Excretion AP Biology Unit 6

Osmolarity Osmolarity = total solute concentration of a solution Which way will the water move? Slide 2 of 26

Question… What would happen if your body did not maintain proper osmolarity? You would either have an excess of water (bloated) or too little water (dehydrated) Cells wouldn’t have the correct balance of solutes and H2O  won’t function properly Slide 3 of 26

Osmoregulators versus Osmoconformers

Osmoconformers Animals whose internal osmolarity changes in relation to their external environment There are limits to this– too high or too low will cause death Marine invertebrates, sharks, rays Ex. Brine Shrimp (Artemia) Slide 4 of 26

Osmoregulators Animals who can maintain their internal osmolarity at a particular level regardless of the external environment Ex. Fish, humans, lots of other animals  Slide 5 of 26

Question… How does the environment one lives in affect how osmoregulation takes place? Depending on the environment one lives in, osmoregulation can be very different Slide 6 of 26

Saltwater Fish Challenge: Prevent too much water from leaving the body (to go into the outside environment) Higher osmolarity outside compared to inside of body Solution… Slide 7 of 26

Freshwater Fish Challenge: Prevent too much water from coming into the body from the outside Higher osmolarity inside body compared to outside Solution… Slide 8 of 26

What about land animals? face the risk of dehydration, lose water by evaporation and waste disposal, gain water by drinking and eating, and conserve water by reproductive adaptations, behavior adaptations, waterproof skin, and efficient kidneys. Student Misconceptions and Concerns The idea that a freshwater fish never drinks can be conceptually challenging, especially for students who have heard the old saying “drinks like a fish”! Consider introducing your discussion of osmoregulation with this remarkable and seemingly counterintuitive fact to generate interest. Teaching Tips Students may better understand the challenges of osmoregulation in freshwater fish if they are reminded of what occurs when humans soak their hands in water. Students will likely recall that this causes the skin on their hands to wrinkle, and some may have noticed that their skin wrinkles even faster in soapy water. Skin absorbs water by osmosis (just as a freshwater fish gains water). Oils on our skin reduce the influx of water. Soapy water, which washes away these oils, speeds up the process. The wrinkling occurs because the skin can expand only in certain areas, creating puckers. © 2012 Pearson Education, Inc. 11

What is Nitrogenous Waste? Metabolic waste produced by cells from the breakdown of Proteins and Nucleic Acids into NH2 groups This waste must be excreted Slide 10 of 26

Most aquatic animals, including most bony fishes Figure 25.5 Proteins Amino acids Nitrogenous bases Nucleic acids NH2 (amino groups) Most aquatic animals, including most bony fishes Mammals, most amphibians, sharks, some bony fishes Birds and many other reptiles, insects, land snails Figure 25.5 Nitrogen-containing metabolic waste products Uric acid Ammonia Urea 13

What are the three major kinds of nitrogenous wastes? Ammonia: Most toxic. Only produced by aquatic animals Urea: Formed by combining Ammonia with CO2; Not as toxic; Released with less water Uric Acid: Least soluble; Excreted with the least amount of water Slide 11 of 26

Excretion in Aquatic Animals For most aquatic animals, excreting ammonia is not an issue - why? Ammonia is highly soluble in H2O, diffuses away rapidly (won’t stay concentrated around them) Aquatic animals continuously lose ammonia from their bodies through diffusion across their gill membranes Slide 12 of 26

Question… Why don’t terrestrial animals and some aquatic animals just excrete dilute ammonia in liquid? Since ammonia is toxic even at fairly low levels, it would have to use a lot of water to dilute it Too much water loss = dehydration Slide 14 of 26

Why do some land animals excrete uric acid instead of urea? Helps conserve H2O because it isn’t very soluble in water  semi solid Ex. Birds, reptiles, insects, some amphibians Slide 16 of 26

Stages of Excretion Figure 25.7 Bowman’s capsule From renal artery Filtration Reabsorption Secretion Excretion Nephron tubule H2O, other small molecules Urine Interstitial fluid Capillary To renal vein Figure 25.7 Major processes of the urinary system 18

