Excretory: Disposal & Osmoregulation Excretion: Disposal of nitrogen-containing wastes Osmoregulation: Control of gain and loss of water and solutes Osmoregulation based largely on regulating solutes Water follows the movement of solutes by osmosis

Excretion: Aquatic Animals Animals must dispose of nitrogenous waste Metabolism produces nitrogenous wastes from breakdown of proteins and nucleic acids Most aquatic animals dispose of their nitrogenous wastes as ammonia Highly soluble in water Diffuses rapidly across cell membranes

Excretory: Saltwater Fish

Excretion: Land Animals Land animals convert ammonia to less toxic compounds Can be safely stored and transported in the body Released periodically by excretory system Requires energy for conversion Different adaptations and type of reproduction determine excretion as urea or uric acid

Excretory: Disposal & Osmoregulation Urea Excreted by mammals, most amphibians, sharks, and some bony fishes Can be stored in concentrated solution but requires water for disposal Uric acid Excreted by birds, reptiles, insects, some amphibians Excreted as solid paste for water conservation Uses more energy for excretion

Excretory

Excretory: Waste Protein and nucleic acid breakdown - nitrogen-containing wastes toxic by-products of Ammonia poisonous but soluble and easily disposed of Urea less toxic, easy to store and excrete Some land animals save water by excreting a virtually dry waste

Excretory: Waste in Urine Urea – from amino acid breakdown Uric Acid – from nucleic acid breakdown Creatinine – muscle metabolism waste product

Excretory System The excretory system expels wastes regulates water and salt balance Two human kidneys each contain ~ million nephrons Urine leaves kidneys via ureters Stored in urinary bladder

Excretory Systen

Each nephron: folded tubule and associated blood vessels 1 Proximal tubule Bowman’s capsule Glomerulus Arteriole from renal artery Capillaries Each nephron: folded tubule and associated blood vessels Arteriole from glomerulus 3 Distal tubule Branch of renal vein From another nephron Collecting duct 2 Loop of Henle with capillary network Nephrons extract filtrate from blood Refine filtrate into much smaller amount of urine D. DETAILED STRUCTURE OF A NEPHRON Figure 25.9D

LE 25-11 Proximal tubule Distal tubule Bowman’s capsule Nutrients H2O NaCI HCO3 – NaCI HCO3 – Blood Some drugs and poisons H+ K+ H+ Filtrate composition H2O Cortex NaCI Medulla Collecting duct HCO3 – H+ Loop of Henle Urea NaCI Glucose Amino acids Some drugs NaCI H2O Reabsorption Urea Secretion NaCI H2O Urine (to renal pelvis)

Excretory: Filtration Filtration (Bowman’s capsule) Blood pressure forces water and many solutes from blood (glomerulus) into nephron

Excretory: Reabsorption / Secretion Controlled secretion of H+ and reabsorption of bicarbonate ions help regulate blood pH Secretion also includes active transport of drugs and poisons Reabsorption of salts and urea allow osmotic reabsorption of water

Excretion: Reabsorption / Secretion PROXIMAL TUBULE – always reabsorb glucose and amino acid - sometimes water, sodium, potassium, calcium depending on need Secretion urea, creatinine, ions, drugs and toxins

Excretory: Reabsorbing Water LOOP OF HENLE - much water reabsorbed via active transport of salt salt concentration in kidney higher in medulla Longer loop – more water conservation (desert animals)

Excretory: Reabsorption/Secretion DISTAL TUBULE specialized “Urine fine tuning” Aldosterone hormone – increases amount of sodium reabsorbed into blood (water follows)

Excretory: Water Reabsorption in Collecting Duct Water reabsorbed ADH (antidiuretic hormone) – cause collecting walls to be permeable to water to be reabsorbed Caffeine interferes with ADH (dehydration)

Excretory: Regulates Blood Pressure Releases RENIN when blood pressure low - enzyme that causes production of chemical (angiotensin II) to constrict blood vessel - Angiotensin II increase aldosterone production

Excretory: Dialysis

Homeostasis: Liver It assists the kidneys by making urea from ammonia breaking down toxic chemicals

Liver Blood from intestines flows through the liver before distribution to the rest of the body Allows liver to adjust blood’s chemical content