Week 7- Microcirculation

Question 1

How does blood enter tissues?

Answer 1

Through arterioles

Question 2

How is blood drained from capillaries to veins?

Answer 2

Via venules

Question 3

What is the keyrole of the cardiovascular system?

Answer 3

Ensuring adequate blood flow through the capillaries

Question 4

What is the equation for flow rate?

Answer 4

Pressure gradient / resistance

Question 5

Define blood flow rate

Answer 5

Volume of blood passing through a vessel per unit time

Question 6

What does increasing pressure gradient do to flow rate?

Answer 6

Increase it

Question 7

What is resistance in terms of blood flow?

Answer 7

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

Question 8

What is the main factor that affects resistance and actually changes?

Answer 8

Vessel radius

Question 9

What is the major determinant to resistance?

Answer 9

Arterioles

Question 10

Why is blood flow to different tissues different if the pressure difference is the same?

Answer 10

Due to differing resistance

Question 11

What is vascular tone?

Answer 11

Arteriolar smooth muscle displaying a state of partial restriction

Question 12

What is the point of vascular tone?

Answer 12

To allow arteries to either contract more or dilate so adjustments both ways are possible

Question 13

Why are radii of arterioles adjusted?

Answer 13

1. Match blood flow to metabolic needs of specific tissues

2. Help regulate systemic arterial blood pessure

Question 14

What is active hyperaemia?

Answer 14

When chemicals act on chemoreceptors on arterioles to increase vasodilation to allow higher blood flow to the area (driven by increased metabolites and increased oxygen usage)

Question 15

What is myogenic autorégulation?

Answer 15

When chemicals act on chemoreceptors on arterioles to cause vasoconstriction, may be physically driven via a drop in blood temperature and increased stretch due to increased BP

Question 16

How does blood flow increase only to tissues that need extra blood?

Answer 16

At tissues that dont need extra blood, they respond to extra stretch and constrict to stop reception of extra blood

Question 17

What arteriolar response will be seen in skeletal muscle arterioles in response to exercise?

Answer 17

Active hyperaemia

Question 18

What arteriolar response will be seen in small intestine arterioles in response to exercise?

Answer 18

Myogenic vasoconstriction

Question 19

What is the equation for cardiac output?

Answer 19

Blood pressure/ total peripheral resistance

Question 20

What is the equation for blood pressure?

Answer 20

Cardiac output x total peripheral résistance

Question 21

Where is the cardiovascular control center?

Answer 21

In the medulla

Question 22

What hormones cause vasoconstriction?

Answer 22

Vasopressin/ADH
Angiotensin II
Adrenaline/noradrenaline

Question 23

What is the purpose of capillary exchange?

Answer 23

The delivery of metabolic substrates to the cells of the organism

Question 24

What is a typical capillary lumen diameter?

Answer 24

7 micrometers

Question 25

What is a typical capillary cell width?

Answer 25

1 micrometer

Question 26

Why is capillary density important?

Answer 26

It depends on how metabolically active the tissue is, more activity requires a higher density

Question 27

What tissue has the highest capillary density and what is it?

Answer 27

Lungs- 3500cm^2/g

Question 28

Describe the structure of capillary

Answer 28

Single line of endothelial cells with small water filled gap junctions in between cells

Question 29

What is the size of acapillary fenestration?

Answer 29

80 nM

Question 30

What tissues may have a discontinuous capillary wall structure?

Answer 30

Bone marrow (to allow white cells to move into blood) Liver (to allow large compounds to get into the liver)

Question 31

What are the 3 type of capillary wall structures?

Answer 31

Continuous Fenestrated Discontinuous

Question 32

What capillary wall structure is found at the blood brain barrier? Describe it

Answer 32

Continuous- there are no gap junctions so only lipid soluble substances can get through freely, otherwise the brain controls what comes in

Question 33

What is bulk flow?

Answer 33

A volume of protein free plasma that filters out of the capillary and mixes with surrounding interstitial fluid and is reabsorbed

Question 34

What does oncotic mean?

Answer 34

To do with proteins

Question 35

What is oncotic force?

Answer 35

Conc of proteins in vessels reduces water potential pulling water into the vessels

Question 36

What is the opposing pressure to oncotic pressure?

Answer 36

Hydrostatic pressure

Question 37

How do arterioles match blood flow to the metabolic needs of specific tissues?

Answer 37

Regulation via intrinsic controls (independant of nervous or endocrine stimulation)

Question 38

How do arterioles help regulate systemic arterial blood pressure?

Answer 38

Regulation via extrinsic controls (travel via nerves or blood)

Question 39

Which is more effective out of ultrafiltration and reabsorption?

Answer 39

Ultrafiltration