1. Chapter 20
The Urinary System

2. Kidney Physiology and Organs of the Urinary Tract
Lesson 20.1
Kidney Physiology and Organs of the Urinary Tract
Describe the location and structure of the kidneys and explain how they act as vital organs in maintaining homeostasis. Also name the parts of a nephron and describe the role each component plays in the balancing of blood and formation of urine.
Identify the other major organs of the urinary system and give the primary function of each.

3. Kidneys Location of the kidneys Gross structure of the kidney
Kidneys lie under back muscles, behind parietal peritoneum, just above waistline
Right kidney is usually a little lower than left
Gross structure of the kidney
Renal cortex—outer layer of kidney
Renal medulla—inner portion of kidney

4. Urinary System A, Anterior view of urinary organs.
B, Surface markings of the kidneys, eleventh and twelfth ribs, spinous processes of L1 to L4, and lower edge of pleura viewed from behind.

5. Urinary System

6. Internal Structure of the Kidney

7. Gross Structure of the Kidney
Renal pyramids—triangular divisions of medulla
Renal columns—cortical tissue that dips down between renal pyramids
Renal papilla—narrow, innermost end of pyramid
Renal pelvis—expansion of upper end of ureter; lies inside kidney
Renal calyces—divisions of renal pelvis

8. Microscopic Structure of the Kidney
Interior of kidney composed of more than 1 million microscopic nephron units
Unique shape of nephron well suited to function
Principle components are renal corpuscle and renal tubule

9. Renal Corpuscle Bowman capsule— cup-shaped top of nephron
Cortical nephrons— 85% of total; located mostly in renal cortex
Juxtamedullary nephrons—have important role in concentrating urine; located near junction between cortex and medullary layers
Bowman capsule— cup-shaped top of nephron
Glomerulus— network of blood capillaries surrounded by Bowman capsule

10. Renal Tubule Proximal convoluted tubule (PCT)—first segment
Henle loop—extension of proximal tubule; consists of descending limb, loop, and ascending limb
Distal convoluted tubule (DCT)—extension of ascending limb of Henle loop
Collecting duct (CD)—straight extension of distal tubule

11. Location of Nephrons

12. Courtesy Andrew P. Evan, Indiana University School of Medicine.
Renal Corpuscle
Courtesy Andrew P. Evan, Indiana University School of Medicine.

13. The Nephron Unit

14. Kidney Function Excrete toxins and nitrogenous wastes
Regulate levels of many chemicals in blood
Maintain water balance
Help regulate blood pressure and volume
Regulate red blood cell production by secreting erythropoietin (EPO)

15. Ureters
Structure
Narrow long tubes with expanded upper end (renal pelvis) located inside kidney
Lined with mucous membrane and muscular layer
Function—drain urine from renal pelvis to urinary bladder
Urinalysis
Examination of the physical, chemical, and microscopic characteristics of urine
May help determine the presence and nature of a pathological condition

16. Ureter Cross Section

17. Urinary Bladder (male)
Structure
Elastic muscular organ, capable of great expansion
Lined with mucous membrane arranged in rugae, like stomach mucosa
Functions
Storage of urine before voiding
Voiding

18. Urethra Structure Functions
Narrow tube from urinary bladder to exterior
Lined with mucous membrane
Opening of urethra to the exterior called urinary meatus
Functions
Passage of urine from bladder to exterior of the body
Passage of male reproductive fluid (semen) from the body

19. Micturition, Renal Physiology, and Disorders of the Urinary Tract
Lesson 20.2
Micturition, Renal Physiology, and Disorders of the Urinary Tract
Describe the process of micturition and the control problems that frequently occur with this process.
Explain the importance of filtration, tubular reabsorption, and tubular secretion in renal physiology.
Discuss the mechanisms that control urine volume.
Explain the purpose and importance of urinalysis.
List the major renal and urinary disorders and explain the mechanism of each.

20. Micturition
Passage of urine from body (also called urination or voiding)
Regulatory sphincters
Internal urethral sphincter (involuntary)
External urethral sphincter (voluntary)
Bladder wall permits storage of urine with little increase in pressure

21. Emptying Reflex Initiated by stretch reflex in bladder wall
Bladder wall contracts
Internal sphincter relaxes
External sphincter relaxes and urination occurs
Enuresis—involuntary urination in young child

22. Retention and Suppression
Urinary retention—urine produced but not voided
Urinary suppression—no urine produced but bladder is normal

23. Urinary Incontinence Urine is voided involuntarily
Urge incontinence—associated with smooth muscle over activity in the bladder wall
Stress incontinence—associated with weakened pelvic floor muscles
Overflow incontinence—associated with urinary retention and over distended bladder
Reflex incontinence occurs in absence of any sensory warning or awareness—common following a stroke or spinal cord injury
Nocturnal enuresis—nighttime bed wetting
Neurogenic bladder—periodic but unpredictable voiding; related to paralysis or abnormal function of the bladder

24. Formation of Urine Filtration Goes on continuously in renal corpuscles
Glomerular blood pressure causes water and dissolved substances to filter out of glomeruli into the Bowman capsule
Normal glomerular filtration rate 125 ml per minute

25. Reabsorption
Movement of substances out of renal tubules into blood in peritubular capillaries
Water, nutrients, and ions are reabsorbed
Water is reabsorbed by osmosis from proximal tubules
Sodium reabsorption occurs in the Henle loop using countercurrent flow

26. Reabsorption
Countercurrent mechanisms keep the medulla hypertonic so that the kidney can reabsorb extra water
Amount of sodium reabsorbed depends on diet
More sodium intake = less sodium reabsorbed, more sodium excreted in urine
Chloride ions passively move into blood, due to negative charge

