1. © 2014 Pearson Education, Inc. The Urinary System

2. © 2014 Pearson Education, Inc. The Urinary System Important functions of the kidneys Maintain the chemical consistency of blood Filters 1 liter of blood every minute, but only 125 ml will enter the tubular system which will eventually form 1cc/minute of urine Send toxins, metabolic wastes, and excess water out of the body Main waste products are three nitrogenous compounds Urea Uric acid Creatinine

3. © 2014 Pearson Education, Inc. Organs of the Urinary System Kidneys – filter blood Ureters – transport urine from each kidney to  Urinary bladder – stores urine Urethra – expels urine from bladder outside of the body

4. © 2014 Pearson Education, Inc. Figure 24.1 Organs of the urinary system. Hepatic veins (cut) Esophagus (cut) Inferior vena cava Adrenal gland Aorta Iliac crest Renal artery Renal hilum Renal vein Kidney Ureter Urinary bladder Rectum (cut) Uterus Urethra

5. © 2014 Pearson Education, Inc. Location and External Anatomy of Kidneys Kidneys are red-brown in color Located retroperitoneally Behind the peritoneum Lateral to T 12 –L 3 vertebrae Average kidney is 12 cm tall, 6 cm wide, 3 cm thick Hilum Is the concave surface Vessels and nerves enter and exit

6. © 2014 Pearson Education, Inc. Location and External Anatomy of Kidneys Fibrous capsule Capsule of dense connective tissue surrounds the kidney Inhibits spread of infections Perirenal fat capsule External to renal capsule Renal fascia External to perirenal fat capsule Contains fat

7. © 2014 Pearson Education, Inc. Figure 24.2b Position of the kidneys abutting the posterior abdominal wall. 12th rib

8. © 2014 Pearson Education, Inc. Figure 24.2a Position of the kidneys abutting the posterior abdominal wall. Peritoneum Anterior Peritoneal cavity (organs removed) Renal vein Renal artery Posterior Aorta Inferior vena cava Renal fascia posterior Perirenal fat capsule Supportive tissue layers Fibrous capsule Body wall anterior

9. © 2014 Pearson Education, Inc. Figure 24.2c Position of the kidneys abutting the posterior abdominal wall. Left renal vein Left kidney Erector spinae muscle in posterior abdominal wall Jejunum Duodenum Liver Inferior vena cava Aorta Right kidney Vertebra L 1

10. © 2014 Pearson Education, Inc. Internal Gross Anatomy of the Kidneys Frontal section through the kidney Renal cortex Superficial region, granular appearance Renal medulla consists of Cone-shaped renal pyramids Renal pelvis Major calices Minor calices

11. © 2014 Pearson Education, Inc. Internal Gross Anatomy of the Kidneys Gross vasculature Renal arteries branch into segmental arteries Segmental arteries branch into interlobar arteries Arcuate arteries branch from interlobar arteries

12. © 2014 Pearson Education, Inc. Figure 24.3 Internal anatomy of the kidney. Renal hilum Renal cortex Renal medulla Renal pelvis Major calyx Papilla of pyramid Minor calyx Ureter Renal pyramid in renal medulla Renal column Fibrous capsule Diagrammatic view Photograph of right kidney, frontal section

13. © 2014 Pearson Education, Inc. Figure 24.4a Blood vessels of the kidney. 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 Frontal section, posterior view, illustrating major blood vessels

14. © 2014 Pearson Education, Inc. Figure 24.4b Blood vessels of the kidney. Path of blood flow through renal blood vessels Glomerulus (capillaries) Nephron-associated blood vessels Afferent glomerular arteriole Efferent glomerular arteriole Cortical radiate artery Peritubular capillaries and vasa recta Arcuate artery Interlobar artery Segmental artery Renal artery Aorta Inferior vena cava Renal vein Interlobar vein Arcuate vein Cortical radiate vein

