1. Chapter 9 The Urinary System
Copyright 2010, John Wiley & Sons, Inc.

2. Copyright 2010, John Wiley & Sons, Inc.
Urinary System
Two kidneys and two ureters
Urinary bladder & urethra
Effector organ for
Regulation of Plasma ion composition
Regulation of Body water Volume (BP)
Regulation of blood pH (with lung)
Production of Hormones
Excretion of waste
Copyright 2010, John Wiley & Sons, Inc.

3. Copyright 2010, John Wiley & Sons, Inc.
Urinary System
Copyright 2010, John Wiley & Sons, Inc.

4. Copyright 2010, John Wiley & Sons, Inc.
Kidney
Divided into cortex –outer portion
Medulla- inner portion
Contain renal pyramids & renal columns
Urine goes into renal pelvis
Edges are made of major & minor calyces
Then out ureter
Copyright 2010, John Wiley & Sons, Inc.

5. Copyright 2010, John Wiley & Sons, Inc.
Kidney
Copyright 2010, John Wiley & Sons, Inc.

6. Copyright 2010, John Wiley & Sons, Inc.
Renal Blood Supply
20-25% resting CO goes through kidneys
 L. & R. renal arteries then
Segmental  interlobar  arcuate  interlobular
 afferent arterioles
 glomerulus (capillary network)
 efferent arterioles
 peritubular capillaries  veins
   renal vein
Capillaris Units –nephrons grouped at pyramids
Copyright 2010, John Wiley & Sons, Inc.

7. Copyright 2010, John Wiley & Sons, Inc.
Renal Blood Supply
Copyright 2010, John Wiley & Sons, Inc.

8. Copyright 2010, John Wiley & Sons, Inc.
Renal Blood Supply
Copyright 2010, John Wiley & Sons, Inc.

9. Copyright 2010, John Wiley & Sons, Inc.
Nephron
Unit of renal function: corpuscle & tubule
Corpuscle: forms filtrate
Glomerulus & Glomerular capsule (cortex)
Proximal convoluted tubule (cortex) 
Descending Loop of Henle (into medulla)
ascending Loop of Henle (into medulla) 
Distal convoluted tubule (cortex) 
Collecting duct minor calyx
Copyright 2010, John Wiley & Sons, Inc.

10. Copyright 2010, John Wiley & Sons, Inc.
Nephron
Copyright 2010, John Wiley & Sons, Inc.

11. Copyright 2010, John Wiley & Sons, Inc.
Basic Operation
Glomerular filtration-filter plasma
Tubular reabsorption
Reabsorb needed compounds & water from filtrate
Tubular Secretion
Secrete some materials into filtrate
Copyright 2010, John Wiley & Sons, Inc.

12. Glomerular Filtration
Two layers of capsule surround glomerulus
Between is capsular space
Podocytes support capillary epithelium
Form filtration membrane
Permeable to water & solute
but not most proteins & blood cells
Copyright 2010, John Wiley & Sons, Inc.

13. Copyright 2010, John Wiley & Sons, Inc.
Filtration Pressure
Blood pressure for filtration
Opposed by colloid osmotic pressure and capsular pressure
Efferent and afferent arteriole diameters adjust to maintain a net filtration pressure
Even with small changes in blood pressure
Copyright 2010, John Wiley & Sons, Inc.

14. Glomerular Filtration Rate
= GFR ml/min
Determines net reabsorption because it determines filtrate flow
ANP(Atrial natriuretic peptide) increases GFR
Responds to increased blood volume
Sympathetic stimulation  vasoconstriction  decreased GFR
 Urine production
a peptide hormone secreted by the myocytes cardiac atria that in pharmacological doses promotes salt and water excretion and lowers blood pressure
Copyright 2010, John Wiley & Sons, Inc.

15. Glomerular Filtration
Copyright 2010, John Wiley & Sons, Inc.

16. Copyright 2010, John Wiley & Sons, Inc.
Tubular Reabsorption
Proximal tubule
~65% Na+ & H2O
Normally 100% nutrients
~100% HCO3- (depends on blood pH)
Active transport of solutes
Osmosis moves water
Cells distal to proximal tubule fine tune reabsorption under control
Copyright 2010, John Wiley & Sons, Inc.

17. Copyright 2010, John Wiley & Sons, Inc.
Tubular Secretion
Takes place all along tubule
Major substances : H+, K+, ammonia, urea, creatine, drugs like penicillin
Helps regulate plasma pH
Diet is acid  urine is typically acidic
Copyright 2010, John Wiley & Sons, Inc.

18. Copyright 2010, John Wiley & Sons, Inc.
Urine Route
Collecting ducts to calyces
Calyces to ureter
Ureter to bladder
Bladder to urethra
Copyright 2010, John Wiley & Sons, Inc.

19. Filtration, Reabsorption, Secretion
Copyright 2010, John Wiley & Sons, Inc.

20. Copyright 2010, John Wiley & Sons, Inc.
Hormonal Regulation
Angiotensin II & aldosterone
Angiotensin II- stimulates NaCl in proximal tube
Aldosterone- increases Na+ reabsorption & K+ secretion in DCT & CD
More ions reabsorbed more water
ANP-increases GFR & inhibits aldosterone action less Na+ reabsorbed
ADH- responds to increased concentration of solute in blood + fall in BP
Copyright 2010, John Wiley & Sons, Inc.

