Anatomy of the Urinary System: Organ Location and Function

1. 24 PART 1 The Urinary System Pages 720-734

2. Organs of the Urinary System • Kidneys • Ureters • Urinary bladder • Urethra

3. Hepatic veins (cut) Esophagus (cut) Inferior vena cava Renal artery Adrenal gland Renal hilum Renal vein Aorta Kidney Iliac crest Ureter Rectum (cut) Uterus Urinary bladder Urethra (a) (b) Organs of the Urinary System Figure 24.1

4. Location and External Anatomy of Kidneys • Located retroperitoneally • Lateral to T12–L3 vertebrae • Average kidney is 12 cm tall, 6 cm wide, 3 cm thick • Hilum • On concave surface • Vessels and nerves enter and exit • Fibrous capsule surrounds the kidney • Perirenal fat—external to renal capsule • Renal fascia—external to perirenal fat

5. Anterior Inferior vena cava Aorta Peritoneal cavity (organs removed) Peritoneum Supportive tissue layers Renal vein Renal fascia anterior posterior Renal artery Perirenal fat capsule Fibrous capsule Body of vertebra L2 Body wall (a) Posterior Jejunum Duodenum Liver Inferior vena cava Left renal vein Aorta Left kidney Right kidney Erector spinae muscle in posterior abdominal wall Vertebra L1 (c) Position of the Kidneys with in the Posterior Abdominal Wall Figure 24.2a, c

7. Internal Gross Anatomy of the Kidneys • Frontal section through the kidney • Renal cortex • Renal pyramids • Renal pelvis • Major calices • Minor calices • Gross vasculature • Renal arteries branch into segmental arteries • Segmental arteries branch into interlobar arteries • Arcuate arteries branch from interlobar arteries

8. Renal hilum Renal cortex Renal medulla Major calyx Papilla of pyramid Renal pelvis Minor calyx Ureter Renal pyramid in renal medulla Renal column Fibrous capsule (a) Photograph of right kidney, frontal section (b) Diagrammatic view Internal Gross Anatomy of the Kidneys Figure 24.3

10. Cortical radiate vein Cortical radiate artery Arcuate vein Arcuate artery Interlobar vein Interlobar artery Segmental arteries Renal vein Renal artery Renal pelvis Ureter Renal medulla Renal cortex (a) Frontal section, posterior view, illustrating major blood vessels Summary of Blood Vessels Supplying the Kidney Figure 24.4a

11. Aorta Inferior vena cava Renal artery Renal vein Segmental artery Interlobar vein Interlobar artery Arcuate vein Arcuate artery Cortical radiate vein Peritubular capillaries and vasa recta Cortical radiate artery Afferent arteriole Efferent arteriole Glomerulus (capillaries) Nephron-associated blood vessels (see Figure 24.9) (b) Path of blood flow through renal blood vessels Summary of Blood Vessels Supplying the Kidney Figure 24.4b

12. Hepatic veins (cut) Esophagus (cut) Inferior vena cava Renal artery Adrenal gland Renal hilum Renal vein Aorta Kidney Iliac crest Ureter Rectum (cut) Uterus Urinary bladder Urethra (a) (b) Organs of the Urinary System Figure 24.1

13. Mechanisms of Urine Production • Filtration • Filtrate of blood leaves kidney capillaries • Reabsorption • Most nutrients, water, and essential ions reclaimed • Secretion • Active process of removing undesirable molecules

14. Afferent arteriole Glomerular capillaries Efferent arteriole Cortical radiate artery Glomerular capsule Rest of renal tubule containing filtrate Peritubular capillary Three major renal processes To cortical radiate vein Glomerular filtration Tubular resorption Tubular secretion Urine Basic Kidney Functions Figure 24.5

