Capillaries (Exam 2 lecture 1)

Capillaries

Site of exchange between blood and tissues

what are capillary walls depth like?

Thin to help diffusion

How many layers are capillary walls?

One

What is the diffusion barrier in capillaries like?

Small

Is true blood velocity throughout capillaries fast or slow?

Slow b/c of the large cross sectional area

What does capillaries having the slowest velocity of blood flow do?

Enhances exchange

First purpose of moving material across capillary walls

Exchange of material between blood and cells

What is most commonly used to exchange material between blood and cells?

Diffusion

Second purpose of movement of material across capillary walls

Normal distribution of extracellular fluid

Bulk flow

Movement of water and solutes based on pressure gradients

Filtration

Movement out of capillary

Absorption

Movement into the capillary

Force driving bulk flow - hydrostatic pressure

Force due to fluid

Second force driving bulk flow - osmotic pressure

Osmotic force exerted on water by non permeating solutes

What is osmotic pressure always ?

Proteins

Oncoctic pressure

Osmotic force of proteins

What does PH mean in relation to the 4 forces?

Hydrostatic

What does pi mean in relation to the 4 forces

Osmotic

PH CAP

Filtration

PH IF

Absorptive

Pi CAP

Absorptive

Pi IF

Filtration

Net filtration pressure

Filtration pressure - absorptive pressure

Hydrostatic (where is fluid going?)

Fluid out of the capillary

Osmotic (where is the fluid going?)

Fluid goes into the capillary