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37 Cards in this Set
- Front
- Back
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What are the 4 cell types in the epidermis? What is the percent composition of each?
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Keratinocytes (80); Melanocytes (10-15); Langerhans cells (3-5); Merkel cells (<1)
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What are the layers of the epidermis (top to bottom)? Also, describe an identifying feature of each.
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Stratum corneum - outermost layer, dead cells "shingles on a roof"
Stratum lucidum - only present in palms and soles of feet Stratum granulosu - basophilic granules Stratum spinosum - desmosomal spines Stratum basilum - proligerative layer of cuboidal cells |
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How long does it take for the entire epidermis to turnover? How long does it take for a keratinocyte to get from the stratum basilum to the corneum?
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30 day turnover; 15 days of travel
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In what layer are melanocytes found?
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Basal
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What is the purpose of melanocytes and how do they work?
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They are dendritic cells with projections. They produce melanin pigment to protect from UV radiation. The melanin is packaged into melanosomes which are transported to the keratinocytes
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What is the embryologic origin of melanocytes?
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Neural crest
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Where does most of the melanin that melanocytes make end up? Why?
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In the basal layer to protect the dividing cells from UV radiation
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What is the difference in melanocytes between dark- and light-skinned people?
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Same number of melanocytes, but more melanin is produced in darker individuals
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What melanocytic enzyme is more active in black skin than white skin?
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Tyrosinase
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What do langerhans cells do and where are they found?
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In the stratum spinosum. They are also a dendritic cell and an antigen presenting cell and are the mediator of the skin's immune response
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What do Merkel cells do and where are they found?
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Found in the epidermis and dermis. They aggregate to form tactile corpuscles (slow adapting touch)
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What is the basement membrane zone?
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It is where the epidermis is attached to the dermis
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What are the layers of the basement membrane zone (dermo-epidermal junction)? (from outside to inside)
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Lamina lucida
Lamina densa (basal lamina) Sublamina densa |
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What are the componensts of the pilosebaceous unit?
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Hair follicle
Sebaceous gland Arrector pili muscle |
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What is the hair cycle? How long is a hair in each stage and what percentage of hair is in each stage?
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Anagen (growth) phase - 3-4 years, 85-90%
Catagen (involutional) phase - 3 days, 1% (growth stalls and the follicle creeps closer to the surface) Telogen (resting) phase - 3 months, 10-14% |
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When hairs fall out in the shower, what stage were they in?
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Telogen (resting) - this is completely normal
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How many hairs fall out in one day (normally)?
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About 100
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What can happen to your hair during a time of great stress?
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Hairs can prematurely get into the telogen phase, which lasts 3 months. After 3 months, they notice much more hair coming out
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Where on the body are sebaceous glands found?
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Everywhere except the palms and soles of the feet; but especially on the face, chest, back, and scalp
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What does the sebaceous gland do?
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Releases sebum, which softens and moisturizes the hair and skin
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What kind of secretion do sebaceous glands use?
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Holocrine
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Where are apocrine sweat glands found?
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Primarily in the axillae and groin (some in the eyelids and external auditory canal)
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Why does sweat smell?
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Although the secretions are odorless, cutaneous microorganisms metabolize the sweat and make it smell
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What activates apocrine sweat glands?
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Excitement or fear (adrenergic innervation)
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How do apocrine sweat glands secrete their fluid?
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The name is actually a misnomer. They use merocrine secretion (exocytosis to release contents into the lumen) as opposed to apocrine (decapitation of cells to release contents without death of the cell)
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Where are eccrine sweat glands found?
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Everywhere except mucous membranes; especially dense on the palms, soles, axillae, and forehead
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What activates/stimulates eccrine sweat glands?
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Thermal, mental, and gustatory stimuli (cholinergic innervation)
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What kind of secretion do eccrine sweat glands use?
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Merocrine secretion
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What are the components of the dermis?
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Connective tissue matrix (collagen, elastic tissue, ground substance, fibroblasts, mast cells, dermal dendrocytes) and epidermal appendages, vessels, and nerves
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What cells make collagen?
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Fibroblasts
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What are the two layers of the dermis?
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Papillary and Reticular
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What are the types of collagen in the dermis and where specifically are they found?
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Type I - reticular dermis
Type III - papillary dermis Type IV - basement membrane (basal lamina) Type VII - basement membrane (anchoring fibrils) |
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What cells produce the elastic tissue and what is it composed of?
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Made by fibroblasts and composed of elastin (protein) and the microfibrillar matrix
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What is ground substance and what cells make it?
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Broadly is the extracellular matrix. Composed of fibronectin and glycosaminoglycans (hyaluronic acid, chondroitin sulfate, and dermatan sulfate). It's purpose is skin hydration, tensile elasticity, and to redistribute pressure forces. Shockingly is made by fibroblasts
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What do fibroblasts do?
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The main cell in the dermis. They produce collage, elastin, and ground substance. They are also the contractile cell during wound healing
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What are the different types of nerve innervation to the dermis/epidermis?
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Free nerve endings (right below epidermis) - temperature, pain, pruritus
Messner's corpuscle (right below epidermis) - fine touch Merkel cell complex (in epidermis) - slow adapting touch Pacinian corpuscle (deep in dermis) - deep pressure, vibration |
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Describe the vascular supply to the dermis/epidermis.
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There is a superficial vascular plexus that sits right below the epidermis and there is a deep vascular plexus deeper in the dermis
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