Overview of the function of the CVS Flashcards
What is the basic structure of the heart
2 pumps
- Right side pumps to pulmonary circulation
- Left side pumps to systemic circulation
What is carried in the blood?
O2 and CO2
Nutrients
Metabolites - kidneys
Hormones
Heart - thermoregulation
How is the heart flexible?
Can vary its output
Arteries can redirect blood flow to where it’s needed most
Veins and venules can store blood
What is the proportion of cardiac output and oxygen consumption for each main organ?
See table in notes
What is Darcey’s law?
Flow = Change in pressure/resistance
How is pressure and resistance related to flow?
Fluid will flow along a tube if there is a difference in pressure, it will flow from end of high pressure to end of low pressure
High pressure = push blood into arteries
Low pressure - blood returns to right side of heart
What is the pressure difference called?
Mean arterial pressure (MAP)
What influences resistance?
Diameter of vessel
- Radius^4
- Selectively redirects flow
- Controlled by arterioles
What do arteries do?
Carry blood away from the heart
What do arterioles do?
Are resistance vessels
Can change diameter and thus how much blood flow goes through vascular beds
Control region flow of blood
What are the role of capillaries?
Exchange of O2 and CO2
What are the roles of veins and venules?
Capacitance vessels
At rest 2/3 blood is stored here
When blood is needed, forces push it back to R heart
Control fractional distribution of blood
What is the fractional distribution of blood?
Proportion of blood in the veins/venule vs rest of systemic circulation
What type of circuit are the pumps and what does this mean?
Series
Output of the R side must equal output of the L side
(if L pumped more than R then there’d be accumulation of blood in lungs)
What are the vascular beds in and what does this mean?
Parallel
They all receive O2 blood at the same time
What does the parallel vascular bed allow for?
All tissue gets oxygenated blood
Allows regional redirection of blood
- If doing exercise can decrease blood to gut/liver and increase blood to skeletal muscle
What are some exceptions to this parallel vascular bed?
Gut and liver arranged in series
- Nutrients absorbed in gut are then passed onto liver to be metabolised
What is the liver blood supply called?
Portal system
What are the features of the aorta?
Elastic arteries
Wide lumen
- low resistance of blood
Thick elastic walls
- can absorb inc in pressure and stretch
Damp pressure variations
What are the features of arteries?
Muscular arteries
Wide lumen
Strong thick, non-elastic wall
Low resistance conduit
What are the features of arterioles?
Resistance vessels
Narrow lumen
Thick contractile wall
Control resistance and therefore flow
Allow regional redirection of blood
What are the features of capillaries?
Exchange vessels
Narrow lumen
Thin wall (single cell thick)
Large surface area to volume ratio
What are the features of venules?
Capacitance vessels (store blood)
Wide lumen
Thin, distensible wall
Allow for fractional distribution of blood
Where does the right and left atrium get blood from?
Right atrium takes blood returning from systemic circulation via vena cava
Left atrium takes blood returning from pulmonary circulation via pulmonary veins
