PowerLecture: Chapter 12

1
PowerLectureChapter 12

• The Urinary System

2
Learning Objectives

• Explain how the chemical composition of
  extracellular fluid is maintained by mammals.
• Describe the components of the human urinary
  system.
• Understand the processes of urine formation and
  excretion.
• Explain the controls that maintain fluid balance
  and blood pressure.
• Explain why kidney disorders can be so damaging
  to human health.

3
Impacts/Issues

• Truth in a Test Tube

4
Truth in a Test Tube

• Urine can be used to determine much about the
  general health and habits of human beings.
• Changes to the composition
• of urine can indicate
• metabolic problems,
• infection, or even pregnancy.
• Urine can also show the
• presence of illegal
• performance enhancing
• drugs in athletes.

5
Truth in a Test Tube

• Urine is a useful indicator of health because
  each day the kidneys filter all of the blood in
  the body a total of 30 times, eliminating excess
  water and harmful solutes.

6
Useful References for Impacts/Issues

• The latest references for topics covered in this
  section can be found at the book companion
  website. Log in to the books e-resources page at
  www.thomsonedu.com to access InfoTrac articles.
• Science Daily Early Prostate Cancer Detected in
  Molecular-Based Urine Test
• InfoTrac NCAA Steps Up Steroid Tests
  Organization Is Making a Far-Reaching Effort to
  Ensure That College Athletes Stay Clean. Kansas
  City Star, June 22, 2006.

7
How Would You Vote?

• To conduct an instant in-class survey using a
  classroom response system, access JoinIn Clicker
  Content from the PowerLecture main menu.
• Do you think employers should be allowed to
  require a person to undergo urine testing before
  being hired?
• a. Yes, drug users are less safe and productive
  employees. Employers have a right to screen them
  out.
• b. No, unless the job involves public safety, it
  is a violation of an employee's privacy.

8
Useful References for How Would You Vote?

• The latest references for topics covered in this
  section can be found at the book companion
  website. Log in to the books e-resources page at
  www.thomsonedu.com to access InfoTrac articles.
• InfoTrac Reasons to Consider Drug Testing.
  Industrial Safety Hygiene News, April 2002.
• InfoTrac Urine Or You're Out Drug Testing Is
  Invasive, Insulting, and Generally Irrelevant to
  Job Performance. Reason, Nov. 2002.
• InfoTrac Street Smarts Just Say Yes. Inc., Nov.
  1, 2004.

9
Section 1

• The Challenge Shifts in Extracellular Fluid

10
Shifts in Extracellular Fluid

• Extracellular fluid (ECF) is comprised of tissue
  fluid, blood plasma, and other fluids such as
  lymph that occurs outside of cells intracellular
  fluid is the fluid inside cells.
• There is a constant exchange of gases and other
  materials between intracellular and extracellular
  fluid.
• The volume and composition of the ECF must remain
  stable for these exchanges to occur.
• The urinary system is responsible for maintaining
  relatively stable conditions in the ECF.

11
Shifts in Extracellular Fluid

• The body gains water from food and metabolic
  processes.
• Absorption of water from liquids and solid foods
  occurs in the gastrointestinal tract.
• Metabolism of nutrients yields water as a
  by-product.
• The body loses water in urine, sweat, feces, and
  by evaporation.
• Water leaves the body by
• excretion in urine, evaporation
• from the lungs and skin,
• sweating, and in feces.

12
Shifts in Extracellular Fluid

• The body exerts the most control over urinary
  excretion, the production of urine.
• The least amount of water is lost in feces.

13
Shifts in Extracellular Fluid

• Solutes enter extracellular fluid from food,
  metabolism, and other ways.
• Solutes enter the body when nutrients and mineral
  ions are absorbed from the GI tract.
• Living cells secrete substances into tissue fluid
  and blood.
• The respiratory system brings oxygen into the
• blood respiring cells add carbon dioxide.

