Chapter 15 Vascular Distensibility

Question 1

What is distensibility?

Answer 1

The ability to accomodate the pulsatile output of the heart and to average out the pressure pulsations

Question 2

Which vessels are the most distensible? How much extra blood can they accomodate

Answer 2

The veins
0.5-1 L

Question 3

How to calculate distensibility

Answer 3

increase in volume/ (inc in pressure x original volume)

Question 4

How to calculate compliance

Answer 4

increase in volume/increase in pressure

Question 5

The total quantity of blood that can be stored in a given portion of the circulation for each mmHg pressure rise is known as

Answer 5

compliance

Question 6

What does the term delayed compliance mean?

Answer 6

A vessel exposed to an increased volume at first exhibits a large increase in pressure, but progressive delayed stretching of smooth muscle in the vessel walls allows the pressure to return to normal in min to hours

Question 7

Two major factors that influence pulse pressure?
How is it calculated?

Answer 7

1. stroke volume output
2. compliance
   stroke volume/arterial compliance

Question 8

Why does pulse pressure increase with age?

Answer 8

decrease in compliance due to arterosclerosis

Question 9

How is pulse pressure affected with aortic valve stenosis? why?

Answer 9

decreased pulse pressure because the diameter of the aortic valve is reduced significantly, decreasing the outflow of blood

Question 10

How is pulse pressure affected with patent ductus arteriosus? why?

Question 11

How is pulse pressure affected with aortic regurgitation? why?

Question 12

describe the transmission of the pulse pressure in the aorta

Answer 12

when the heart ejects blood into the aorta during systole, the proximal portion because distended, but the rising pressure overcomes inertia pushing the distention further and further down the aorta

Question 13

What is damping?

Answer 13

the progressive diminution of the pulsations in the periphery

Question 14

2 causes of damping

Answer 14

1. resistance to blood movement in the vessels
2. compliance of the vessels

Question 15

The blood in the right atrium is known as

Answer 15

central venous pressure

Question 16

Factors that increase right venous volume and therefore pressure (3)

Answer 16

1. increased blood volume
2. increased large vessel tone
3. dilation of the arterioles (dec PVR and allows rapid flow of blood from the arteries to the veins)

Question 17

Normal right atrial pressure

Answer 17

0 mmHg (atmospheric pressure)

Question 18

What happens with a rise in right atrial pressure?

Answer 18

Blood begins to back up into the large veins, causing them to enlarge or even collapse

Question 19

Normal pressure in the abdominal cavity? What happens when it rises?

Answer 19

6 mmHg
the pressure in the veins of the legs must rise above the abdominal pressure before the abdominal veins will open

Question 20

Why is the pressure in the veins of the feet the highest?

Answer 20

gravitational pressure

Question 21

T/F: The neck veins of a person standing upright collapse almost completely due to gravitational pressure

Answer 21

true

Question 22

What is the venous pump system

Answer 22

valves are arranged in the veins to move venous blood flow in the direction of the heart, and each time a person moves their legs, venous blood is propelled toward the heart

Question 23

Why can a circulatory system function normally after 20% blood loss?

Answer 23

The veins are a blood reservoir and constrict

Question 24

Name the 4 specific blood resevoirs

Answer 24

1. spleen
2. liver
3. large abdominal veins
4. venous plexus beneath the skin