Excretory Process Filtration: Initial movement of fluid and solutes from the body Selective Reabsorption: Water and desirable solutes are reabsorbed into the body Secretion: Excess waste solute is added to the filtrate Excretion: Modified filtrate is expelled from the body Slide 17 of 26

Invertebrate: Flatworm Excretory System Protonephridia are tiny tubules that interstitial fluid moves through Filtrate is produced through the action of ciliated “flame bulb cells” Filtrate modified as it flows and exits through openings in the body wall Slide 21 of 26

Invertebrate: Earthworms Due to pressure from blood water and solutes are pushed from the blood into the metanephridia Reabsorption and Secretion takes place between metanephridium and capillaries Stored urine excreted through external openings Slide 23 of 26

Vertebrates: What are the major organs of the urinary system? Kidneys – produce urine Ureters – carries urine from the kidneys to bladder Bladder – stores urine Urethra – releases the urine

25.6 The urinary system plays several major roles in homeostasis Nephrons are the functional units of the kidneys, extract a fluid filtrate from the blood, and refine the filtrate to produce urine. Student Misconceptions and Concerns 1. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively returning to it what you wish to store. 2. Before addressing the human urinary system, challenge each student in your class to explain how a drink of water may end up as urine. Consider having students write out their answers on a 3 x 5 card in class. This quick survey will likely reveal misunderstandings that would otherwise be concealed by quiet students’ reluctance to speak up. Students might suggest that some sort of tube transports fluid from the digestive tract to the kidneys or urinary bladder. Such surveys provide a useful means of gauging the initial assumptions of your students as they approach a new subject. Teaching Tips 1. A moderately full human urinary bladder holds about 500 ml (or 1 pint) of fluid. The bladder’s maximum capacity may be up to double that volume, although if overdistended, it may burst! 2. Students must understand that blood consists of two main components, cells and plasma. If your course has not covered Chapter 23, consider assigning Module 23.12 to ensure that they have this important background knowledge. 3. During the production of urine, blood cells remain within blood vessels, and components of the plasma are filtered out and selectively reabsorbed. Students may appreciate your making this important distinction early on in the discussion of renal functions. © 2012 Pearson Education, Inc. 23

Nephron Blood Processing: Filtration: Will blood cells and proteins be filtered into the nephron? Blood Processing: Filtration: Arteries transport blood to the kidney (nephron) Urea, water, Glucose, and salts (minerals) are filtered out by diffusion/active transport No!! Way too Big!!!

Nephron Blood Processing: 2) Reabsorption: Substances still needed by the body are removed from the filtrate and reenter the blood via diffusion/active transport Ex: glucose, water, minerals (NOT urea)

Nephron Blood Processing: Secretion: Kidneys remove certain substances from the blood and add them to the filtrate. Ex: Salts, Water

Nephron Blood Processing: Excretion: Urine has been formed! Will be moved to the bladder to be excreted from the body

Animation: Nephron Introduction Student Misconceptions and Concerns 1. The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively returning to it what you wish to store. 2. Before addressing the human urinary system, challenge each student in your class to explain how a drink of water may end up as urine. Consider having students write out their answers on a 3 x 5 card in class. This quick survey will likely reveal misunderstandings that would otherwise be concealed by quiet students’ reluctance to speak up. Students might suggest that some sort of tube transports fluid from the digestive tract to the kidneys or urinary bladder. Such surveys provide a useful means of gauging the initial assumptions of your students as they approach a new subject. Teaching Tips 1. A moderately full human urinary bladder holds about 500 ml (or 1 pint) of fluid. The bladder’s maximum capacity may be up to double that volume, although if overdistended, it may burst! 2. Students must understand that blood consists of two main components, cells and plasma. If your course has not covered Chapter 23, consider assigning Module 23.12 to ensure that they have this important background knowledge. 3. During the production of urine, blood cells remain within blood vessels, and components of the plasma are filtered out and selectively reabsorbed. Students may appreciate your making this important distinction early on in the discussion of renal functions. Animation: Nephron Introduction Right click on animation / Click play © 2012 Pearson Education, Inc. 28