14
Fig. 12.1, p. 213
food, water intake
oxygen intake
elimination of carbon dioxide
DIGESTIVESYSTEM
RESPIRATORYSYSTEM
nutrients, water, salts
oxygen
carbon dioxide
CARDIOVASCULAR SYSTEM
URINARYSYSTEM
water, solutes
elimination of food residues
rapid transport to and from all living cells
elimination of excess water, salts, wastes
15
Shifts in Extracellular Fluid

• Solutes leave the ECF by urinary excretion, in
  sweat, and during breathing.
• Respiratory exhalation rids the body of carbon
  dioxide all other major wastes of metabolism
  leave in urine.
• Uric acid is formed in reactions that degrade
  nucleic acids too much uric acid in the ECF
  crystallizes in joints, causing gout.
• Ammonia is formed when amino groups are removed
  from amino acids it is turned into urea in the
  liver and either reabsorbed or excreted.
• Other products of protein degradation are also
  excreted.

16
Shifts in Extracellular Fluid

• The kidneys filter a variety of substances from
  the blood, including nitrogen, sodium, potassium,
  and calcium.
• Sodium, potassium, and calcium are called
• electrolytes because a solution in which they
  are
• dissolved will carry an electric current.
• Only 1 of the water that enters the kidneys is
• excreted in urine most is returned to the
  blood.

17
Animation Water and Solute Balance
CLICKTO PLAY
18
Useful References for Section 1

• The latest references for topics covered in this
  section can be found at the book companion
  website. Log in to the books e-resources page at
  www.thomsonedu.com to access InfoTrac articles.
• Medicinenet.com Electrolytes
• InfoTrac Gouty Arthritis A Primer on Late-Onset
  Gout. Geriatrics, July 2005.

19
Section 2

• The Urinary SystemBuilt for Filtering and Waste
  Disposal

20
The Urinary System Built for Filtering and
Waste Disposal

• Each kidney is a bean-shaped organ about the size
  of a rolled up pair of socks.
• A kidney has several internal lobes an outer
• cortex wraps around the central medulla.
• The whole kidney is wrapped in a coat of
  connective tissue called the renal capsule.
• The central cavity of the kidney is the renal
  pelvis.

21
Fig. 12.2c, p. 214
kidney cortex
kidney medulla
renal artery
renal vein
renal pelvis
renal capsule
ureter
22
Animation Kidney Structure
CLICKTO PLAY
23
The Urinary System Built for Filtering and
Waste Disposal

• Kidneys have several functions
• They produce erythropoietin, which stimulates
  production of red blood cells.
• They aid in calcium absorption from food.
• Kidneys make renin, an enzyme that helps regulate
  blood pressure.
• Their main function is to remove metabolic wastes
  and maintain fluid balance.
• The urinary system also consists of tubelike
  ureters that carry urine to the urinary bladder
  for storage until urination urine leaves the
  bladder through the urethra.

24
Animation Human Urinary System
CLICKTO PLAY
25
Fig. 12.2ab, p. 214
heart
POSTERIOR
diaphragm
adrenal gland
kidney
abdominal aorta
inferior vena cava
ureter
ANTERIOR
urinary bladder
urethra
26
Fig. 12.2b, p. 214
POSTERIOR
vertebral column
right kidney
left kidney
peritoneum
abdominal cavity
ANTERIOR
27
The Urinary System Built for Filtering and
Waste Disposal

• Nephrons are the kidney filters.
• Each lobe of the kidney contains blood vessels
  and over a million thin tubes called nephrons,
  which filter water and solutes from the blood.
• The wall of the nephron balloons around a cluster
  of blood capillaries called the glomerulus the
  balloon is called the Bowmans capsule the rest
  of the nephron is a winding tubule.
• Filtrate from the Bowmans capsule enters the
  proximal tubule, passes through the loop of Henle
  and into the distal tubule, and finally empties
  into a collecting duct.

28
The Urinary System Built for Filtering and
Waste Disposal
proximal tubule (orange)
distal tubule (brown)
Bowmans capsule (red)

• Some parts of the nephron allow absorption of
  water and solutes, other parts do not.

