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Chapter 26, part 2

Chapter 26, part 2. The Urinary System. Renal tubule and blood flow. Blood travels from efferent arteriole to peritubular capillaries Vasa recta Renal tubule begins at renal corpuscle Includes glomerulus and Bowman’s capsule Blood leaves the nephron via the efferent arteriole.

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Chapter 26, part 2

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  1. Chapter 26, part 2 The Urinary System

  2. Renal tubule and blood flow • Blood travels from efferent arteriole to peritubular capillaries • Vasa recta • Renal tubule begins at renal corpuscle • Includes glomerulus and Bowman’s capsule • Blood leaves the nephron via the efferent arteriole

  3. Glomerulus anatomy • Podocytes cover lamina densa of capillaries • Project into the capsular space • Pedicels of podocytes separated by filtration slits

  4. Figure 26.8 The Renal Corpuscle Figure 26.8a, b

  5. Figure 26.8 The Renal Corpuscle Figure 26.8c, d

  6. Functional anatomy of the nephron • Proximal convoluted tubule (PCT) • Actively reabsorbs nutrients, plasma proteins and ions from filtrate • Released into peritubular fluid • Loop of Henle • Descending limb • Ascending limb • Each limb has a thick and thin section PLAY Animation: Urinary System Anatomy

  7. Functional anatomy of the nephron • Distal convoluted tubule (DCT) • Actively secretes ions, toxins, drugs • Reabsorbs sodium ions from tubular fluid PLAY Animation: Urinary System Dissection and Flythrough

  8. SECTION 26-3Principles of Renal Physiology

  9. Urine production maintains homeostasis • Regulating blood volume and composition • Excreting waste products • Urea • Creatinine • Uric acid

  10. Basic processes of urine formation • Filtration • Blood pressure • Water and solutes across glomerular capillaries • Reabsorption • The removal of water and solutes from the filtrate • Secretion • Transport of solutes from the peritubular fluid into the tubular fluid

  11. Carrier Mediated Transport • Filtration in the kidneys modified by carrier mediated transport • Facilitated diffusion • Active transport • Cotransport • Countertransport • Carrier proteins have a transport maximum (Tm) • Determines renal threshold

  12. Reabsorption and secretion • Accomplished via diffusion, osmosis, and carrier-mediated transport • Tm determines renal threshold for reabsorption of substances in tubular fluid

  13. Renal function • Most regions of the nephron perform a combination of functions • General functions can be identified • Filtration in the renal corpuscle • Nutrient reabsorption along the PCT • Active secretion at PCT and DCT • Loops of Henle regulate final volume and solute concentration

  14. Figure 26.9 An Overview of Urine Formation Figure 26.9

  15. SECTION 26-4Renal Physiology: Filtration and the Glomerulus

  16. Filtration pressures - Glomerular filtration • Occurs as fluids move across the glomerulus • In response to glomerular hydrostatic pressure (GHP) and blood pressure in the glomerular capillaries • Capsular hydrostatic pressure (CsHP) opposes GHP • Blood colloid osmotic pressure (BCOP) opposes GHP • Net hydrostatic pressure (NHP) = GHP – CsHP • Filtration (FP) = NHP – BCOP

  17. Figure 26.10 Glomerular Filtration Figure 26.10

  18. Figure 26.10 Glomerular Filtration Figure 26.10a, b

  19. Glomerular filtration rate (GFR) • Amount of filtrate produced in the kidneys each minute • Factors that alter filtration pressure change GFR

  20. Factors controlling the GFR • A drop in filtration pressure stimulates Juxtaglomerular apparatus (JGA) • Releases renin and erythropoietin

  21. Figure 26.11 The Response to a Reduction in the GFR Figure 26.11a

  22. Figure 26.11 The Response to a Reduction in the GFR Figure 26.11b

  23. Sympathetic activation • Produces powerful vasoconstriction of afferent arterioles • Decreases GFR and slows production of filtrate • Changes the regional pattern of blood flow • Alters GFR • Stimulates release of renin by JGA

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