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Flashcards in Epithelium Deck (57):
1

general features of epithelia

linked tightly together by intracellular junctions, found in the lining of all cavities and surfaces

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major function of epithelia

barriers between two compartments

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epithelium

free apical surface, and basal surface that rests on a non-living layer of ECM (basement membrane)

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basement membrane

non living layer ECM, consists of true lamina (secreted by epi cells) and reticular lamina (secreted by conn. tissue cells)

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classification of epithelia

simple, stratified, pseudostratified // squamous, cuboidal, columnar

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simple epithelia

one layer of cells, all cells touch both free apical surface and basal surface touching basement membrane

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stratified epithelia

more than one layer of cells, In a stratified epithelium, the apical or superficial layer of cells faces the free surface and is separated from the basal lamina by one or more layers of cells.

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pseudostratified epithelia

all cells rest on the basal lamina, but only some have a free surface. arrangement of the nuclei is distinctive.

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squamous features

wide, flat, nuclei bulging out of apical surface

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cuboidal

cube-shaped. nucleus is round, and in the centre of the cell. cells that are wider than tall = low cuboidal

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columnar

taller than wide. nucleus is elongated, and on the basal side

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modifications

apical surface usually has modifications - microvilli, cilia, and stereocilia

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parenchyma

secretory section of glandular tissue

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types of tissues

epithelia, connective, nerve, muscle

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places you find epithlia

sheets of cells lining cavities and open spaces.

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functions of epithelium

barrier, protection, absorption, secretion, transport

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how does epithelia protect?

abrasion resistance - layers of dead cells (skin), mucous secreting cells; line outside of digestive organs and protect as they all slosh and bump into each other

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what does epi do to increase absorption + secretion?

fold a lot to increase SA

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how much blood vessel content?

no blood vessels

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types of apical specializations?

microvilli, cilia, stereocilia

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microvili features

cylindrical projections; 0.5-1.0 microns, increase surface area for absorption, create a "brush border" pattern, seen in digestive tract and kidney, <50% size of nucleus

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microvili structure

actin, hollow inside, cannot actively move, core joins actin cytoskeleton, cannot usually see individual microvili

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stereocilia features

modified microvilli, very long (75% cell), sparse and ragged looking, found in inner ear and male reproductive system

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cilia features

10x bigger microvilli, pinched appearance (beer bottle), sweeping motion moves material, found in respiratory and female reproductive (egg and uterus), has dark line beneath it (basal body)

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cilia structure

microtubule skeleton (axenome), 9+2 arrangement of microtububles, anchor in cell = basal body = most important feature is dark line at the apical surface

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epithelia are tightly packed. what holds them together?

cell junctions: tight junctions, adherens junctions, gap junction, and desmosomes IN THAT ORDER.

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tight junction features

membranes are closely opposed, most apical of all the junctions, prevent movements between cells, chicken-wire/fishnet feature, occluding junction (no liquid can pass through)

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adherens junction features

apical lateral cell junctions (just below tight junction), encircle cell completely, long parallel densities (space), NOT occluding aka liquid will get past them, consist primarily of cadherins

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desmosome features

strong and lateral adhesion, static and structural, PROMINENT KERATIN FILAMENT WEB, parallel densities, usually straight, same cadherin famile as adherence junction, not concractile

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gap junction features

tightly opposed membranes, generally below adherens junctions, collection of pores (connexons), regulates cell to cell communication through free movement of small molecules between cells

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terminal bars features

all cell adhesion sites, artifact of fixation = vertical line with tiny little bulges

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types of basal specialization

basement membrane, cell substrate adhesion

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role of basement membrane

separates epithelium from connective tissue

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basement membrane layers

basal lamina of epithelial origin (laminins), reticular lamina of connective tissue origin (often see collagen fibrils)

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where find simple squamous? what surface modifications would you find?

lining all cavities, and all blood vessels, found where exchange occurs; no surface modifications

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what is mesothelium

lines all organs; simple squamous

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what is endothelium

lines all blood vessels; simple squamous

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where find simple cuboidal? what are its functions? what surface modifications would you find?

lining tubes and glands; secretory and absorpative; mv/c/sc

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where find simple columnar? what surface modifications would you find?

lines tubes (kidney, gallblader); apical modifications (mc/c/sc)

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where would you find ciliated simple columnar cells?

oviduct only; no goblet cells present

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where would you find simple columnar cells with microvili?

digestive tract - goblet cells are present here

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where would you find pseudostratified columnar cells? what surface modifications would you see?

respiratory tract - will be ciliated; male reproductive tract - will be stereociliated

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what layer should you look to in identifying which epithelium it is?

apical

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where would you find stratified squamous epithelium?

moist areas: nose, mouth, reproductive tract; where skin meets interior

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what distinct feature does keratonized stratified squamous epithelium have?

no nuclei

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where would you find transitional epithelium? why?

bladder - transition is very stretchy

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what features does transitional epithelium have?

pillow-like apical cells; these are flat when stretched (full) bladder

48

what are the different glands? contrast them

exocrine and endocrine; exocrine secretes to free surface + is connected to surface + can form ducts; endocrine secretes to circulatory system + is not connected to surface + cannot form ducts + always round

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what are the different types of exocrine glands? define them.

merocrine/eccrine (secretes directly), apocrine (vesicle), and holocrine (whole cell)

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what is a goblet cell? what does it do?

unicellular exocrine gland; secretes mucous in the digestive and respiratory system

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what is a duct?

multicellular exocrine gland; it's a specialised secretory unit

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which types of glands do you find in pancreas?

both exocrine and endocrine; the exocrine are secreting digestive enzymes and are arranged into ducts, while the endocrine are secreting insulin and arranged into cords

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why is epithelia so prone to cancer?

highly mitotic

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adenocarcinoma?

glandular cancer, excessive glandular tissue

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skin carcinoma?

common and metastatic, treated by excision

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are moles carcinoma?

no, they are a proliferation of melanocytes, and do increase susceptibility to cancer

57

what do different burn degrees mean?

1st = surface epi 2nd = penetrates epi 3rd = penetrates connective tissue