Capillary Solute and Fluid Exchange I Flashcards
What are the 4 passive transport processes?
diffusion(conc grad), convection(pressure grad), osmosis(osmotic pressure by water grad), electrochemical flux(electrical and conc grad like ion flow through a nerve).
What controls the rate of solute transport?
Properties of passive diffusion
Properties of solutes and membrane
Properties of capillaries
Concept of permeability
What does the following equation mean?
t = x^2 / 2D
Passive transport over short distances because: time taken (t) for one randomly moving molecule to move a net distance (x) in one specific direction increases with the distance squared.
D = diffusion coefficient for molecule within the medium.
What are the properties of solute affecting transport?
Concentration gradient
Size of solute
Lipid solubility of solute
What are the properties of the membrane affecting transport?
Membrane thickness
Aqueous pores in the membrane
Carrier-mediated transport
Active transport mechanisms
How much of a substance is transported per time - give the solute movement equation?
What are the units of solute movement?
Js = -DA (deltaC/x) D - diffusion coefficient A - area (deltaC/x) - concentration gradient (C1-C2) across distance x Units = mass per unit time
Why is there a negative sign in the solute movement equation?
Due to the solutes flowing ‘down’ a concentration gradient.
What is an intercellular cleft in a capillary?
10-20nm wide gaps between the ends of 2 cells - can influence solute transfer.
What is a glycocalyx?
A -ve charged material that covers endothelium, blocking solute permeation and access to transport mechanisms.
Give the name of the large pore system that influences solute transport.
Caveola-vesicle system.
Define permeability.
The rate of solute transfer by diffusion across unit area of membrane per unit concentration difference.
How freely a solute crosses a membrane.
How does increased blood flow affect diffusion rate?
More blood flow means higher concentration of solutes in capillaries - more exchange - less time for equilibration.
What other factor controls diffusion rate?
Fall in interstitial concentration - more solute used due to metabolism - increases concentration difference.
How does recruitment of capillaries affect diffusion rate?
Dilation of arterioles means more capillaries perfused and so more total SA for diffusion - shortens diffusion distance.
