Waste Removal & the Human Urinary System Sections 3.7 – 3.8 Bio 391

Learning Goals The types of nitrogenous wastes –(ammonia, urea, uric acid) Urea is the breakdown product of protein Structure of kidney: nephrons, Bowman’s capsule, glomerulus, tubules Organs of excretory system: kidneys, adrenal glands, ureters, bladder, urethra

Waste Removal Removing wastes is essential to homeostasis. Organisms in water … –Don’t worry about drying out –Concern – excreting excess water Ex: Paramecium’s contractile vacuole Some removal mechanisms –Simple Organisms All wastes Hydra, sponges –Fish CO 2 salt

Metabolic N-Wastes From the digestion of what macromolecules? Amino groups  ammonia –very TOXIC to cells Methods of Removal: –Aquatic organisms – immediate, direct ammonia release –Convert to urea Less toxic, can be stored for a while Conserves water over ammonia –Uric Acid Birds & reptiles Crystal form, “pastey” Conserves even more water

Metabolic N-Wastes Most toxic >>>>>>>>>>>>> least toxic Most water >>>>>>>>>>>> least water –Ammonia >>> urea >>> uric acid Evolution of different methods… –Related to water availability Conserve water Is water available to dilute it if immediately released?

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

The Excretory System Regulates chemical composition of body fluids Removes metabolic wastes Retains the proper amounts of water, salts, and nutrients. Includes the kidneys, liver, lungs, and skin.

Nitrogen 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

The Urinary System 2 Kidneys 2 ureters 1 bladder 1 urethra Nephron = “functional unit”

Urinary System Blood to filter  renal artery into kidney Blood filtered – waste=urine Urine leaves through ureter urinary bladder (stored) Drains out urethra

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.

Function of the Nephron FILTRATION: in the glomerulus and nephron 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, NH 3 –Selectively secretes for excretion

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.

CONTROL OF THE KIDNEY ADH: Antidiuretic Hormone: – “Against peeing” Blood pressure is low from water loss –Sensed by hypothalamus –stimulates pituitary gland to release ADH to  Water is reabsorbed into blood from distal tubule –Blood pressure increases  water in blood =  blood volume =  pressure

Control of Kidneys Aldosterone –Controls excretion of Na+ and K+ –High [K+]  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