Tubular reabsorption returns useful water and solutes from the filtrate to the blood. Because the nephrons filter as much as 180 liters of fluid per day, recovering most of that fluid is essential for maintaining blood volume and a stable internal environment.
Reabsorption occurs in the proximal convoluted tubule (PCT), loop of Henle, distal convoluted tubule (DCT), and collecting ducts. Each region has different membrane properties and transport proteins, so each handles particular substances in distinct ways.
All flashcards
What is tubular reabsorption?
Movement of water or solutes from tubular fluid toward the blood, usually through the interstitial fluid.
What is tubular secretion?
Movement of substances from the blood or surrounding tissue into tubular fluid.
What is symport?
Movement of two or more substances in the same direction across a membrane.
What is secondary active transport?
Transport in which an ion gradient provides energy to move another substance against its gradient.
How does facilitated diffusion differ from simple diffusion?
Both move substances down a concentration gradient without directly using ATP, but facilitated diffusion requires a specific channel or carrier.
Quiz questions
What happens in the thick ascending limb of the loop of Henle?Answer: It reabsorbs Na⁺, K⁺, and Cl⁻ while remaining effectively impermeable to water.
What can happen when filtered glucose exceeds the PCT transport maximum?Answer: Some glucose remains in tubular fluid and may appear in urine.
How does ADH increase water recovery in collecting ducts?Answer: It promotes insertion of aquaporins into the apical membrane of principal cells.
What is a principal effect of aldosterone in collecting-duct principal cells?Answer: It increases sodium recovery and can increase potassium secretion.
How do the vasa recta help preserve the medullary osmotic gradient?Answer: Their slow exchange returns reabsorbed water while limiting solute washout from the medulla.
Based on Anatomy and Physiology 2e by J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.