Lecture 3

Question 1

what can allow to see the basement membrane?

Answer 1

periodic acid-Schiff reaction (PAS)

Question 2

how does the PAS reaction work?

Answer 2

Periodic acid reacts with glucose moieties, creating fuchsin sulphurous acid, which is a colorless leukofuchsin (Schiff reagent) that reacts with aldehydes, producing a magenta color.

Question 3

what is the composition of the basement membrane?

Answer 3

proteoglycans, glycoproteins, collagen and a layer of reticular fibers underlies the basement membrane

Question 4

composition of a proteoglycan

Answer 4

50% sugar and 50% protein (long protein core with sugar “fibers”)

Question 5

function of peoteoglycans

Answer 5

since they are negatively charged, they hold water, which give a spongy texture to the tissue

Question 6

composition of glycoproteins

Answer 6

10% sugar and 90% protein, usually have a specific function

Question 7

what is heparin sulfate?

Answer 7

a proteoglycan that is synthesized by epithelial cells

Question 8

what are some of the glycoproteins found in the basement membrane?

Answer 8

laminin, Nidogen-1 (used to be called entactin), and fibronectin

Question 9

role of laminin

Answer 9

• cross shaped glycoprotein
• links surface of epithelial cells to the basement membrane

Question 10

role of nidogen-1

Answer 10

• small glycoprotein
• essential component of BM

Question 11

role of fibronectin

Answer 11

adhesive glycoprotein that binds the PM of epithelial cells to heparan sulfate

Question 12

what are the collagens of the BM

Answer 12

Type IV collagen -synthesized by the epithelial cells.
Type VII collagen (anchoring filaments)
Type III collagen (reticular fibers)

Question 13

another name for BM

Answer 13

basal lamina

Question 14

functions of the BM

Answer 14

1. structural attachment of epithelial cells to the CT
2. Compartmentalization: isolate epithelial cells and muscle cells
3. Filtration: movement of molecules is in part regulated by ionic charges (important in kidney)
4. Help maintain polarity of epithelial tissues (important so that the stem cells know were to grow – aka go up)
5. Tissue scaffolding: help scaffold regeneration

Question 15

characteristics of all epithelial tissues

Answer 15

1. Cells are closely associated with little extracellular space
2. Cells are strongly attached via intracellular junctions
3. Line body surfaces and body cavities
4. Specialization -absorption, secretion, sensation, contractility
5. Cells are polarized
6. Epithelial tissues rest on a basement membrane