1 An albatross can drink salt water – how can they do this without getting sick?!

2 If you eat a lot of salt, what happens to your urine? Thought Questions: If you do not drink enough water, what happens to your urine? If you drink excess water, what happens to your urine?

3 Lecture 12 Outline (Ch. 44) I.Homeostasis II.Water Balance III. Animal Excretory Systems IV.Human Urinary System I.Bladder II.Kidneys V.Water Control VI.Preparation for next lecture

4 Maintains homeostasis of body fluids via water balance aka ‘Excretory System’ Urinary System Osmolarity, (solute concentration of solution), determines movement of water across selectively permeable membranes Hypoosmotic: lower solute conc, higher water Hyperosmotic: higher solute conc, lower water

5 Excrete salt ions from gills Gain water, salt ions from food Osmotic water loss from gills, body surface Excrete salt ions & little water in scanty urine from kidneys Gain water, salt ions from seawater (a) Osmoregulation in a saltwater fish Uptake water, ions in food Uptake salt ions by gills Osmotic water gain from gills, body surface Excretion of large amounts of dilute urine (b) Osmoregulation in a freshwater fish Water Balance Osmoconformer: isoosmotic with surrounding Osmoregulator: control internal osmoslarity

6 Water gain (mL) Water loss (mL) Urine (0.45) Urine (1,500) Evaporation (1.46) Evaporation (900) Feces (0.09)Feces (100) Derived from metabolism (1.8) Derived from metabolism (250) Ingested in food (750) Ingested in food (0.2) Ingested in liquid (1,500) Water balance in a kangaroo rat (2 mL/day) Water balance in a human (2,500 mL/day) Water Balance

7 Flatworms use protonephridia Animal Excretory Systems Simplest system Wastes stored in excretory pore, drawn out by water environment Tubule Tubules of protonephridia Cilia Interstitial fluid flow Opening in body wall Nucleus of cap cell Flame bulb Tubule cell

8 Animal Excretory Systems Remaining waste excreted Capillary network Components of a metanephridium: External opening Coelom Collecting tubule Internal opening Bladder Worms use metanephridia Collect body waste

9 Most urinary waste nitrogenous – from digesting protein Vertebrate Urinary System Blood filtered by kidneys Fish excrete ammonia (toxic at high levels) Land vertebrates convert to urea – add to urine To reduce water-loss, desert animals (reptiles, snakes, birds) excrete uric acid (non-toxic, hydrophobic) Desert kangaroo rat – excretes very concentrated urine

10 urethra left renal artery left kidney left renal vein left ureter urinary bladder Human Urinary System 1) Kidneys Blood w wastes brought by renal artery to kidney Filtered blood carried away by renal vein 2) Ureters Transport urine away from kidney 3) Bladder Stores urine Max capacity ~ 1 L 4) Urethra Transport urine from bladder to outside body

11 Bladder Ureter Urogenital diaphragm Internal urethral sphincter (involuntary) External urethral sphincter (voluntary) Human Urinary System - Bladder Micturition (urination) Gotta pee? Stretch stimulates contractions Sphincters control release

12 Human Urinary System - Bladder Sensory Input (spinal cord) (-) Stretch (~200 ml) (-) Brain

13 Urinary Disasters Tycho Brahe: When you SHOULD go The infamous candiru: When NOT TO go

14 Human Urinary System - Kidneys Urine forms in the nephron, ~1 million/kidney Kidney Structure Renal cortex Renal medulla Renal artery Renal vein Ureter Renal pelvis nephron Renal cortex Renal medulla

15 Each nephron is a filter: Glomerulus- network of capillaries Bowman’s capsule- cup around glomerulus Loop of Henle- Tubule network for adjusting water, salt, and waste levels Collecting duct- carries fluid from nephron Human Urinary System - Kidneys Afferent arteriole from renal artery Glomerulus Bowman’s capsule Proximal tubule Peritubular capillaries Distal tubule Efferent arteriole from glomerulus Collecting duct Branch of renal vein Descending limb Ascending limb Loop of Henle

