Lecture 6: Epithelial cell specializations

Question 1

Occluding Junctions/Tight Junctions

Answer 1

Separate lumen from intercellular space and maintains polarity of the cell; made of occludin/claudin proteins, Z01-Z03, AF-6 proteins

Question 2

Zonula adherens

Answer 2

located deep to zonula occludens; forms strong bond btw adj. cells, serves as anchor for actin network; made of cadherines, cytoplasmic face actin filaments; attachment proteins- catenins, vincuin, alpha-actinin

Question 3

Desmosomes (macula adherens)

Answer 3

Deep to adhering junctions, scattered; provide structural integrity, large number in stratified squamous, achoring for intermediate filaments (keratin/tonofilaments); inside cell –>intercellular space is filaments–>desmoplakin–>desmoglein–>desmocollin

Question 4

Terminal Bar

Answer 4

Tight junction, zonula adherens, madula adherens all line up and form dark bar

Question 5

gap junction

Answer 5

deep to junctional complex, serves as communication between cells, common in embryonic tissue; regulated by Ca++, pH, cAMP; composition is 6 connexin transmembrane proteins

Question 6

Hemidesmosomes

Answer 6

Basal plasma membrane; anchors cytoskeleton (intermediate filaments) to basement membrane; made of integrin proteins on basement membrane and laminin-5

Question 7

Functions of basement membrane

Answer 7

1. Physical Support
2. Cell attachment
3. Barrier that selectively lets through things
4. Growth/differentiation
5. Regeneration of above tissue
6. Special functions: ultrafiltration in kidney, blood-air barrier, tumor metastasis

Question 8

Cilia

Answer 8

Longer and thicker than microvilli
20 microtubules (tubulin), a central pair surrounded by 9 doublets, doublets connected by dynein arm, have ATPase activity; inserts into basal body in cytoplasm (9 triplets of microtubules); functions clean airway, transport of ovum, sperm tails

Question 9

Microvilli

Answer 9

Thinner and shorter than cilia, actin, made of 20-30 filaments each. Covered by glycoprotein (glycocalyx) contrant/elongate, nut no active mvmnt. Create fuzzy covering on top of cells (striated border)

Question 10

Stereocilia

Answer 10

Long microvilli that were mistaken for cilia; found in epididymus pseudostratified columnar cells, believed to facilitate absorption and secretion, sperm transport is aided by large volumes of secretion