epithelial cells

Question 1

epithelial tissue

Answer 1

lines all tubes of the body and faces the open spaces (ie skin, GI tract). Functions in protection, active transport, biochemical mod, detox, communication between tissues, substance transport, respond to stimuli. Lay on top of connective tissue (including blood vessels) by their basal surface. Not vascularized, muscle and neurons also lie on connective tissue

Question 2

classification of epithelia

Answer 2

simple (single layer), stratified (multi layer, outer layer do not touch basal lamina), pseudostratified (some cells don?t reach free surface, but all touch basal lamina), squamous (flat), cuboidal (cube-like), columnar (taller than width), transitional (in bladder, stratified but when stretched go to cuboidal and squamous

Question 3

polarity

Answer 3

based on membrane and intracellular contents. Cytoskeleton plays an important role, as do pumps, secretory pathways, and membrane composition. Function includes unidirectional secretion or absorption, trans-epithelial transport of ions, endocytosis, exocytosis, transcytosis, localization and orientation of intercellular signaling.

Question 4

cell junctions

Answer 4

tight junctions, adherins, gap junctions

Question 5

tight junctions

Answer 5

link adjacent epithelial cells, forms a seal that separates apical and basolateral components, made of occludins and claudins, limit movement between cells, forces transport to go through epithelia, important in polarity

Question 6

Adherins

Answer 6

made of cadherins, important for structual integrity, control signaling, Desmosomes are a type of e-cadherin that interacts with intermediate filaments (in skin)

Question 7

Gap junctions

Answer 7

in cardiac muscle, form channels, allows passage via diffusion of small molecules between cells

Question 8

cell surface mods on epithelial cells

Answer 8

microvilli, cilia, basolateral surface mods

Question 9

microvilli

Answer 9

small protrusions loaded with actin, important for absorbtion rate by increasing surface area of cell

Question 10

cilia

Answer 10

long wavy arms of microtubules, used for moving substances along epithelial sheet. Also sensory cilia that are not motile (in vestibular bar cells of ear.

Question 11

basolateral surface mods

Answer 11

infolds and outfolds, lack structual organization of microvilli and cilia, increase surface area, seen in cells that transport heavily across basolateral surface

Question 12

basal laminae

Answer 12

made of collagen, laminin, multidomain proteins; porous to small molecules, form attachment deep to epithelial cells and superficial to tissues, specific to attached tissue, very diverse

Question 13

functions of basal laminae

Answer 13

connects various tissues, serve as barrier to cell movement, some promote filtration (ie kidneys), information-containing scaffold that dictates epithelial cell attachment and dynamics of transport

Question 14

Hemidesmosome

Answer 14

core protein is integrin, interacts with intermediate filaments

Question 15

focal adhesions

Answer 15

like adherin juntions, organize signalling complexes controlling polarity, gene expression, transport, etc within epithelial cells

Question 16

exocrine glads

Answer 16

secrete materials onto apical side, generally multicellular, have two main components; 1) secretory units, clumps of secretory epithelial cells, produce and release bulk of secretions. 2) Ducts - tubular structures emanate from secretory units, passageways to conduct secretions to destinations, epithelia can modify secretions by secretory and ion transport. secrete unidirectionally from apical surface (except holocrine), secrete mucus and serous.

Question 17

endocrine glands

Answer 17

no ducts, secrete into clood stream, produce specific hormones, act over long distances, organized as clumps or chords of cells, embedded/surrounded by connective tissue containing capillary network. Each clump surrounded by basal lamina, hormone molecules cross basal surface and basal lamina to reach blood stream, most endocrine cells secrete from the basolateral membrane

Question 18

epithelial to mesenchymal transition

Answer 18

epithelia derived from all 3 primary germ laters. Early development, epithelia form, then disassemble, and reform in new patterns until proper morphology achieved, often disassemble and move into mesenchymal (connective) tissue, from here can migrate to other locations, or transfrom into non-epithelial cell lines. some embryonic epithelia serve as signaling centers thar organize patterns of formation

Question 19

epithelial-derived cancers

Answer 19

Stem cells common target of disease (especially caner). Epithelial cancer is most common type (carcinomas). Exocrine carcinomas = adenocarcinomas, many embryogenic pathways used in caner (TGF beta, wnt signalling, sonic hedgehog, tyrosine kinases, notch). developmental pathways have different outcomes in different cell types, important clinically (ie WNT signaling in colon cancer, FAP specifically). APC mutated = beta catenin increases proliferation and de-differentiation

Question 20

histological examination

Answer 20

section material from biopsy, put on slide, look at under microscope, fix tissue with chemical, then slice thinly.

Question 21

general stains

Answer 21

bind acidic or basic compounds, see what is stained and not what isnt.

Question 22

looking at slide

Answer 22

nucleus is usually dark, mucus fails to bind dye and appears white (unless dye binds carbs), if something is not fixed it can leach out and won’t be scene, main thing is find nucleus and compare from there

Question 23

immunohistology

Answer 23

specific staining; immunohistochemistry and immunofluoresence