KIDNEY CORTEX
KIDNEY MEDULLA
collecting duct (tan)
loop of Henle (yellow)
Figure 12.3a
29
Animation Structure of the Nephron
CLICKTO PLAY
30
The Urinary System Built for Filtering and
Waste Disposal

• Special vessels transport blood to, in, and away
  from nephrons.
• An afferent arteriole delivers blood to each
  nephron where it enters the glomerulus for
  filtration the glomerular capillaries are much
  more permeable than other capillaries.
• Glomerular capillaries merge to form an efferent
  arteriole.
• The efferent arteriole splits to form the
  peritubular capillaries, which eventually carry
  filtered blood into venules and out of the
  kidneys.

31
Fig. 12.3b, p. 215
efferent arteriole
afferent arteriole
glomerular capillaries inside Bowmans capsule
peritubular capillaries threading around tubular
nephron regions
32
Useful References for Section 2

• The latest references for topics covered in this
  section can be found at the book companion
  website. Log in to the books e-resources page at
  www.thomsonedu.com to access InfoTrac articles.
• InfoTrac Renal Anatomy and Overview of Nephron
  Function. Nephrology Nursing Journal, April 2003.

33
Section 3

• How Urine Forms Filtration, Reabsorption, and
  Secretion

34
How Urine Forms Filtration, Reabsorption, and
Secretion

• Filtration removes a large amount of fluid and
  solutes from the blood.
• In filtration, blood pressure forces filtrate out
  of the glomerular capillaries into the Bowmans
  capsule, then into the proximal tubule.
• Blood cells, proteins, and other large solutes
  cannot pass into the capsule water, glucose,
  sodium, and urea, however, are forced out of the
  blood.

35
How Urine Forms Filtration, Reabsorption, and
Secretion

• Next, reabsorption returns useful substances to
  the blood.
• Reabsorption takes place across the walls of the
  proximal tubules.
• Water, glucose, and salt diffuse through the
  tubule wall active transport then moves glucose
  and sodium ions into the tissue fluid.
• Negatively charged ions follow the sodium into
  the tissues water also follows.
• Solutes are actively transported from the tissues
  to the peritubular capillaries, water follows,
  and reabsorption is complete.

36
How Urine Forms Filtration, Reabsorption, and
Secretion

• Any solutes and water remaining in the tubules
  become part of urine.

37
How Urine Forms Filtration, Reabsorption, and
Secretion

• Secretion rids the body of excess hydrogen ions
  and some other substances.
• During secretion, urea, excess hydrogen ions, and
  excess potassium ions are returned to the
  nephrons to add to forming urine.
• This process maintains the bodys acid-base
  balance and also rids the body of drugs, uric
  acid, hemoglobin breakdown products, and other
  wastes.

38
How Urine Forms Filtration, Reabsorption, and
Secretion

• Urination is a controllable reflex.
• The internal urethral sphincter (involuntary
  control) regulates urine flow from the bladder
  into the urethra during urination.
• The external urethral sphincter (voluntary
  control) opens to void urine from the body.

39
Animation Urine Formation
CLICKTO PLAY
40
Fig. 12.4, p. 216
a Filtration. Occurs at glomerular capillaries in
Bowmans capsule.
b Reabsorption. Occurs all along a
nephrons tubular parts.
distal tubule
proximal tubule
c Secretion. Starts at proximal tubule and
continues all along the nephron tubule.
CORTEX
peritubular capillaries
MEDULLA
loop of Henle
increasing solute concentration
d Urine is concentrated in loop of Henle and
collecting duct.
Urine flows from collecting duct into renal
pelvis.
loop of Henle
41
Animation Reabsorption and Secretion
CLICKTO PLAY
42
glomerular capillaries enclosed by Bowmans
capsule
efferent arteriole (to peritubular capillaries)
Bowmans capsule
filtrate to proximal tubule
afferent arteriole (from renal artery)
Fig. 12.5a, p. 217
43
transport protein
Na glucose
Na, glucose
Cl
Cl
H2O
H2O
interior of tubule
wall of tubule
tissue fluid
peritubular capillary
Fig. 12.5b, p. 217
44
H
H
K
K
urea
urea
interior of tubule
wall of tubule
tissue fluid
peritubular capillary
Fig. 12.5c, p. 217
45
Useful References for Section 3

• The latest references for topics covered in this
  section can be found at the book companion
  website. Log in to the books e-resources page at
  www.thomsonedu.com to access InfoTrac articles.
• InfoTrac Renal Hemodynamics An Overview.
  Nephrology Nursing Journal, Aug. 2003.
• InfoTrac Glomerular Filtration An Overview.
  Nephrology Nursing Journal, June 2003.

