Lymphology Association of North America (LANA) Practice Exam

Under normal physiological circumstances, what best describes plasma colloid osmotic pressure?

1. The ability of plasma proteins to hold water

2. All are true

3. The colloid osmotic pressure in plasma is greater than in interstitial fluid

4. The colloid osmotic pressure prevents excessive loss of water through filtration

The correct answer is: All are true

Plasma colloid osmotic pressure refers to the pressure exerted by proteins in the plasma, primarily albumin, which serves to retain water in the intravascular space. This characteristic is crucial for maintaining fluid balance in the body. The assertion that plasma proteins possess the ability to hold water accurately describes one aspect of plasma colloid osmotic pressure. This property allows the plasma to attract and retain water, which is essential for preventing edema and maintaining normal blood volume. Additionally, it is true that colloid osmotic pressure in the plasma is typically greater than that found in interstitial fluid. This difference in osmotic pressure drives water to move from the interstitial space back into the bloodstream, where effective circulation and nutrient transport occur. Colloid osmotic pressure also plays a vital role in preventing the excessive loss of water from the circulatory system through filtration. By exerting an opposing pressure against hydrostatic pressure, it helps to maintain fluid equilibrium, ensuring that only a regulated amount of fluid transits between the blood and surrounding tissues. Given that all these statements accurately represent different facets of plasma colloid osmotic pressure, the choice that states "All are true" appropriately encompasses the comprehensive understanding of this physiological phenomenon.