15. Nephron Structure • Nephron is composed of • Renal corpuscle • Renal tubule

16. Renal cortex Renal medulla Glomerular capsule: parietal layer Renal pelvis Basement membrane Ureter Kidney Podocyte Fenestrated endothelium of the glomerulus Renal corpuscle Glomerular capsule Glomerulus Glomerular capsule: visceral layer Distal convoluted tubule Microvilli Mitochondria Proximal convoluted tubule Highly infolded plasma membrane Proximal convoluted tubule cells Cortex Medulla Distal convoluted tubule cells Thick segment Thin segment Nephron loop Descending limb Ascending limb Nephron loop (thin-segment) cells Collecting duct Principal cell Intercalated cell Collecting duct cells Renal Tubule Figure 24.7

17. The Nephron • Renal corpuscle—first part of nephron • Glomerulus and glomerular capsule • Glomerulus—tuft of capillaries • Capillaries of glomerulus are fenestrated • Glomerular (Bowman’s) capsule • Parietal layer—simple squamous epithelium • Visceral layer—consists of podocytes

18. Filtration Membrane • The filtration membrane • Filter that lies between blood in the glomerulus and capsular space • Consists of three layers • Endothelium of the capillary • Slits between foot processes of podocytes • Basement membrane

19. Filtration Membrane • Basement membrane and slit diaphragm • Hold back most proteins • Allow through • Water • Ions • Glucose • Amino acids • Urea

20. Glomerular capsular space Efferent arteriole Cytoplasmic extensions of podocytes Afferent arteriole Filtration slits Proximal convoluted tubule Podocyte cell body Glomerular capillary covered by podocyte- containing visceral layer of glomerular capsule Parietal layer of glomerular capsule (a) Renal corpuscle Fenestrations (pores) Glomerular capillary endothelium (podocyte covering and basement membrane removed) Foot processes of podocyte (b) Glomerular capillary surrounded by podocytes Renal Corpuscle and the Filtration Membrane Figure 24.6a, b

21. Filtration membrane Capillary endothelium Capillary Basement membrane Foot processes of podocyte of glomerular capsule Filtration slit Slit diaphragm Plasma Filtrate in capsular space Foot processes of podocyte Fenestration (pore) (d) Three parts of the filtration membrane Renal Corpuscle and the Filtration Membrane Figure 24.6d

22. Renal Tubule • Filtrate proceeds to renal tubules from glomerulus • Proximal convoluted tubule • Nephron loop • Descending limb • Thin segment • Thick segment • Distal convoluted tubule • Collecting ducts • Receive urine from several nephrons • Play an important role in conserving body fluids

23. Renal cortex Renal medulla Glomerular capsule: parietal layer Renal pelvis Basement membrane Ureter Kidney Podocyte Fenestrated endothelium of the glomerulus Renal corpuscle Glomerular capsule Glomerulus Glomerular capsule: visceral layer Distal convoluted tubule Microvilli Mitochondria Proximal convoluted tubule Highly infolded plasma membrane Proximal convoluted tubule cells Cortex Medulla Distal convoluted tubule cells Thick segment Thin segment Nephron loop Descending limb Ascending limb Nephron loop (thin-segment) cells Collecting duct Principal cell Intercalated cell Collecting duct cells Renal Tubule Figure 24.7

24. Figure 24.8a Histology of the nephron. Distal convolutedtubules (clear lumens) Renal corpuscle Squamous epitheliumof parietal layer ofglomerular capsule Glomerularcapsular space Glomerulus Proximal convolutedtubules (fuzzy lumensdue to long microilli) Photomicrograph of renal cortical tissue (230)

25. Thin segments of nephron loop Vasa recta with blood cells within Collecting ducts (b) Photomicrograph through the renal medulla (215X) Micrograph through the Renal Medulla Figure 24.8b

26. Classes of Nephron • Cortical nephrons • 85% of nephrons • Juxtamedullary nephrons • 15% of nephrons • Contribute to kidney’s ability to concentrate urine

