Cardiovascular systems 7 - Microcirculation

Question 1

How can flow rate be calculated?

Answer 1

Pressure gradient/resistance

Question 2

Define blood flow rate.

Answer 2

Volume of blood passing through a vessel per unit time

Question 3

How is pressure gradient measured?

Answer 3

Mean arterial pressure - pressure B

Question 4

Define resistance in relation to blood flow?

Answer 4

Hindrance to blood flow due to friction between moving fluid and stationary vascular walls.

Question 5

What is the response to an increase in stroke volume?

Answer 5

Pressure gradient increases, blood flow increases

Question 6

What is the response to an increase in arteriolar vasoconstriction?

Answer 6

Increased resistance and decreased blood flow.

Question 7

What do arterioles display a state of partial constriction?

Answer 7

• So that vasodilation or vasoconstriction can occur.

- Called vascular tone

Question 8

What is active hyperaemia?

Answer 8

• Increase in blood flow to organs due to increased metabolic activity and oxygen usage
• Causes vasodilation

Question 9

What is myogenic autoregulation?

Answer 9

• Decrease in blood flow due to low blood temperature

- Vasoconstriction of arteries occurs.

Question 10

What mechanism limits flow of blood to skeletal muscle at rest?

Answer 10

• Precapillary sphincters

- They close off some capillaries, as skeletal muscle has dense capillary networks

Question 11

What are the three types of capillaries?

Answer 11

• Continuous (found in muscle and fat, cells are joined by tight junctions)
• Fenestrated capillaries
• Discontinuous ( bone marrow and liver)

Question 12

What type of capillary is present in the blood brain barrier?

Answer 12

• Continuous capillary layout with tight junctions

- This allows tight control of what enters the brain, water soluble substances need transport proteins.

Question 13

Describe starlings hypothesis.

Answer 13

• There needs to be a balance between hydrostatic pressure of blood in capillaries and osmotic attraction of blood for the surrounding fluids.
• Osmotic pressure of proteins of the serum determines absorption

Question 14

Describe the movement of fluid from the capillaries.

Answer 14

• High hydrostatic pressure causes fluid to move out the capillary into the tissue fluid
• Oncotic pressure of the blood is higher than that in the tissue fluid so reabsorption occurs.
• There is always a slight loss of fluid from blood

Question 15

Describe the role of the lymphatic system.

Answer 15

• Blunt ended vessels drain excess tissue fluid

- Drains to right lymphatic duct and thoracic duct, reentering blood in the subclavian veins

Question 16

What is the overall purpose of circulation?

Answer 16

To provide adequate perfusion of tissue