Kidney Physiology II

1
Kidney Physiology II

• YU Yanqin (???),
• Zhejiang University, School of Medicine

2
Urinary concentration and dilution

• Concentrative urine???
• Osmolality of urine gt plasma osmolality
  (300mOsm/L H2O)
• Diluted urine???
• Osmolality of urine lt plasma osmolality

3
Formation of Diluted Urine

• Isosmotic reabsorption of water at proximal
  tubule
• Impermeable of water at thick ascending limb
• ?ADH? ?Reabsorption of water at distal tubule and
  collecting duct ? Diluted urine

4
Formation of Concentrative Urine

• ?ADH? ? Reabsorption of water at distal tubule
  and collecting duct ? Concentrative Urine
• ADH---key element of urinary concentration and
  dilution

What is the drive force of water reabsorption at
distal tubule and collecting duct ?
5
The Osmotic Gradient of the Renal Medulla
6
Formation of Osmotic Gradient of the Renal Medulla
Permeability of the Tubular System
7
Permeability of the Tubular System
H2O NaCl Urea
Thin descending limb _ _
Thick ascending limb _ Actively transport _
Thin ascending limb _
Distal tubule ADH Actively transport _
Cortical collecting duct ADH Actively transport _
Inner medullary collecting duct ADH Actively transport
8
Formation of Osmotic Gradient of the Renal Medulla
A
C
B

• The countercurrent theory
• 1. Countercurrent multiplication????

9
(No Transcript)
10
1.Countercurrent multiplication
11
Establishing of Osmotic Gradient of the Renal
Medulla

• ? Outer medulla reabsorption of NaCl at thick
  ascending limb ? hyperosmolality
• Inner medulla
• 1) urea recycling
• 2) reabsorption of NaCl at thin ascending limb?
  hyperosmolality

12
Urinary concentration and dilution.swf
13
The Countercurrent Theory

• 2. Countercurrent exchange ????

14
2. Countercurrent exchange
15
Maintenance of the Osmotic Gradient in the Medulla
Vasa recta
16
Maintenance of the Osmotic Gradient in the Medulla

• The vasa recta Countercurrent exchanger

17
SummaryFormation of Concentrated or Dilute
Urine

• In the presence of ADH
• Collecting duct permeable to water ?
  excretion of a concentrated urine
• In the absence of ADH
• Collecting duct impermeable to water ?
  excretion of a diluted urine

18
Factors that affect the concentration and
dilution of the urine

• 1) Damage of renal medulla
• Resulting in an impairment of the
  concentrating ability
• 2) Loop diuretics
• such as frusemide, inhibiting the Na/ K/
  2Cl- co-transport system in the thick ascending
  limb

19
Factors that affect the concentration and
dilution of the urine

• 3) Lack of urea in the body
• such as malnutrition, reducing the osmotic
  gradient established in the renal medulla
• 4) Increased velocity of blood flow in the vasa
  recta
• carrying away amount of NaCl ? reducing the
  osmotic gradient in the medulla

20
Humoral Control of Renal Functions

• Antidiuretic hormone (?????,ADH)
• Synthesis in supraoptic and paraventricular
  nuclei(???????)
• Release from the posterior pituitary

21
Mechanism of ADH Antidiuresis

• Increasing water permeability of collecting duct
• Insertion of aquaporins??? in apical membrane

22
Diabetes Insipidous???
23
Regulation of ADH Release

• Plasma osmolality
• Plasma osmolality ? ?()hypothalamic
  osmoreceptors ? production and release of ADH ?
  ?urine ?
• Blood volume
• Blood volume ? ? ()baroreceptor reflex
  atrial stretch receptors ? ADH release ? ?urine
  ? ? Blood volume ?

24
Water diuresis ???

• Physiologic water diuresis is a response to water
  load
• Slightly decreased plasma osmolality (drinking
  bulk water)? ADH?? Increased urine flow until
  plasma osmolality increases

25
Humoral Control of Renal Functions

• Aldosterone ???
• Secreted by the glomerulosa ??? of the adrenal
  cortex
• To increase the reabsorption of Na in the distal
  tubule and early collecting duct, coupled to
  secretion of K

26
Mechanism of Aldosterone Action

• To increase number of Na channels
• To increase activity of Na pumps

27
Regulation of Aldosterone Secretion

• 1. Renin-Angiotensin System (??-???????)

28
Regulation of Aldosterone Secretion

• 2. Plasma concentrations of sodium and potassium
• K ? ? Aldosterone secretion ??
• Na ? ? Aldosterone secretion ?
• 3. Adrenocorticotrophin (????????,ACTH)
• Necessary for Aldosterone secretion, but
  little effect in controlling the secretion rate

29
Ingesting too much potassium stimulates aldosteron
e secretion from the adrenal cortex aldosterone
increases sodium reabsorption at the expense
of increased potassium secretion. Also shown
here is an indication that more potassium in the
filtrate leads to greater potassium excretion in
the urine.
30
Decreased blood volume and ingesting too
much potassium both stimulate aldosterone
secretion from the adrenal cortex aldosterone
increases sodium reabsorption at the expense
of increased potassium secretion.
31
Humoral Control of Renal Functions

• Atrial natriuretic peptides (?????,ANP)
• Synthesis in the cardiac atrial muscle cell
• Leading to increased excretion of salt water
• Its mechanism

32
Regulation of ANP Release

• Stretch of the atrium
• Extracellular fluid volume and blood volume
• Plasma sodium concentration