Figure 25.6 Anatomy of the human excretory system Renal cortex Aorta Renal medulla Inferior vena cava Renal artery (red) and vein (blue) Kidney Ureter Urinary bladder Renal pelvis Urethra The urinary system Ureter Bowman’s capsule 1 Proximal tubule Arteriole from renal artery Glomerulus Capillaries The kidney 3 Distal tubule Bowman’s capsule Arteriole from glomerulus Collecting duct Tubule Renal cortex Branch of renal vein From another nephron Branch of renal artery Figure 25.6 Anatomy of the human excretory system Branch of renal vein Collecting duct Renal medulla 2 Loop of Henle with capillary network To renal pelvis Detailed structure of a nephron Orientation of a nephron within the kidney 29

The urinary system Aorta Inferior vena cava Figure 25.6_1 Aorta Inferior vena cava Renal artery (red) and vein (blue) Kidney Ureter Figure 25.6_1 Anatomy of the human excretory system: the urinary system (part 1) Urinary bladder Urethra The urinary system 30

Renal cortex Renal medulla Renal pelvis Ureter The kidney Figure 25.6_2 Renal cortex Renal medulla Renal pelvis Ureter Figure 25.6_2 Anatomy of the human excretory system: the kidney (part 2) The kidney 31

Orientation of a nephron within the kidney Figure 25.6_3 Bowman’s capsule Tubule Renal cortex Branch of renal artery Branch of renal vein Collecting duct Renal medulla Figure 25.6_3 Anatomy of the human excretory system: nephron orientation (part 3) To renal pelvis Orientation of a nephron within the kidney 32

Arteriole from renal artery Glomerulus Capillaries Figure 25.6_4 Bowman’s capsule 1 Proximal tubule Arteriole from renal artery Glomerulus Capillaries 3 Distal tubule Collecting Duct Arteriole from glomerulus Branch of renal vein From another nephron Figure 25.6_4 Anatomy of the human excretory system: nephron structure (part 4) 2 Loop of Henle with capillary network Detailed structure of a nephron 33

25.7 Overview: The key processes of the urinary system are filtration, reabsorption, secretion, and excretion Filtration Blood pressure forces water and many small molecules through a capillary wall into the start of the kidney tubule. Reabsorption refines the filtrate, reclaims valuable solutes (such as glucose, salt, and amino acids) from the filtrate, and returns these to the blood. Student Misconceptions and Concerns The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively returning to it what you wish to store. Teaching Tips 1. Students must understand that blood consists of two main components, cells and plasma. If your course has not covered Chapter 23, consider assigning Module 23.12 to ensure that they have this important background knowledge. 2. During the production of urine, blood cells remain within blood vessels, and components of the plasma are filtered out and selectively reabsorbed. Students may appreciate your making this important distinction early on in the discussion of renal functions. 3. Some drugs are excreted in urine. This is the basis of drug testing using samples of a person’s urine. Making this simple connection can help generate interest and improve comprehension in your students. 4. Many students do not know about interstitial fluid or its functions. They may think that blood delivers nutrients directly to cells, perhaps through direct contact between capillaries and cells. Instead, interstitial fluids typically act as an intermediate and promote homeostasis in many ways. Interstitial fluid is discussed in detail in Module 23.7, which may not have been addressed previously in your class. © 2012 Pearson Education, Inc. 34

H2O, other small molecules Figure 25.7_1 Bowman’s capsule From renal artery Filtration Nephron tubule H2O, other small molecules Interstitial fluid Figure 25.7_1 Major processes of the urinary system (part 1) Capillary 35

Reabsorption Secretion Excretion Nephron tubule Urine To renal vein Figure 25.7_2 Reabsorption Secretion Excretion Nephron tubule Urine To renal vein Capillary Figure 25.7_2 Major processes of the urinary system (part 2) 36

