which causes the increased concentrations of Cl- and Na+ in the lumen of the small intestine. Elevated concentrations of these two ions results in the lumen of the small intestines becoming hyperosmotic compared to the cells lining the intestines. This in turn causes the diffusion of large amounts of water through osmosis into the lumen of the intestine from the cells and blood stream. The water passes out of the body as diarrhea, leaving the body dehydrated.

4). Cystic fibrosis is a genetic disease that results in thick mucus secretions that clog up air passages in the lungs. Faulty chloride ion channels keep Cl- and Na+ in the cells that line the airways increasing the intracellular ion concentrations. How does this cause the mucus in the airways to become thick?
Answer: This is a similar situation of that seen in cholera but in the opposite direction. Normally, chloride ions (Cl-) pass out of the cells lining the airways through chloride ion channels. Sodium ions (Na+) follow the Cl- out of the cells due to the electrochemical gradient created by the movement of Cl-. The movement of ions out of the cells makes the cells hypoosmotic compared to the lumen of the airways. Water passes out of the cells and blood stream through osmosis and into the airways, thinning the mucus that flushes out impurities. In cystic fibrosis, the chloride channel doesn't function properly so Cl- remains in the cells, likewise Na+ remains in the cells. The cells are hyperosmotic compared to the lumen of the airways so water remains in the cells and bloodstream. Without water passing into the airways, the mucus