1. 11.3 The kidney Objectives Define excretion.
Draw and label a diagram of the kidney.
Annotate a diagram of a glomerulus and associated nephron to show the function of each part.
Explain the process of ultrafiltration, including blood pressure, fenestrated blood capillaries and basement membrane.
Define osmoregulation.
Explain the reabsorption of glucose, water and salts in the proximal convoluted tubule, including the roles of microvilli, osmosis and active transport.

2. Objectives of Topic 11.3
Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water balance of the blood
Explain the differences in the concentration of proteins, glucose and urea between blood plasma, glomerular filtrate and urine.
Explain the presence of glucose in the urine of untreated diabetic patients.

3. Why do we need excretory system?
To remove toxic wastes.
Metabolism produces toxic by-products.
Nitrogenous wastes are toxic breakdown products of proteins and nucleic acids.
Animals dispose of nitrogenous wastes in different ways.
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
Student experience with osmoregulation not pertaining to their bodies may be quite limited. However, many students are familiar with the pasty white color of bird droppings. Consider beginning your discussion of nitrogenous wastes by asking your class to explain why bird droppings are white.
© 2012 Pearson Education, Inc. 3

4. TOXIC WASTES 1- Ammonia (NH3) is poisonous,
too toxic to be stored in the body,
soluble in water, and
easily disposed of by aquatic animals.
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
Student experience with osmoregulation not pertaining to their bodies may be quite limited. However, many students are familiar with the pasty white color of bird droppings. Consider beginning your discussion of nitrogenous wastes by asking your class to explain why bird droppings are white.
© 2012 Pearson Education, Inc. 4

5. TOXIC WASTES
2- Urea is
produced in the vertebrate liver by combining ammonia and carbon dioxide,
less toxic,
easier to store, and
highly soluble in 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
Student experience with osmoregulation not pertaining to their bodies may be quite limited. However, many students are familiar with the pasty white color of bird droppings. Consider beginning your discussion of nitrogenous wastes by asking your class to explain why bird droppings are white.
© 2012 Pearson Education, Inc. 5

6. TOXIC WASTES 3. Uric acid is
excreted by some land animals (insects, land snails, and many reptiles),
relatively nontoxic,
largely insoluble in water,
excreted as a semisolid paste, conserving water, but
more energy expensive to produce.
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
Student experience with osmoregulation not pertaining to their bodies may be quite limited. However, many students are familiar with the pasty white color of bird droppings. Consider beginning your discussion of nitrogenous wastes by asking your class to explain why bird droppings are white.
© 2012 Pearson Education, Inc. 6

7. 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 7

8. The urinary system
forms and excretes urine and
regulates water and solutes in body fluids.
In humans, the kidneys are the main processing centers of the urinary system.
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  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 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. 8

9. 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 9

10. 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 10

11. 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 11

12. 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 12

13. Nephrons Urine is are the functional units of the kidneys,
extract a fluid filtrate from the blood, and
refine the filtrate to produce urine.
Urine is
drained from the kidneys by ureters,
stored in the urinary bladder, and
expelled through the urethra.
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 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. 13

14. 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 14

15. Filtration Reabsorption
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 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. 15

16. 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 16

17. 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 17

18. Reabsorption Secretion Excretion Nephron tubule Urine To renal vein
Figure 25.7_2
Reabsorption
Secretion
Excretion
Nephron tubule
Urine
To renal vein
Figure 25.7_2 Major processes of the urinary system (part 2)
Capillary 18

19. 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 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. 19

20. 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 20

21. 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. 21

22. High NaCl concentration in the medulla promotes reabsorption of water.
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: Collecting Duct
Animation: Effect of ADH
Animation: Loop of Henle and Distal Tubule
© 2012 Pearson Education, Inc. 22

23. 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) 23

24. 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 24

25.   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) 25

26. 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. 26

27. CONNECTION: Kidney dialysis can be lifesaving
Kidney failure can result from
hypertension,
diabetes, and
prolonged use of common drugs, including alcohol.
A dialysis machine
removes wastes from the blood and
maintains its solute concentration.
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. The loss of one kidney in a human typically results in enlargement of the remaining kidney, a process known as compensatory hypertrophy. As your time permits, this can provide material for a class discussion or for a special-topic assignment for students with a particular interest.
2. The unfortunate shortage of kidneys and other organs available for transplant is a major health issue. Consider discussing this problem with your class. Many state and federal organ donation organizations can by located by a quick Internet search. The National Kidney Foundation site includes information on kidney donation.
© 2012 Pearson Education, Inc. 27

28. Line from artery to apparatus
Figure 25.9
Line from artery to apparatus
Pump
Tubing made of a selectively permeable membrane
Dialyzing solution
Line from apparatus to vein
Figure 25.9 Kidney dialysis
Fresh dialyzing solution
Used dialyzing solution (with urea and excess ions) 28

29. Line from artery to apparatus
Figure 25.9_1
Line from artery to apparatus
Pump
Tubing made of a selectively permeable membrane
Dialyzing solution
Line from apparatus to vein
Figure 25.9_1 Kidney dialysis (part 1)
Fresh dialyzing solution
Used dialyzing solution (with urea and excess ions) 29

30. Figure 25.9_2
Figure 25.9_2 Kidney dialysis (part 2) 30