Cell Processes Lecture 23

Question 1

Epithelial tissues can be arranged in

Answer 1

single or multiple layers

Question 2

Epithelial cells form the boundary

Answer 2

between the body’s organs or between the body and the external environment

Question 3

Epithelial tissue are subject to physical breakdown so

Answer 3

undergo constant and rapid renewal process

Question 4

Functions of the epithelial tissue

Answer 4

• protection
• filtration
• secretion
• absorption
• excretion
• neuroendocrine function

Question 5

Glandular Epithelium

Answer 5

• develop from epithelial cells that sink below the epithelium surface during development
• secreting portion of glands

Question 6

Structure of exocrine glands

Answer 6

• simple or branched structure
• end pieces contain secretory or acini cells
• openings are made of ductile cell (transport properties)

Question 7

Glandular secretion

Answer 7

Contain 2 types

i) Acinar cells which create a primary secretion rich in organic molecules
ii) Duct cells which modify the composition o the primary secretion by either absorbing or secreting specific ions

Question 8

What separates epithelial cells from their neighbours

Answer 8

lateral intercellular space

Question 9

The laminal edges of epithelial cells are held together at

Answer 9

laminal edges

Question 10

Tight Junctions are composed of

Answer 10

thin bands that encircle the cell and make contact with thin bands from adjacent cells

Question 11

Tight Junctions act as

Answer 11

A barrier (which restricts the movement of substances through the intercellular spaces between cells) and a fence (which prevents the membrane proteins from diffusing in the plane of the lipid bilayer)

Question 12

Tight juncions separate epithelial cells into

Answer 12

Apical membrane (faces lumen of the organ or cavity) and Basolateral membrane (that adheres to the adjacent basement membrane and interfaces with the blood)

Question 13

What are the two ways transport can occur across the cell

Answer 13

Transcellular and Paracellular

Question 14

What is paracellular transport governed by

Answer 14

laws of diffusion and tightness of junction

Question 15

What can be measured during paracellular transport

Answer 15

electrical resistance to ion flow through tight junctions (the higher the more tight junctions)

Question 16

Epithelial tissue can be classifieed as

Answer 16

Leaky epithelium - paracellular transport dominates and Tight epithelium - transcellular transport dominates`

Question 17

From Proximal —> Distal

Answer 17

• Leaky to tight epithelium
• low to high electrical resistance
• low to high number of strands
• para (bulk) to transcellular (hormonally controlled)

Question 18

Transcellular transport

Answer 18

primary and secondary active transport in combination with passive diffusion through ion channels to produce transport across the epithelial tissue

Question 19

Transport can either be

Answer 19

Absorption (lumen to blood) or Secretion ( blood to lumen)

Question 20

Transepithelial transport can be broken down into

Answer 20

1) entry and exit steps - for absorption entry is apical but for secretion it is the basolateral)
2) electrochemical gradient (entry or exit —> passive or active)
3) electroneutrality (movement of positive or negative ion will attract a counter ion)
4) osmosis