Biophysics and tissue fluid

Question 1

Equation for blood flow

Answer 1

Blood flow (cm3/s)= change in pressure / resistance

Question 2

What does Poiseuilles law show about resistance?

Answer 2

Flow is proportional to 4th power of radius and change in pressure- so small change in pressure has a big change on flow, flow is inversely proportional to the viscosity and the length

Question 3

Law of Laplace

Answer 3

Transmural peressure(p) = tension / radius

Question 4

What changes to blood flow happen in the arterioles?

Answer 4

35mmHg 9lower pressure, blood velocity decrease

Question 5

What percentage of blood is in the capillaries?

Answer 5

5%

Question 6

What is the velocity in the capillaries?

Answer 6

0.07cm/s

Question 7

Tissue fluid formation depends on what?

Answer 7

Hydrostatic pressure, difference in colloid osmotic pressure and capillary filtration coefficient

Question 8

What does histamine do to capillaries?

Answer 8

Make capillary beds more leaky

Question 9

Causes of abnormal tissue fluid level?

Answer 9

haemorrhage (blood pressure reduces so more reabsorption), capillary damage (fluid efflux increasing tissue fluid protein and COP, oedema- increase venous BP increasing hydrostatic pressure due to heart failure, venous obstruction and pregnancy, inflammatory oedema caused by histamine, hypoproteinaemia (fall in plasma proteins in nephrosis starvation), exercise oedema (increases hydrostatic pressure causing swelling of 25%