B1W4: Blood Flow Properties Flashcards
Polycythemia rubra vera
Increase in hematocrit (spleen grows)
Leads to hyperviscosity, hypertension, itchy skin
Where in the circulation is blood pressure the highest?
Pulmonary arteries
Key players of circulation
- 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
Amount of blood in diff. parts circulation
7% of blood in heart
9% in pulmonary vessels
13% in arterioles and capillaries
64% in veins
Pulsate Pressure
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
Highest velocity part of circulation
aorta
Flow of blood
Need pressure gradient (flows high to low)
indirectly proportional to resistance
F=change in P/R
Units of resistance
mmHg x min/L OR PRU (mmHg x sec/mL)
Blood pressure equation
BP=F/A in mmHg
1 mmHg=1.36 cm H2O
Conductance equation
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
Poiseuille’s Law
F=(change in P)(pi)(r^4) / 8(viscocity)L
Laminar flow
Steady state, RBC in middle lane
Streamlines do not cross unlike turbulent flow
Series resistance
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
Parallel resistance
1/R1 + 1/R2 + 1/R3 = 1/RT
total resistance less than lowest
MAP
2/3 diastolic P + 1/3 pulse pressure
Changes in arterial systolic pressure
arteriosclerosis: arterial vessels harden, increase systolic P
aortic stenosis: AV valve does not open fully, decrease systolic pressure
Changes in arterial diastolic P
Patent ductus arteriosus: decreased resistance (from skipping capillaries) decreases pressure
Aortic regurgitation: aortic valve does not close fully, backflow, arterial pressure down
Right atrial pressure
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)
Blood resevoirs
Spleen, liver, abdominal veins, venous plexus, skin, heart, lungs
Effect of gravity on veins
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!