46
Section 4

• How Kidneys Help Manage Fluid Balance and Blood
  Pressure

47
How Kidneys Help Manage Fluid Balance and Blood
Pressure

• The total volume of body fluids doesnt vary much
  because the kidneys make adjustments to keep the
  volume of extracellular fluid, and blood in
  particular, in a normal range.
• Water follows salt as urine forms.

48
How Kidneys Help Manage Fluid Balance and Blood
Pressure

• The loop of Henle pulls more water and salts from
  the filtrate to return it to the body.
• The descending part of the loop sits in salty
  tissue fluid water is drawn out of the tube to
  be reabsorbed.
• The salt concentration of the remaining fluid in
  the loop rises until it matches the concentration
  of the surrounding tissues.
• In the ascending limb of the loop, water is
  inhibited from passing through the wall of the
  loop, but sodium is actively transported out of
  the loop.

Figure 12.6
49
Fig. 12.6, p. 218
Na
Cl
H2O
loop of Henle
kidney medulla saltiest near turn
50
How Kidneys Help Manage Fluid Balance and Blood
Pressure

• Salt continues to be removed in the distal
  tubule, but not water as salt leaves the
  filtrate, salt gradients become steep, driving
  reabsorption of solutes into the peritubular
  capillaries.
• Urea helps boost the gradient by diffusion out of
  the collecting duct, taking water with it.

51
How Kidneys Help Manage Fluid Balance and Blood
Pressure

• Hormones control whether kidneys make urine that
  is concentrated or dilute.
• Antidiuretic hormone (ADH) is secreted by the
  brain in response to a decrease in extracellular
  fluid ADH causes the distal tubules and
  collecting ducts to become permeable to water,
  which moves back into the blood capillaries.

52
Fig. 12.7, p. 219
ADH targets
aldosterone target
KIDNEY CORTEX
KIDNEY MEDULLA
53
e ResponseReceptors in brain detect the increase
in blood volume. Signals for ADH secretion stop.
a Stimulus Water loss reduces blood volume.
Sensors in the brain trigger release of ADH.
b ADH makes distal tubules, collecting ducts more
permeable to water.
c Kidneys reabsorb more water, so less water
leaves in urine.
d The blood volume rises.
Fig. 12.8, p. 219
54
a Stimulus Water loss reduces blood volume.
Sensors in the brain trigger release of ADH.
e ResponseReceptors in brain detect the increase
in blood volume. Signals for ADH secretion stop.
b ADH makes distal tubules, collecting ducts more
permeable to water.
c Kidneys reabsorb more water, so less water
leaves in urine.
d The blood volume rises.
Stepped Art
Fig. 12.8, p. 219
55
How Kidneys Help Manage Fluid Balance and Blood
Pressure

• Decreases in the volume of extracellular fluid is
  sensed by cells in the efferent arterioles these
  cells, part of the juxtaglomerular apparatus,
  release renin.
• Renin stimulates production of angiotensin I,
  which is converted to angiotensin II.
• Angiotensin II stimulates the adrenal cortex of
  the kidney to make aldosterone, which causes
  cells of the distal tubules and collecting ducts
  to increase reabsorption of salts.
• Caffeine and alcohol are diuretics, substances
  that promote loss of water.

56
Fig. 12.9, p. 219
57
Fig. 12.9a, p. 219
(efferent arteriole leaving the glomerus)
renin-secreting cells in juxtaglomerular
apparatus
distal tubule
Bowmans capsule
proximal tubule
(afferent arteriole leading into glomerus)
58
Fig. 12.9b, p. 219
Receptors in kidneys, elsewhere detect
falling sodium level
Renin released from cells in the JGA
Angiotensinogen converts to angiotensin I
Angiotensin II
Aldosterone secreted (from adrenal glands)
Aldosterone acts on distal tubules
Sodium (and water) reabsorbed
59
How Kidneys Help Manage Fluid Balance and Blood
Pressure

• A thirst center monitors sodium.
• When solute concentration in the extracellular
  fluid rises, the amount of saliva produced by the
  salivary glands drops a dry mouth stimulates the
  thirst center of the brain.
• Stimulation of the thirst center and release of
  ADH cause liquid-seeking behavior.

