Overview of CVS Flashcards
Whats the function of the CVS?
Bulk flow of:
- O2/CO2
- Nutrients/Metabolites
- Hormones
Also regulation of body temp.
Why must the left & right pumps of the heart have equal outputs?
Otherwise blood will accumulate in the pulmonary or systemic circulations.
Most systemic vascular beds are in parallel, whats the benefit of this?
Every region is oxygenated simultaneously.
Allows regional redirection of blood as needed, instead of 100% of blood flowing through every region.
Some vascular beds are arranged in series, why?
The anterior pituitary is in series with the hypothalamus because it releases factors which need to act on the Ant. Pit. to make it release hormones.
The liver is in series with the gut so the nutrients digested by the gut can be stored in the liver.
How is blood flow divided between vascular beds?
Blood flow to a vascular bed is usually equal to the oxygen consumption of that tissue. (e.g. skeletal muscle uses 20% of the bodies O2 and receives 20% of the cardiac output)
What factors influence blood flow?
Flow = pressure difference/vascular resistance
The pressure difference is between the mean arterial pressure and central venous pressure.
How does constriction of arterioles alter the flow?
Arterioles constrict to decrease the radius.
The vascular resistance is inversely proportional to the radius to the 4th power.
So decreasing radius massively increases the vascular resistance thus decreasing flow.
What are the categories of vessels?
Elastic Arteries - Aorta
Muscular Arteries - Other Arteries
Resistance Vessels - Arterioles
Exchange Vessels - Capillaries
Capacitance Vessels - Venules/Veins
What classifies an elastic artery? (Aorta)
They have a wide lumen and elastic wall.
They dampen any pressure differences.
What classifies muscular arteries? (Arteries)
They have a wide lumen and a strong non-elastic wall,
They function as low resistance conduits.
What classifies resistance vessels? (Arterioles)
They have a narrow lumen and a thick contractile wall,
They alter their radius to control flow and direction of blood.
Classify an exchange vessel? (Capillaries)
A Narrow lumen and tiny thin wall
Classify capacitance (venules/Veins) vessels?
A Wide lumen with a distensible wall.
They act as a low resistance conduit and reservoir of blood.
How is blood fractionally distributed?
Around 2/3 of blood is in the veins/venules at rest.
What is the myocardium?
Heart muscle making up the wall of the heart.