15. © 2014 Pearson Education, Inc. Internal Gross Anatomy of the Kidneys Nerve supply—renal plexus A network of autonomic fibers An offshoot of the celiac plexus Supplied by sympathetic fibers from Lowest thoracic splanchnic nerve First lumbar splanchnic nerve

16. © 2014 Pearson Education, Inc. Microscopic Anatomy of the Kidneys Nephron is the functional unit of the kidney Over 1 million nephrons in each kidney

17. © 2014 Pearson Education, Inc. Mechanisms of Urine Production Filtration Filtrate of blood leaves kidney capillaries Resorption Most nutrients, water, and essential ions reclaimed Secretion Active process of removing undesirable molecules

18. © 2014 Pearson Education, Inc. Figure 24.5 Basic mechanisms of urine formation. Afferent glomerular arteriole Glomerular capillaries Efferent glomerular arteriole Glomerular capsule Renal tubule and collecting duct containing filtrate Peritubular capillary To cortical radiate vein Cortical radiate artery Urine Glomerular filtration Tubular resorption Tubular secretion Three major renal processes: 2 3 2 3 1 2 3 1 1 2 3

19. © 2014 Pearson Education, Inc. Nephron Structure Nephron is composed of Renal tubule Renal corpuscle

20. © 2014 Pearson Education, Inc. Nephron Structure 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

21. © 2014 Pearson Education, Inc. Filtration Membrane The filtration membrane Filter that lies between blood in the glomerulus and capsular space Consists of three layers 1.Fenestrated endothelium of the capillary 2.Filtration slits between foot processes of podocytes 3.Basement membrane

22. © 2014 Pearson Education, Inc. Filtration Membrane Basement membrane and slit diaphragm Hold back most proteins Allow passage of Water Ions Glucose Amino acids Urea

23. © 2014 Pearson Education, Inc. Figure 24.6a Renal corpuscle and the filtration membrane. Efferent glomerular arteriole Afferent glomerular arteriole Glomerular capsular space Proximal convoluted tubule Parietal layer of glomerular capsule Glomerular capillary covered by podocyte- containing visceral layer of glomerular capsule Renal corpuscle

24. © 2014 Pearson Education, Inc. Figure 24.6b Renal corpuscle and the filtration membrane. Podocyte cell body Fenestrations (pores) Glomerular capillary endothelium (podocyte covering and basement membrane removed) Cytoplasmic extensions of podocytes Filtration slits Foot processes of podocyte Glomerular capillary surrounded by podocytes

25. © 2014 Pearson Education, Inc. Figure 24.6d Renal corpuscle and the filtration membrane. Capillary Capillary endothelium Basement membrane Foot processes of podocyte of glomerular capsule Filtration slit Slit diaphragm Filtration membrane Plasma Filtrate in capsular space Foot processes of podocyte Fenestration (pore) Three parts of the filtration membrane

26. © 2014 Pearson Education, Inc. Renal Tubule Filtrate proceeds to renal tubules from glomerulus Proximal convoluted tubule Nephron loop Descending limb Descending thin limb (DTL) Ascending thin limb (ATL) Thick ascending limb (TAL) Distal convoluted tubule

27. © 2014 Pearson Education, Inc. Renal Tubule Collecting ducts Receive urine from several nephrons Play an important role in conserving body fluids Posterior pituitary secretes ADH Increases permeability of collecting ducts and distal convoluted tubules to water

28. © 2014 Pearson Education, Inc. Figure 24.7 Location and structure of nephrons. Renal cortex Renal medulla Renal pelvis Ureter Kidney Renal corpuscle Glomerular capsule Glomerulus Distal convoluted tubule Proximal convoluted tubule Cortex Medulla Thick limb Thin limb Glomerular capsule: visceral layer Proximal convoluted tubule cells Fenestrated endothelium of the glomerulus MicrovilliMitochondria Highly infolded plasma membrane Podocyte Basement membrane Distal convoluted tubule cells Nephron loop (thin-limb) cells Principal cell Intercalated cell Collecting duct cells Glomerular capsule: parietal layer Nephron loop Descending limb Ascending limb Collecting duct

