Characteristics of Epithelial Tissues III

Question 1

Microvilli(brush Borders)

Answer 1

-Are fingerlike projections of hte apical cell membrane supported by cross-linked actin bundles -Are non-motile -Tend to form a uniform brush border acros the apical membrane -primarily function to increase the surface area of absorption -Are found on the intestinal epithelium and on parts of renal tubules -form a uniformed layer and extension of the cell membrane -In the Villi there are a core of actin filaments which are corss linked and relatively stiff

Question 2

Microvillus structure

Answer 2

-Actin filament core -Actin filament core extend into the terminal web:

• A netwrok of cytoskeletal proteins(ex.intermediate filaments such as keratins) under the apical membrane of the cell
• The distal end of the actin filament core is capped by formin which interacts with the barbed ends of the actin filaments
  
  • formin regulates the assembly of the actin filaments at the barbed ends -
• The actin filaments that make up the core are cross-liked by villin and fimbrin
• The core actin filaments connect to the intermediate filaments of the web
• terminal web-lie just below the cell membrane and the actin filament core tie into this web and improve the integrity of the core
• actin filament are polarized and have different properties on each end

Question 3

Cilia

Answer 3

• 9 peripheral doublets+central pair of microtubuels
• each doublet consists of
  
  • Alpha tubule
    
    • 13 protofilaments(building blocks of microtubules and arrange themselves one on top of each other)
    • radial spokes extending to sheath around central pair
    • Pairs of dynein arms projecting to Beta unit of next doublet
  • Beta tubule:
    
    • 10-11 potofilaments
• can bend in either direction depending on which doublets are involved and supported by other molecules which keep it intact
  *

Question 4

Describe picture

Answer 4

• Principal functions of hte inner sheath and radial spokes is the stabilization of axonemal bending
• Tektins are filamentous proteins extending along the microtubules. Togetehr with nexin links ,tktins may provide a scaffold to microtubules or have a role in the assembly of axoneme-associated structures
• Relative position of A and B tubules and their dynein side arms give each cross section of the axoneme a distinct polarity and clockwise orientation(1 to 9 direction)

Question 5

Formin

Answer 5

-Protein of the cap and interacting with the fast growing barbed ends of F-actin–promotes the elongation of unbrached F-actin

Question 6

Brush Border

Answer 6

• Formed by a closely packed layer of microvilli– at the apical domain of the intestinal columnar epithelial cells. The brush border is also seen in cuboidal epithelial cells of hte proximal convoluted tubule(nephron)

Question 7

Answer 7

Stratified squamos non keratinized

Question 8

Answer 8

Keratinized stratified squamos

Question 9

Answer 9

Simple Cuboidal

Question 10

Answer 10

Simple Cuboidal

Question 11

Answer 11

Simple Columnar

Question 13

Answer 13

Simple Cuboidal

Question 14

Answer 14

Transitional Epithelium

Question 15

Answer 15

Simple Columnar

Question 16

Answer 16

Pseudostratified ciliated columnar

Question 17

Answer 17

Stratified columnar

Question 18

Answer 18

Stratified squamos