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Chapter 43

Chapter 43. Anatomy of the Urinary System. Functions of the kidney. Excretory Keeps the electrolyte balance Keeps the acid-base balance Keeps the water balance. Gross anatomy . Kidney The right kidney is in a lower position than the left.

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Chapter 43

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  1. Chapter 43 Anatomy of the Urinary System

  2. Functions of the kidney • Excretory • Keeps the electrolyte balance • Keeps the acid-base balance • Keeps the water balance

  3. Gross anatomy • Kidney • The right kidney is in a lower position than the left. • Located at the superior lumbar region of the dorsal body wall • Hilus • Renal artery, vein and ureter

  4. Figure 25.3

  5. Gross anatomy • Capsules • They hold the kidney in place and also protect them • Adipose capsule • Fibrous capsule

  6. Gross anatomy • Cortex • Superficial kidney region immediate bellow the capsule • Light color • Medulla • Darker color • Deep to the cortex

  7. Gross anatomy • Medullary pyramids • Base • Papilla or apex • Renal columns • Cortical tissue between the pyramids • Minor calyces • Major calyces

  8. Gross anatomy • Renal pelvis • Cavity formed by the joining of the major calyces and is continuous with the ureter • Blood flow to the kidneys • Aorta • Renal arteries • Segmental arteries (5 branches) • Interlobar arteries

  9. Gross anatomy • Arcuate arteries • Interlobular arteries • Afferent arterioles • Supply the nephron • Glomerulus (capillaries) • Efferent arterioles

  10. Gross anatomy • Peritubular capillaries • Interlobular veins • Arcuate veins • Interlobar veins • Renal veins • Inferior vena cava • There is no segmental veins

  11. Gross anatomy • Ureters • Drain urine from the kidney to thebladder • Bladder • Trigone • 2 ureteral orifices • 1 urethral orifice

  12. Gross anatomy • Detrusor muscle • Rugae • Parietal peritoneum

  13. Gross anatomy • Urethra • Drains urine from the bladder • Males • Belongs to the urinary and reproductive systems • Prostatic, membranous, penile or spongy • Female • Belong to the urinary system only

  14. Figure 25.18a

  15. Gross anatomy • Internal urethral sphincter • Smooth muscle • Superior to the external one • External urethral sphincter • Skeletal muscle • Inferior to the internal one

  16. Microscopic anatomy of the kidney • Nephrons • Functional unit of the kidneys • Formed by: 1) Glomerulus • Glomerular capsule or Bowman’s capsule • Visceral layer with podocytes cells that interdigitate with each other and cling to the endothelial cells. Pedicels

  17. Microscopic anatomy of the kidney • Capsular space • Parietal layer • Renal corpuscle • Glomerulus + Bowman's capsule 2) Renal tubules • Proximal convoluted tubules (PCT) • Simple cuboidal epithelium with microvilli

  18. Microscopic anatomy of the kidney • Loop of Henle • Descending loop • Thick filament • Thin filament with simple squamous epithelium and small number of microvilli

  19. Microscopic anatomy of the kidney • Ascending loop • Thick filament • Thin filament - simple squamous epithelium • Distal convoluted tubule (DCT) • Simple cuboidal epithelium

  20. Microscopic anatomy of the kidney • Collecting ducts • Receives urine from many nephrons • Run through the medullary pyramids • Papillary ducts • Collect urine from the collecting ducts • Empty the urine into the minor calyces

  21. Microscopic anatomy of the kidney • Types of nephrons • Cortical • Located within the renal cortex • Juxtamedullary • Locted at the cortex-medulla junction • Loops of Henle penetrate the medulla

  22. Figure 25.5a

  23. Microscopic anatomy of the kidney • Renal circulation for the nephron • Glomerular capillaries • It produces the filtrate • It is a high hydrostatic pressure capillary bed because: • It is fed by 2 arterioles • The afferent arterioles is larger than the efferent

  24. Microscopic anatomy of the kidney • Peritubular capillary bed • Low pressure capillaries • Porous walls • Absorbs contents of the filtrate

  25. Microscopic anatomy of the kidney • In the cortical nephrons the efferent arterioles will form the peritubular capillaries. From there the blood will flow to the vein system

  26. Microscopic anatomy of the kidney • In the juxtamedullary nephrons, the peritubular capillaries descend immediately into the medulla and give rise to the vasa recta. They run parallel to the loop of Henle and from there the blood will flow to the vein system

  27. Microscopic anatomy of the kidney • Juxtaglomerular apparatus (JGA) • Macula densa • Specialized epithelial cells of the DCT • Juxtaglomerular cells • Specialized smooth muscle cells of the wall of the arterioles

  28. Figure 25.6

  29. Urine formation • Filtration • Filtrate is forming by the passage of fluid from the afferent arteriole to the Bowman’s capsule • Reabsorption • Occurs mainly in the PCT • It is passive for water • It is active for many substances

  30. Urine formation • Secretion • Substances pass from the tubular cells or from the blood to the tubular lumen • It happens mainly on the DCT

  31. Bladder • For urine storage • Micturition or voiding • Mechanism of micturition • Urine is collected until it reaches 200 ml • Stretching of the bladder wall • Activation of the stretching receptors • Impulse is sent through the parasympathetic fibers

  32. Bladder • Impulse reaches the CNS • CNS sends motor command for the bladder to contract • Relaxation of the internal sphincter • Urine passes to the posterior portion of the urethra • Voiding or not (voluntary action)

  33. Bladder • Incontinence • Lack of voluntary control of the external urethral sphincter • Microscopy • Transitional epithelium • Detrusor muscle • Inner longitudinal layer • Central circular layer • Outer longitudinal layer

  34. Kidney dissection • Whole kidney • Hylus • Capsule: fibrous and fat • Ureter

  35. Kidney dissection • Frontal cut • Cortex • Medulla • Pyramids • Papilla • Columns • Calyces: major, minor • Pelvis

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