21. Copyright 2010, John Wiley & Sons, Inc.
Hormonal Regulation
ADH: important to body water balance
Increased concentration of solute in blood + fall in BP  ADH
With no ADH: DCT & CD walls are impermeable to water dilute urine
With ADH: water reabsorption occurs concentrated urine
Copyright 2010, John Wiley & Sons, Inc.

22. Copyright 2010, John Wiley & Sons, Inc.
Components of Urine
Urine = 1-2 l /day
95% water
+ urea, creatine, K+, ammonia, uric acid, Na+, Cl-, Mg2+, sulfate, phosphate & Ca2+
Depends on diet and state of health
See table 21.3
Creatine (/ˈkriːətiːn/ or /ˈkriːətɪn/) is a nitrogenous organic acid that occurs naturally in vertebrates and helps to supply energy to all cells in the body
Copyright 2010, John Wiley & Sons, Inc.

23. Regulation of Water Reabsorption
Copyright 2010, John Wiley & Sons, Inc.

24. Copyright 2010, John Wiley & Sons, Inc.
Urine Route
Collecting ducts calyces
Ureter
Lined with mucus & transitional epithelium
Pass under bladder
Full bladder prevents backflow
Bladder- directly in front of rectum
Can stretch ( ml)
Smaller in females because of uterus
Three layers of detrussor muscle
 Urethra- internal urethral sphincter
External urethral sphincter (voluntary)
Copyright 2010, John Wiley & Sons, Inc.

25. Copyright 2010, John Wiley & Sons, Inc.
Urine Route
Copyright 2010, John Wiley & Sons, Inc.

26. Micturition = Urination
Autonomic reflex- internal sphincter
Responds to stretch like rectum
Parasympathetic  detrusor muscle contraction
Conscious control-external sphincter
Copyright 2010, John Wiley & Sons, Inc.

27. Copyright 2010, John Wiley & Sons, Inc.
Aging
Kidneys shrink- decrease in capacity
Thirst decreases  dehydration
 urinary tract infections
Males: prostate enlargement frequent urination & slow flow
Females: more prone to leakage of external sphincter (incontinence)
Both: nocturia
Nocturia (derived from Latin nox, night, and Greek [τα] ούρα, urine), also called nycturia (Greek νυκτουρία), is the need to get up in the night to urinate,
Copyright 2010, John Wiley & Sons, Inc.

28. Fluid, Electrolyte and Acid-Base Balance
Copyright 2010, John Wiley & Sons, Inc.

29. Copyright 2010, John Wiley & Sons, Inc.
Fluid Compartments
Total body water = 55-60% of lean body mass
Remainder: solid parts of bone, muscles, tendons
Major compartments (3): ICF, IF, plasma
Intracellular fluid (ICF): inside cells= 2/3
Extracellular Fluid (ECF): outside cells = 1/3
Interstitial fluid (IF): 80% of ECF
Includes: lymph; cerebrospinal, synovial, pericardial, pleural and peritoneal fluids; fluid in eyes and ears
Blood plasma: 20% ECF
Copyright 2010, John Wiley & Sons, Inc.

30. Copyright 2010, John Wiley & Sons, Inc.
Fluid Compartments
Copyright 2010, John Wiley & Sons, Inc.

31. Barriers Between Compartments
Plasma membrane: between ECF and ICF
Blood vessel walls: between plasma and interstitial fluid
Fluid balance correct distribution of water & solutes
Water redistributes rapidly by osmosis
Thus fluid balance depends on solute (electrolyte) balance
Copyright 2010, John Wiley & Sons, Inc.

32. Copyright 2010, John Wiley & Sons, Inc.
Fluid Balance
Fluid balance requires
Appropriate total volume of body fluid
Appropriate distribution of water and solutes
Fluid balance depends on solute (electrolyte and nonelectrolyte) balance
Fluids and electrolytes are closely linked
Water redistributes rapidly by osmosis
Copyright 2010, John Wiley & Sons, Inc.

33. Fluid Balance Interactions Animations
Water and Fluid Flow
You must be connected to the internet to run this animation.
Copyright 2010, John Wiley & Sons, Inc.

34. Copyright 2010, John Wiley & Sons, Inc.
Water Gain and Loss
Gain: ingestion + metabolic reactions
Ingestion (food and drink): 2300 mL/day
Metabolism: 200 mL/day
Gain should = loss
Daily intake = daily output. Both 2500 mL/day
Loss: skin, lungs, kidneys, GI tract
Kidneys: ~1500 mL/day
Skin: sweat evaporates ~600 mL/day
Lungs: 300 mL/day; more if fever
GI tract: ~100 mL/day; more if diarrhea
Copyright 2010, John Wiley & Sons, Inc.

