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Mammalogy (Spring 2015 Althoff) • Urinary (Excretory) Systems Overview • Body Fluid Regulation LEC 10A Overview of Excretion External Environment gut lungs kidney Blood TISSUES CELLS skin liver Body Fluid Regulation • Keys here: ION & H20 concentrations • Key ions: Na+, Cl-, K+ and HCO3• Body fluids gain mineral ions from eating foods and drinking fluids • Excretion is the primary way the body loses ions • H20: in via eating foods that contain H20, and drinking H20…and via metabolism (e.g. cellular respiration produces H20 = metabolic water Differences in Osmolarity (i.e., solute concentration • If difference in concentration between two regions, H2O tends to move from regions of greater concentrations to regions of lower concentrations. • Thus H20 moves to regions of highest ION CONCENTRATIONS Fishes & Body Fluid Regulation FRESHWATER FISH DOES NOT DRINK salt actively taken up by gills passive gain of water across body surface and through gills large amounts of hypotonic urine contain little salts Fishes & Body Fluid Regulation MARINE FISH passive loss of water through gills salt actively excreted by gills DRINKS SEAWATER small amounts of isotonic urine Contains some salts Nitrogenous Waste Products • NITROGENOUS WASTES = breakdown of various molecules, including nucleic acids and amino acids • AMINO ACIDS NOT used for protein synthesis are broken down by the body to generate energy or converted to fats or carbs that can be stored… • …this requires amino groups (-NH2) be removed excreted as ammonia, urea, or uric acid Nitrogenous Wastes PROTEINS amino acids -NH2 ammonia Need water to excrete Need energy to produce urea uric acid Nitrogenous waste • Ammonia habitat water animals aquatic invertebrates. bony fishes amphibian larvae toxicity highest • Urea land adult amphibians mammals 2nd highest • Uric acid land insects birds reptiles lowest Maintenance System (1 of 3…digestive & respiratory other 2) • URINARY SYSTEM—kidneys, bladder, & tubes A) rids blood of metabolic wastes B) helps regulate fluid level & chemical content of blood • EXCRETION = rids body of metabolic wastes (remember cellular metabolism) and breakdown of substances that enter the body (non-digestive system). Major role in maintaining HOMESTASIS Metabolic wastes OUT FUNCTIONS of the Urinary System Regulate water content of blood Regulate ion concentrations: Na+, Ca+, K+, Cl- Regulate pH of blood Produce erythropoietin RBC production increases Eliminate cellular waste such as urea, drugs, etc. Organs of the URINARY System • Kidney (2) • Ureter (1 per kidney) • Urinary bladder • Urethra ORGANS • KIDNEYS – where urine is made • URETERS— muscular tubing carrying urine from kidney to bladder • BLADDER— muscular bag that stores urine until urination (holds ~600 ml) • URETHRA— carries urine out of body URETHRA –some important “minute” • Length: 20 cm long, 4 cm long • Passes through prostate gland in don’t have). (females --prostate gland contributes fluid to semen that serves as buffer by raising pH of semen to >6.5 to overcome 3.5-4.0 pH environment of vagina • If prostate gland enlarges, it reduces urethrea’s ability to maintain original diameter 600 ml capacity, …..internal sphincter “relaxed” at 250 ml INTERNAL SPHINCTER EXTERNAL SPHINCTER KIDNEY is “the” functional unit of the urinary system Kidney MACROanatomy • Blood supply • Cortex • Medulla • Renal Pelvis Kidney- NEPHRON • • • • Functional unit of the kidney 1,000,000 per kidney Actually produces urine Transerves the renal cortex and renal medulla • Very detailed structurally speaking Kidney • Nephron MICROanatomy Nephron Detail Afferent arteriole Efferent arteriole GLOMERULUS Glomerular capsule Proximal convoluted tubule (PCT) Loop of the Nephron Distal convoluted tubule (DCT) Collecting duct 4 5 3 2 1 8 3 6 7 GLOMERULAR FILTRATION SEM picture Of a glomerulus 1 NEPHRON CAPS 2 Site where, if high blood pressure or injury, RBC “escape” an end up in urine Proximal convoluted tubule (PCT) CROSS-SECTIONAL view Microvilli (many per cell) URINE FORMATION 3 GLOMERULAR FILTRATION 1 TUBULAR ABSORPTION TUBULAR 2 SECRETION 4 And….then there is urine Keep in mind nephron transverses Cortex AND medulla regions of the kidney Glomerular FILTRATION • Blood is “filtered” (but typically only things dissolved…not formed elements of blood) • Filtrate is one-way….balance of blood moves on through blood vessel • Blood in urine “happens” here….before it gets to the bladder…. BAD!!!! Tubular REABSORPTION • H20 taken out of urine (was part of blood that “filtered out” (60-70%) • NaCl (salts) taken out (think….osmosis process here) (60-70%) • Urine becomes more and more concentrated Tubular SECRETION • Drugs secreted from blood DCT (distal convulated tubule) • K+, H+, etc. Secreted from blood DCT (active transport!!!) • NaCl could be reabsorbed here ??? (if low in concentration) • H2O still being taken out of urine, becomes more and more concentrated 1 3 osmosis active transport 2 diffusion 4 Processes and materials “moved” Osmosis • H2O Active Transport • NaCl • Nutrients Diffusion • Urea • NaCl • • • • Drugs K+ H+ NH3 3 1 2 4 Changes in concentrations of H20, salts, etc. INSIDE & OUTSIDE the tubules as urine it flows from renal cortex to renal medulla and back up to renal cortex…. The KING of minimizing H20 loss from the process of urine formation! KANGAROO RATS (Dipodomys sp.) Controlling pH of the blood….. H+ CAPILLARY H++NH3 NH4 HCO3- KIDNEY TUBULE NH4 = ammonium Hormones & the Urinary System • RENIN – promotes retention of NaCl • ANH – (atrial natriuretic hormone) suppresses retention of NaCl • ADH – (antidiuretic hormone) increases H20 taken out of urine • DIRURETICS including alcohol, caffeine drinks: they inhibit ADH, thus not as much reabsorption of H20 • Aldosterone– secreted by kidneys promotes K+ secretion. SUMMARY: Urine Formation • • • • • • Glomerulus Proximal con. tubule Distal con. tubule Ureter Bladder Urethra H20 retention is… • Diuretics • Antidiuretics decreased increased Kidney Stones