3.1 Structure and Function of Blood Vessels

Question 1

How much blood do we have (in litres, and as a percentage of our bodyweight)

Answer 1

~5 litres (7-8% bodyweight)

Question 2

Is there more blood in veins or arteries and arterioles?

Answer 2

Veins

Question 3

What is meant by systemic circulation?

Answer 3

Everything except lungs

Question 4

What percentage of blood is in the heart and lungs?

Answer 4

About 16%

Question 5

Do veins or arteries have more smooth muscle? Why does this make sense?

Answer 5

• Arteries have more smooth muscle
• They carry blood which is at much higher pressures

Question 6

What is the tunica intima? What is the name of the connective tissue within the tunica intima?

Answer 6

• Endothelium on inside of blood vessels
• Connective tissue is called lamina propria
  (Tunica = latin for coat)

Question 7

What is the tunica media? What does it contain?

Answer 7

• Smooth muscle
• Elastic fibres (give elasticity to the blood vessel)
• Connective tissue (supplies oxygen and nutrients to muscle cells)

Question 8

What is the tunica adventitia? What does it contain?

Answer 8

• Connective tissue
• Nerve fibres (control diameter)

Question 9

Where are substances exchanged throughout the cardio system?

Answer 9

Capillaries

Question 10

What is transmural pressure?

Answer 10

Pressure gradient across a vessel wall - stiffer wall means lower elasticity and higher transmural pressure.

Question 11

What is hydrostatic pressure?

Answer 11

The pressure exerted due to the density and gravity of the fluid.

Question 12

Why are arteries like highways?

Answer 12

• You can transport quick, but you cannot stop and exchange goods.

Question 13

Diameter of arteries

Answer 13

from mm to 100s of micrometer

Question 14

What are the two types of large arteries? Give some examples of each.

Answer 14

• Elastic (aorta, pulmonary arteries)
• Muscular (femoral artery, radial & brachial arteries)

Question 15

How do the composition of the tunica media differ between muscular and elastic arteries?

Answer 15

Elastic: more elastic fibres in tunica media
Muscular: more smooth muscle in tunica media

Question 16

Explain systole vs diastole

Answer 16

Systolic pressure is exerted on blood vessels when the heart pushes blood around the body.
Diastolic pressure is less than systolic pressure, and occurs when the ventricles relax and refill with blood

Question 17

Explain the Windkessel effect

Answer 17

During systole, the (elastic) aorta expands and stores some blood which is released during diastole, thus maintaining constant flow.

Question 18

Diameter of arteriole

Answer 18

5-30 micrometer

Question 19

How many layers of smooth muscle in arteriole?

Answer 19

1-4

Question 20

How do arterioles regulate blood pressure

Answer 20

Changes in diameter (can have a huge effect)

Question 21

Why does blood flow slowest at the capillaries?

Answer 21

Most time for exchange of goods

Question 22

Is the pressure of pulmonary circulation smaller or greater than that of systemic circulation? How does this effect the size of the aorta vs pulmonary artery?

Answer 22

Pulmonary circulation is much lower in pressure. Therefore, the pulmonary artery does not need as much smooth muscle as the aorta.

Question 23

Relationship between blood flow and pressure difference (delta P)

Answer 23

Proportional

Question 24

Relationship between radius and blood flow

Answer 24

Proportional to the fourth power of the radius

Question 25

Relationshio between blood flow and vessel length (L)

Answer 25

Inversely proportional

Question 26

Relationship between blood flow and viscosity

Answer 26

Inversely proportional

Question 27

What blood vessels are involved in microcirculation?

Answer 27

Arterioles, capillaries, venules

Question 28

How do veins overcome the hydrostatic pressure to get blood back to the heart?

Answer 28

They are next to muscles, and the muscles get the blood flowing when they contract. This is why you shouldn’t sit all day

Question 29

Why do veins need valves?

Answer 29

So that blood cannot flow back.

Question 30

What does it mean that lymphatic vessels start “blind”

Answer 30

They start somewhere, they are not continuous

Question 31

What goes into lymphatic vessels (in terms of the cardiovascular system)?

Answer 31

Everything that is filtered from the capillaries, but not reabsorbed in the venules

Question 32

Do lymphatic vessels have valves?

Answer 32

Yes

Question 33

Where does afferent lymph drain?

Answer 33

Into “home lymph node” (like a local pub), where they are filtered.

Question 34

Where does lymph go once it leaves the lymph nodes?

Answer 34

Drains via an efferent lymphatic vessel into the right lymphatic duct (right superior area) or the thoracic duct (everywhere else)