Microcirculation 5

Question 1

What is blood flow rate?

Answer 1

Volume of blood passing through a vessel per unit time

Question 2

What is the equation for flow rate?

Answer 2

Flow = Delta pressure/ Vascular resistance 
F = DP/R

Question 3

What is resistance?

Answer 3

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

Question 4

What factors affect resistance?

Answer 4

• blood viscosity
• vessel length
• vessel radius

Question 5

What are the major resistance vessels?

Answer 5

Arterioles

Question 6

What is the major determinant of blood flow?

Answer 6

Resistance of the arterioles in the organs

Question 7

`What is vascular tone?

Answer 7

State of partial constriction when at rest displayed by arteriolar smooth muscle

Question 8

What two functions are the radii of the arteries adjusted for?

Answer 8

1) Match blood flow to the metabolic needs of specific tissues
2) Help regulate arterial blood pressure (for extrinsic reasons)

Question 9

What is active hyperemia?

Answer 9

An increase n blood flow to an organ that is due to an increased metabolic activity of said organ or tissue.

Chemical environment stimuli

Question 10

Example of arterioles responding to physical environment stimuli?

Answer 10

Vasoconstriction when ice applied to swollen ankle to reduce swelling.

Question 11

What is myogenic vasoconstriction

Answer 11

Blood vessels constrict to prevent increase of blood flow into tissue. this is arterioles responding to stretch, often when increased bp/HR

Question 12

What regulates constriction and dilation of the vessels?

Answer 12

Adrenoreceptors

Alpha = constriction of arterioles
Beta = in heart, increase rate

Question 13

What hormones cause vasoconstriction and subsequent increase in arterial blood pressure?

Answer 13

Angiotensin 2 and Vasopressin and noradrenaline/adrenaline as well as increased sympathetic activity

Question 14

What is the BP entering the arterioles?

Answer 14

93mmHg

Question 15

What is the BP exiting the arterioles?

Answer 15

37mmHg

Question 16

How are capillaries designed for transport of substrate?

Answer 16

1) Thin wall ( 1 mm thick)
2) thin vessels (7mm diameter)
3) Extensive branching

Question 17

What do capillaries aim to do?

Answer 17

• minimise diffisuion distance
• maximise diffusion time
• maximise surface area

Question 18

What does capillary density show?

Answer 18

How metabolically active a tissue is (more density=more metabolically active

Question 19

What are the 3 types of capillaries?

Answer 19

• continuous
• discontinuous
• fenestrated

Question 20

What is Bulk flow?

Answer 20

a volume of protein-free plasma
filters out of the capillary, mixes with the
surrounding interstitial fluid (IF) and is
reabsorbed

Question 21

What are the two main pressures that affect fluid movement into and out of capillaries?

Answer 21

• Hydrostatic Pressure

- Oncotic Pressure

Question 22

Where does lymph drain to?

Answer 22

• Thoracic Duct
• Right lymphatic duct
• Right subclavian vein
• Left subclavian vein

Question 23

How much fluid is removed by the lymphatic system daily?

Answer 23

3L

Question 24

How is oedema caused?

Answer 24

Rate of production of fluid > rate of removal of fluid