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The Urinary System Chapter 24 – Lecture Notes

The Urinary System Chapter 24 – Lecture Notes

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The Urinary System Chapter 24 – Lecture Notes

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  1. The Urinary SystemChapter 24 – Lecture Notes to accompany Anatomy and Physiology: From Science to Life textbook by Gail Jenkins, Christopher Kemnitz, Gerard Tortora

  2. Chapter Overview 24.1 Kidney Functions 24.2 Urinary Path 24.3 Nephron Structure 24.4 Nephron Function 24.5 Glomular Filtration 24.6 Tubular Reabsorption and Secretion 24.7 Hormonal Regulation 24.8 Antidiuretic Hormone 24.9 Urine Transport 24.10 Fluid and Acid-Base Balance

  3. Essential Terms kidney • produces urine to remove waste from the body by filtration of blood nephron • structure within kidney that actually filters the blood and composed of several parts nitrogen waste • produced by protein catabolism micturition • process of releasing urine from the body

  4. Introduction Urinary System • Eliminates non-useful metabolic byproducts such as nitrogenous wastes • Comprised of two kidneys, two, ureters, one urinary bladder and one urethra • Returns most water and useful solutes are to bloodstream • Urine results from filtration of blood plasma • Kidneys help maintain homeostasis

  5. Concept 24.1Kidney Functions

  6. Kidney Functions • Regulate various properties of the blood • Ionic composition • pH • Volume • Pressure • Glucose level • Produces hormones • Excretes waste and foreign substances

  7. Figure 24.1

  8. Concept 24.2Urinary Path

  9. Paired kidneys are retroperitoneal organs • Renal hilum • Area for entry and exit of nerves, blood and lymphatic vessels and ureter exit • 3 layers of connective tissue • Renal capsule – deep • Maintains shape and forms barrier • Adipose capsule – middle • Cushions and supports • Renal fascia – superficial • Anchors to abdominal wall

  10. Figure 24.2a

  11. Figure 24.2b

  12. Internal Anatomy • Renal cortex • Renal Medulla • Renal Pyramids • Renal papilla • Renal columns • Renal lobe • Nephrons – functional unit of kidney, filters blood • Papillary ducts • Minor and major calyces • Renal pelvis • Renal sinus

  13. Figure 24.3a

  14. Figure 24.3b

  15. Blood Supply • Renal arteries • Afferent vessels supply 20 - 25% of resting cardiac output • Segmental arteries • Interlobar arteries • Arcuate arteries • Interlobular arteries • Afferent arteriole • One per nephron and divides into glomerulus • Glomerulus • Network of glomerular capillaries to filter blood

  16. Figure 24.4a

  17. Figure 24.4b

  18. Blood Supply • Glomerulus • Glomerular capillaries form efferent arteriole • Peritubular capillaries • Vasa recta • Interlobular veins • Arcuate veins • Interlobar veins • Renal vein • Efferent vessel carries blood to inferior vena cava

  19. Concept 24.3Nephron Structure

  20. 2 Parts of Nephron • Renal corpuscle • Filters blood plasma • Glomerulus • Glomerular (Bowman’s) capsule • Renal tubule • Refines filtered fluid • Proximal convoluted tubule (PCT) • Loop of Henle (LOH) • Distal convoluted tubule (DCT)

  21. Figure 24.5a

  22. Figure 24.5b

  23. Nephron Structure • Loop of Henle • Descending limb of loop of Henle • Ascending limb of loop of Henle • Cortical nephrons – 80-85% of nephrons • Corpuscles in outer cortex with short loops of Henle • Juxtamedullary nephrons – 15-20% • Corpuscles deep in cortex with long loops of Henle • Thin and thick ascending limb • Distal convoluted tubule • Collecting duct • Papillary ducts

  24. Nephron Structure – Histology • Glomerular Capsule • Podocytes • Capsular space • Renal tubule and collecting duct • Macula densa • Juxtaglomerular (JG) cells • Both comprise Juxtaglomerular (JGA) apparatus • Regulate blood pressure within kidneys

  25. Figure 24.6a

  26. Figure 24.6b

  27. Concept 24.4Nephron Function

  28. Functions of Nephron • Glomerular filtration • Tubular reabsorption • Tubular secretion • Removes substances from blood as waste

  29. Figure 24.7

  30. Concept 24.5Glomerular Filtration

  31. Filtration Membrane • Leaky barrier formed by endothelial cells and podocytes • 3 layers • Glomerular endothelial cell • Fenestrations • Mesangial cells • Basal lamina • Pedicles form filtration slits

  32. Figure 24.8a

  33. Figure 24.8b

  34. Filtration Process • Use of pressure to force fluids and solutes through a membrane • 3 reasons for large volume through renal corpuscles • Large surface area of glomerular capillaries • Mesangial cells • Thin, porous filtration membrane • High glomerular capillary blood pressure

  35. Net Filtration Pressure (NFP) • NFP = GBHP – CHP – BCOP • Glomerular blood hydrostatic pressure (GBHP) • Promotes filtration • Capsular hydrostatic pressure (CHP) • Opposes filtration • Blood colloid osmotic pressure (BCOP) • Opposes filtration

  36. Figure 24.9

  37. Glomerular Filtration Rate (GFR) • Mechanisms that affect filtration pressure • Adjust blood flow • Alter available glomerular capillary surface area • GFR controlled by 3 mechanisms • Renal autoregulation • Negative feedback by macula densa • Neural regulation • Hormonal regulation

  38. Figure 24.10

  39. Renal Autoregulation • Renal Autoregulation • Myogenic mechanism • Tubuloglomerular feedback • Neural Regulation • Sympathetic neurons release norepinephrine to vasoconstrict afferent arterioles • Hormonal Regulation • Angiotensin II reduces GFR • Atrial natriuretic peptide (ANP) increases GFR

  40. Table 24.1

  41. Concept 24.6Tubular Reabsorption and Secretion

  42. Tubular Reabsorption • Return filtered water to body • 99% of filtered water is reabsorbed by epithelial cells • Solutes reabsorbed by active and passive mechanisms • Maintains homeostasis

  43. Table 24.2

  44. Tubular Secretion • Removes substances from blood to tubular fluid forming urine • Removal of H+ regulates blood pH • Eliminates waste from body

  45. Reabsorption Routes • Paracellular reabsorption – passive • Between adjacent tubule cells • Transcellular reabsorption • Through tubule cells • Na+/K+ pumps on basolateral membranes insures one way transport • Apical membrane • Basolateral membrane

  46. Figure 24.11

  47. Transport Mechanisms • Primary active transport • Secondary active transport • Coupled • Symporters or antiporters • Obligatory water reabsorption • Water follows solutes • Facultative water reabsorption • Regulated by ADH

  48. Reabsorption and Secretion in PCT • Most water reabsorbed by PCT • Na+ symporters in apical membrane of cells comprising PCT reabsorb: • Na+ • Glucose • Amino acids • Lactic acid • Water-soluble vitamins • Other nutrients

  49. Figure 24.12

  50. Reabsorption and Secretion in PCT • Na+/H+ antiporters carry Na+ into cell and H+ out to the lumen into tubular fluid • Carbonic anyhdrase (CA) catalyzes production of carbonic acid (H2CO3) • Important for homeostasis of blood pH • Symporters and antiporters enhance reabsorption of water, important ions, and minerals • Ammonia (NH3) and urea secreted by PCT into tubular fluid