Excretory System Tony Serino, Ph.D. BIO 201 Misericordia Univ.

Excretory System Remove wastes from internal environment Wastes: water, heat, salts, urea, etc. Excretory organs include: Lungs, Skin, Liver, GI tract, and Kidneys Urinary system account for bulk of excretion

Water Balance Adapted to Specific Habitats Humans die with as little as 12% water loss

Conformer vs. Regulators Osmoconformers –are isoosmotic with their environment; therefore there is no tendency for the animal to gain or lose water. All osmoconformers are marine and live in water that has a stable composition. Most marine invertebrates are osmoconformers. Note: while these organism are isoosmotic to their environment, their ionic composition may differ considerably from the surrounding environment. Osmoregulators –maintain their internal osmotic environment independent of the external environment; such as freshwater and terrestrial habitats

Osmoregulators in Fresh and Salt Water Marine species live in strongly dehydrating environment. Freshwater species live in a hydrating environment and may lose large amounts of salts Survive by drinking large amounts of sea water and excreting large amounts of salt. Drink almost no water and excrete large amounts of dilute urine, and replace salt in their food and uptake through their gills

Nitrogen Waste Forms Ammonia is a breakdown product from protein and NA catabolism, highly toxic (NH 4 +) interferes with mitochondria function Ammonia must be diluted with large quantities of water for safe levels – accomplished by mainly aquatic species which can allow ammonia to diffuse directly to ext. environ. (highly energy efficient) Urea –less toxic, can be stored and excreted with minimal water loss; but takes energy to produce Uric Acid –is relatively non-toxic, fairly insoluable, secreted as dry paste with little water loss, but most costly to make

Protonephridia Network of blind ended tubule connected to an external opening and ending in a flame bulb Flame bulb: cap cell with cilia and tubule cell. Form a filtration membrane where the cells meet. The cilia hang inside lumen of tubule forcing fluid down tubule and drawing water through filter Found mostly in flatworms Function mostly in water balance; wastes can diffuse directly from cells to exterior because of limited thickness of organism

Metanephridia Found in many annelids Each segment of worm has a pair of metanephridia with its funnel-like end (nephrostome) projecting into the anterior segment The nephrostome is ciliated, these draw fluid into the tubules The tubules have a capillary bed and adjustments are made to the concentrations of the fluid.

Malpighian Tubules Found mostly in insects and other terrestrial arthropods A series of blind ended tubes arising from the midgut Tube epithelium secrete wastes and salts into tube from hemolymph Hindgut performs reabsorption N waste is passed as nearly pure uric acid crystals

Mammalian Urinary System

Urine Formation a.Pressure Filtration b.Reabsorption c.Secretion d.Reabsorption of water d