29. © 2014 Pearson Education, Inc. Classes of Nephron Cortical nephrons 85% of nephrons Juxtamedullary nephrons 15% of nephrons Contribute to kidney’s ability to concentrate urine

30. © 2014 Pearson Education, Inc. Figure 24.9 Cortical and juxtamedullary nephrons and their blood vessels. Kidney Nephron loop Arcuate artery Arcuate vein Descending limb of nephron loop Ascending limb of nephron loop Peritubular capillaries Vasa recta Cortex- medulla junction Efferent arteriole Afferent arteriole Efferent arteriole Distal convoluted tubule Collecting duct Cortical radiate vein Cortical radiate artery Juxtamedullary nephron Long nephron loop Glomerulus closer to the cortex-medulla junction Efferent arteriole supplies vasa recta Cortical nephron Short nephron loop Glomerulus further from the cortex-medulla junction Efferent arteriole supplies peritubular capillaries Glomerulus (capillaries) Renal corpuscle Glomerular capsule Proximal convoluted tubule Peritubular capillary bed Glomerulus Afferent arteriole Efferent arteriole

31. © 2014 Pearson Education, Inc. Blood Vessels Associated with Nephrons Nephrons associate closely with two capillary beds Glomeruli Peritubular capillaries in cortical nephrons or vasa recta in juxtamedullary nephrons

32. © 2014 Pearson Education, Inc. Blood Vessels Associated with Nephrons Glomeruli Produce filtrate that becomes urine Fed and drained by arterioles Afferent glomerular arteriole Efferent glomerular arteriole

33. © 2014 Pearson Education, Inc. Blood Vessels Associated with Nephrons Glomeruli Efferent arteriole has a smaller diameter than afferent arteriole Generates approximately 1 liter of filtrate every 8 minutes 99% of filtrate is resorbed by tubules

34. © 2014 Pearson Education, Inc. Blood Vessels Associated with Nephrons Peritubular capillaries Arise from the efferent arterioles draining cortical glomeruli Are adapted for absorption Low-pressure, porous capillaries

35. © 2014 Pearson Education, Inc. 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

36. © 2014 Pearson Education, Inc. Juxtaglomerular Complex Juxtaglomerular complex Functions in regulating blood pressure An area of specialized contact between the terminal end of the ascending loop and afferent arteriole Granular cells—modified smooth muscle cells with secretory granules (similar to endocrine) Contain the hormone renin Renin—secreted in response to falling blood pressure in afferent arteriole

37. © 2014 Pearson Education, Inc. Juxtaglomerular Complex 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

38. © 2014 Pearson Education, Inc. Juxtaglomerular Complex Mesangial cells Located around capillaries of the glomerulus and constrict to control blood flow They also detect glucose levels by sending processes (membrane extensions) into the lumen of the capillary Extraglomerular mesangial cells Interact with macula densa and granular cells Help regulate blood pressure

39. © 2014 Pearson Education, Inc. Figure 24.10 Juxtaglomerular complex. Glomerular capsule Efferent glomerular arteriole Afferent glomerular arteriole Glomerulus Efferent glomerular arteriole Capsular space Parietal layer of glomerular capsule Foot processes of podocytes Podocyte cell body (visceral layer) Red blood cell Proximal tubule cell Lumens of glomerular capillaries Endothelial cell of glomerular capillary Mesangial cells between capillaries Renal corpuscle Juxtaglomerular complex Macula densa cells of the ascending limb of nephron loop Extraglomerular mesangial cells Granular cells Afferent glomerular arteriole Juxtaglomerular complex

40. © 2014 Pearson Education, Inc. 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

41. © 2014 Pearson Education, Inc. Figure 24.11 Microscopic structure of the ureter, cross section (12  ). Lumen Mucosa Adventitia Transitional epithelium Lamina propria Muscularis Longitudinal layer Circular layer