25.7 Overview: The key processes of the urinary system are filtration, reabsorption, secretion, and excretion Substances in the blood are transported into the filtrate by the process of secretion. By excretion the final product, urine, is excreted via the ureters, urinary bladder, and urethra. Student Misconceptions and Concerns The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively returning to it what you wish to store. Teaching Tips 1. Students must understand that blood consists of two main components, cells and plasma. If your course has not covered Chapter 23, consider assigning Module 23.12 to ensure that they have this important background knowledge. 2. During the production of urine, blood cells remain within blood vessels, and components of the plasma are filtered out and selectively reabsorbed. Students may appreciate your making this important distinction early on in the discussion of renal functions. 3. Some drugs are excreted in urine. This is the basis of drug testing using samples of a person’s urine. Making this simple connection can help generate interest and improve comprehension in your students. 4. Many students do not know about interstitial fluid or its functions. They may think that blood delivers nutrients directly to cells, perhaps through direct contact between capillaries and cells. Instead, interstitial fluids typically act as an intermediate and promote homeostasis in many ways. Interstitial fluid is discussed in detail in Module 23.7, which may not have been addressed previously in your class. © 2012 Pearson Education, Inc. 37

Figure 25.7 Major processes of the urinary system Bowman’s capsule From renal artery Filtration Reabsorption Secretion Excretion Nephron tubule H2O, other small molecules Urine Interstitial fluid Capillary To renal vein Figure 25.7 Major processes of the urinary system 38

Reabsorption in the proximal and distal tubules removes 25.8 Blood filtrate is refined to urine through reabsorption and secretion Reabsorption in the proximal and distal tubules removes nutrients, salt, and water. pH is regulated by reabsorption of HCO3– and secretion of H+. Student Misconceptions and Concerns The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively returning to it what you wish to store. Teaching Tips Many students do not know about interstitial fluid or its functions. They may think that blood delivers nutrients directly to cells, perhaps through direct contact between capillaries and cells. Instead, interstitial fluids typically act as an intermediate and promote homeostasis in many ways. Interstitial fluid is discussed in detail in Module 23.7, which may not have been addressed previously in your class. © 2012 Pearson Education, Inc. 39

High NaCl concentration in the medulla promotes reabsorption of water. 25.8 Blood filtrate is refined to urine through reabsorption and secretion High NaCl concentration in the medulla promotes reabsorption of water. Student Misconceptions and Concerns The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively returning to it what you wish to store. Teaching Tips Many students do not know about interstitial fluid or its functions. They may think that blood delivers nutrients directly to cells, perhaps through direct contact between capillaries and cells. Instead, interstitial fluids typically act as an intermediate and promote homeostasis in many ways. Interstitial fluid is discussed in detail in Module 23.7, which may not have been addressed previously in your class. © 2012 Pearson Education, Inc. 40

Animation: Bowman’s Capsule and Proximal Tubule Student Misconceptions and Concerns The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively returning to it what you wish to store. Teaching Tips Many students do not know about interstitial fluid or its functions. They may think that blood delivers nutrients directly to cells, perhaps through direct contact between capillaries and cells. Instead, interstitial fluids typically act as an intermediate and promote homeostasis in many ways. Interstitial fluid is discussed in detail in Module 23.7, which may not have been addressed previously in your class. Animation: Bowman’s Capsule and Proximal Tubule Right click on animation / Click play © 2012 Pearson Education, Inc. 41

Animation: Collecting Duct Student Misconceptions and Concerns The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively returning to it what you wish to store. Teaching Tips Many students do not know about interstitial fluid or its functions. They may think that blood delivers nutrients directly to cells, perhaps through direct contact between capillaries and cells. Instead, interstitial fluids typically act as an intermediate and promote homeostasis in many ways. Interstitial fluid is discussed in detail in Module 23.7, which may not have been addressed previously in your class. Animation: Collecting Duct Right click on animation / Click play © 2012 Pearson Education, Inc. 42

