Capillaries I - Solute Exchange Flashcards
What does metabolism create?
The need to transport solutes and fluids
Which molecules can get through the cell membrane and which need help?
Non polar molecules can get through easily and larger polar molecules need help
What are the four passive transport processes?
Diffusion
Convection
Osmosis
Electrochemical flux
What does diffusion rely on?
Concentration gradient
What does convection rely on?
Pressure gradient
What does osmosis rely on?
Osmotic pressure gradient
What does electrochemical flux rely on?
Electrical and chemical gradients
Give an example of convection transport
Blood flow from heart to blood vessels
Give an example of electrochemical flux
Ion flow across cell membranes
Where does solute and fluid exchange occur?
At capillaries
Where are capillaries in higher density?
In highly active tissues (muscles, liver, heart, kidney, brain)
What three things does rate of solute transport depend on?
Properties of passive diffusion, solutes and membranes and capillaries
What are the properties of passive diffusion?
Concentration, rate and distance
What are the properties of solutes and membranes described by?
Ficks law
What properties of the solute affect transport?
Concentration gradient, size of solute and lipid solubility of the solute
What are the properties of the membrane that affect transport?
- membrane thickness/ composition
- aqueous pores in the membrane
- carrier mediated transport
- active transport mechanisms
What is ficks law? (Description)
A mathematical concept that shows the properties of solutes and membranes affecting transport
(Essentially how much of a substance is transported per unit time)
What are the three types of capillaries called?
Continuous, fenestrated and discontinuous
What are the features of a continuous capillary?
- moderate permeability; tight gaps between neighbouring cells; constant basement membrane
What are the features of a fenestrated capillary?
- high water permeability, fenestration structures and modest disruption of membrane
What are the features of a discontinuous capillary?
- very large fenestration structures and a disrupted membrane
Give some examples of a continuous capillary
Blood-brain barrier
Muscle, skin, fat and connective tissue
Give some examples of a fenestrated capillary
High water turnover tissues like salivary glands, kidneys, eyes and gut mucosa
Give some examples of a discontinuous capillary
When movement of cells is required; RBCs in liver, spleen and bone marrow
What are the layers of a capillary?
(From inside out)
Cellular membrane, single layer of endothelial cells, a cellular basement membrane made of connective tissue
How do you get into the capillary?
Either go through the cells or between them
What are the three main properties of capillaries?
Intercellular cleft, caveolae and vesicles and glycocalyx
How wide are the intercellular clefts?
10-20nm wide
What are caveolae and vesicles?
It’s a large pore system (exo and endocytosis)
What is the glycocalyx?
Covers endothelium and its negatively charged. Blocks solute permeation and access to transport mechanisms, it’s highly regulated
What is permeability?
The rate of solute transfer by diffusion across unit area of membrane per unit concentration difference
How does blood flow control diffusion rate?
More blood brings more solutes. Increased blood volume means less time for equilibration to occur across capillaries
How does a fall in interstitial concentration control diffusion rate?
During metabolism more solute is used up, which means there is a bigger concentration difference.
Metabolism increases blood flow
How does capillary recruitment control diffusion rate?
Dilation of arterioles leads to increased number of capillaries per fused which increases total surface area for diffusion.