42. © 2014 Pearson Education, Inc. 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. © 2014 Pearson Education, Inc. Urinary Bladder Urachus—closed remnant of the allantois of umbilical cord – it looks like a raised ridge outside of the bladder Prostate In males Lies directly inferior to the bladder Surrounds the urethra

44. © 2014 Pearson Education, Inc. Figure 24.12 Position of the urinary bladder in reference to the pelvic organs. Ureter not illustrated in (b) Uterus Urinary bladder Ductus deferens Pubic symphysis Urethra Urachus Sagittal section through male pelvis, urinary bladder shown in lateral view Sagittal section through female pelvis Prostate Vagina

45. © 2014 Pearson Education, Inc. Urinary Bladder Urinary bladder is composed of three layers 1.Mucosa—transitional epithelium 2.Thick muscular layer—detrusor 3.Fibrous adventitia

46. © 2014 Pearson Education, Inc. Figure 24.13 Histology of the bladder. Lumen of the bladder Transitional epithelium Lamina propria Muscular layer (detrusor) Micrograph of the bladder wall (25  ) Epithelium lining the lumen of the bladder (285  ) Transitional epithelium Lamina propria Basement membrane

47. © 2014 Pearson Education, Inc. Figure 24.14a Structure of the urinary bladder and urethra. Peritoneum Ureter Rugae Detrusor Adventitia Ureteric orifices Trigone of bladder Bladder neck Internal urethral sphincter Prostate Prostatic urethra Spongy urethra Erectile tissue of penis External urethral orifice Male. The long male urethra has three regions: prostatic, intermediate part, and spongy. Intermediate part of urethra External urethral sphincter Urogenital diaphragm

48. © 2014 Pearson Education, Inc. Figure 24.14b Structure of the urinary bladder and urethra. Peritoneum Ureter Rugae Detrusor Ureteric orifices Bladder neck Internal urethral sphincter External urethral sphincter Urogenital diaphragm Urethra Female Trigone External urethral orifice

49. © 2014 Pearson Education, Inc. 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. © 2014 Pearson Education, Inc. Urethra Internal urethral sphincter Involuntary smooth muscle External urethral sphincter Voluntarily inhibits urination Relaxes when one urinates

51. © 2014 Pearson Education, Inc. Urethra In females Length of 3–4 cm In males—20 cm in length; three named regions Prostatic urethra Passes through the prostate gland Intermediate part of urethra Through the urogenital diaphragm Spongy (penile) urethra Passes through the length of the penis

52. © 2014 Pearson Education, Inc. Figure 24.15 Micturition. Pons Pontine micturition center Lower thoracic or upper lumbar spinal cord ()() ()() Inferior hypogastric ganglion Hypogastric nerve Bladder Pelvic nerves 1 4 2 3 5 Pelvic splanchnic nerves External urethral sphincter Internal urethral sphincter Visceral afferent Sympathetic Somatic efferent Parasympathetic Interneuron ()() ()() Visceral afferent impulses from stretch receptors in the bladder wall are carried to the spinal cord and then, via ascending tracts, to the pontine micturition center. Integration in pontine micturition center initiates the micturition response. Descending pathways carry impulses to motor neurons in the spinal cord. Parasympathetic efferents stimulate contraction of the detrusor and open the internal urethral sphincter. 1 2 3 Sacral spinal cord Sympathetic efferents to the bladder are inhibited. Somatic motor efferents to the external urethral sphincter are inhibited; the sphincter relaxes. Urine passes through the urethra; the bladder is emptied. 4 5

53. © 2014 Pearson Education, Inc. Disorders of the Urinary System Urinary tract infections More common in females Burning sensation during micturition Renal calculi Kidney stones Bladder cancer 3% of cancers—more common in men Kidney cancer Arises from epithelial cells of uriniferous tubules

54. © 2014 Pearson Education, Inc. The Urinary System Throughout Life Kidney and bladder function declines with advancing age Nephrons decrease in size and number Tubules are less efficient at secretion and resorption Filtration declines Recognition of desire to urinate is delayed Loss of muscle tone in the bladder