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185 Cards in this Set
- Front
- Back
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skin acts as barrier against what 3 things
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pathogens
dehydration UV radiation |
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how does skin prevent dehydration
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lipids produced by epithelial cells of the skin prevent water loss and consequent dehydration of underlying tissues
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what compound in skin acts as barrer to UV radiation
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melanin pigment
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skin maintains which 2 components of homeostasis?
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water and salt
temperature |
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skin maintains water and salt homeostasis
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content via sweat glands
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temperature is maintained via ____ & ____
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sweat glands
vasculature |
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4 functions of skin
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barrier
sensory secretory immune |
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skin includes what 2 layers
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epidermis
dermis |
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epidermis is what type of epithelium?
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stratified squamous keratinized epithelium
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keratinocytes =
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epithelial cells of the epidermis
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culmination of differentiation as keratinocytes migrate to apical layer
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loss of keratinocyte organelles, including nucleus
allows cell to be completely filled with keratin |
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thick vs. thin skin is defined histologically by _____
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thickness of the epidermis
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thick vs. think skin is defined anatomically by ____
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thickness of the dermis
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where is histologically thick skin present?
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palms of hands
soles of feet |
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dermis
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dense irregular CT deep to epidermis
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which layer of skin contains vessels, lymphatics, nerves, glands and deep portions of hair follicles?
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dermis
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where is thickest dermis found?
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dorsal body surface
especially interscapular region |
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hypodermis, aka:
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superficial fascia
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function of hypodermis
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provides a connection between dermis and underlying muscle
allows skin to move over muscle |
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composition of hypodermis
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loose CT with variable amounts of adipose tissue
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primary cell type in epidermis, in terms of numbers
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keratinocytes
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kertainocytes derive from which cells?
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stem cells in stratum basale
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5 layers (strata) of keratinocytes
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S. basale
S. spinosum S. granulosum S. lucidum S. corneum |
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what happens when migration and differentiation of keratinocytes are disrupted?
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loss of cohesive, waterproof barrier function of epidermis
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Stratum basale, aka:
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stratum germinativum
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stratum basale
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single cell layer of relatively undifferentiated cuboidal cells
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S. basale cells are linked
to each other by ____ to the basal lamina by ____ |
S. basale cells are linked
to each other by desmosomes to the basal lamina by hemidesmosomes |
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histological characteristics of S. basale cells
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basophilic - many ribosomes
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what do ribosomes primarily synthesize in keratinocytes?
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keratin
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tonofilaments
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intermediate filaments made of keratin
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when do stem cells in stratum basale undergo mitosis?
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only at night
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thinest lasyer of epidermis
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stratum spinosum
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shape of stratum spinosum cells
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polygonal
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spiny appearance of stratum spinosum cells is due to...
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large numbers of desmosome attachments maintaining connections between adjacent cells as cells shrink during tissue processing
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what are desmosomes of S. spinosum linked to?
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tonofilaments
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as cells of the S. spinosum continue to make tonofilaments, the filaments are grouped into ____
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tonofilbrils
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membrane-coated granules synthesized by S. spinosum
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lamellar granules
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what do lamellar granules contain?
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lipids - important for water barrier
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how many cell layers in S. granulosum?
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3-5 cell layers
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how much of cytoplasmic space of S. granulosom cells is filled with keratin?
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85%
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keratin in s. granulosum cells is embedded in a matrix of _____
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keratohyalin granules
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keratohyalin granules are (eosinophilic/basophilic)?
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basophilic
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in what layer are the contents of lamellar granules discharged?
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s. granulosum
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the discharge of lamellar granules creates what?
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a lipid-based, waterproof barrier
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cells of which layer synthesize and secrete steroid sulfatase?
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stratum granulosum
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function of steroid sufatase
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removes cholesterol sulfate,
thereby removing intercellular links between keratinocytes so that cells can eventually slough off |
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function of cholesterol sulfate
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helps maintain adhesion between keratinocytes
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S. lucidum is found only...
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in histologically thick skin
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thin, lightly staining, refractile layer
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S. lucidum
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what occurs in S. lucidum layer?
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lysosomes in keratinocytes rupture, destroying cell organelles
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after organelle death, cells of S. lucidum contain what?
