Microcirculation

Question 1

Define blood flow rate

Answer 1

Volume of blood passing through a vessel per unit of time

Question 2

What are the 3 main factors that affect resistance in a vessel

Answer 2

Vessel length
Blood viscosity
Vessel radius

Question 3

Define vascular tone

Answer 3

Normal display of a state of partial constriction by arteriolar smooth muscle

Question 4

What is the normal pressure of blood entering and leaving the arterioles

Answer 4

93mmHg - 37 mm Hg

Question 5

What are the two functions of adjustment of arterioles

Answer 5

Match blood flow to metabolic needs of specific tissues

Help regulate systemic arterial blood pressure

Question 6

How is the matching of flow to metabolic needs (function 1) driven

Answer 6

Chemically or physically by local (intrinsic) controls

Question 7

Describe how the matching of flow to metabolic needs (function 1) can be chemically driven

Answer 7

Tissues produce metabolites as they increase in oxygen usage, directly causing vasodilation to increase blood flow

Question 8

Describe how the matching of flow to metabolic needs (function 1) can be physically driven

Answer 8

example: blood temp.
Arterioles constrict to reduce blood flow and preserve heat
Stretching due to blood pressure also causes constriction

Question 9

How regulation of systemic arterial blood pressure (function 2) driven

Answer 9

Extrinsic controls

Neural or hormonal

Question 10

Describe how the medulla exerts neural control on regulation of systemic arterial blood pressure (function 2)

Answer 10

Vasoconstriction (may decrease blood flow to some organs)

SNS through adrenaline

Question 11

Which hormones affect systemic arterial blood pressure (function 2)

Answer 11

vasopressin
Angiotensin II
Adrenaline/noradrenaline

Question 12

How is diffusion maximised in capillaries

Answer 12

surface area
diffusion distance
time for diffusion

Question 13

Which tissues will have dense capillary networks

Answer 13

high metabolically active tissues e.g. skeletal muscle

Question 14

Describe the continuous structure of capillaries

Answer 14

Linear singular cell wall with small water-filled gap junctions
Gap junctions allow small water-soluble to diffuse through

Question 15

Describe the fenestrated structure of capillaries and where is it found

Answer 15

glomerulus

certain substances of certain sizes are selectively allowed through fenestrae

Question 16

Describe the discontinuous structure of capillaries and where can it be found

Answer 16

Bone marrow, liver

Large gaps

Question 17

Describe the structure of capillaries in the blood-brain barrier

Answer 17

Continuous without gap junctions

No water-soluble molecules are allowed through without an active protein transporter

Question 18

Define bulk flow

Answer 18

Volume of protein-free plasma filtering out of the capillary to mix with the surrounding interstitial fluid and then being reabsorbed

Question 19

Compare the structure of lymphatic vessels and blood vessels

Answer 19

Lymphatic vessels are blunt ended and not continuous

Flaps instead of valves for unidirectional flow

Question 20

What are the roles of the lymph vessels

Answer 20

Removing excess interstitial fluid

Immune surveillance via lymph nodes

Question 21

Where does the lymph drain into

Answer 21

Right lymphatic duct/ thoracic duct and the right and left subclavian veins

Question 22

Compare flow in the lymph to flow in the vessels

Answer 22

No pump to induce flow in the lymph vessels