Animation: Effect of ADH Student Misconceptions and Concerns The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively returning to it what you wish to store. Teaching Tips Many students do not know about interstitial fluid or its functions. They may think that blood delivers nutrients directly to cells, perhaps through direct contact between capillaries and cells. Instead, interstitial fluids typically act as an intermediate and promote homeostasis in many ways. Interstitial fluid is discussed in detail in Module 23.7, which may not have been addressed previously in your class. Animation: Effect of ADH Right click on animation / Click play © 2012 Pearson Education, Inc. 43

Animation: Loop of Henle and Distal Tubule Student Misconceptions and Concerns The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively returning to it what you wish to store. Teaching Tips Many students do not know about interstitial fluid or its functions. They may think that blood delivers nutrients directly to cells, perhaps through direct contact between capillaries and cells. Instead, interstitial fluids typically act as an intermediate and promote homeostasis in many ways. Interstitial fluid is discussed in detail in Module 23.7, which may not have been addressed previously in your class. Animation: Loop of Henle and Distal Tubule Right click on animation / Click play © 2012 Pearson Education, Inc. 44

Urine (to renal pelvis) Figure 25.8 Bowman’s capsule Proximal tubule Distal tubule Nutrients H2O 1 H2O NaCl HCO3 NaCl HCO3 Blood Some drugs and poisons H K H 3 Collecting duct Cortex Filtrate composition Medulla H2O Salts (NaCl and others) HCO3 H Urea Glucose Amino acids Some drugs Interstitial fluid Loop of Henle 2 NaCl NaCl H2O Urea Figure 25.8 Reabsorption and secretion in a nephron NaCl H2O Reabsorption Secretion Filtrate movement Urine (to renal pelvis) 45

Bowman’s capsule Proximal tubule Nutrients H2O HCO3 NaCl Blood Figure 25.8_1 Bowman’s capsule Proximal tubule Nutrients H2O NaCl HCO3 Blood Some drugs and poisons H Cortex Filtrate composition Medulla H2O Salts (NaCl and others) HCO3 H Urea Glucose Amino acids Some drugs Figure 25.8_1 Reabsorption and secretion in a nephron (part 1) Reabsorption Secretion Filtrate movement 46

  Proximal tubule Distal tubule Nutrients H2O H2O NaCl HCO3 NaCl Figure 25.8_2 Proximal tubule Distal tubule Nutrients H2O 1 H2O NaCl HCO3 NaCl HCO3 Some drugs and poisons H K  H  3 Collecting duct Cortex Medulla Interstitial fluid Loop of Henle 2 NaCl NaCl H2O Figure 25.8_2 Reabsorption and secretion in a nephron (part 2) Reabsorption Urea NaCl Secretion H2O Filtrate movement Urine (to renal pelvis) 47

25.9 Hormones regulate the urinary system Antidiuretic hormone (ADH) regulates the amount of water excreted by the kidneys by signaling nephrons to reabsorb water from the filtrate, returning it to the blood, and decreasing the amount of water excreted. Diuretics inhibit the release of ADH and include alcohol and caffeine. Student Misconceptions and Concerns The kidney’s role in filtration and selective reabsorption may initially be confusing to many students. The process is a bit like cleaning up a closet by removing all the contents and then selectively returning to it what you wish to store. Teaching Tips Students may be particularly interested in the diuretic effects of alcohol and caffeine. The text notes that the diuretic effects of alcohol may contribute to some of the symptoms of a hangover. However, the concentration of alcohol and caffeine are important factors. Higher urine output resulting from the high consumption of low-alcohol (1–5%) beer may largely be the consequence of increased water consumption. Drinks with higher alcohol levels, such as shots of hard liquor (gin, vodka, whiskey) or higher caffeine levels (espresso) and low fluid volume would be expected to better reveal the diuretic effects. © 2012 Pearson Education, Inc. 48