Renal Physiology

1
Renal Physiology

• Jim Pierce
• Bi 145b
• Lecture 6, 2008-9

2
Renal Function

• We talked about
• Body Fluids
• Renal Blood Flow
• Glomerular Filtration
• Secretion and Absorption
• The Loop of Henle and Creating Gradients

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Renal Function

• Now well talk about
• Regulation of Body Volumes
• Acid Base Balance

4
Renal Physiology

• The Kidneys Plan
• Process large volumes for efficiency
• Reabsorb Volume
• Fix Osmolarity
• Adjust Acid-Base Balance
• Adjust Electrolytes

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Body Fluids
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Body Fluids

• When things are normal, we are
• EUVOLEMIC
• (good volume)
• Too much volume? Hypervolemic
• Too little volume? Hypovolemic

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Body Fluids

• These words refer to Body Volume
• TOTAL body sodium
• TOTAL body water
• As we will see, the bodys sensing mechanisms are
  in the vascular space.

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Kidney Plan

• So the first thing the kidney mustdecide is on
  Total Body Volume
• There are several different neurohormonal
  mechanisms to determine body volume

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Hormonal Effects
These are just the main players
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Hormonal Effects

• The two biggest players are
• Renin Angiotensin Aldosterone Axis
• Absorption of NaCl and H2O
• ADH (Antidiuretic Hormone)
• Absorption of Free H2O

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Regulation of Body Fluids
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Regulation of Body Fluids
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Regulation of Body Fluids

• Volume is most important
• Hypervolemia, or Volume Expansionwill lead to
  release of sodium
• This is done by NOT ABSORBING IT!

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Volume Control
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Regulation of Body Fluids

• Volume is most important
• Hypovolemia, or Volume Contractionwill lead to
  absorption of sodium
• This is done by absorbing sodiumAT ALL COST

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Volume Control
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Volume Control

• How is this done?

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Volume Control
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Regulation of Body Fluids
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Volume Control
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Regulation of Body Fluids
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Proximal Tubule
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Distal Tubule, Collecting Duct
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Regulation of Body Fluids

• Volume is Number One
• Once Volume is betterOsmolarity is fixed by
  ADH

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ADH
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Body Fluids

• When we think about Sodium
• Every sodium has bound water
• Every sodium water complextakes up volume
• The total volume is a function of total body
  sodium
• The concentration of sodium is the proportion of
  free water

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Body Fluids

• When we think about Sodium
• Every sodium has bound water
• We generally balance charge with chlorine
• The reason why Na gt Cl is that wealso
  balance charge with Bicarbonate

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Body Fluids
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Body Fluids

• Electrolytes
• Can be commercially boughtin various sports
  drinks
• Drinking Salt Water replaces Volume
• If drink is Hypertonic it steals water from ICF
• If drink is Hypotonic it pushes water into ICF

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Body Fluids

• Electrolytes
• Drinking Salt Water replaces Volume
• If drink is Hypertonic it steals water from ICF
• If drink is Hypotonic it pushes water into ICF
• Thus
• The quantity of salt represents volume
• The concentration of sodium representsdistributio
  n of water between ECF and ICF

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Body Fluids

• So much of understanding fluids willbe
  understanding kinetics
• Rates of fluid intake and output from the body
• Rates of fluid movement between different
  compartments

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Body Fluids
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Body Fluids
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Body Fluids
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Body Fluids
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Cases

• 30 Year Old Man with a gunshot wound to the leg
• 30 Year Old Manwith several days of diarrhea
• 30 Year Old Manwith burns over his legs

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Acid Base Balance

• The body produces huge amounts (millimolar) of
  acid from metabolism
• The body maintains pH in the nanomolar range

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Acid Base Balance

• There are two types of protons carried in the
  blood
• Volatile acids that result from CO2 conversion
  to bicarbonate and protons
• Non-volatile acids that result from proton
  dissociation from other molecules (lactic acid,
  protein metabolism)

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Acid Base Balance
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Acid Base Metabolism
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Acid Base Metabolism

• A high pH is called an alkalemia
• A low pH is called an acidemia
• A particular derangement that causes an increase
  in pH is called an alkalosis
• A particular derangement that causes a decrease
  in pH is called an acidosis.

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Acid Base Metabolism

• If an acidosis or alkalosis is caused by changes
  in ventilation, it is called a Respiratory
  acidosis/alkalosis
• If is not caused by ventilation, then it is
  called a Metabolic acidosis/alkalosis

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Acid Base Metabolism

• The lungs contribute to acid base homeostasis
  by
• Controlling pCO2

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Acid Base Metabolism

• How much acid is excreted via the lung?
• An amount of acid equivalent to the amount of
  volatile acid produced through metabolism

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Acid Base Metabolism

• The kidneys contribute to acid base homeostasis
  by
• absorbing filtered bicarbonate
• excreting acid
• These two things are essentially equivalent

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Acid Base Metabolism

• How much acid is excreted via the kidney?
• An amount of acid equivalent to the amount of
  non volatile acid produced through metabolism

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Bicarbonate Absorption
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Proximal Tubule Acid-Base Function
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LoopAcidBaseFunction
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Alpha Intercalated Cell
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Beta Intercalated Cell
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Acid Trapping
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Acid Trapping
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Acid Metabolism
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Acid Base Disorders
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Questions?