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The Excretory System
- The excretory system is responsible for the removal of nitrogenous wastes and for osmoregulation.
- The functional unit of the kidney is the nephron. Filtration takes place in the glomerulus where pressure drives water small molecules across the glomerular membrane
- Reabsorption of water and substances such as NaCl, amino acids and glucose takes place in in the proximal convoluted tubule. Other substances are secreted into the PCT.
- Aquaporins in the descending loop of Henle allow for water reabsorption in this segment of the tubule.
- The ascending loop of Henle is impermeable to water. The ascending loop of Henle maintains the concentration gradient from cortex to medulla by transporting NaCl into the interstitium.
- In the distal convoluted tubule both reabsorption and secretion take place.
- The collecting duct is permeable to water when acted upon by antidiuretic hormone (ADH). ADH stimulates the reabsorption of water by the kidney.
- Aldosterone is released in response to low blood pressure or blood volume and stimulates the reabsorption of Na+ by the distal convoluted tubule.
The Excretory System
Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.
- Intro
- Nitrogenous Wastes
- Osmoregulation
- Types of Excretory Systems
- The Human Excretory System
- Filtration, Reabsorption and Secretion
- The Nephron
- The Nephron, cont.
- Antidiuretic Hormone
- Aldosterone
- Example 1: Nephron of an Aquatic Mammal
- Example 2: Uric Acid & Saltwater Fish
- Example 3: Nephron
- Example 4: Gastrointestinal Infection

































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