Anatomy & Hemodynamics

Question 1

Describe the series and parallel arrangement of the circulatory system, and its purposes.

Answer 1

Series: right & left heart arranged “in series;” no direct connection; output of left and right sides of heart must be closely matched

Parallel arrangement of vasculature (think of a ladder with organs on each rung

• Oxygenated blood visits only one organ system before returning to pulmonary circulation
• Changes in metabolic demand or blood flow in one organ do not significantly affect other organs
• Blood flow to different organs can be individually varied to match demand.

EXCEPTION: hepatic circulation — large fraction of hepatic blood supply is via intestinal circulation

Question 2

Describe the functions of the CV system

Answer 2

• Distribute dissolved gases & nutrients.
• Removes metabolic waste
• Contributes to systemic homeostasis by controlling temp, O2 supply, pH, ionic composition, nutrient supply
• Quickly adapts to changes in conditions and metabolic demands

Question 3

What vessel regulates BP, and what are it’s key features?

Answer 3

Arterioles:
• highly innervated by autonomic nerves, circulating hormones, and local metabolites (tunica media)
• primary site of regulation of vascular resistance, via changes in diameter

Question 4

What is the primary “capacitance vessel” of the body?

Answer 4

Veins and venules “store” most of blood volume.

Question 5

Describe the arrangement of the microcirculation

Answer 5

Capillaries, the site of gas, nutrient, and waste exchange.

Flow thru cap beds is determined by osmotic concentration and pressure gradient (regulated via constriction/dilation of arterioles & precapillary sphincters, which are smooth muscle bands at junction of arteriole and capillaries

Question 6

Describe the function of the lymphatic system

Answer 6

Less numerous and more porous than caps

Lymph flows into lymphatic capillaries in response to:

• increased interstitial pressure
• contraction of smooth muscle in lymph vessel
• contraction of surrounding skeletal muscle

Edema occurs when interstitial fluid > capacity of lymphatic system

Question 7

What’s the flow equation? Describe how changes in vascular resistance determine the distribution of cardiac output among tissues.

Answer 7

Q = ΔP/R
This can be applied to Cardiac Output, where:
CO = (Pa - Pv) / TPR

TPR = Total Periph Resistance

Question 8

What is Poiseuille’s Law?

Answer 8

ΔP * pi * r^4
Q = ——————
8 * n * l

n = viscosity, l = length

Question 9

Explain how the pulsatile flow of blood produced by the heart is converted to steady flow in the capillary beds.

Answer 9

Increased compliance (elasticity) in aorta and main arteries dampens pulsatile flow and helps transform flow into continuous for microcirculation. The biggest pressure drop occurs in the arterioles

Question 10

Define vascular compliance.

Answer 10

Stretchyness of a vessel (math: C = ΔV / ΔP)
Veins > arteries
Younger aortas are more stretchy than older

Question 11

What is LaPlace’s Law?

Answer 11

ΔP * r
T = ————–
u
Tension, transmural Pressure, radius, u = thickness

Question 12

6. Understand Fick’s Principle and know how it can be used to determine transcapillary efflux.

Answer 12

Basically, blood flow to an organ can be calculated using a marker substance as long as we know the consumption rate and starting & ending concs.

Flow = O2 consump rate / ( [Oa] - [Ov] )

Question 13

Understand how the balance between hydrostatic and oncotic pressure in a capillary bed determines the direction of transcapillary transport (Starling’s Equation)

Answer 13

Net flux is the balance between hydrostatic pressure (outward/filtration) and oncotic pressure (inward/reabsorption). Equation:
Flux = k * ( ( Pc - Pi ) - ( πc - πi ) )

k = konstant, P = hydrostatic, π = osmotic
(c = cap, i = interstitial)