27. Cortical nephron Juxtamedullary nephron • Has long nephron loop and glomerulus closer to the corticomedullary junction • Efferent arteriole supplies vasa recta • Has short nephron loop and glomerulus further from the corticomedullary junction • Efferent arteriole supplies peritubular capillaries Efferent arteriole Glomerular capillaries (glomerulus) Cortical radiate vein Renal corpuscle Cortical radiate artery Glomerular (Bowman’s) capsule Afferent arteriole Collecting duct Proximal convoluted tubule Distal convoluted tubule Afferent arteriole Efferent arteriole Peritubular capillaries Cortex Medulla Ascending or thick limb of the nephron loop Renal pelvis Ureter Corticomedullary junction Arcuate vein Kidney Vasa recta Arcuate artery (a) Nephron loop Descending or thin limb of nephron loop Afferent arteriole Glomerulus Efferent arteriole Peritubular capillary bed (b) Classes of Nephron Figure 24.9

28. Blood Vessels Associated with Nephrons • Nephrons associate closely with two capillary beds • Glomeruli • Peritubular capillaries in cortical nephrons or vasa recta in juxtamedullary nephrons

29. Blood Vessels Associated with Nephrons • Glomeruli • Produce filtrate that becomes urine • Fed and drained by arterioles • Afferent and efferent arteriole • Efferent arteriole has a smaller diameter than afferent arteriole • Generate 1 liter of fluid every 8 minutes • 99% of filtrate is resorbed by tubules

30. Blood Vessels Associated with Nephrons • Peritubular capillaries • Arise from the efferent arterioles • Are adapted for absorption • Low-pressure, porous capillaries • All molecules secreted by nephrons into urine are from peritubular capillaries

31. Cortical nephron Juxtamedullary nephron • Has long nephron loop and glomerulus closer to the corticomedullary junction • Efferent arteriole supplies vasa recta • Has short nephron loop and glomerulus further from the corticomedullary junction • Efferent arteriole supplies peritubular capillaries Efferent arteriole Glomerular capillaries (glomerulus) Cortical radiate vein Renal corpuscle Cortical radiate artery Glomerular (Bowman’s) capsule Afferent arteriole Collecting duct Proximal convoluted tubule Distal convoluted tubule Afferent arteriole Efferent arteriole Peritubular capillaries Cortex Medulla Ascending or thick limb of the nephron loop Renal pelvis Ureter Corticomedullary junction Arcuate vein Kidney Vasa recta Arcuate artery (a) Nephron loop Descending or thin limb of nephron loop Afferent arteriole Glomerulus Efferent arteriole Peritubular capillary bed (b) Classes of Nephron Figure 24.9

32. Blood Vessels Associated with Nephrons • Vasa recta • Continue from efferent arterioles of juxtamedullary nephrons • Are thin-walled looping vessels • Descend into the medulla • Are part of the kidney’s urine concentrating mechanism

33. Juxtaglomerular Apparatus • Juxtaglomerular apparatus • Functions in regulating blood pressure • An area of specialized contact between terminal end of the ascending limb and afferent arteriole • Granular cells—modified smooth muscle cells with secretory granules • Contain the hormone renin • Renin—secreted in response to falling BP in afferent arteriole

34. Glomerular capsule Glomerulus Efferent arteriole Parietal layer of glomerular capsule Foot processes of podocytes Afferent arteriole Podocyte cell body (visceral layer) Capsular space Red blood cell Proximal tubule cell Efferent arteriole Juxtaglomerular apparatus Macula densa cells of the ascending limb of nephron loop Lumens of glomerular capillaries Extraglomerular mesangial cells Granular cells Endothelial cell of glomerular capillary Afferent arteriole Mesangial cells between capillaries Juxtaglomerular apparatus Renal corpuscle Juxtaglomerular Apparatus Figure 24.10

35. Juxtaglomerular Apparatus • Macula densa—end of nephron loop • Adjacent to granular cells • Tall, closely packed epithelial cells • Monitor solute concentration in the filtrate • Signal granular cells to secrete renin • Initiates renin-angiotensin mechanism

