Chapter 38: Excretory System

Functions of the Excretory System a. Collect water and filter body fluids b. Remove and concentrate waste products from body fluids and return other substances to body fluids as necessary for homeostasis homeostasis c. Eliminate excretory products from the body - Include the kidneys (removes the most metabolic waste via urine),liver, lungs, and skin *** Responsible for regulating water balance in various body fluids - Osmoregulation is the active regulation of the osmotic pressure of an organism's fluids to maintain the homeostasis of the organism's water content; that is it keeps the organism's fluids from becoming too dilute or too concentrated (balance b/w sodium & water)osmotic pressureorganism homeostasiswater

ANIMAL EXCRETORY STRUCTURES PROTOZOA: CELL MEMBRANE (DIFFUSION) CONTRACTILE VACUOLE (EXCESS WATER) FLATWORM(PLANARIA): FLAME CELLS EARTHWORM: NEPHRIDIA, SKIN GRASSHOPPER: MALPHIGIAN TUBULES, TRACHEAE CRAYFISH: KIDNEYS, GILLS HUMAN: LUNGS, SKIN, LIVER, KIDNEYS SNAKE: KIDNEYS

ANIMAL EXCRETORY STRUCTURES

Made-up of the kidneys, ureters, bladder, and urethra. Nephron, an evolutionary modification of the nephridium  the kidney's functional unit Waste is filtered from the blood and collected as urine in each kidney Urine leaves the kidneys by ureters, and collects in the bladder  can distend to store urine that eventually leaves through the urethrauretersbladderurethra

Renal artery  brings blood into kidneys Renal vein  takes blood back to heart

Nephron- Urine Production Urine Production 1. Filtration in the glomerulus and nephron capsule 2. Reabsorption in the proximal tubule 3. Tubular secretion in the Loop of Henle Components of The Nephron a. Glomerulus: mechanically filters blood b. Bowman's Capsule: mechanically filters blood c. Proximal Convoluted Tubule: reabsorbs 75% of the water, salts, glucose, and amino acids d. Loop of Henle: countercurrent exchange, which maintains the concentration gradient e. Distal Convoluted Tubule: tubular secretion of H ions, potassium, and certain drugs

Kidney Nephron Cortex Medulla Renal artery Renal vein Ureter To the bladder Bowman’s capsule Glomerulus Capillaries Collecting duct To the ureter Loop of Henle Artery Vein Structure of the Kidneys Section 38-3

Filtration Most filtration occurs in the glomerulus. Blood pressure forces water, salt, glucose, amino acids, and urea into Bowman’s capsule. Proteins and blood cells are too large to cross the membrane; they remain in the blood. The fluid that enters the renal tubules is called the filtrate. Reabsorption As the filtrate flows through the renal tubule, most of the water and nutrients are reabsorbed into the blood. The concentrated fluid that remains is called urine. The Nephron Section 38-3

KANGAROO RAT – LIVE IN HYPERTONIC ENVIRONMENT ADAPTATIONS VERY EFFICIENT KIDNEYS, WHICH ALLOW IT TO LIVE WITHOUT DRINKING! HAVE A LONGER LOOP OF HENLE IN THEIR NEPHRONS, CAUSING THEM TO PRODUCE URINE THAT IS 5 TIMES MORE CONCENTRATED THAN HUMANS DON’T SWEAT, AND LOSE WATER ONLY THROUGH EVAPORATION DURING GAS EXCHANGE RETAIN 90% OF THEIR WATER, AND 10% COMES FROM THEIR DIET