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Understanding Renal Physiology: Filtrate Processing & Secretion

Dive into the complexities of renal physiology, including reabsorption, secretion, and the production of concentrated urine through detailed processes in the nephrons and collecting ducts. Explore the key functions of the urinary system.

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Understanding Renal Physiology: Filtrate Processing & Secretion

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  1. Chapter 26, part 3 The Urinary System

  2. SECTION 26-5Renal Physiology: Reabsorption and Secretion

  3. 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

  4. Figure 26.12 Transport Activities at the PCT PLAY Animation: Proximal Convoluted Tubule Figure 26.12

  5. 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

  6. Figure 26.13 Countercurrent Multiplication and Concentration of Urine Figure 26.13a

  7. Figure 26.13 Countercurrent Multiplication and Concentration of Urine Figure 26.13b

  8. Figure 26.13 Countercurrent Multiplication and Concentration of Urine Figure 26.13c

  9. 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)

  10. Figure 26.14 Tubular Secretion and Solute Reabsorption at the DCT PLAY Animation: Distal Convoluted Tubule Figure 26.14

  11. Figure 26.14 Tubular Secretion and Solute Reabsorption at the DCT Figure 26.14c

  12. 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

  13. 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

  14. Figure 26.15 The Effects of ADH on the DCT and Collecting Ducts Figure 26.15

  15. Figure 26.15 The Effects of ADH on the DCT and Collecting Ducts Figure 26.15a, b

  16. Function of the vasa recta • Removes solutes and water • Balances solute reabsorption and osmosis in the medulla

  17. 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

  18. 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

  19. Figure 26.16 A Summary of Renal Function Figure 26.16a

  20. Figure 26.16 A Summary of Renal Function Figure 26.16b

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