36. Juxtaglomerular Apparatus • Mesangial cells • Located around base of the glomerulus • Regulated blood flow within the glomerulus • Extraglomerular mesangial cells • Interact with macula densa and granular cells • Help regulate blood pressure

37. Glomerular capsule Glomerulus Efferent arteriole Parietal layer of glomerular capsule Foot processes of podocytes Afferent arteriole Podocyte cell body (visceral layer) Capsular space Red blood cell Proximal tubule cell Efferent arteriole Juxtaglomerular apparatus Macula densa cells of the ascending limb of nephron loop Lumens of glomerular capillaries Extraglomerular mesangial cells Granular cells Endothelial cell of glomerular capillary Afferent arteriole Mesangial cells between capillaries Juxtaglomerular apparatus Renal corpuscle Juxtaglomerular Apparatus Figure 24.10

38. Ureters • Carry urine from the kidneys to the urinary bladder • Oblique entry into bladder prevents backflow of urine • Histology of ureter • Mucosa—transitional epithelium • Muscularis—two layers • Inner longitudinal layer • Outer circular layer • Adventitia—typical connective tissue

39. Peritoneum Ureter Rugae Detrusor muscle Adventitia Ureteric orifices Trigone of bladder Bladder neck Internal urethral sphincter Prostate Prostatic urethra Membranous urethra External urethral sphincter Urogenital diaphragm Spongy urethra Erectile tissue of penis (a) Male. The long male urethra has three regions: prostatic, membranous, and spongy. External urethral orifice Structure of the Urinary Bladder and Urethra Figure 24.14

40. Kidney Renal pelvis Ureter Urinary bladder Ureters

41. Lumen Adventitia Circular layer Muscularis Longitudinal layer Transitional epithelium Mucosa Lamina propria Microscopic Structure of the Ureter Figure 24.11

42. Urinary Bladder • A collapsible muscular sac • Stores and expels urine • Full bladder—spherical • Expands into the abdominal cavity • Empty bladder—lies entirely within the pelvis

43. Urinary Bladder • Urachus—closed remnant of the allantois • Prostate gland • In males • Lies directly inferior to the bladder • Surrounds the urethra

44. Ureter not illustrated in (b) Uterus Urachus Urinary bladder Ductus deferens Pubic symphysis Prostate Vagina Urethra (a) Sagittal section through male pelvis, urinary bladder shown in lateral view (b) Sagittal section through female pelvis Urinary Bladder Figure 24.12

45. Urinary Bladder • Urinary bladder is composed of three layers • Mucosa—transitional epithelium • Thick muscular layer—detrusor muscle • Fibrous adventitia

46. Figure 24.13 Histology of the bladder. Lumen of the bladder Transitionalepithelium Laminapropria Muscular layer(detrusor) Transitionalepithelium Basementmembrane Laminapropria Epithelium lining the lumenof the bladder (285) Micrograph of the bladderwall (25)

47. Peritoneum Ureter Rugae Detrusor muscle Adventitia Ureteric orifices Trigone of bladder Bladder neck Internal urethral sphincter Prostate Prostatic urethra Membranous urethra External urethral sphincter Urogenital diaphragm Spongy urethra Erectile tissue of penis (a) Male. The long male urethra has three regions: prostatic, membranous, and spongy. External urethral orifice Structure of the Urinary Bladder and Urethra Figure 24.14

48. Peritoneum Ureter Rugae Detrusor muscle Ureteric orifices Bladder neck Internal urethral sphincter Trigone External urethral sphincter Urogenital diaphragm Urethra External urethral orifice (b) Female Structure of the Urinary Bladder and Urethra Figure 24.14

49. Urethra • Epithelium of urethra • Transitional epithelium • At the proximal end (near the bladder) • Stratified and pseudostratified columnar—mid urethra (in males) • Stratified squamous epithelium • At the distal end (near the urethral opening)

50. Urethra • Internal urethral sphincter • Involuntary smooth muscle • External urethral sphincter • Voluntarily inhibits urination • Relaxes when one urinates