Cardio III Flashcards
What is the formula for flow velocity in a vessel? Define each variable.
flow = A x v
Where A is cross-sectional area
v is mean velocity
What vessels are capacitance vessels?
Veins and venules
What vessels are exchange vessels?
Capillaries
What are resistance vessels?
Small arteries and arterioles
What are distribution vessels?
Large artery and aorta
Name the sequence of branching that takes place from the heart and back towards the heart.
Aorta, large artery, small artery, arteriole, capillaries, venule, vein, vena cava
The blood comes back to the heart via the […]
venae cavae (2 vena cava)
Name the two venae cavae and their function.
Inferior vena cava: carries deoxygenated blood from the legs, feet, and organs in the abdomen and pelvis back into the heart.
Superior vena cava: carries deoxygenated blood from the upper body.
How do the numbers of aorta, arteries, arterioles, capillaries, venules, veins, and vena cava differ from one another (order of magnitude) in the systemic circulation?
Aorta: 1
Arteries: 160
Arterioles: 50 M
Capillaries: 10 B
Venules: 100 M
Veins: 200
Vena cava: 2
How do the aorta, arteries, arterioles, capillaries, venules, veins, and vena cava differ in terms of diameter?
Aorta: 25 mm
Arteries: 4
Arterioles: 0.03
Capillaries: 0.006
Venules: 0.02
Veins: 5
Vena cava: 30
How do the aorta, arteries, arterioles, capillaries, venules, veins, and vena cava compare in terms of length?
Aorta: 40 cm
Arteries: 10
Arterioles: 0.2
Capillaries: 0.1
Venules: 0.2
Veins: 10
Vena cava: 40
How do the aorta, arteries, arterioles, capillaries, venules, veins, and vena cava compare in terms of wall thickness?
Aorta: 2 mm
Arteries: 1
Arterioles: 0.02
Capillaries: 0.001
Venules: 0.007
Veins: 0.5
Vena cava: 1.5
Describe how the cross-sectional area of the vascular bed varies as blood travels throughout.
As you move from aorta to capillaries, the total cross-sectional area increases, As you move from capillaries to vena cava, the total cross-sectional area decreases again.
Describe how the velocity flow changes throughout the vascular bed as blood flows throughout
As you move from aorta to capillaries, the velocity of blood flow decreases. As you move from capillaries to vena cava, the velocity increases again. However, note that the speed in the aorta is higher than in the vena cava.
Explain why the velocity of blood changes throughout the vascular bed.
The total flow is the same throughout the entire vascular. If the area is going up but the flow is staying the same, the speed of the flow must be changing. This is why in the aorta, it’s very fast, while in the capillaries, it’s very slow.
ow does the speed of blood in the aorta compare to that of the vena cava? Why?
The speed in the aorta is higher than in the vena cava. This is because the sum of the cross-sectional areas of the 2 venae cavae is bigger than the aorta, so the blood flows more slowly in each vena cava.
Name 4 advantages of a branching vascular bed network.
- Any cell is close to a capillary.
- A high total area of the walls of the capillaries, promoting diffusion (Fick’s law)
- A low blood flow velocity in the capillaries, allowing time for exchange.
- High total cross-sectional area, lowering the resistance.
What are the typical units for blood pressure?
Arterial blood pressure: mm Hg
Venous pressure cm H2O
What is the typical arterial blood pressure?
120/80 mm Hg
What is the typical central venous pressure?
5-10 cm H2O
How does pressure change as you move down the systemic vascular tree?
Decreases as you move from aorta to capillaries to veins. The most dramatic drop occurs in the small arteries and arterioles, which is why they’re resistance vessels.
What vessels experience the largest differences in mean pressure across them? What does this indicate about them?
Arterioles and small arteries. This indicates that the resistance to flow is very high in these, hence their designation as resistance vessels, so a bigger pressure is needed to get the same flow.
What vessels experience the largest differences in mean pressure across them? What does this indicate about them?
Arterioles and small arteries. This indicates that the resistance to flow is very high in these, hence their designation as resistance vessels, so a bigger pressure is needed to get the same flow.
