Waste Removal & the Human Urinary System Sections 3.7 – 3.8 Bio 391 http://www.youtube.com/watch?v=glu0dzK4dbU

Waste Removal Organisms in water … Some removal mechanisms Removing wastes is essential to homeostasis. Organisms in water … Don’t worry about drying out Must worry about excreting excess water Ex: Paramecium’s contractile vacuole Some removal mechanisms Simple Organisms Excretes all wastes through external surface Hydra, sponges More complex organisms (ie. Fish) CO2 – removed through gills Salt is removed through gills in salt water fish

Metabolic Nitrogenous Wastes Created from the digestion of proteins Amino acids Amino groups  ammonia Ammonia is very TOXIC to cells Methods of Removal: Immediate, direct ammonia release More simple aquatic organisms water “flushes” it out Convert ammonia to urea Less toxic, can be stored for a while Allows for conservation of water Humans, mammals, some fish, amphibians Convert to uric Acid Released as crystal form, “pastey” Conserves even more water Birds & desert reptiles

Ammonia >>> urea >>> uric acid Metabolic N-Wastes Ammonia >>> urea >>> uric acid Most toxic Least toxic Requires most water Requires least water Evolution of different methods… Related to water availability and whether or not ammonia can be diluted Further adaptations aid in conserving water

Lungs Skin Human Urinary System Kidneys Nephrons Excretory tubules in humans Processes blood, filtering out N-wastes Regulates water balance – adjusts salt concentration in blood Lungs Skin

Nitrogenous Waste Digestion: Protein to amino groups Amino acids turned into ammonia and converted to urea in the liver Urea enters circulation (blood) Urea is concentrated by the kidneys Removed as urine Unused, unwanted chemicals will eventually get into our blood stream. They are often diluted in our body fluids (plasma). We want the chemicals to leave the body, but we want to keep our water (and some of the nutrients/chemicals) 7

Nephron = “functional unit” The Urinary System 2 Kidneys 2 ureters 1 bladder 1 urethra Nephron = “functional unit” A “division” of the excretory system. All vertebrates have paired kidneys. 8

Urinary System Blood into kidney via renal artery Blood filtered in nephron (waste=urine) Urine leaves kidney via ureter Urine stored in urinary bladder Drains out urethra

Components of The Nephron Glomerulus: mechanically filters blood Bowman's Capsule: mechanically filters blood Proximal Convoluted Tubule: Reabsorbs 75% of the water, salts, glucose, and amino acids Loop of Henle: Countercurrent exchange, which maintains the concentration gradient NaCl moves by active transport and diffusion Distal Convoluted Tubule: Tubular secretion of H+ ions, potassium, and certain drugs. Collecting Duct: Collects all wastes

Functions of the Nephron FILTRATION: in the glomerulus and Bowman’s capsule. Driven by blood pressure REABSORPTION: begins in proximal tubule Salts, amino acids, sugars, vitamins Water follows Active Transport & Osmosis Tubular SECRETION into the distal tubule K+, H+, drugs, NH3 Products are removed via excretion http://www.youtube.com/watch?v=glu0dzK4dbU http://www.youtube.com/watch?NR=1&v=aQZaNXNroVY&feature=fvwp http://www.youtube.com/watch?v=3THZeaMfuSw&NR=1&feature=endscreen

Homeostasis by the Kidney Maintain volume of extracellular fluid Maintain ionic balance in extracellular fluid Maintain pH and osmotic concentration of the extracellular fluid. Excrete toxic metabolic by-products such as urea, ammonia, and uric acid.

CONTROL OF THE KIDNEY Blood pressure is low due to dehydration ADH: Antidiuretic Hormone: “Against peeing” Blood pressure is low due to dehydration Sensed by hypothalamus in brain stimulates pituitary gland to release ADH (travels to kidney) Water is reabsorbed into blood from distal tubule Blood pressure increases  water in blood =  blood volume =  pressure = ADH presence is reduced

CONTROL OF THE KIDNEY Aldosterone (adrenal hormone) Controls excretion of Na+ and K+ High [K+] in blood aldosterone released by adrenal gland Causes more secretion of K+ into nephron, lowering blood K+ and therefore aldosterone Negative Feedback Regulation – substances inhibit their own formation

Production to Urine