33
Renal Clearance?????

• Defined as the volume of plasma required to
  supply the amount of a substance X to be excreted
  in urine per unit time

34
Use of Clearance Methods to Quantify Kidney
Function

• UxV GF R E
• GGFR
• FFiltration concentration

35
Use of Clearance Methods to Quantify Kidney
Function

• Inulin clearance as a measure of glomerular
  filtration

36
Use of Clearance Methods to Quantify Kidney
Function

• Clearance of para-aminohippuric acid as a measure
  of renal plasma flow
• Para-aminohippuric acid (PAH) freely through the
  glomerulus
• Almost all the remaining PAH in the plasma is
  secreted into the tubule

37
Use of Clearance Methods to Quantify Kidney
Function

• Renal clearance as a calculation of tubular
  reabsorption or secretion
• By comparison of inulin clearance with
  clearances of different solutes
• ? Clt125ml/min-----has reabsorption
• ? Cgt125ml/min-----has secretion

38
Micturition ??

• Innervation of the bladder and urethra

39
Micturition
40
Micturition

• Innervation of the bladder and urethra
• 1) Parasympathetic pelvic nerves???
• To cause contraction of the detrusor
  muscle of the bladder and opening of the internal
  sphincter
• 2) Sympathetic hypogastric nerves????
• To induce closure of the internal
  sphincter
• 3) Somatic pudendal nerves????
• To induce contraction of the external
  sphincter

41
Micturition Reflex

• Micturition occurs when the intravesicular
  pressure reaches 70 cmH2O via a reflex action

Pdet, cm H2O
50 0
0 volume 300 ml
42
Higher Control of Micturition

• Inhibitory and facilitatory centers in the
  cerebral cortex and pons

43
Pathways of Micturition Reflex
44
Micturition reflex

• ??????400500ml??????????()?????????????????
  ?????????????????????????????,????????????????????
  ????(???)?????

45
Micturition reflex
46

• Enuresis??

47
Summary

• Terms
• Water diuresis
• Renal clearance
• List the factors that affect the concentration
  and dilution of the urine

48
General Question

• What are the change of urine and its mechanism
  when one sweats a great deal and drinks little
  water?

49
Intensive Reading

• Textbook of Medical Physiology (Guyton Hall)
• Page 309
• Page 313-324
• Page 366-368

50
Questions

• 1.???????????????????????
• 2.??????????,?????????????
• 3.3Kg?????,??????20?????5ml,???????????????
• 4.??????????,?????????????????????
• 5.????????????????????????
• 6.????????????????????
• 7.??????????????NaCl???????????
• 8.????????????????????
• 9.????????????????

51
???????????????????????

• 1.?????????????????????????,?????????
• ??????????????,??????????,???????????,??????,?????
  ???????????,???????,???????
• ??????????,????????????????????,??ADH????????,????
  ????????????,?????,???????????????,????,????????,
  ???????????????????????

52
??????????,?????????????

• 2.??????,??????????,???????,???????
• ????(1)??????????,?????????????????,????????????(
  2)?????,??????????????????????????????????????????
  ??????????ADH??,???ADH????,?????????????????,?????
  ?,????,???????
• ??,????,?????????????,??????????,??????,?????

53
3Kg?????,??????20?????5ml,???????????????

• 3.????,???????????3Kg??,????240ml,?????????5ml20
  1(?),???????500mg/100ml,???????,?????????????????
  ????,???????,???????,????,????,????????????

54
??????????,?????????????????????

• 4.?????,??????,???????80-180mmHg(10.7-24Kpa)???,??
  ???????,????????,???????????????????????,????,????
  -???????????,??????,?????????????,??????,????????,
  ??????????,????,??????????,?????????,?????????????
  ??????????????

55
????????????????????????

• 5.??????????????????????????,?????????????,???????
  ?,???????,??????????????
• ??????????,?????????,??ADH,????????????????,??????
  ??????????
• ?????????????,??????,?Na?K?Ca2?,?Na/
  K???,???????,???Na?K????,?Na/ K?????Na/
  K???,????,???Na?K?????????????Ca2???????
• ?????,??H?????????????,?HCO3-???????H-
  Na????,??H????NH3????,NH4Cl????????H??,??????
  ?????????,?????pH???????????

56
6.????????????????????

• 6.????????????????????,??????????,????????????????
  ???,?????????????????,?????????????????????,??????
  ??????????,???????????????????,??????????NaCl???,?
  ???????????????????????,????????????,?????????,???
  ???????????????????????

57
??????????????NaCl???????????

• 7.????????NaCl???????????????????H2O?NaCl?????????
  ???????????H2O??,?NaCl???????????NaCl?????,?????,
  ????????NaCl??????????????????????????????,????Na
  Cl,??????,???????????????????????,??????????H2O?
  ???,NaCl???????NaCl????,??????????,??????????????
  ????NaCl,????????,???NaCl????,????????????????????
  ?NaCl???????????

58
????????????????????

• 8.??????????????,????????80mmHg(10.7Kpa)?,????????
  
• (1)???????,??????,??????,??????,??????,?????
• (2)????,???????,????????????ADH??,????????????????
  ?,
• (3)????,??-?????-?????????,???????,????Na?K?????
  ???
• ??????????,??????

59
????????????????

• 9.?????????????????
• (1)??????????????????????????
• (2)???????????????????,????,???????????
• (3)???????????????????????,?????????????,?????????
  ???????????
• (4)???????????????,?????????,??????,??????,???????