Cardio - Vascular Function Flashcards
What is the pressure and resistance of the aorta and large arteries?
Blood pressure is high (110mmHg) and resistance is low
-average pressure change from aorta to large arteries is relatively the same
When does blood pressure begin to drop and why?
When blood reaches the small arteries is where we encounter resistance
Where is the greatest resistance?
In the arterioles
-accounts for ~1/2 the total resistance in the entire systemic circulation
What is the pressure in the arterioles?
55mmHg
What is the blood pressure of blood going from arterioles to capillaries?
40mmHg
What is the blood pressure within the capillaries?
20mmHg
What is the blood pressure when blood goes from capillaries to venules?
10-15mmHg
What is the blood pressure when blood finally reaches the right atrium?
Pressure is almost 0
-encounters small but significant amount of resistance
What drives the blood through the vessels?
Pressure change through the system
What causes the blood to flow through circulation?
Drop in pressure from high (aorta) to low (veins)
What is blood flow effected by?
Pressure change (or pressure gradient) between 2 points and resistance in the circulatory system
Simplified, what is the resistance effected by?
Radius of the vessel
- smaller the radius the greater the resistance
- values normally don’t change much
What is the equation for blood flow?
(P1-P2) x r^4
-therefore small changes in the radius will have a large effect on blood flow
What does flow into vessels have to equal?
Flow out of vessels
-division of quantities can be different but the overall output has to be the same
What happens to the pressure gradient if one vessel radius is reduced?
The vessels before and after the reduced radius vessel will increase output and therefore increase the blood flow
Which change in blood flow is better?
Change in radius diameter is better for us than a change in pressure
What pressure and volume characteristics contribute to circulation?
structural properties
What is blood velocity?
Is the speed at which the blood is moving through a particular blood vessel (cm/sec)
What is blood flow?
The volume of blood moving through a set of vessels (L/min)
What is the blood flow a rest?
5ml/min
-same throughout the systemic system
Why is mean blood velocity higher in aorta then vena cava but blood flow stays the same?
Because the vena cava has a slightly larger diameter
- inorder to have the same blood flow, blood has to move faster through the narrow vessels (aorta)
- therefore velocity is higher in the aorta than the vena cava
What happens when you keep dividing into more vessels?
The velocity decreases
Why is velocity so low in capillaries ?
Since there is so many of them, the same amount of blood is spread out further to maximize diffusion
-as they start to reunite with the venues velocity starts to increase but not as high as the aorta because the diameter of the vena cava is bigger
What are the 3 layers of arteries and veins?
- Outer layer (tunica externa)- fibrous connective tissue
- Mid layer (tunica media)- Smooth muscle and elastic tissue
- Inner layer (tunica interna)- Endothelial cells
What are capillaries only made up of endothelial cells?
To permit the diffusion of substances into and out of the blood
What does the function of a vessel/artery depend on?
The content of each of the 3 tissues
What are the blood characteristics like in the aorta and large arteries?
high 120mmHg and pulsatile
high blood velocity
What is the structure like of the aorta and large arteries like?
Large diameters
Lots of elastic tissue
Relatively thin walls which can be easily distended = low resistance to blood flow
-average blood pressure doesn’t drop much
What is the purpose of the aorta and large arteries?
“shock absorbers” when he heart ejects blood into these vessels (up to 70ml) so the arteries can absorb the amount of blood being pumped out
Distributes blood
