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32 Cards in this Set
- Front
- Back
What are the basic characteristics of epithelium? Functions?
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made up of cells closely packed and arranged, in a single layer or in multiple layers, upon a basal lamina
Cover external surfaces, line internal surfaces, form glands |
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Describe the sidedness of epithelial cells.
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Cells exhibit polarity; apical side faces lumen (hollow interior or external world), lateral (contain inter-cellular junctions), and basal (usually has underlying connective tissue) surfaces
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What feature dictates epithelial cell subtype?
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Cell shape at apical layer
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What three cell junctions occur in epithelial cells? Describe their location relative to one another.
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Tight (occluding) junctions occur most apical, on lateral surface
Beneath them are adhering junctions (hold cells together) Beneath them are gap junctions (communicators) |
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Contrast the zonula occludens with the zonula/macula adherens.
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Zonula (belt) occludens (cellular material can't past through): belt-like junction; ring around apical-lateral area; ~plastic on six pack of beer
Macula (spot) adherens (holds cells together; either belt-like or spot like) |
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What is the main role of zonula occludens?
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Regulate permeability in epithelial tissues, act as backup to already selective cell membrane
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What are adhering junctions comprised of? Describe their subatomic structure.
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Strands of integral membrane proteins that seal off space between adjacent cells.
Cadherin cell-cell adhesion proteins spans two adjacent cells and is anchored on each side by cytpolasmic accessory molecules, the catenins. Actin-based filaments then extend from catenin into apical terminal web to provide support. |
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What are macula adherens? Describe their subatomic structure.
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Literally: "spot adhesion"; aka desmosomes
Cadherin cell-cell adhesion proteins spans two adjacent cells and is anchored on each side by cytpolasmic accessory molecules, the catenins. Intermediate filaments (KERATIN) then extend from catenin and anchor in terminal web. |
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What is the main role of gap junctions? Describe their subatomic structure.
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Permit electrical and metabolic coupling between cells
Junctions formed by groups of six proteins (CONNEXINS) arranged in hexagonal doughnut around central pore, forming a CONNEXON (doughnut hole). Adjacent connexons from adjacent cells align to form channel. |
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Contrast zonula adherens with macula adherens.
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They're both adhering junctions.
Zonula adherens = circumferential belt Macula adherens = spot adhesion; aka desmosome; occur more basal than belt adhesions |
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What is the role of a brush border? What is it constructed of? AKA?
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Microvilli (little fingers); increases sell surface area, allow for absorption and secretion
Contains regular membrane infoldings with actin core |
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Describe the subatomic structure of cilia. What roles do they serve?
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emanate from basal body of microtubule organizing center and feature a 9+2 array of MT's, such that 9 pairs of MT's arrange in a circle and 1 pair of MT's form the pore
Cilia sweep material past apical surface; good for moving debris, mucus, other cells |
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What are the characteristic features of the basal surface of epithelial cells?
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Infoldings to increase membrane surface area for desmosome, transport processes; hemi-desmosomes to anchor cell to basal lamina (these are adhering junctions but no adj cell for other half of desmosome)
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What is the basal lamina? Describe some of its roles.
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network of extracellular molecules that form epithelial-connective tissue interface. Provides mechanical support and acts as sieve to excluse proteins, but allow small molecs to pass through.
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Contrast simple epithelium with stratified epithelium. Roles?
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SImple: one cell layer thick; used in filtration, diffusion, absorption, secretion
Stratified: many layers thick; used for protection, renewal |
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Describe simple squamous epithelial cells. Where would they be found?
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Thin layer of flat, attenuated (broadened) cells. Will be found in areas needing quick diffusion (blood vessel linings, filtration in bowman's capsule in kidney, gas diffusion in alveoli)
SQUISHED nuclei |
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Describe simple cuboidal epithelial cells. Where can they be found?
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Cells are cube-like, found in glands (thyroid), and tubules (nephron)
Nucleus is rounder, more cytoplasmic real estate |
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Describe simple columnar epithelium. Where can they be found?
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tall, rectangular in profile, nuclei are more basal region of cytoplasm
Found in lining of GI tract |
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Describe pseudostratified columnar epithelial cells. Where can they be found?
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all cells contact basal lamina, but not all reach the surface; cells vary in shape
nuclei at different levels Show up in lining of respriratory tract, vas deferens |
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How would you visually differentiate between cilia and microvilli?
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Cilia are a lot longer than microvilli
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Describe the structure of stratified squamous epithlium. Where would it be found?
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Layers of cells; cells are flattened at surface (may be keratinized if external); base is mitotically active (allows for constant renewal)
Bottom most layer is youngest, oldest, most dx/dy'd cells on top; cells joined by mostly ADHERING jns Found in areas of friction, but not absorption, e.g, epidermis, esophagus, vagina |
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Describe transitional epihtelium. Where is it found?
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Unique apical surface cells that are dome-shaped; can change to flat shape (hence the name transition cells); rich in occluding junctions to prevent leakage
Present in urinary bladder and lining of ureters |
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Describe stratified cuboidal epithelium. Where is it found?
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UNCOMMON. Ovarian follicles.
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Describe stratified columnar epithelium. Where is it found?
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UNCOMMON; large excretory ducts of sweat glands
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What are glands? What are their two main subcategories? How do they differ?
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Epithelial cells specialized for secretion.
Exocrine: glands which secrete via a duct into a lumen Endocrine: no duct, secrete basally into a vascular supply |
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Draw the four simple types of exocrine glands.
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Tubular: upside down cursive l
Branched tubular: chicken foot Coiled tubular: flaccid penis Branched alveolar: three leaf clover |
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Draw the two compound types of exocrine glands.
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Tubular: three, connected four-toed chicken feet
Alveolar: three connected branches of three leaf clovers |
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List all simple epithelial types, their roles (if applicable), and where they can be found.
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Squamous: quick diffusion; blood vessel lining, Bowman's capsule (kidney), gas diffusion in alveoli
Cuboidal: blank; glands, tubules Columnar: blank; lining of GI tract Pseudostratified: black; respiratory tract lining, vas def |
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List all stratified epithelial types, their roles (if applicable), and where they can be found.
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Squamous: areas of friction NOT absorption (keratinized if external); high in adherens jns; skin, esophagus, vagina
Transition: prevent leakage; dome-shaped or flat shaped on top, lots of occluding jns; bladder, ureters Cuboidal: uncommon; ovarian follicle Columnar: uncommon; sweat glands |
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Which class of stratified epithelial cells can be keratinized? Under what circumstances would they be keratinized?
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Stratified squamous; if exposed to external environment (would see lots of dead cells on top)
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Which class of stratified epithelial cells exhibit a high number of occluding junctions?
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Transitional
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Which class of stratified epithelial cells exhibit a high number of adherens junctions?
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Stratified squamous
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