Anatomy & Physiology
SIXTH EDITION
Chapter 26, part 3
The Urinary System
PowerPoint® Lecture Slide Presentation prepared by
Dr. Kathleen A. Ireland, Biology Instructor, Seabury Hall, Maui, Hawaii
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Frederic H. Martini
Fundamentals of
SECTION 26-5
Renal Physiology: Reabsorption and Secretion
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Reabsorption and secretion at the PCT
• Glomerular filtration produces fluid similar to
plasma without proteins
• The PCT reabsorbs 60-70% of the filtrate
produced
• Reabsorption of most organic nutrients
• Active and passive reabsorption of sodium and
other ions
• Reabsorption of water
• Secretion also occurs in the PCT
PLAY
Animation: Early Filtrate Processing
PLAY
Animation: Glomerular filtration
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Figure 26.12 Transport Activities at the PCT
PLAY
Animation: Proximal Convoluted Tubule
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Figure 26.12
The loop of Henle and countercurrent
multiplication
• Countercurrent multiplication
• Between ascending and descending limbs of
loop
• Creates osmotic gradient in medulla
• Facilitates reabsorption of water and solutes
before the DCT
• Permits passive reabsorption of water from
tubular fluid
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Figure 26.13 Countercurrent Multiplication and
Concentration of Urine
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Figure 26.13a
Figure 26.13 Countercurrent Multiplication and
Concentration of Urine
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Figure 26.13b
Figure 26.13 Countercurrent Multiplication and
Concentration of Urine
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Figure 26.13c
Reabsorption and secretion at the DCT
• DCT performs final adjustment of urine
• Active secretion or absorption
• Absorption
• Tubular cells actively resorb Na+ and Cl• In exchange for potassium or hydrogen ions
(secreted)
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Figure 26.14 Tubular Secretion and Solute
Reabsorption at the DCT
PLAY
Animation: Distal Convoluted Tubule
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Figure 26.14
Figure 26.14 Tubular Secretion and Solute
Reabsorption at the DCT
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Figure 26.14c
Reabsorption and secretion along the collecting
system
• Water and solute loss is regulated by aldosterone
and ADH
• Reabsorption
• Sodium ion, bicarbonate, and urea are
resorbed
• Secretion
• pH is controlled by secretion of hydrogen or
bicarbonate ions
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Control of urine volume and osmotic
concentration
• Urine volume and osmotic concentration are
regulated by controlling water reabsorption
• Precise control allowed via facultative water
reabsorption
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Figure 26.15 The Effects of ADH on the DCT
and Collecting Ducts
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Figure 26.15
Figure 26.15 The Effects of ADH on the DCT
and Collecting Ducts
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Figure 26.15a, b
Function of the vasa recta
• Removes solutes and water
• Balances solute reabsorption and osmosis in
the medulla
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Composition of normal urine
• Varies with the metabolic and hormonal events of
the body
• Reflects filtration, absorption and secretion
activity of the nephrons
• Urinalysis is the chemical and physical analysis of
urine
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Summary of renal function:
• Each segment of nephron and collecting system
contribute
• Glomerulus
• PCT
• Descending limb
• Thick ascending limb
• DCT and collecting ducts
• Concentrated urine produced after considerable
modification of filtrate
PLAY
Animation: Late Filtrate Processing
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Figure 26.16 A Summary of Renal Function
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 26.16a
Figure 26.16 A Summary of Renal Function
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Figure 26.16b