Haemodynamics and Microcirculation

Question 1

what is fluid flow a measure of

Answer 1

blood volume/ time

NB. not the same as fluid velocity = distance/ time

Question 2

what are the 3 types of blood flow in vessels

Answer 2

laminar flow= arteries, veins
turbulent flow= ascending aorta, ventricles
single file flow= capillaries

Question 3

blood flow is proportional to…

Answer 3

tube length

blood viscosity

Question 4

blood flow is inversely proportional to…

Answer 4

tube radius raised to 4th power

Question 5

which vessels are arranged in parallel

Answer 5

all vessels except for pulmonary trunk, aorta

Question 6

how does blood vessels in series affect the resistance

Answer 6

increase total resistance

Question 7

how does blood vessels in parallel affect the resistance

Answer 7

decrease total resistance

Question 8

how is distending pressure calculated

Answer 8

pressure inside - pressure outside (transmural pressure)

Question 9

what is compliance of a vessel

Answer 9

how ready is vessel to alter blood volume as pressure changes occur

Question 10

which vessel has high compliance

Answer 10

veins- thin-walls, easily stretched ….. volume reservoirs

Question 11

which vessel has the lowest compliance

Answer 11

arteries…..pressure reservoirs

Question 12

what is the ‘micro-circulation’

Answer 12

circulation of blood through the arterioles, cappillaries, venules

Question 13

is blood flow uniform in the capillary network- why

Answer 13

not uniform

dependant on arteriole smooth muscle

Question 14

what is responsible for short-term auto regulation of blood flow in capillary network

Answer 14

1. local hypoxia= relaxation of arteriole smooth muscle= low resistance= more blood flow
2. metabolism products (H+, CO2, K+)= relaxation of smooth muscle= low resistance= more blood flow
3. nitric oxide (relaxing factor)= releases calmodium= relaxation of smooth muscle

Question 15

what is the myogenic response

Answer 15

how each single smooth muscle cell responds to changes in bp and alter flow as a result. negative feedback controls this.

Question 16

what is responsible for long-term auto regulation of blood flow in capillary network

Answer 16

increase the number of microcirculatory vessels supplying blood to tissue
enlargement of existing vessels

Question 17

which capillaries do hydrophilic solutes enter

Answer 17

h20, ions, organic mols= fenestrated capillaries

Question 18

which capillaries do lilophillic solutes enter

Answer 18

02, h20= continual capillaries

Question 19

which end of capillary network does net movement of fluid out of capillaries take place- filtration

Answer 19

arterial end

Question 20

which end of capillary network does net movement of fluid in of capillaries take place- reabsorption

Answer 20

venous end

Question 21

why is there a net loss of fluid from capillary network

Answer 21

the net effect of forces acting on capillaries is not in equilibrium= 1.5 mL lost
lymph nodes bring it back