60
Useful References for Section 4

• The latest references for topics covered in this
  section can be found at the book companion
  website. Log in to the books e-resources page at
  www.thomsonedu.com to access InfoTrac articles.
• InfoTrac Urinary Concentration and Dilution.
  Nephrology Nursing Journal, MayJune 2004.

61
Section 5

• Removing Excess Acids and Other Substances in
  Urine

62
Removing Excess Acids and Other Substances in
Urine

• The bodys acid-base balance, the relative
  amounts of acidic and basic substances in
  extracellular fluid, is maintained in part by the
  kidneys.
• Kidneys maintain acid-base balance by controlling
  the levels of bicarbonate in the blood.

63
Removing Excess Acids and Other Substances in
Urine

• When the blood is too acid, water and carbon
  dioxide combine in cells in the wall of the
  nephron tubules to give rise to bicarbonate and
  H.
• The bicarbonate enters the peritubular
  capillaries and from there it enters the blood to
  neutralize acid.
• The H in the tubules enters the filtrate to
  combine with phosphate, ammonia, or bicarbonate
  to be excreted.
• When the blood is too alkaline, less bicarbonate
  is reabsorbed into the blood.

64
peritubular capillary
cells of tubule wall
tubule interior
H2O
CO2
enzyme action
(carbonic acid)
H2CO3
tissue fluid
HCO 3
H
H ammonia
bicarbonate enters bloodstream
H phosphate
excreted in urine
Fig. 12.10, p. 220
65
Removing Excess Acids and Other Substances in
Urine

• Many other substances end up in urine once
  filtered from the blood traces of drugs excess
  glucose, which is a sign of diabetes pus, a sign
  of infection and even blood, a sign of
  infection, cancer, or injury.

66
Useful References for Section 5

• The latest references for topics covered in this
  section can be found at the book companion
  website. Log in to the books e-resources page at
  www.thomsonedu.com to access InfoTrac articles.
• InfoTrac Urine Albumin Considered Independent
  Marker for Kidney, Cardiovascular Disease. Heart
  Disease Weekly, July 4, 2004.

67
Section 6

• Kidney Disorders

68
Kidney Disorders

• Kidney stones are deposits of uric acid, calcium
  salts, and other substances that have settled out
  of urine and collected in the renal pelvis.
• Small stones can pass out during urination, but
  larger stones can inhibit urination.
• Lithotripsy uses sound waves to fragment the
  stones so they can pass out in the urine.

69
Kidney Disorders

• Inflammation of the bladder (cystitis) or kidneys
  (pyelonephritis) is the result of infections to
  the urinary tract nephritis is general
  inflammation of the kidneys and can be severe
  enough to limit function.
• Polycystic kidney disease is an inherited
  disorder in which cysts form in the kidneys and
  gradually destroy normal tissue.
• Glomerulonephritis describes a variety of
  disorders that disrupt the flow of blood through
  the glomeruli of the kidneys.

70
Kidney Disorders

• Dialysis refers to the exchange of substances
  across a membrane between solutions of differing
  compositions in hemodialysis, a machine is
  connected to an artery or vein, blood enters the
  tubes of the machine, and
• materials are removed
• from the blood before
• it is returned to the body.

Figure 12.11
71
Animation Kidney Dialysis
CLICKTO PLAY
72
Useful References for Section 6

• The latest references for topics covered in this
  section can be found at the book companion
  website. Log in to the books e-resources page at
  www.thomsonedu.com to access InfoTrac articles.
• National Institute of Diabetes and Digestive and
  Kidney Disease National Kidney and Urologic
  Diseases Information Clearinghouse
• InfoTrac Filter Fault Is Kidney Failure. The
  Economic Times, April 24, 2006.
• InfoTrac Battle Well Fought Miami Herald, July
  13, 2006.

73
Video Buffer System
CLICKTO PLAY
74
Video Reabsorption and Secretion
CLICKTO PLAY