PHYS Microcirculation, Veins & Venous Return

Question 1

Change in function of precapillary sphincters in during rest vs during exercise.

Answer 1

Rest: Smooth muscle contracts precapillary sphincters
Exercise: Smooth muscle relaxes precapillary sphincters to enable blood flow through true capillaries.

Question 2

Force driving filtration at capillaries

Answer 2

Hydrostatic pressure/blood pressure

Question 3

Force opposing filtration at capillaries

Answer 3

Plasma osmotic/colloidal oncotic pressure via plasma proteins

Question 4

Factors enabling venous return to the heart

Answer 4

1. Pressure gradient (due to change in pressure btw veins & R atrium)
2. Skeletal muscle ‘pump’
3. Respiratory pump

Question 5

If the thoracic duct is severed, venous drainage from which part of the body would not be affected?

Answer 5

Right thorax.
This is because the thoracic duct drains everything except the R thorax, which drains into the R lymphatic duct.