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keratin filaments
eleidin |
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eleidin
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poorly staining, refractile keratin
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layer at end point of keratinocyte differentiation
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S. corneum
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plasmalemmae of S. corneum cells
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intact, thickened plasmalemmae
contain stabilized array of keratin filaments |
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keratinocytes of s. corneum, aka:
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corneocytes
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external surface of corenocyte plasamlemma is linked to ...
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lipids from lamellar body secretions, forming a waterproof layer
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cells in deepest layers of s. corneum still have what?
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desmosome attachments
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what allows sloughing off of apical layers of s. corneum?
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loss of desmosome attachments
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length of time to renew epidermis
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15 - 30 days
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homeostasis in epidermal renewal involves regulation of what 3 things?
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rate of cell division within stratum basale
differentiation of keratinocytes weakening of intercellular bonds to allow sloughing of surface corneocytes |
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2 regulatory factors in homeostasis of epidermal renewal
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retinol (vitamin A)
growth factors |
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2 growth factors involved in epidermal renewal
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keratinocyte GF
epidermal GF |
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role of retinol in epidermal renewal
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required for differentiation of epithelia, including epidermis
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3 skin diseases that reflect errors in keratinocyte structure or rate of cell renewal
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ischthyosis
pemphigus vulgaris psoriasis |
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ichthyosis
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disorder of steroid sulfatase
causes superficial cells of s. corneum to remain linked --> abnormally thick s. corneum |
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pemphigus vulgaris
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autoimmune disease affecting desmogleins, a component of desmosomes
weakening of desmosomes between keratinocytes produces blisters between cell layers |
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psoriasis
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accelerated rate of keratinocyte turnover
tissue renewed too quickly for synthesis of keratin componenets to keep up intercellular linkages weak & skin flakes excessively |
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3 cell types other than keratinocytes found in epidermis
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melanocytes
Langerhan's cells Merkel's cells |
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melanocytes derive from what embryological structure?
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neural crest
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where are melanocytes located?
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superficial dermis and basal layer of epidermis
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melanocytes are renewed from ___ ____ in the _____
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melanocytes are renewed from STEM CELLS in the HAIR FOLLICLE
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In H&E, melanocytes stain...
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clear
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does number of melanocytes differ with race/ethnicity?
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no
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by what is skin pigmentation is determined?
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number and size of melanosomes in keratinocytes and melanocytes
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number of melanocytes______ with age
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decreases
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decrease in melanocytes with age contributes to increased risk of ____
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skin cancer
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melanocytes make ____ with keratinocytes
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gap junctions
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T/F: melanocytes and keratinocytes are linked by desmosome
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FALSE: melanocytes and keratinocytes are only linked by gap junctions
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melanin is derived from which amino acid?
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tyrosine
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melanosomes
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melanin-containing, membrane-bound granules in melanocytes
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pigment donation
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melanosomes previously transported to tips of melanocyte processes are phagocytosed along with tip of process by neighboring keratinocyte
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epidermal melanin unit
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melanocyte + keratinocyte that eats its melanosomes
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melanocyte-keratinocyte interations control ...
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the skin's exposure to UV light
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melanin synthesis is controlled by what type of signals from which cells?
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paracrine signals from keratinocytes
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What do keratinocytes release ____ & _____ in response to exposure to UV light
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ACTH
alpha-MSH (melanocyte stimulating hormone) |
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ACTH & alpha-MSH bind what receptor?
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MC1-R on melanocytes
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result of MC1-R binding
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melanocytes increase melanin synthesis
keratinocytes uptake melanin, which decreases their UV exposure |
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MC1-R is what type of receptor
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Gs-coupled transmembrane protein
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all human variations in skin color and hair color known so far are due to variations in _____
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MC1-R
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wavelength range of UV light
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290-400nm
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most common form of skin CA
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basal cell carcinoma
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basal cell carcinoma arises from ...
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transformation of keratinocytes in s. basale
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most serious form of skin CA
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melanoma
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melanoma arises from transformation of...
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melanocytes
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which is more mutagenic, UVA or UVB?
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UVB
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UV light interferes with what immune function in skin?
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antigen presenting function of Langerhans cells
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beneficial effects of UV light
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UVB converts 7-dehydrocholesterol to vitamin D3
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which cells synthesize 7-dehydrocholesterol?
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keratinocytes
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conversion of 7-dehydrocholesterol to vitamin D is hindered by the presence of _____
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melanin
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increased amounts of melanin pigment within keratinocytes can reduce...
