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General functions of the skin
Largest organ. Barrier function, vitamin d synthesis, sensory function, and thermoregulation
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Identify and describe tissue type and cells found in epidermis
Stratified squamous keratinized epithelium (dead cells filled with keratin). Keratinocytes make up most of epidermis. Also scattered with merkel cells (touch receptors), melanocytes (pigment), and langerhan cells (macrophages-immune-)
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What are the layers of the skin from top to bottom?
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum basale
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Identify and describe stratum corneum
Up to 30 layers thick, dead scaly keratinized cells that form a protective waterproof surface. Cells flake off in this layer
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Identify and describe stratum lucidum
Dead keratinocytes packed full of a clear protein. Transparent because no nuclei or organelles. Palms and feet
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Identify and describe stratum granulosum
3-5 layers of thick keratinocytes. Dark stained keratin granules prevent diffusion of nutrients into superficial layers. Cells start to die
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Identify and describe stratum spinosum
Thickest in epidermis aside from thick skin stratum corneum. Keratinocytes produce lots of keratin. Desmosomes keep water in.
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Identify and describe stratum basale
Single layer of stem cell that produces new keratinocytes. Take about 30-40 days to move thru all layers. Also has melaninocytes.
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Identify thick skin
- 5 layers (including stratum lucidum)
- Forms calluses
- Lots of sweat glands
- No hair follicle glands
- Nerve endings are more densely packed
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Identify thin skin
- 4 layers (no stratum lucidum)
- Everywhere on body except callous areas
- Less sweat glands
- Has hair follicles
- Less touch receptors
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Describe process of growth of keratinocytes
Stem cells divide intensely in stratum basale to form new keratinocytes. In granulosum they begin to die and in lucidum and corneum they are dead. In corneum they flake off and are replaced.
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Identify and describe melanin
- Pheomelanin (red-yellow) and eumelanin (brown-black) pigment.
- Produced by melanocytes, transferred to keratinocytes.
- Color depends on amount and type of melanin produced.
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Identify and describe carotene
- Yellow pigment that accumulates in top stratum corneum layer, deep dermis, and hypodermics.
- Gives skin yellowish hue
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Identify and describe hemoglobin
- Red pigment in RBCs
- Gives body a pinkish color. Lack of results in a pale color of skin
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Identify tissue types and structures of papillary layer of dermis (superficial)
- Thin layer (1/5 of dermis)
- Well vascularized
- Loosely organized tissue allows for macrophage movement
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Identify function of papillary layer of dermis
- Supports epidermis
- Fingerprints
- Tensile strength and elasticity
- Pain, temp, and texture
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Identify tissue types and structures of reticular layer of dermis (deepest)
- Thicker layer (4/5 of skin)
- Connective fibrous dense irregular tissue
- Less vascularized
- Has hair follicles
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Identify function of reticular layer
- Barrier
- Sensation of tickle, itch, vibration
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General functions of the subcutaneous layer
Energy reservoir, thermal insulation, cushioning of organs and gender distribution, anchors skin to underlying tissue
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What is the significance of adipose tissue
Adipocytes are filled with fat which keeps the body warm during cold situations.
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Why is it good and bad to have adipose tissue in the subcutaneous layer
- BAD: contributes to total vessel length in overweight/obesity
- GOOD: perfect for delivering medicine directly into the bloodstream
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What are the benefits of the skin being a multilayered organ
- It provides barrier function and resistance to abrasion
- The skins elasticity and tensile strength would not be with just one layer/tissue type.
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Eccrine gland describe
Sweat gland; duct that empties onto body surface. Widely distributed (palms, forehead, chest); thermal regulation, mineral filled sweat, no odor
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Apocrine gland describe
Sweat gland; ducts empty to hair follicles-begin in puberty; limited distribution (groin, armpit, beards); proteins+lipids added to sweat, ODOR (scent glands)
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Holocrine gland describe
Subaceous (oily) gland; short ducts empty into hair follicle -begin in puberty; anywhere hair is present; produces sebum which lubricates hair, acne
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Cerumimous gland describe
Exocrine; only in ear canal; cerumen waterproofs ear, kills bacteria
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Describe nails
Hard keratin in dead cells of stratum corneum; protection and grip
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Describe hair
Hair follicle (hair grows in bulb, nerve ending wraps around receptor; almost everywhere; goosebumps, hair color; nerve receptor
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Describe meissner corpuscle
Nerve endings wrapped by connective tissue; in papillary layer of dermis; responsible for touch and texture
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Describe pacinian corpuscle
Encapsulated nerve wrapped by connective tissue; in reticular layer of dermis; responsible for skin stretching, tickles
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Describe pain receptors
Unencapsulated nerve endings; in papillary layer of dermis; detects pain
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Describe temperature receptors
Unencapsulated nerve endings; in papillary layer of dermis; detect temp change, separate cold and warm
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Growth cycle of hair follicle
- Cyclical
- Anagen portion- continuous growth; Cartagen portion- no growth, follicle shrivels; telogen portion- total resting period
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Why is there no hair or sebaceous glands in the palms?
It would interfere with grip
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Why is there so much sweat glands in the palms?
Contributes to fingerprints
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