Lecture 9+10+DLA

Question 1

What is Darcy’s law?

Answer 1

Flow = Pressure / Resistance

Question 2

What are the three kinds of pressure in the CV system?

Answer 2

1. Driving pressure - pressure along the length of a vessel
2. transmural pressure- influences the diameter of the blood vessel
3. hydrostatic pressure - pressure created by the weight of blood (important in capillaries)

Question 3

What is the equation for driving pressure?

Answer 3

DP = MAP - RAP

Question 4

How to determine Cardiac output

Answer 4

CO = MAP- CVP/ TPR

CVP is usually 0, unless in heart failure

Question 5

What is Poiseuille’s Law?

Answer 5

Flow = pressure X pi x R(4) / 8 x viscosity x length

Resistance = 8 x viscosity x length / pi x radius (4)
resistance is most sensitive to changes in radius

Question 6

What blood vessel has the greatest resistance?

Answer 6

Arterioles

capillaries have the greatest when they are in series not in parallel
one capillary not a capillary bed

Question 7

What happens during vasodilation in the arterioles?

Answer 7

short-term = increased pressure at capillaries, increased edema

septic shock or anaphylaxis occurs during massive vasodilation. (hypotension, reduced tissue perfusion, changes in HR)

exercise- massive reduction in resistance, but blood flows to other areas to maintain MAP

Question 8

Graves disease

Answer 8

immune disorder that leads to hyperthyroidism, thus arteriolar vasodilation

reduced arteriolar resistance leads to reduced dampening of pulsatile arterial pressure in capillaries

pulsatile flow can be seen in the capillaries in fingernail beds

Question 9

vasoconstriction in the arterioles?

Answer 9

short-term = reduced pressure at capillaries

pre-eclampsia is the result of major vasoconstriction, thus reduced pressure in capillaries and reduced tissue perfusion.

Question 10

capacitance and resistance vessels?

Answer 10

capacitance = venules and veins (affect preload)

resistance = arterioles (affect afterload)

Question 11

regulating flow to the organs?

Answer 11

blood distribution is in parallel and the pressure between the aorta and the arteries are similar

Question 12

what affects resistance?

Answer 12

sympathetic’s = vasoconstriction (endothelin and serotonin)

vasodilators = nitric oxide, histamine adenosine

small arteriole radius leads to a larger resistance

Question 13

velocity equation?

Answer 13

velocity = flow / cross sectional area

capillaries have the largest cross sectional area and have the slowest velocity.

Question 14

Reynold’s equation?

factors that impact turbulence and what leads to that?

Answer 14

factors that increase turbulence:
high flow velocity
large vessel diameter
high blood density

factors that decrease turbulence:
increase viscosity

Reynold’s number determines whether flow will be laminar or turbulent

Re = velocity x diameter x pressure / viscosity

turbulence usually occurs due to defective valves and narrowed blood vessels

Question 15

La Place’s law?

clinical example?

Answer 15

Pressure = 2(tension) / radius

aneurysm:
a point can be reached where the wall cannot generate any more wall tension

Question 16

compliance of arteries and veins?

Answer 16

veins are compliant - for a small change of pressure they increase their volume greatly

arteries are not compliant - large pressure does not change their volume to much

Question 17

venoconstriction and venodilation

Answer 17

increased sympathetic = venoconstriction
gets blood out of the veins and shifts it towards the heart

decreased sympathetic = venodilation
allows for more venous pooling and decreases venous return

Question 18

pulse pressure equation?

Answer 18

PP = SBP - DBP

Question 19

How to calculate mean arterial pressure?

Answer 19

MAP = P (diastolic) + 1/3 x P(sys) - P (dias)

Question 20

Fick principle?

Answer 20

Rate of O2 removal = O2 pulmonary flow in artery - O2 pulmonary flow out in vein

Question 21

physical factors of microcirculation

Answer 21

1. hydrostatic pressure - capillary pressures drive fluid out of capillaries and into interstitial space
2. oncotic pressure - keep fluids in capillaries and drive reabsorption
3. capillary walls - more permeable
4. lymphatic drainage - remove excess interstitial fluid

Question 22

starling-landis equation

Answer 22

net filtration pressure = hydrostatic pressure - oncotic pressure

NFP = (Pc - Pif) - (pi c - pi if)

if NFP is +, filtration occured
if NFP is -, filtration is occuring

Question 23

Edema locations?

Answer 23

subcutaneous tissue = peripheral edema

lungs = pulmonary edema

abdominal cavity = ascites

Question 24

Physical factors that cause edema?

Answer 24

increased venous pressure = increased capillary hydrostatic pressure = increased capillary filtration = edema (due to heart failure or hypertension)

loss of plasma proteins = lower plasma oncotic pressure and lower capillary reabsorption = edema

surgery or radiotherapy = damaged lymph nodes = defective lymph drainage = lymphedema

Question 25

hypoalbuminemia

Answer 25

occurs:
cirrhosis and hepatitis
increased albumin clearance
pregnancy

results in:
reduced oncotic pressure
less fluid reabsorbed
more fluid in interstitial fluid

Question 26

edema causes

Answer 26

RV failure = ankle swelling (tissue edema)

LV failure = fluid in lungs (pulmonary edema)

hepatic fibrosis = ascites