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available vitamin D
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what disease may occur in children with insufficient vitamin D3?
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ricketts
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what disease may occur in individuals in whom epiphyseal closure with insufficient vitamin D3?
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osteomalacia
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eumelanin
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brown/black melanin pigment
protects cells from mutagenic effects of UV light |
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pheomelanin
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red/yellow melanin pigment
causes greater mutagenic risk when exposed to UV light found in skin of lightly-pigmented people, esp. with red hair |
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when pheomelanin is exposed to UV light, it does what?
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forms free radicals
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in what layer of the epidermis are most Langerhans cells found?
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s. spinosum
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Langerhans cells are involved in the initiation of what type of hypersensitivity
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contact hypersensitivity
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2 factors of neoplasm increased by UV light
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increasing likelihood of formation of transformed cells
decreasing Langerhans ability to present transformed cells |
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where are Merkel's cells found?
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s. basale
higher density in fingertips, lips, oral cavity and outer root sheath of hair follicle |
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clusters of Merkel's cells are associated with what?
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enlarged terminal sensory nerve fibers that form slowly adapting mechanoreceptors that mediate tactile sensation
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3 age-related changes in epidermis
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thinner
keratin changes - increased permeability of skin number of melanocytes decreases |
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dermal-epidermal junction
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basement membrane with dermal papillae
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rete ridges
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downward projecting epidermal ridges that interdigitate from dermal papillae
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function of rete ridge interdigitation
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increase contact area between epidermis and dermis
ergo, increases mechanical stability of skin |
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papillary layer of dermis
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highly cellular loose CT
abundant type III collagen & some type I extensive capillary network |
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function of capillary network in papillary layer of dermis
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thermoregulation
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capillary network in papillary layer of dermis supplied by...
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small vessels at interface btw papillary and reticular layer = subpapillary plexus
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reticular layer of dermis compared to papillary layer
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deeper and thicker than papillary layer
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composition of reticular layer of dermis
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dense irrecular CT
type I collagen & abundant elastin large blood vessels, lymphatics, nerves near hypodermis |
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large vessels in reticular layer near hypodermis
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cutaneous plexus
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what two things does the cutaneous plexus supply?
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subpapillary plexus
dermal structures |
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In all skin, free nerve endings mediate sensation of ____ & ____
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temperature
nociception |
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Meissner's corpuscles
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tactile receptors
encapsulated nerve endings foudn in dermal papillae |
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what mediates rapidly adapting responses to low frequency vibrations
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Meissner's corpuscles
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Pcinian corpuscles
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encapsulated nerve endings found in deep dermis and superficial hypodermis
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what do Pacinian corpuscles detect?
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high frequency vibration
deep pressure |
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encapsulation of Pacinian corpuscles involves...
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concentric layers of Schwann cells wrapped around the nerve ending
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Ruffini's corpscles
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found deeper in the dermis
mediate slowly adapting responses to touch |
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4 types of sensory structures in skin
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free nerve endings
Meissner's corpuscles Pacinian corpuscles Ruffini's corpuscles |
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arteriovenous anastomoses are present where in the skin?
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reticular and hypodermal regions, especially in apical skin
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DM neuropathies causing fissures and cracks in skin
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disturbed thermoregulation of apical skin
skin damage in apical and non-apical skin disturbed control of sweating |
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invasion of microorganisms subsequent to DM neuropathic skin fissures -->
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gangrene
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subcutaneous plexus
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larger arteries and veins in hypodermis
supply or drain vessels of cutaneous plexus |
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epithelium of hair follicle
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invagination of the epidermis extending deep into dermis
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hair bulb
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termination of hair follicle
cup-like structure in contact with richly vascularized dermal papilla |
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outermost layer of follicular epithelial cells in hair follicle
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outer root sheath
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where does cell differentiation begin in hair follicle?
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outer root sheath
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outer root sheath is continuous with what layer of epidermis?
