Ch 3 Venous Physiology

Question 1

What is edema?

Answer 1

Swelling due to accumulation of fluid

Question 2

What is hydrostatic pressure?

Answer 2

-Major force affecting venous system
-Pressure within vascular system due to the weight of blood compared to a reference point (RA of heart)

Question 3

What is transmural pressure?

Answer 3

Pressure on walls of a vessel

Question 4

What is starling equilibrium?

Answer 4

The movement of fluid across the capillary

Question 5

Veins are known as the ___ vessels of the body?

Answer 5

Capacitance

(this is the volume of blood that a vessel can hold at any given pressure, w/o a large increase in BP)

Question 6

The venous side of the circulatory system holds how much of the total blood volume of the body?

Answer 6

2/3

(66% venous, 30% arterial, 3-4% capillaries)

Question 7

When veins are distended, they have high or low resistance?

Answer 7

Low, almost no resistance to blood flow (due to circular shape)

Question 8

When veins are partially empty, they will have high or low resistance?

Answer 8

High resistance to blood flow (due to elliptical shape)

Question 9

How can veins increase blood flow resistance w/o causing an increased pressure gradient to the heart?

Answer 9

B/c veins have the ability to change their shape

Question 10

Does hydrostatic pressure increase in higher or lower portions of the body?

Answer 10

Lower - b/c of the weight of the column of blood within the vessels

(meaning the farther below the reference point, RA, the greater the pressure)

Question 11

What 2 components make up vessel pressure?

Answer 11

Dynamic pressure due to contraction of heart + hydrostatic pressure

Question 12

Does hydrostatic pressure affect the arteries or veins?

Answer 12

Both! Since the dynamic pressure is very low in veins, the HSP plays a greater role in determining the overall venous pressure

Question 13

When in supine, the hydrostatic pressure is ___?

Answer 13

Negligible - b/c the arteries + veins are at the same level as the RA

(meaning pressure throughout the vascular system is roughly equal to the dynamic pressure)

Question 14

When standing, an individual will add a hydrostatic pressure component of approx __ mm Hg at the ankle?

Answer 14

102 mm Hg

Question 15

When standing, will the pressure gradient across the capillary bed change or remain the same as it was in supine?

Answer 15

Remain the same, b/c the same amount of hydrostatic pressure is added in both the arteries + veins

Question 16

Is there a change in the ability to exchange nutrients across the capillary bed when supine vs standing?

Answer 16

No change!

Question 17

What happens to the hydrostatic pressure + pressure gradient when we lift our hand above our head?

Answer 17

They both decrease

Question 18

During exercise, the pressure in the veins falls below ___ mm Hg? How does this affect the pressure gradient?

Answer 18

Below 20, it increases the pressure gradient (to 177 mm Hg) across the capillaries

Question 19

How does an increased pressure gradient help during exercise?

Answer 19

It increases blood flow needed

Question 20

What shape will the vein be at low, equal + high transmural pressures?

Answer 20

Low: dumbbell (empty)
Equal: elliptical (partially empty)
High: circular (fully distended)

Question 21

Compression stockings ___ tissue pressure, which ___ transmural pressure? This then ___ total area of the vein + ___ blood pooling? Fill in with increase or decrease

Answer 21

Increase, decrease, decreases, decreases

Question 22

What does the starling equilibrium describe?

Answer 22

The movement of fluid across the capillary (either out or into the capillary)

Question 23

What is osmotic pressure?

Answer 23

Pressure exerted by fluid when there is a difference in concentrations of solutes across the capillary endothelium

Question 24

Does standing increase or decrease capillary pressure?

Answer 24

Increase, it forces fluid out of capillaries into interstitial tissue

Question 25

What causes edema?

Answer 25

Increase in capillary pressure

Question 26

What are 2 things we can do to reduce edema?

Answer 26

-Use compression stockings (increases interstitial pressure)

-Elevate legs (decreases hydrostatic + intracapillary pressure)

Question 27

In the presence of a DVT, what will happen to the normal phasic venous flow from the lower extremities?

Answer 27

May be reduced or absent