - engulf foreign antigens that invade epidermis
Stratum granulosum - 1-5 layers of flattened keratinocytes - relies on capillaries in underlying dermis for nourishment - contains intermediate filaments (pre-keratin) - keratohyaline granules help form keratin - lamellated granules contain a waterproofing glycolipid
Stratum lucidum (thick skin only) - few rows of flat, dead keratinocytes - cells are identical to those in stratum corneum
Stratum corneum - thick layer of dead keratinocytes - keratinocytes are flat sacs filled with keratin - protects skin against abrasion and penetration - intercellular glycolipid keeps layer waterproof
submaxillary plexus - located just below the dermal papillae - supplies superficial dermal tissue, dermal papillae, and epidermis
dermal plexus - between the hypodermis and dermis - nourishes the hypodermis and deep dermis
papillary layer - made up of areolar CT proper - contains dermal papillae
dermal papillae - finger-like projections that interface with overlying epidermis and increase surface area for exchange - on palms and soles, they lie atop dermal ridges that make epidermal ridges ==> finger prints
reticular layer - 80% of thickness of the dermis - dense irregular CT - thick bundles of interlacing collagen and elastic fibers - separations between collagen bundles form cleavage lines - extreme stretching can tear the collagen, causing stretch marks
flexure lines - arise from the deep part of the dermis - result from the repeated folding of the skin
hypodermis - deep to the skin - also called superficial fascia - contains areolar and adipose CT - anchors skin to underlying structures - helps insulate the body
types of skin pigments - melanin - carotene - hemoglobin
parts of a nail - distal free edge - body - root - nail bed: bed of deep epidermis on which nail rests - nail matrix: thickened proximal end where active nail growth occurs - lunule - nail folds - eponychium
hair - flexible strand of dead, keratinized cells - root: embedded in the skin - shaft: projects above skin surface
layers of hair - medulla: central core which consists of large cells and air spaces - cortex: surrounds the medulla and contains several layers of flattened cells - cuticle: outermost layer with single layer of cells that overlap
Hair papilla - connective tissue which is a nipple-like bit of the dermis that protrude into each hair bulb
hair matrix - epithelial cells in hair bulb, just above papilla, which proliferate to form the hair shaft
Hair follicle - extend from epidermis into dermis - associated with arrector pili muscle, which causes hair to stand erect in response to fear, cold, etc.
hair cross-sections round cross-section = straight hair oval cross-section = wavy hair flattened cross-section = kinky hair
Hair color - hair pigment made by melanocytes at base of hair follicle; it's transferred into cells of the hair root - different proportions of 2 types of melanin combine to make the common hair colors
hair types - vellus hairs: fine and short body hairs of women and childen - terminal hairs: longer and coarser hair of scalp, axillary, and pubic area in adults
Sebaceous glands - occur over whole body except palms & soles - secrete sebum (oily) - simple alveolar glands - holocrine secretion: entire cell breaks up to form secretion - most associated with hair follicle
Sebum - oily substance - collects dirt - softens & lubricates hair and skin
Eccrine glands (merocrine) - most numerous sweat gland - produce true sweat; present on palms, soles & forehead
Sweat - 99% water with some salts - contains traces of metabolic wastes - a blood filtrate
Apocrine glands - large sweat glands confined to axillary, anal, & genital areas - ducts open into hair follicles - musky odor - gland activity increases with sexual foreplay - signal information about a person's immune system
First degree burn - burn where only the epidermis is damaged
second degree burn - epidermis and upper part of dermis are damaged - blisters appear with fluid accumulation between epidermal and dermal layers - skin heals with little or no scarring
third degree burn - damages entire thickness of skin - burned area appears white, red, or blackened - skin heals with permanent scarring
skin cancer - basal cell carcinoma: least malignant and most common - squamous cell carcinoma: arises from keratinocytes of stratum spinosum - melanoma: cancer of melanocytes; most dangerous type
embryonic origins of skin - epidermis: develops from ectoderm - dermis and hypodermis: develop from mesoderm - melanocytes: develop from neural crest cells which are ectoderm in origin
Created by: peckman12