Biology 201 Dr. Edwin DeMont St. Francis Xavier University Body Fluid Regulation

St. Francis Xavier University Osmoregulation Excretion of is usually associated with the regulation of water and solute (ionic) balance through a physiological process called osmoregulation. Osmosis is associated with the movement of water down its concentration gradients.

St. Francis Xavier University Osmosis Demonstration

St. Francis Xavier University Aquatic animals Osmoregulation is an important concern for aquatic animals – which are surrounded by water. Large differences in the process for marine or fresh water animals.

St. Francis Xavier University Osmosis : Marine Animals WW FF Water tends to move out of FishSugar = ions

St. Francis Xavier University Osmoregulators Salt water fish Water tends to move out of Fish and Ammonia

St. Francis Xavier University Osmosis : Fresh water Fish FF WW Water tends to move into Fish Sugar = ions

St. Francis Xavier University Osmoregulators Fresh water fish Water tends to move into Fish and Ammonia

St. Francis Xavier University Invertebrate Excretory Systems Fresh water flatworm: - Nitrogenous wastes diffuse across body surface - Flame cells eliminate excess water Water tends to move into animal. Demonstration

St. Francis Xavier University Excretion Excretion is the elimination of metabolic waste products such as carbon dioxide, water, nitrogen and ions. Protein metabolism produces various nitrogenous wastes.

St. Francis Xavier University Nitrogen Metabolism Amino acid metabolism yields ammonia (NH 3 ) 1.Ammonia or ammonium ions must be highly diluted and rapidly excreted; 2.or be converted to less toxic forms: urea or uric acid. Interferes with Na + /K + ATPase transporters of cell membranes by substituting for K + Ammonium ion can be toxic Ammonia alters acid-base balance as it binds to protons and becomes ammonium ion (NH 4 + )

St. Francis Xavier University Ammonia Most aquatic animals – including most bony fishes and most invertebrates rely on ammonia excretion, usually via gills. Most terrestrial animals do not have this option so convert ammonia to urea or uric acid (usually in the liver) and transport to the excretory organs. This works because: 1. Water outside the animal is plentiful to dilute ammonia 2. Molecule is small and uncharged so readily penetrates most membranes.

St. Francis Xavier University Urea Urea is the primary nitrogenous waste of most adult amphibians and mammals. Urea is 10 – 100 times less toxic than ammonia and when it is removed takes two nitrogens per molecule. Urea is produced from two ammonium ions and a bicarbonate ion using ATP.

St. Francis Xavier University Uric Acid In other terrestrial animals – insects, birds and most reptiles uric acid is usually the primary nitrogenous waste. Production of uric acid is more metabolically expensive to produce than urea but is less toxic because it is highly insoluble, removes four nitrogens per molecule and is excreted in a semisolid form.

St. Francis Xavier University Invertebrate Excretory Systems

St. Francis Xavier University Invertebrate Excretory Systems Initiated by K + secretion into lumen Fluid more +ve so Cl - attracted KCl makes tubule fluid concentrated so water moves in via osmosis. Infusion of water generates a bulk flow down the tubule Metabolic wastes such as uric acid secreted and transported down system

St. Francis Xavier University Urinary System

St. Francis Xavier University Anatomy: Nephron

St. Francis Xavier University Vertebrate Excretory Systems Glomerulus – filtration apparatus Walls of capillaries contain small perforations that as as filters. Blood pressure forces fluid through the slits. The filtrate contains small molecules, ions and the primary nitrogenous wastes either uric acid or urea. Large proteins and blood cells do not get filtered.

St. Francis Xavier University Physiology: Countercurrent Osmosis Overview