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Keratinocytes
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Layers of the epidermis (top to bottom)
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Integument
Skin and its appendages
| Question | Answer |
|---|---|
| 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
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