B1W4: Blood Flow Properties

Question 1

Polycythemia rubra vera

Answer 1

Increase in hematocrit (spleen grows)

Leads to hyperviscosity, hypertension, itchy skin

Question 2

Where in the circulation is blood pressure the highest?

Answer 2

Pulmonary arteries

Question 3

Key players of circulation

Answer 3

• arteries: high pressure transport to organs
• Arterioles: control/distribute flow (highest resistance)
• Capillaries: exchange of nutrients
• Venules: collect blood from capillaries and store
• Veins: bring blood back to heart

Question 4

Amount of blood in diff. parts circulation

Answer 4

7% of blood in heart

9% in pulmonary vessels

13% in arterioles and capillaries

64% in veins

Question 5

Pulsate Pressure

Answer 5

The idea that BP rises and falls with each heart beat (hence we get systolic and diastolic pressures)

Pulse pressure=systolic-diastolic

Due to waves and contractions of smooth muscle

Question 6

Highest velocity part of circulation

Answer 6

aorta

Question 7

Flow of blood

Answer 7

Need pressure gradient (flows high to low)

indirectly proportional to resistance

F=change in P/R

Question 8

Units of resistance

Answer 8

mmHg x min/L OR PRU (mmHg x sec/mL)

Question 9

Blood pressure equation

Answer 9

BP=F/A in mmHg

1 mmHg=1.36 cm H2O

Question 10

Conductance equation

Answer 10

Opposite of resistance

C=1/R

As C up, R down

C is proportional to d^4

This means that diameter is primary determinant of blood flow; a small decrease in diameter is a huge increase in R

Question 11

Poiseuille’s Law

Answer 11

F=(change in P)(pi)(r^4) / 8(viscocity)L

Question 12

Laminar flow

Answer 12

Steady state, RBC in middle lane

Streamlines do not cross unlike turbulent flow

Question 13

Series resistance

Answer 13

R1 + R2 + R3 = RT

RT higher than greatest individual resistance

If this were true for circulation, the flow would be the same throughout whole system. An increase in R in one part would cause a decrease in flow to all others

Question 14

Parallel resistance

Answer 14

1/R1 + 1/R2 + 1/R3 = 1/RT

total resistance less than lowest

Question 15

MAP

Answer 15

2/3 diastolic P + 1/3 pulse pressure

Question 16

Changes in arterial systolic pressure

Answer 16

arteriosclerosis: arterial vessels harden, increase systolic P

aortic stenosis: AV valve does not open fully, decrease systolic pressure

Question 17

Changes in arterial diastolic P

Answer 17

Patent ductus arteriosus: decreased resistance (from skipping capillaries) decreases pressure

Aortic regurgitation: aortic valve does not close fully, backflow, arterial pressure down

Question 18

Right atrial pressure

Answer 18

Determined by heart pumping out blood and flow of blood to veins; should be 0, equal balance unless heart failure (veins in neck go up if this is true)

Question 19

Blood resevoirs

Answer 19

Spleen, liver, abdominal veins, venous plexus, skin, heart, lungs

Question 20

Effect of gravity on veins

Answer 20

Below heart, P increased by gravity

Above heart, P decreased by gravity

BUT because valves and movement of skeletal muscle around veins, we can counter this!