Chapter 26
The Urinary System
I. Overview of the Urinary System
(Independent review of material - text pages 952-955, figs 26.1-26.5)
II. The Nephron
A. Basic Nephron Anatomy
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The renal corpuscle
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The renal tubule
B. Nephron functions include:
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Production of filtrate
Reabsorption of organic nutrients
Reabsorption of water and ions
Secretion of waste products into tubular fluid
C. Nephron Classification
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Cortical nephrons
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Juxtamedullary nephrons
D. Blood flow to/around nephron
E. Glomerulus/Bowman's Capsule anatomy
F. Functional anatomy of the nephron
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Proximal convoluted tubule (PCT)
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Reabsorbs needed nutrients, water and ions from filtrate
Loop of Henle
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Concentration of urine via reabsorption of water
Distal convoluted tubule (DCT)
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Actively secretes ions, toxins, drugs into tubular fluid
Reabsorbs sodium ions and water from tubular fluid
III. Basic Principles of Renal Physiology
A. Urine production maintains homeostasis
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Regulating blood volume and composition
Excreting waste products
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Urea
Creatinine
B. Basic processes of urine formation
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Filtration
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Reabsorption
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Secretion
IV. Renal Physiology - Glomerular Filtration
A. Filtration pressures - Glomerular filtration pressure (GFP)
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In response to glomerular hydrostatic pressure (GHP)
• Capsular hydrostatic pressure (CsHP) opposes GHP
• Blood colloid osmotic pressure (BCOP) opposes GHP
Net hydrostatic pressure (NHP) = GHP – CsHP
Net hydrostatic pressure (NCOP) = BCOP – CsCOP
Filtration (GFP) = NHP – NCOP
B. Glomerular filtration rate (GFR)
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Amount of filtrate produced in the kidneys each minute
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Factors controlling the GFR
V. Renal Physiology – Reabsorption and Secretion
A. Reabsorption and secretion at the PCT
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Glomerular filtration produces fluid similar to plasma without proteins
The PCT reabsorbs 60-70% of the filtrate produced
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Reabsorption of most organic nutrients
Active and passive reabsorption of sodium and other ions
Reabsorption of water
Secretion also occurs in the PCT
B. The loop of Henle and countercurrent multiplication
C. Reabsorption and secretion at the DCT
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DCT performs final adjustment of urine
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Active secretion or reabsorption
Reabsorption
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Tubular cells actively reabsorb Na+ and Cl- and water - controlled by hormones
Usually in exchange for potassium or hydrogen ions (secreted)
Urea is reabsorbed in collecting ducts
D. Control of urine volume and osmotic concentration
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Urine volume and osmotic concentration are regulated by controlling water reabsorption