35. Copyright 2010, John Wiley & Sons, Inc.
Water Balance
Copyright 2010, John Wiley & Sons, Inc.

36. Copyright 2010, John Wiley & Sons, Inc.
Regulation of Gain
Thirst center in hypothalamus
~2% dehydration will cause  BP
Increase in body osmolality  dry mouth  thirst
Hormonal responses
High osmolality  hypothalamus releases ADH  water retention by kidneys
 BP  renin released from kidney  angiotensin II  aldosterone  water retention by kidneys
Sensation of thirst may be decreased, especially in elderly
Copyright 2010, John Wiley & Sons, Inc.

37. Copyright 2010, John Wiley & Sons, Inc.
Regulation of Gain
Copyright 2010, John Wiley & Sons, Inc.

38. Regulation of Salt and Water Loss
Urinary NaCl loss mainly determines body fluid volume
Na+ = main solute in ECF determining osmosis
Fluid intake varies so loss must vary also
ANP, angiotensin II and aldosterone regulate
ADH regulates water loss
Copyright 2010, John Wiley & Sons, Inc.

39. Regulation of Salt and Water Loss
Copyright 2010, John Wiley & Sons, Inc.

40. Copyright 2010, John Wiley & Sons, Inc.
Movement of Fluid
ICF and ECF are normally at the same osmolality
Water moves freely
 interstitial fluid osmolality  cell swelling and vice versa
Most often due to Na+ change
ADH responds rapidly: prevents significant cell change
Copyright 2010, John Wiley & Sons, Inc.

41. Electrolytes in Body Fluids
Functions of electrolytes
Confined to compartments; control osmosis
Help maintain acid-base balance
Carry electrical currents
Serve as cofactors for enzymes
Copyright 2010, John Wiley & Sons, Inc.

42. Electrolyte Distribution
Electrolyte content of ICF and ECF differ significantly
ICF: K+ major cation; protein, HPO42-: anions
ECF: Na+ major cation; Cl- major anion
Na+/K+ pump maintains the cation difference
The two ECF fluids are similar
Electrolytes in plasma similar to those in IF
One difference: plasma contains more protein than interstitial fluid (IF)
Colloid osmotic pressure (due largely to plasma proteins) “holds onto” fluid in capillaries
Copyright 2010, John Wiley & Sons, Inc.

43. Electrolyte Distribution
Copyright 2010, John Wiley & Sons, Inc.

44. Copyright 2010, John Wiley & Sons, Inc.
Other Electrolytes
K+ high in ICF, low in ECF
Regulated by aldosterone
Mg2+ and SO42- high in ICF, low in ECF
Ca2+ high in ECF, low in ICF
Regulated in plasma (PTH, calcitriol, and calcitonin)
Bones serve as Ca2+ reservoir
Copyright 2010, John Wiley & Sons, Inc.

45. Copyright 2010, John Wiley & Sons, Inc.
Acid- Base Balance
Input: diet, products of metabolism
Such as lactic acid, ketones
Output
Lungs: exhale CO2
Kidney: can eliminate H+ or HCO3-
Regulatory mechanisms
Buffers: fastest but incomplete
Respiratory responses: fast but incomplete
Renal responses: slowest but complete elimination
Copyright 2010, John Wiley & Sons, Inc.

46. Copyright 2010, John Wiley & Sons, Inc.
1: Buffer Systems
Protein in cells or plasma
Carboxyl and amino groups of amino acids
Hemoglobin (protein) in red blood cells
Carbonic acid-bicarbonate
Especially important in plasma
CO2 + H2O  H2CO3 ↔ HCO3- + H+
Phosphate
H2PO4-  H+ + HPO42-
HPO4 2 is a variation of phosphoric acid
Copyright 2010, John Wiley & Sons, Inc.

47. 2: Exhalation of Carbon Dioxide
H+ + HCO3- ↔ H2CO3 ↔ CO2 + H2O
Decrease of CO2 ↔ decrease of H+
Increase of CO2 ↔ increase of H+
Change of rate and depth of ventilation rapidly alters plasma pH
Negative feedback loop regulates
carbonic acid
Copyright 2010, John Wiley & Sons, Inc.

48. 2: Exhalation of Carbon Dioxide
Copyright 2010, John Wiley & Sons, Inc.

49. Copyright 2010, John Wiley & Sons, Inc.
3. Renal Responses
Kidney Excretion of H+
Slow but only way to actually eliminate acid or base
Secrete H+ and replace with HCO3-
Copyright 2010, John Wiley & Sons, Inc.

50. Copyright 2010, John Wiley & Sons, Inc.
Imbalances
Acidosis: arterial blood pH < 7.35
 Depresses CNS
Below pH 7.0 can be fatal
Alkalosis: arterial blood pH > 7.45
 Overexcitation of CNS
Muscle spasms, convulsions
Compensation
Respiratory or renal mechanisms
Respiratory very rapid; renal slower
Copyright 2010, John Wiley & Sons, Inc.

51. Copyright 2010, John Wiley & Sons, Inc.
Aging
Decrease in control of water and electrolyte balance can lead to pH problems
Decreases in respiratory and renal functioning
Decreased capacity to sweat
Copyright 2010, John Wiley & Sons, Inc.