Intro to CVS Flashcards
Why do we need a CVS?
Get oxygen and nutrients close to cells
reduce diffusion pathway
Why can’t body cells be supplied by oxygen and nutrients in the surroundings?
Large distance between oxygen/nutrients and cells
take too long to diffuse into the cells from the surroundings
What part of the CVS has oxygen and nutrients close to the cells?
Capillaries
What are capillaries made up of?
Single layer of endothelial cells
their basement membrane
How does the structure of capillaries aid in diffusion of oxygen and nutrients?
They are thin walled
How do lipid-soluble molecules diffuse across capillaries? Give an example of two molecules that do this
Across the cell membranes of endothelial cells
oxygen and carbon dioxide
How do small water-soluble molecules diffuse across capillaries?
In between endothelial cells
What does the rate of diffusion depend on?
Area available for exchange
Diffusion resistance
Concentration gradient
How does area available for exchange affect diffusion?
Bigger area means faster rate of diffusion
What is diffusion resistance? Give some examples
Factors that oppose diffusion
e.g. nature of molecule e.g. water-soluble
barrier
longer pathway
What does area available for exchange depend on?
Capillary density - the amount of capillaries in a certain amount of tissue
What sort of tissues have a high capillary density? Why?
Metabolically active
because require more oxygen and nutrients
How does the concentration gradient affect the rate of diffusion?
Greater concentration gradient means faster rate of diffusion
What does the concentration gradient of oxygen in the blood depend on?
Rate of use by tissue
Rate of blood flow through capillary bed
If a tissue uses lots of oxygen, how does this affect the conc. gradient?
More oxygen moves from blood to tissues
reduces conc. gradient
If a tissue has an increased rate of blood flow, how does affect the conc. gradient of oxygen?
Replaces oxygen in blood
increases conc. gradient
What is the perfusion rate?
The rate of blood flow into a tissue
Which two organs require a constant blood flow?
Brain
Kidneys
What sort of perfusion rate do metabolically active tissues have? Why?
Higher perfusion rate
because demand more oxygen and nutrients
When does blood flow to the heart and skeletal muscle increase?
With exercise
When does blood flow to the gut increase?
After eating
When does blood flow to the skin increase?
When body temperature is high
What is the cardiac output at rest of the average 70kg man?
5L/min
What is the maximum cardiac output of the average 70kg man?
25L/min
