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Epidermis: stratified squamous epithelium
Dermis: connective tissue layer |
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—on palms and sole, and corresponding surfaces on fingers and toes
Has sweat glands, but no hair follicles or oil glands
Epidermis 0.5 mm thick |
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covers rest of the body
Epidermis about 0.1 mm thick
Possesses hair follicles, sebaceous glands, and sweat glands |
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Resistance to trauma and infection
Keratin
Acid mantle
Other barrier functions
Waterproofing
UV radiation
Harmful chemicals
Vitamin D synthesis
Skin first step
Liver and kidneys complete process |
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Definition
—keratinized stratified squamous epithelium
Dead cells at the surface packed with tough protein called keratin
Lacks blood vessels
Depends on the diffusion of nutrients from underlying connective tissue
Sparse nerve endings for touch and pain |
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| Five types of cells of the epidermis |
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Definition
Keratinocytes – 90%
Synthesize keratin
Stem cells
Undifferentiated cells that give rise to keratinocytes
Melanocytes – 8%
Tactile (Merkel) cells
Touch receptor cells associated with dermal nerve fibers
Dendritic (Langerhans) cells
Macrophages; originate in bone marrow
Stand guard against toxins, microbes, and other pathogens that penetrate skin |
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Term
| Stratum basale / germinativum |
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Definition
A single layer of cuboidal to low columnar stem cells and keratinocytes resting on the basement membrane
Melanocytes and tactile cells are scattered among the stem cells and keratinocytes
Cells attached to each other / basement membrane by desmosomes and hemidesmosomes |
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Definition
Produce more and more keratin filaments which causes cell to flatten; the higher up in this stratum, the flatter the cells appear
Dendritic cells found throughout this stratum
Named for artificial appearance created in histological section
Numerous desmosomes and cell shrinkage produces spiny appearance
Consists of several layers of keratinocytes |
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Definition
Consists of three to five layers of flat keratinocytes
Contains coarse dark-staining keratohyalin granules
Contain lamellar granules that release lipid that repels water |
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Definition
Seen only in thick skin on palms and soles of feet
Keratinocytes are densely packed with eleidin
Cells have no nucleus or other organelles
Zone has a pale, featureless appearance with indistinct boundaries |
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Up to 30 layers of dead, scaly, keratinized cells
Form durable surface layer
Surface cells flake off (exfoliate)
Resistant to abrasion, penetration, light, heat, chemicals, bacteria, and water loss |
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| where are keratinocytes produced |
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Definition
| produced deep in the epidermis by stem cells in stratum basale |
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| —thick accumulations of dead keratinocytes on the hands or feet |
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Papillary layer
Reticular layer |
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Definition
—superficial zone of dermis
Thin zone of areolar tissue in and near the dermal papilla
Allows for mobility of leukocytes and other defense cells should epidermis become broken
Rich in small blood vessels |
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—upward fingerlike extensions of the dermis
Friction ridges on fingertips that leave fingerprints |
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—deeper and much thicker layer of dermis
Consists of dense, irregular connective tissue
Stretch marks (striae): tears in the collagen fibers caused by stretching of the skin due to pregnancy or obesity |
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Definition
Subcutaneous tissue:
More areolar and adipose than dermis
Pads body:
Binds skin to underlying tissues
Drugs introduced by injection
Highly vascular and absorbs them quickly
Subcutaneous fat:
Energy reservoir
Thermal insulation
8% thicker in women |
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Term
| what is melanin and what 2 kinds are there? |
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Definition
most significant factor in skin color
Produced by melanocytes by converting tyrosine to melanin
Accumulate in the keratinocytes of stratum basale and stratum spinosum
Eumelanin—brownish black
Pheomelanin—a reddish yellow sulfur-containing pigment |
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| Explain and describe how the skin heals itself from minor trauma. |
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Definition
1)injury occurs, mast cells release histamine to dialate + increase blood flow, blood plasma seeps in w/ platelets and clotting proteins,
2)blood clot forms, scab formation, macrophages begin to digest tissue debris
3)fibroblastic (reconstructive) phase starts 3-4 days into injury, granulation tissue forms, blood clot gets removed + replaced by collagen
4)epithelial cells on surface infiltrate area of scab until that falls off, epthelium regenerates but connective tissue scars (fibrosis), last phase is called remodeling or maturation phase, can take up to 2 years |
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| People of different skin colors have the same number of melanocytes, but why different skin color then? |
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Definition
Dark-skinned people
Produce greater quantities of melanin
Light-skinned people
Melanin clumped near keratinocyte nucleus
Melanin breaks down more rapidly |
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| describe the normal and pathological colors that the skin can have, and explain their causes |
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—blueness of the skin from deficiency of oxygen in the circulating blood
Airway obstruction (drowning or choking)
Lung diseases (emphysema or respiratory arrest)
Cold weather or cardiac arrest |
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—abnormal redness of the skin due to dilated cutaneous vessels
Exercise, hot weather, sunburn, anger, or embarrassment |
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