Lecture 7 - Structure and Function of Epithelia Flashcards
What does epithelia consist of?
Epithelia consists of 1 or more layers of epithelial cells, a basement membrane, as well as supporting tissues (such as extracellular matrix and cells).
What are the two sides of epithelia?
apical and basolateral
What is the apical membrane also referred to as?
luminal or mucosal membrane
What does the apical membrane face?
Lumen
What does the basolateral membrane face?
the interstitial fluid/internal body
What are features found at the apical membrane?
microvilli and the tight junction
What features are found at the basolateral membrane?
It is the membrane that contains the basement membrane and the basal membrane which lines the lateral intercellular space
What are common characteristics of the basolateral membrane?
- High K+ permeability
- High water permeability
- Housekeeping transporters
Why do we have housekeeping transporters in the basolateral membrane?
As Na+ concentration inside the cell is low, Na+ can enter the cell via passive transport. However, in order to move Na+ out of the cell, active transport is required, hence the need for housekeeping transporters
What are some examples of housekeeping transporters?
Na+,K+-ATPase (Always in basolateral membrane)
Ca2+-ATPase and Na+/Ca2+ exchanger
Na+/H+ exchanger (NHE-1)
What are common characteristics of the apical membrane?
Selective permeability to ions
Absence of housekeeping transporters
Variable water permeability
What is the overall function of absorptive epithelia?
transport of solutes from the mucosal membrane to the serosal (outside to inside)
What is absorption driven by?
Absorption is driven by the active transport of Na+ (Na/K-ATPase)
What are the two types of absorptive epithelia?
Leaky and tight
What seperates leaky and tight absorptive epithelia?
a) Transport properties derived from electrical characteristics
b) Apical membrane transport pathways
c) Hydraulic conductivity (relative water flow)
d) Responsiveness to hormones
e) Location within organs
What are the eletrical characteristics of absorptive epithelia?
Voltage and resistance