27. Reabsorption of Ions and Water

28. Reabsorption of Glucose
Glucose is reabsorbed from the proximal tubules back into the blood for use as energy
If there is too much glucose, like in diabetes mellitus, blood concentration can reach a level called the renal threshold
Filtrate contains more glucose than can be reabsorbed
Glucose is left behind in the urine and is a sign of diabetes

29. Reabsorption of Glucose

30. Secretion
Movement of substances into urine in the distal and collecting ducts from blood in peritubular capillaries
Hydrogen ions, potassium ions, urea, uric acid, creatinine, and certain drugs are secreted by active transport
Ammonia is secreted by diffusion

31. Formation of Urine

32. Control of Urine Volume
ADH—secreted by posterior pituitary; promotes water reabsorption by collecting ducts; reduces urine volume, a salt- and water-retaining hormone
Aldosterone—secreted by adrenal gland, triggered by RAAS process; promotes sodium and water reabsorption in nephron; reduces urine volume
ANH—one of the peptide hormones (ANPs) secreted by atrial cells in heart; promotes loss of sodium and water into kidney tubules; increases urine volume

33. Urine concentration 33

34. Renin-Angiotensis-Aldosterone System (RAAS)
Affects both the blood pressure and blood plasma volume
Renin (secreted by the JG apparatus) converts angiotensin to angiotensin l
ACE converts angiotensin 1 to angiotensin 11
Angiotensin 11 affects the blood pressure by vasoconstriction of arterioles
Angiotensin 11 affects the blood volume by promoting the adrenal cortex to secrete aldosterone to promote water reabsorption by the kidney

35. Abnormal Amounts of Urine
Normal urine- the nephrons make about liters of filtrate are made a day but normal urine out put is about liters a day (1ml/kg/hr)
Anuria—absence of urine
Oliguria—scant amounts of urine (less than 500ml a day)
Polyuria—an unusually large amount of urine (over 2.5 liters per day)
Dysuria— Painful urination (burning)

36. Urinalysis
Definition—the physical, chemical, and microscopic examination of urine
Color, turbidity, odor, and specific gravity are used as diagnostic clues
Chemical analysis provides pH, urea concentration, or presence of abnormal chemicals, like proteins or glucose
After being centrifuged, so heavier cells are separated, those cells can be examined for tell-tale "casts," or small particles deposited in the renal tubules

37. Elimination of Urine The Urine
95% water, 5% dissolved solids and gases
pH averages 6.0
Specific gravity measures amount of dissolved substances
Normal range (very dilute) to (very concentrated)

38. Elimination of Urine (cont.)
Normal constituents of urine
Nitrogenous waste products
Urea
Uric acid
Creatinine
Electrolytes
Sodium and chloride ions
Sulfates
Phosphates
Pigments (e.g., urochrome, bile pigments, food pigments)

39. Elimination of Urine (cont.)
Abnormal constituents of urine
Glucose
Albumin
Blood
Ketones
White blood cells
Casts

40. Renal and Urinary Disorders
Obstructive disorders interfere with normal urine flow, possibly causing urine to back up and cause hydronephrosis or other kidney damage
Hydronephrosis—enlargement of renal pelvis and calyces caused by blockage of urine flow
Renal calculi (kidney stones) —crystallized mineral chunks in renal pelvis or calyces; may block ureters, causing intense pain called renal colic
Tumors—renal cell carcinoma (kidney cancer) and bladder cancer; often characterized by hematuria (blood in the urine)

41. Kidney stones 41

42. Imagine of Bladder Cancer

43. Ileal conduit 43

44. Hydronephrosis

45. Renal Calculi

46. Urinary Tract Infections (UTIs)
Often caused by gram-negative bacteria
Urethritis—inflammation of the urethra
Cystitis—inflammation or infection of the urinary bladder
Pyelonephritis—inflammation of renal pelvis and connective tissues of the kidney; may be acute (infectious) or chronic (autoimmune)

47. Glomerular Disorders
Result from damage to the glomerular-capsular membrane of the renal corpuscles
Nephrotic syndrome accompanies many glomerular disorders
Proteinuria—protein in the urine
Hypoalbuminemia—low plasma protein (albumin) level; caused by loss of proteins to urine
Edema—tissue swelling caused by loss of water from plasma as a result of hypoalbuminemia

48. Glomerular Disorders, Cont'd.
Acute glomerulonephritis caused by delayed immune response to a streptococcal infection
Chronic glomerulonephritis is a slow inflammatory condition caused by immune mechanisms and often leads to renal failure

49. Kidney Failure
Kidney failure, or renal failure, occurs when the kidney fails to function
Acute renal failure—abrupt reduction in kidney function that is usually reversible
Chronic renal failure—slow, progressive loss of nephrons caused by a variety of underlying diseases
Polycystic kidney disease (PKD)—numerous fluid-filled cysts destroy kidney tissue as they grow; hereditary

50. Polycystic Kidney Disease

51. Progression of Kidney Failure
Stage 1—early in this disorder, healthy nephrons often compensate for the loss of damaged nephrons
Stage 2—often called renal insufficiency; loss of kidney function ultimately results in uremia (high BUN levels) and its life-threatening consequences
Stage 3—called uremia or uremic syndrome; complete kidney failure results in death unless a new kidney is transplanted or an artificial kidney substitute is used

52. Three Stages of Chronic Renal Failure

53. Disorders of the Urinary System
Renal Failure (cont.)
Renal dialysis and kidney transplantation
Dialysis
Hemodialysis
Peritoneal dialysis
Kidney transplantation
Final option for treatment of kidney failure

54. Dialysis 54