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s. basale
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end product of differentiation in hair follicle epithelium
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hair shaft - filament composed primarily of keratin
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innermost part of hair follicle
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hair shaft
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erector pili muscle
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smooth muscle which attaches each follicle to the dermis
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site where erector pili muscle attaches to outer root sheath is called the
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"bulge"
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hair follicle cycle
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growth
PCD regrowth |
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anagen
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growth period of hair follicle cycle
epithelial cells grown down from bulge to form hair bulb hair shaft beings to form and grow |
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length of anagen for scalp hair
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6-10 years
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growth of hair follicle reflects an interaction between ____ & _____
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follicular epithelial cells
& dermal fibroblasts |
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catagen
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PCD stage of hair follicle cycle
epidermal cells deep to bulge die & hair follicle regresses up to level of bulge dermal papilla is pulled upward & hair shaft becomes loose |
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for scalp hair, catagen lasts how long?
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2-3 weeks
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telogen
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hair follicle extends only into upper dermis
follicular epithelial cells are quiescent |
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how long does telogen last for scalp hair?
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a few months
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cycling rate of hair follicles is determined by which 2 things?
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location
intercellular signals produced by dermal papilla |
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hair loss associated with drugs or hormone change is due to...
|
changes in rate of hair follicle cycling
NOT to loss of hair follicles themselves (except in rare autoimmune disorders) |
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what hormones stimulate hair growth after puberty?
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androgens
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high levels of androgens cause ___
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hirsutism (excessive hair growth)
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adrogenic alopecia
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male pattern baldness
more follicles are in telogen phase, with shortened anagen phase |
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why do anti-cancer drugs cause hair loss?
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they target rapidly dividing cells, thus preferentially affecting epithelial cells of the anagen phase follicle
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3 things that initiate anagen in hair follicle
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trauma
minoxidil ACTH |
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role of bulge cells in wound healing
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bulge cells = source of stem cells for renewal of epidermis as a whole
stem cells for melanocytes are alos in the bulge |
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burns in which deep structures of hair follicles are spared are more easily healed b/c
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bulge cells remain
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besides bulge cells, add'l source of stem cells during wound healing
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sweat gland epithelial cells
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dermal sheath cells
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fibroblasts immediately basal to follicular epithelium
may be special mesenchymal stem cells, capable of regenerating the dermis |
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3 types of glands in dermis
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sebaceous
sweat mammary |
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sebaceous gland
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sac-like acinus opening into hair follicle
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cells of sebaceous gland are derived from...
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outer root sheath of follicular epithelium
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type of secretion done by sebaceous gland
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holocrine
gradually accumulate fat droplets and then burst open |
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sebum
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secretory product mixed with cell debris from PCD accompanying secretion
|
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2 protective lipids in sebum
|
vitamin E - antioxidant
fatty acids - inhibit growth of streptococcae |
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acne vulgaris results from
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hyperkeratinization of the follicular epithelial cells
overproduction of sebum colonization of anaerobic bacterium P. acnes |
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sebum production is positively regulated by what hormone
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androgens
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secretory portion of eccrine sweat glands consists of...
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simple, coiled tubular glands
+ 2 types of cells: clear & dark |
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clear cells of eccrine sweat glands produce
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a watery secretion
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dark cells of eccrine sweat glands have
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granules of mucus-rich glycoprotein
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secretory units of eccrine sweat glands are surrounded by...
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contractile myoepithelial cells
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duct portion of eccrine sweat glands consists of...
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spiral duct of stratified cuboidal cells
duct penetrates epidermis, so contents can be expelled on to surface no myoepithelial cells |
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apical duct cells have what type of channels?
|
CFTR Cl- channels
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what do CFTR Cl- channels do?
|
resorb salts and water as needed to maintain salt and water balance
|
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sweat is an ______ rich in ____ & ____ and _____
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sweat is an ULTRAFILTRATE rich in NaCl, NH3 and uric acid
|
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what type of innervation regulates sweating
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sympathetic innervation (cholinergic)
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where are apocrine sweat glands
|
axillae
areolae of nipples anal regions |
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secretions of apocrine sweat glands are more _____ eccrine sweat glands
|
viscous
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when do apocrine gland secretion begins after ____
|
puberty
|
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mammary glands are modified ____ sweat glands
|
apocrine
|
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mammary gland is a _____ _____ gland
|
compound tubuloalveolar gland
|
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epithelium changes along mammary gland ducts
|
stratified squamous @ lactiferous duct
stratified cuboidal @ duct simple cuboidal/columnar @ductules |
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what does loose CT within mammary gland lobules contain?
|
mast cells
plasma cells MALT |
