Question

1. What role did the gastrointestinal system play in altering the osmolarity of the plasma for the varying beverage tonicities (hypotonic, hypertonic, and isotonic)? Compare and contrast the differences in gastric fluid osmolarity, plasma osmolarity, and plasma volume between the subjects ingesting a hypotonic, hypertonic, and isotonic beverage. Recall that the body maintains plasma osmolarity between 280mOsm and 300mOsm.

Answer 1

Hypotonic is the solution in which the concentration of the solute in less than the concentration of solvent.

Isotonic solution is the solution in which the concentration of the solute and the solvent is comparable.

Hypertonic is the solution in which the concentration of solute is higher than the concentration of the solvent.

The gastrointestinal system plays a very important role in maintaining the osmolarity of the plasma.As, the major absorption of substances takes place in the small intestine by passive diffusion.Small intestine of gastrointestinal system plays the major role.

When the plasma osmolarity is hypertonic, the cells in the release water to increase the water content in the hyper tonic solution.

When the plasma osmolarity is hypertonic, the small intestine increases the absorption of fluid to maintain the plasma osmolarity.

But the solution is isotonic, the the small intestine absorbs only the required amount of nutrients and fluid to balance the solute.

Plasma osmolarity means the concentration of the solute and solvent in the blood plasma. Plasma osmolarity is used to measure the fluid balance of the body.

Where is the gastric fluid osmolarity is the concentration of of solute and solvent in the gastric fluids like hydrochloric acid, lipase, Pepsin etc. The concentration of gastric fluid results in absorption or secretion of fluid from the stomach or other organs.

When we drink or eat a hypertonic beverage/substance, during their digestion the macromolecules are produced due to which the the solution becomes hyperosmotic as it moves in the instestine. To regulate the hyperosmolarity of the solution, the cells present in the lumen release fluid to maintain the osmolarity.

Once the nutrients are absorbed by the intestine the osmolarity of hyperosmotic solution starts Decreasing & the water can be reabsorbed.

The gastric fluids are acidic so that food can be digested properly by the enzymes which makes the food hyperosmotic. The plasma and cells in lumen releases water to maintain osmolarity.

In case of hypotonic, the fluid is absorbed in large quantities in the lumen & the plasma concentration will also decrease.