Pressure and Flow in Veins

Question 1

What is pressure like in veins?

Answer 1

Low

Question 2

Describe the pressure difference between the veins and venules and the right venule.

Answer 2

Small pressure change as veins and venules push blood into the right atria.

Question 3

RECAP- describe the structure of veins and venules.

Answer 3

Distensible and collapsible so can store a lot of blood.
Thin walls.

Question 4

What can the distensible structure of veins mean in terms of influences?

Answer 4

As veins are very thin, they are susceptible to external influences, like flow.

Question 5

Does gravity affect where the blood goes in the body?

Answer 5

Yes

Question 6

Does gravity affect the driving pressure of the blood in the body?

Answer 6

No

Question 7

What happens to blood when you go from sitting to standing?

Answer 7

Blood will go down your body and pool at venules in your feet, causing the venules to increase in size due to the volume of blood.

Question 8

What can happen when people, particular taller people, stand up after sitting.

Answer 8

They can go light headed or even faint

Question 9

What is the term used to describe the light headed feeling experienced when going from sitting/lying to standing?

Answer 9

Orthostatic (postural) hypotension

Question 10

Describe what happens regarding blood flow etc. when most of the blood is in the venules in the legs and the arteries have less blood to pump in the heart.

Answer 10

End diastolic value decreases
Preload decreases
Stroke volume decreases
Cardiac outflow decreases
Mean arterial pressure decreases.

Question 11

What could happen if your mean arterial pressure fell too much?

Answer 11

Tissues and organs wouldn’t be adequately perfused leading to things like postural/orthostatic hypertension.

Question 12

What would happen to the pressure in the column of blood as you moved closer to the head after lying?

Answer 12

Pressure would become increasingly negative.

Question 13

What would happen to compensate for this lower pressure?

Answer 13

As pressure in the vessel is less than the pressure outside of the vessel, the vessel will collapse and there will be less volume so pressure will increase.

Question 14

Is the point of collapse due to pressure often seen?

Answer 14

No as it usually occurs under the clavicle.

Question 15

What would happen to the pressure in your head area if your central venous pressure increased?

Answer 15

The point of collapse would move further up your neck and may become visible as the jugular vein could be pushing out.

Question 16

What can a raised jugular venous pressure be used to estimate?

Answer 16

Central venous pressure.

Question 17

What else can affect pressure and flow in the veins, other than gravity?

Answer 17

Skeletal muscle pump.

Question 18

What are the veins and venules in your legs surrounded by?

Answer 18

Skeletal muscle.

Question 19

What happens when the skeletal muscle surrounding veins and venules contracts?

Answer 19

It becomes shorter and fatter

Question 20

What happens to the veins when skeletal muscle contracts?

Answer 20

It squeezes the veins and venules and pushes blood in both directions- towards the heart and towards the feet.

Question 21

What limits the back flow of blood in your veins and venules?

Answer 21

Valves

Question 22

Give examples of rhythmic exercise.

Answer 22

Walking, cycling, running

Question 23

What happens to the veins/ venules in your legs during rhythmic exercise?

Answer 23

Skeletal muscle contracts and squeezes the extra capacitance back to the heart, increasing venous return and end diastolic volume..

Question 24

What happens to fill rate and end diastolic volume during exercise?

Answer 24

They both decrease

Question 25

What offsets the reduced fill rate and end diastolic volume?

Answer 25

Activity of the skeletal muscle pump.

Question 26

What may happen to patients lying in hospital beds for long periods of time or those going on a long haul flight?

Answer 26

They may develop deep vein thrombosis.

Question 27

Why do people get deep vein thrombosis?

Answer 27

Increased venous pooling in the legs and static blood is more likely to clot.

Question 28

How can you prevent deep vein thrombosis?

Answer 28

Wearing travel socks or specialised DVT socks

Question 29

How do these DVT socks work?

Answer 29

Tight fitting so compress the vessels in the legs and push the blood back to the heart more quickly.

Question 30

List the five things that can affect venous return to the heart.

Answer 30

Gravity
Skeletal muscle pump
Respiratory pump
Venomotor tone
Systemic filling pressure

Question 31

What does respiratory pump do in terms of venous return?

Answer 31

Increases venous return
Increases diastolic volume

Question 32

What happens to pressure upon inspiration?

Answer 32

Diaphragm moves down and causes a negative pressure within the thorax and a positive pressure below.
The positive pressure below gets transmitted down to the vessels and causes a larger pressure gradient, pushing blood back to the heart and increasing venous return.

Question 33

What happens to blood return when you are breathing faster and deeper?

Answer 33

Increase of blood return to the heart.

Question 34

How can respiratory pump help to offset the decreased filling time and diastolic volume experienced upon exercising?

Answer 34

Respiratory pump will direct more blood to the heart when increase in rate and depth of breathing.

Question 35

What is meant by tone?

Answer 35

Ongoing activity

Question 36

What type of muscle are veins and venules surrounded by?

Answer 36

Smooth muscle.

Question 37

What is smooth muscle innervated by?

Answer 37

Sympathetic NS

Question 38

Discuss how venomotor tone can help increase end diastolic volume.

Answer 38

The release of adrenaline and noradrenaline binds to adrenergic receptors on that smooth muscle, causes them to contract and squeeze that capacitance back to the heart increasing EDV.

Question 39

What is systematic filling pressure?

Answer 39

Pressure created by ventricles and transmitted through vascular tree to the veins

Question 40

What happens to systemic filling pressure upon exercise?

Answer 40

It increases