16 Human Urinary System - Kidneys Filtration Water, nutrients, and wastes - filtered from glomerulus into Bowman’s capsule

17 Human Urinary System - Kidneys Reabsorption In proximal tubule, most water along with bicarbonate, K+, and NaCl are reabsorbed into blood. Proximal tubule Distal tubule Filtrate CORTEX Loop of Henle OUTER MEDULLA INNER MEDULLA Key Active transport Passive transport Collecting duct Nutrients NaCl NH 3 HCO 3  H2OH2O KK HH NaCl H2OH2O HCO 3  KK HH H2OH2O NaCl H2OH2O Urea

18 Human Urinary System - Kidneys Proximal tubule Distal tubule Filtrate CORTEX Loop of Henle OUTER MEDULLA INNER MEDULLA Key Active transport Passive transport Collecting duct Nutrients NaCl NH 3 HCO 3  H2OH2O KK HH NaCl H2OH2O HCO 3  KK HH H2OH2O NaCl H2OH2O Urea Loop of Henle –increasing osmolarity cortex to medulla –active transport of Na + & Cl – at ascending loop

19 Human Urinary System - Kidneys Secretion In distal tubule, additional wastes (like H+ and K+) are actively secreted into the tubule from the blood Proximal tubule Distal tubule Filtrate CORTEX Loop of Henle OUTER MEDULLA INNER MEDULLA Key Active transport Passive transport Collecting duct Nutrients NaCl NH 3 HCO 3  H2OH2O KK HH NaCl H2OH2O HCO 3  KK HH H2OH2O NaCl H2OH2O Urea

20 Human Urinary System - Kidneys Concentration Proximal tubule Distal tubule Filtrate CORTEX Loop of Henle OUTER MEDULLA INNER MEDULLA Key Active transport Passive transport Collecting duct Nutrients NaCl NH 3 HCO 3  H2OH2O KK HH NaCl H2OH2O HCO 3  KK HH H2OH2O NaCl H2OH2O Urea At collecting duct, additional water (and NaCl) leaves; urine more concentrated than blood.

21 Human Urinary System - Kidneys Two-solute model: NaCl and Urea are moved into the kidney medulla The filtrate in the nephron passes into this area three times Osmolarity of interstitial fluid (mOsm/L) Key Active transport Passive transport INNER MEDULLA OUTER MEDULLA CORTEX H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O 1, NaCl H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O Urea 1, NaCl

Thirst Hypothalamus ADH Pituitary gland Osmoreceptors in hypothalamus trigger release of ADH. STIMULUS: Increase in blood osmolarity (for instance, after sweating profusely) Homeostasis: Blood osmolarity (300 mOsm/L) Drinking reduces blood osmolarity to set point. H 2 O reab- sorption helps prevent further osmolarity increase. Increased permeability Distal tubule Collecting duct 22 Body detects dehydration. Signal from hypothalamus to posterior pituitary. Posterior pituitary releases ADH into the bloodstream. ADH (antidiuretic hormone) allows more water reabsorbed into the blood. Concentrated urine produced Water Balance

23 Water Balance Urine: Waste and remaining water from nephron 95% water / 5% solutes (ions, urea) Alcohol interferes with ADH Production of dilute urine – Dehydration Headache Fatigue Nausea

Things To Do After Lecture 12… Reading and Preparation: 1.Re-read today’s lecture, highlight all vocabulary you do not understand, and look up terms. 2.Ch. 44 Self-Quiz: #1, 3, 4, 6(correct answers in back of book) 3.Read chapter 44, focus on material covered in lecture (terms, concepts, and figures!) 4.Skim next lecture. “HOMEWORK” (NOT COLLECTED – but things to think about for studying): 1.Compare and contrast the four different types of excretory systems. 2.Diagram the nephron, labeling regions and describing uptake/excretion at each region. 3.Explain the parts of the human urinary system. 4.Discuss the role of ADH – location of secretion and effect.