1. AP BIO/MEMIS The Excretory System

2. Why excretion & osmoregulation? Animal Cells can’t survive a net water gain/loss Need to get rid of nitrogenous waste (poison)

3. Intracellular Waste What waste products?  what do we digest our food into…  carbohydrates = CHO  CO 2 + H 2 O  lipids = CHO  CO 2 + H 2 O  proteins = CHON  CO 2 + H 2 O + N  nucleic acids = CHOPN  CO 2 + H 2 O + P + N | ||| H H N C–OH O R H –C–

4. Nitrogenous waste disposal Ammonia (NH 3 )  very toxic  carcinogenic  very soluble  easily crosses membranes  must dilute it & get rid of it… fast! How you get rid of nitrogenous wastes depends on  who you are (evolutionary relationship)  where you live (habitat) aquatic terrestrial terrestrial egg layer

5. Nitrogen waste  Aquatic organisms  can afford to lose water  Ammonia: most toxic  Terrestrial  need to conserve water  Urea: less toxic  Terrestrial egg layers  need to conserve water  need to protect embryo in egg  uric acid: least toxic

6. Osmoregulation Water balance freshwater hypotonic water flows into cells & salt loss saltwater hypertonic water loss from cells land dry environment need to conserve water may also need to conserve salt Why do all land animals have to conserve water?  always lose water (breathing & waste)  may lose life while searching for water hypertonic hypotonic

7. Freshwater animals Water removal & nitrogen waste disposal remove surplus water  use surplus water to dilute ammonia & excrete it  need to excrete a lot of water so dilute ammonia & excrete it as very dilute urine  also diffuse ammonia continuously through gills or through any moist membrane overcome loss of salts  reabsorb in kidneys or active transport across gills

8. Land animals Nitrogen waste disposal on land  need to conserve water  must process ammonia so less toxic  urea = larger molecule = less soluble = less toxic - 2NH 2 + CO 2 = urea - produced in liver  kidney  filter solutes out of blood  reabsorb H 2 O (+ any useful solutes)  excrete waste - urine = urea, salts, excess sugar & H 2 O - urine is very concentrated - concentrated NH 3 would be too toxic Urea costs energy to synthesize, but it’s worth it! mammals

9. Egg-laying land animals Nitrogen waste disposal in egg o no place to get rid of waste in egg o need even less soluble molecule - uric acid = BIGGER = less soluble = less toxic - birds, reptiles, insects

10. Various Excretory Mechanisms – for osmoregulation and removal of wastes Contractile Vacuoles paramecium & amoebas vacuole fills with water, merges with plasma membrane and releases water to environment

11. Flame Cells In Platyhelminthes, ie, planaria Spread out along branched tube system Body fluids filtered across flame cells Cilia move fluids through system Wastes excreted from tube system through pores

12. Flame Cells

13. Nephridia Occur in pairs in each section of annelids Consist of nephrostome (ciliated opening), collecting tubule and excretory pore Body fluids selectively filtered as they pass through tube, materials to be retained, secreted back to body fluids, concentrated wastes excreted through tube at far end

14. Nephridia

15. Malphigian Tubules Tubes attached to midsection of digestive tract Collect body fluids from hemolymph Fluids, containing both wastes and materials to be retained pass to midgut Pass to hindgut, materials to be retained pass back through walls of digestive tract, wastes excreted through anus

16. Malphigian

17. Vertebrate kidney Millions of individual filtering tubes called nephrons Produce urine that passes through ureter to bladder for temp storage, excreted through urethra

18. Transformation of Blood Filtrate to Urine 1. In the proximal tubule, secretion and reabsorption changes the volume and composition of the filtrate. The pH of body fluids is controlled, and bicarbonate is absorbed, as are NaCl and water. 2. In the descending loop of Henle, reabsorption of water continues. 3. In the ascending loop of Henle, the filtrate loses salt without giving up water and becomes more dilute.

19. Transformation of Blood Filtrate to Urine 4. In the distal tubule, K +, NaCl levels are regulated, as is filtrate pH. 5. The collecting duct carries the filtrate through the medulla to the renal pelvis, and the filtrate becomes more concentrated by the movement of salt.

20. Urea 2NH2 + CO2 = urea combined in liver Requires energy to produce Carried to kidneys by circulatory system N H H N H H C O

21. Mammalian System - filtration body fluids (blood) collected water & soluble material removed - reabsorption reabsorb needed substances back to blood - secretion pump out unwanted substances to urine - excretion remove excess substances & toxins from body

22. Nephron: Filtration Filtered out H2O glucose salts / ions urea Not filtered out cells proteins

23. Nephron: Re-absorption Proximal tubule reabsorbed NaCl active transport Na+ Cl- follows by diffusion H2O glucose HCO3-(bicarbonate - buffer for blood pH)

24. Nephron: Re-absorption Loop of Henle  descending limb many aquaporins in cell membranes  high permeability to H2O  low permeability to salt  reabsorbed H2O

25. Nephron: Re-absorption Loop of Henle - ascending limb  low permeability to H2O - Cl- pump - Na+ follows by diffusion  reabsorbed salts  maintains osmotic gradient

26. Nephron: Re-absorption Distal tubule  reabsorbed salts H2O HCO3- (bicarbonate)

27. Nephron: Reabsorption & Excretion Collecting duct  reabsorbed H2O excretion  urea passed through to bladder

28. Osmotic control in nephron How is all this re- absorption achieved?  tight osmotic control to reduce the energy cost of excretion  as much as possible, use diffusion instead of active transport

29. Summary  Not filtered out (remain in blood) cells ◆ proteins  Reabsorbed: active transport Na+ ◆ amino acids Cl- ◆ glucose  Reabsorbed: diffusion Na+ ◆ Cl-  Reabsorbed: osmosis H2O  Excreted urea ◆ H2O  any excess solutes

30. Maintaining Water Balance High Solutes In brain ADH

31. Maintaining Water Balance High blood osmolarity level -too many solutes in blood - dehydration, salty foods - release ADH (anti-diuretic hormone) from pituitary (in brain) - increases permeability of collecting duct & reabsorption of water in kidneys - increase water absorption back into blood - decrease urination - also stimulates thirst = drink more

32. Low solutes renin activates angiotensinogen angiotensin triggers aldosterone increases absorption of NaCl & H2O in kidney

33. Maintaining Water Balance Low blood osmolarity level or low blood pressure - JGA releases renin in kidney - renin converts angiotensinogen to angiotensin - angiotensin causes arterioles to constrict - increase blood pressure - angiotensin triggers release of aldosterone from adrenal gland - increases reabsorption of NaCl & H2O in kidneys - puts more water & salts back in blood