PHGY 214 Lecture Notes - Lecture 3: Tight Junction, Facilitated Diffusion, Transcellular Transport
12 May 2016
School
Department
Course
Professor
Document Summary
The filtered fluid contains nutrients, electrolytes, and other substances that the body cannot lose. The filtered materials return to the blood by tubular reabsorption. Reabsorption is a two-step process: active or passive transport from the tubule fluid into the renal interstitium, active or passive transport from interstitium into the bloodstream. Tubule is permeable to water and 67% of water and na is absorbed there and the remaining waste products in the tubule become highly concentrated: compare transcellular/ paracellular absorption of a solute. Transcellular transport is across the epithelium layer and through the cell. To be reabsorbed, a substance must transverse five distinct barriers. Paracellular transport is movement across an epithelial cell layer through tight junctions. * 95% go through transcellular transport: compare active and passive transport of a solute. Passive transport involves diffusion from a high to low concentration. There is no expenditure of energy; however, it may involve mediated transport through facilitated diffusion.
