Hole's Human Anatomy & Physiology (Shier), 12th Edition

Chapter 20: Urinary System

Fluid Exchange Across the Walls of Capillaries

Why does fluid need to leave the capillaries? In the capillaries much of the fluid component of the blood leaves the vessels and directly with the interstitial fluid bathing the adjacent cells before returning to the capillaries. The fluid is carrying oxygen gas and small solutes such as sugars and salts. The oxygen and other molecules can then directly diffuse into the cells without having to first diffuse across the wall of the capillary.

View the animation below, then complete the quiz to test your knowledge of the concept.



1.

The fluids leave the capillaries at the arterial end because...
A)the net filtration pressure of the blood is higher at the arterial end than it is at the venous end.
B)the net filtration pressure of the blood is higher at the venous end than it is at the arterial end.
C)the net filtration pressure of the interstitial fluid is higher at the arterial end than it is at the venous end.
D)the net filtration pressure of the interstitial fluid is higher at the venous end than it is at the arterial end.
E)the osmotic pressure is higher at the arterial end than it is at the venous end.
2.

The fluids reenter the capillaries at the venous end because...
A)the net filtration pressure of the blood is higher at the arterial end than it is at the venous end.
B)the net filtration pressure of the blood is higher at the venous end than it is at the arterial end.
C)the net filtration pressure of the interstitial fluid is higher at the arterial end than it is at the venous end.
D)the net filtration pressure of the interstitial fluid is higher at the venous end than it is at the arterial end.
E)the osmotic pressure is higher at the venous end than it is at the arterial end.
3.

Approximately what percent of fluid that exits the capillaries at the arterial end renters the capillaries at the venous end?
A)60%
B)70%
C)80%
D)90%
E)100%
4.

The lymphatic capillaries reabsorb as much as 20% of the fluid lost by the blood capillaries.
A)True
B)False
5.

The net osmotic pressure is equal at both the arterial and the venous ends of the capillary.
A)True
B)False
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