1. Large artery 2. Arteriole 3. Capillary 4. Venule 5. Vein

Lecture 10: Cardiovascular System, Hemodynamics Flashcards by Kenny Lu

Heart valve flow order

R: tricuspid (AV) -> semilunar pulmonary
L: mitral (AV) (aka bicuspid) -> semilunar aortic

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L vs R ventricle

L ventricle wall is thicker than the right due to greater systemic resistance vs pulmonary

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Valve opening/closing

Opening/closing depends on ΔP between areas; valves themselves have little resistance. Creates unidirectional flow. Leakage = incompetent valves

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Types of CV vessels

Large artery
Arteriole
Capillary
Venule
Vein

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Large artery

Low resistance conducting vessel; elastic/pressure reservoir

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Arteriole

Primary effector of peripheral resistance to control blood distribution via dilation/constriction

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Capillary

Highest total cross-sectional area and smallest individual radius. Fluid/gas/nutrient exchange; uptake of waste/secreted products

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Venule

Migration site for WBCs, capacitance vessels; high compliance

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Vein

Low R high capacitance vessels; high compliance

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Compliance

ΔV / ΔP; defines change in volume for a given change in pressure.

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Windkessel effect

Refers to the elastic pressure reservoir property of the aorta. During ejection the aorta stretches out as flow in > runoff. When the heart relaxes, runoff continues and the aorta shrinks.

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Hydrostatic pressure

P = ρgh
Weight of water column (note the static part)

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Lateral pressure

Outward pressure of MOVING fluid

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Laminar vs turbulent flow

Laminar flow is smooth and ordered, turbulent is chaotic. Turbulent flow is what produces sounds (blood colliding w/ vessel walls)

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Flow equation

Q = ΔP / R
For CVS, CO = P_aorta - P_Ratrium / TPR

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Resistance of a vessel

R = 8ηL / πr^4
Most important is radius^4; other factors don’t change much physiologically

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Features of a system in series

Q is the same everywhere
Total ΔP = sum of ΔP in each segment
Total R = sum of R in each segment
Greatest ΔP drop occurs in highest R segment

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2 pumps in series

The CVS is 2 pumps (L + R heart) in series; thus Q is the same everywhere; CO = venous return

Features of a system in parallel

Total Q = sum of Qs in each branch
Total ΔP = sum of ΔP in each branch
1 / total R = 1 / R_A + 1 / R_B + …
Largest Q goes to path with least R

Flow velocity

v = Q / A; flow per cross-sectional area. Thus capillaries, w/ most cross-sectional area, have slowest flow allowing more gas exchange.

Bernoulli’s equation and total fluid energy

E total = E lateral + KE + gravitational PE + heat energy loss to R

Energy is conserved. In terms of P, P1 (lateral) + 1/2ρv^2 (KE1) + ρgh (PE1) = P2 + KE2 + PE2

Reynold’s number

N_R = ρdv / η
Describes propensity of laminar flow to become turbulent. >4000 usually turbulent; most notable is with change in diameter/velocity e.g. stenosis

Reticulocytes

Young RBCs; still have ribosomes, lose after ~1 day

Required substances for RBCs

Iron
Folic acid + Vit. B12

Iron (RBCs)

Hemochromatosis = excess accumul. Binds to ferritin for liver storage, transported in plasma by transferrin. Homeostatic control mostly by intestines.

Erythropoietin

Hormone that directly controls erythropoiesis in bone marrow; erythrocyte progenitor proliferation.

Anemia

Decreased blood ability to carry O2, due to: -Fewer total RBCs -Less Hb per RBC -Combo

Polycythemia

More RBCs than normal; more O2 carrying capacity but also thicker blood putting more strain on heart.

Blood cells

-RBCs -Leukocytes (WBCs) -Platelets (megakaryocyte fragments)

Hematopoietic growth factors

HGFs stimulate proliferation/differentiation of various blood cell progenitors

Bulk flow

Movement of all blood constituents together

2 halves of circulation

1. Pulmonary 2. Systemic

Microcirculation

Arterioles + capillaries + venules

Systemic circuit

L vent -> aorta -> artery branches -> arterioles -> capillaries -> venules -> veins -> inf/sup vena cava -> R atrium

Pulmonary circuit

R vent. -> pulmonary trunk -> 2x pulmonary arteries (1 per lung) -> arteries -> microcirculation -> 4x pulm. veins -> L atrium

Parallel arrangement of systemic artery branches

Parallel systemic arteries ensure all organs/tissues get fresh oxygenated blood; all get fraction of L vent blood. Allows independent regulation of blood flow

Portal systems

Exceptions usual anatomical path with 1st capillary bed, veins, then 2nd capillary bed before veins and heart return. E.g. liver, anterior pituitary

Hemodynamics

Blood pressure, flow, resistance. Q = ΔP / R

Poiseuille's Law

Describes factors for R; more friction = more resistance. Viscosity = intermolecular friction, length/radius = surface-molecule friction. Viscosity increases w/ hematocrit

Pulse pressure

Systolic - diastolic pressure

Factors for magnitude of pulse pressure

Everything affecting systolic and diastolic P Stroke volume, ejection seed, arterial compliance

Mean Arterial Pressure

MAP = DP + 1/3(pulse P) Average pressure driving blood over entire cardiac cycle. Same throughout entire body, remember relative arteriole P determines different arteriole flow

Intrinsic tone

Aka basal tone. Baseline spontaneous contractile activity of arteriolar smooth muscle. External stim. increase/decrease this tone