What is a potential consequence if the water level in the intracellular fluid becomes too low?

A. Protein concentration increases in the blood plasma: Hydrostatic pressure drives the filtration of water and small solutes, leaving large plasma proteins behind. While the relative concentration of proteins may rise slightly as fluid leaves, this is a result of the filtration process. The primary effect is volume movement.

B. Fluid and nutrients are filtered out into surrounding tissues: High hydrostatic pressure at the arterial end of a capillary overcomes the inward pull of oncotic pressure. This net filtration pressure forces water and dissolved nutrients into the interstitial space. This process is essential for delivering oxygen and glucose to cells.

C. Fluid is reabsorbed into the capillaries: Reabsorption occurs when the colloid osmotic pressure, exerted by plasma proteins, is greater than the capillary hydrostatic pressure. This typically happens at the venous end of the capillary bed. It allows metabolic wastes to enter the bloodstream for excretion.

D. Fluid movement halts between compartments: Fluid movement only halts when hydrostatic and osmotic pressures reach an equilibrium point where net filtration is zero. In a functioning circulatory system, these pressures are dynamic to ensure continuous exchange. Constant movement is required for systemic nutrient delivery.

A. Hypotonic; swelling or lysis: Rapid ingestion of free water dilutes the extracellular fluid, reducing its osmolarity relative to the intracellular compartment. Water moves into the cells via osmosis to balance the concentration gradient. This influx causes cellular edema and potentially ruptures the plasma membrane.

B. Isotonic; no change to the cells: An isotonic state occurs when the solute concentration in the plasma matches that of the intracellular fluid. Pure water lacks the electrolytes necessary to maintain this equilibrium. Therefore, cellular volume would not remain stable following the rapid intake of large volumes.

C. Hypotonic; crenation: While the plasma becomes hypotonic, crenation is the result of water leaving the cell, not entering it. Crenation occurs only in hypertonic environments where the exterior solute concentration is higher than the interior. Hypotonicity always leads to expansion rather than shrinkage.

D. Hypertonic; swelling or lysis: A hypertonic plasma would possess a higher osmolarity than the cytoplasm, which would pull water out of the cell. This choice incorrectly pairs a hypertonic state with cellular swelling. Swelling is strictly a consequence of a lower external osmotic pressure.

E. Hypertonic; crenation: Ingesting plain water decreases plasma osmolarity, making it hypotonic, not hypertonic. Hypertonicity typically follows dehydration or excessive salt intake. While crenation is the correct cellular response to hypertonicity, the initial premise of the plasma state is incorrect.