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The Urinary System and Tract

The Urinary System and Tract. A continued examination. Figure 26.10 Glomerular Filtration. Figure 26.10a, b. Glomerular filtration rate (GFR). Amount of filtrate produced in the kidneys each minute Factors that alter filtration pressure change GFR. Factors controlling the GFR.

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The Urinary System and Tract

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  1. The Urinary System and Tract A continued examination

  2. Figure 26.10 Glomerular Filtration Figure 26.10a, b

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

  4. Factors controlling the GFR • A drop in filtration pressure can activate local mechanisms--results in vasodilation of afferent arterioles and vasoconstriction of efferent arterioles----> increase in glomerular (filtration) pressure • A drop in filtration pressure stimulates Juxtaglomerular apparatus (JGA) • Releases renin and erythropoietin

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

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

  7. Sympathetic activation • Produces powerful vasoconstriction of afferent arterioles • Decreases GFR and slows production of filtrate • Usually in response to big drop in blood pressure • Changes the regional pattern of blood flow • Alters GFR

  8. 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)

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

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

  11. 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

  12. 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

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

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

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

  16. 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

  17. 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

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

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

  20. Chapter 26, part 4 The Urinary System

  21. SECTION 26-6Urine Transport, Storage, and Elimination

  22. Urine production ends with fluid entering the renal pelvis • Rest of urinary system transports, stores and eliminates • Ureters • Bladder • Urethra

  23. Figure 26.17 A Radiographic View of the Urinary System Figure 26.17

  24. The ureters • Pair of muscular tubes • Extend from renal pelvis to the bladder • Peristaltic contractions force urine toward the urinary bladder

  25. The urinary bladder • Hollow, muscular organ • Reservoir for the storage of urine • Contraction of detrusor muscle voids bladder • Internal features include • Trigone • Neck • Internal urethral sphincter • Ruggae

  26. Figure 26.19 Organs for the Collection and storage of Urine Figure 26.19a

  27. Figure 26.19 Organs for the Collection and storage of Urine Figure 26.19b

  28. Figure 26.19 Organs for the Collection and storage of Urine Figure 26.19c

  29. The urethra • Extends from the urinary bladder to the exterior of the body • Passes through urogenital diaphragm (external urinary sphincter) • Differs in length and function in males and females

  30. Figure 26.20 The Histology of the Organs that Collect and Transport Urine Figure 26.20a

  31. Figure 26.20 The Histology of the Organs that Collect and Transport Urine Figure 26.20b, c

  32. Micturition reflex and urination • Urination coordinated by micturition reflex • Initiated by stretch receptors in wall of bladder • Urination requires coupling micturition reflex with relaxation of external urethral sphincter

  33. Figure 26.21 The Micturition Reflex Figure 26.21

  34. Figure 26.21 The Micturition Reflex Figure 26.21

  35. SECTION 26-7Aging and the Urinary System

  36. Changes with aging include: • Decline in the number of functional nephrons • Reduction of GFR • Reduced sensitivity to ADH • Problems with the micturition reflex

  37. You should now be familiar with: • The components of the urinary system and their functions • The location and structural features of the kidneys • The structure of a nephron, and the processes involved in the formation of urine • The normal characteristics, composition, and solute concentrations of a representative urine sample

  38. You should now be familiar with: • The factors that influence filtration pressure and the rate of filtrate formation • The types of transport mechanisms found along the nephron • How antidiuretic hormone and aldosterone levels influence the volume and concentration of urine

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