Lecture 11 - Arterial and Venous Systems and Lymphatics

Question 1

What is vascular distensibility?

Compare the distensibility of systemic/pulmonary veins and arteries.

Answer 1

• the ability of a vessel to change volume due to an increase in pressure
• increase in volume / (increase in pressure x original volume)
• veins are 8x more distensible than arteries
• systemic and pulmonary veins are comparably distensible
• pulmonary arteries are 6 times more distensible than systemic arteries

Question 2

What is vascular compliance?

Answer 2

-capacitance; quantity of blood that can be stored in a vessel due to a rise in pressure

• compliance = increase in volume / increase in pressure
• or-
• vascular distensibility x original volume

Question 3

Capacitance is (directly/inversely) __________ proportionate to volume and (directly/inversely) __________ proportionate to pressure.

Answer 3

Directly; indirectly

Question 4

What is elastance?

Answer 4

• tendency of a vessel to recoil toward its original dimension after removal of a distending force
• the inverse of compliance

Question 5

What is pulse pressure?

Answer 5

-pulse pressure = stroke volume / arterial compliance

Question 6

What conditions cause abnormal pulse pressures and why?

Answer 6

Aortic valve stenosis:

Ateriosclerosis: pulse pressure increases because of loss of elastance

Patent ductus arteriosus: blood is shunted to right side of heart

Aortic regurgitation: blood flows back into the left atrium

Question 7

What is mean arterial pressure?

Answer 7

• time weighted average of arterial pressure with respect to time
• MAP = diastolic pressure + 1/3 pulse pressure

Question 8

What is central venous pressure and what factors affect it?

Answer 8

-pressure in the right atrium

Modifying factors:

• ability of heart to pump blood out of right atrium/ventricle
• tendency of blood to flow into right atrium

Question 9

What factors increase venous return?

Answer 9

• increase blood volume
• increased peripheral venous pressures
• dilation of arterioles

Question 10

What happens to intravascular pressure following blood loss or gain?

Answer 10

There is a respective dramatic increase or decrease in pressure followed by a delayed return in pressure towards normal

Question 11

Describe the structure of a capillary.

Answer 11

Arteriole:

• control blood flow into tissue by regulating diameter
• continuous muscular coat

Metarteriole:

• just prior to true capillaries
• loss of continuous coat and replacement with precapilary sphincters

Capillaries:

• after precapillary sphincters
• diameter 4-9μm

Venule

Question 12

What structures are present in the capillary walls?

Answer 12

Slit pores:

• intercellular clefts
• allow for rapid diffusion of water, soluble ions, and small molecules

Plasmalemmal vesicles:

• formed by caveolins
• used in endocytosis and trans cytosine

Pores
-present in certain organs such as liver, GI, and kidneys

Question 13

The most important factor regulating vasomotion is __________.

Answer 13

Oxygen concentration

Question 14

The rate of diffusion of water across the capillary is __________ times __________ (greater/lower) than the flow of plasma through the capillary.

Answer 14

80; greater

Question 15

The rate of diffusion of a substance is __________ proportional to the __________ differences of the substance.

Answer 15

Directly; concentraiton

Question 16

What determines the direction of diffusion of a fluid?

Answer 16

Starling forces:

• capillary pressure (outward)(Pc)
• interstitial fluid pressure (inward)(Pif)
• capillary plasma colloid osmotic pressure (inward)(Π)
• interstitial fluid colloid osmotic pressure (outward)(Πif)

Net filtration pressure:
-NFP = Pc - Pif - Πp + Πif

Question 17

What factors affect lymph flow?

Answer 17

interstitial fluid pressure (directly)

• capillary hydrostatic pressure
• decreased plasma colloid osmotic pressure