Refresher of M1 Renal Physiology Flashcards Preview

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Flashcards in Refresher of M1 Renal Physiology Deck (36):

What are some functions of the kidney? (7)

  1. Excretion of metabolic waste products
  2. Water and Electrolyte balance
  3. Regulation of body fluid osmolality and electrolyte concentrations
  4. Regulation of arterial pressure
  5. Regulation of acid-base balance
  6. Secretion, metabolism, and excretion of hormones
  7. Gluconeogenesis


The central physiologic role of the kidneys is to control the ______ and ________ of the body fluids

Volume; composition


Intracellular fluid = __ of total body water

Extracellular fluid = __ of total body water





The average 70 kg man will have ____ liters of total body water

____ liters will be in th ECF and ____ will be in the ICF

42 liters

ECF: 14 Liters

ICF: 28 Liters

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What is osmolarity?

The concentration of osmotically active particles in total solution expressed in terms of mOsm/liter of water


What is the average osmolarity of the ECF and ICF?

280-300 mOsm/liter


What are the units of osmolality?

When does osmolality = osmolarity?

Osmolality: mOsm/kg of solvent (water)

In relatively dilute solutions such as those found in the body, osmolality = osmolarity


Describe the changes in volume and osmolarity upon adding solutions of...

Isotonic NaCl

Hypotonic NaCl

Hypertonic NaCl

  • Isotonic NaCl
    • Volume of extracellular compartment increases
    • No change in osmolarity
  • Hypotonic NaCl:
    • Volume of extracellular and intracellular compartments increase
    • Osmolarity decreases in both comparments
  • Hypertonic NaCl:
    • Extracellular volume increases, intracellular volume decreases
    • Osmolarity increases in both

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What four kidney processes determine the composition of urine?

  1. Filtration
  2. Reabsorption
  3. Secretion
  4. Excretion

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What is the glomerular filtrate?

What is filtered and excluded from this filtrate?

The glomerular filtrate is an ultrafiltrate of plasma formed by the net effect of Starling Forces to move (filter) fluid out of the glomerular capillaries and into Bowman's space

Most large proteins, substances bound to protein, and cellular elements are excluded from glomerular filtrate


What are the physical forces causing filtration by glomerular capillaries and what are their average values?

Glomerular hydrostatic pressure (60 mmHg)

Glomerular Colloid Osmotic Pressure (32 mmHg)

Bowman's capsule pressure (18 mmHg)


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Normal values for...

Renal plasma flow:

Glomerular Filtration Rate:

Efferent Plasma Flow:

Renal plasma flow: 700 ml/min

Glomerular Filtration Rate: 125 ml/min

Efferent Plasma Flow: 575 ml/min


GFR = Kf x [(PGC + πBS) - (πGC + PBS)]

What do these terms mean?


  • Kf = ultrafiltration coefficient (product of hydraulic permeability)
  • PGC = Glomerular Capillary Hydrostatic Pressure
  • πGC = Glomerular Capillary Oncotic Pressure
  • PBS = Bowman's Space Hydrostatic Pressure
  • πBS = Bowman's Space Oncotic Pressure


Which of the following is more associated with a change in urine output?

Renal blood flow

Arterial Pressure

Glomerular Filtration Rate

Arterial Pressure


What is the myogenic autoregulation mechanism?

Intrinsic property of blood vessels

Stretch of vascular smooth muscle, as experienced during an increase in arterial pressure, elicits a contraction which elevates vascular resistance and maintain blood flow (and GFR) constant


How does tubuloglomerular feedback affect GFR and RBF autoregulation?

In response to an elevation of perfusion pressure, increased fluid is filtered leading to increased delivery of NaCl to the macula densa. This increased delivery elicits an increase in vascular resistance


Angiotensin II preferentially constricts the _______ arteriole



How do the following hormones affect GFR?



Angiotensin II:

Endothelial Derived Nitric Oxide:


Norepinephrine/Epinephrine: Decrease

Endothelin: Decrease

Angiotensin II: Decrease or no change

Endothelial Derived Nitric Oxide: Increase

Prostaglandins: Increase


What are the 3 layers that make up the filtration barrier?

Capillary wall (fenestrated)

Basement membrane



What is the main determinant of filtration barrier permeability?



What types of selection are associated with the filtration barrier?

Size-selection: more permeable to small molecules

Charge selective: more permeable to positively charged molecules


What are the components of the podocyte foot process contractile system which are linked to the slit diaphragm

Nephrin (N) and P-cadherin (P-C)


What is the function of the thin descending loop of henle?

Reabsorption of water secondary to cortical-medullary osmotic gradient

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What is the function of the thin ascending loop of Henle?

  • Impermeable to water
  • Passive reabsorption of sodium, dilution of tubular fluid
  • Permeable to urea, urea is secreted


What are the transport characteristics of the thick ascending loop of Henle?

  • Reabsorbs 25% of filtered Na+ by the Na+/K+/2Cl- transport
  • Lumen positive potential drives paracellular reabsorption of sodium, potassium, magnesium and calcium
  • Impermeable to water, dilutes tubular fluid

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Loop diuretics block the ________ transporter  in the _____ _____ loop of henle

Na+/2Cl-/K+ transporter; thick ascending

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Transport characteristics of the early distal tubule?

  • Reabsorbs Na+, Cl-, Ca++ and Mg++
  • Not permeable to water
  • Thiazide-sensitive segment

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Thiazide diuretics block ____ transport in the _____ ______ tubule

NaCl; early distal

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What are the transport characteristics of the principal cells of the late distal tubule and cortical collecting duct?

  • Reabsorbs Na+ and secretes K+
  • Regulated by aldosterone
  • Water permeability regulated by ADH

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Na+ and K+ transport in the principal cells of the late distal tubule and cortical collecting duct are blocked by which drugs?

What is the name of the sodium channel on the apical membrane of the principal cells?

  • Aldosterone antagonists
    • Spironolactone
    • Eplerenone
  • Na+ channel blockers
    • Amiloride
    • Triamterene

The channel is called the ENaC (epithelial sodium channel)

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What are the transport characteristics of the medullary collecting duct?

  • Reabsorbs Na+
  • ADH stimulated water reabsorption
  • Urea reabsorption in medullary CD

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How does aldosterone act on tubular reabsorption?

It acts in principal cells of the late distal tubule and collecting duct

Increases Na+ reabsorption, increases K+ secretion


How does Angiotensin II affect tubular reabsorption?

  • Acts primarily in the proximal tubule
  • Increases Na+ and water reabsorption, increases H+ secretion


How does ADH affect tubular reabsorption?

  • Acts in principal cells of late distal tubule and collecting duct, inner medullary collecting duct
  • Increases water reabsorption (aquaporins)


How does ANP affect tubular reabsorption?

  • Acts in the distal tubule and collecting duct
  • Decreases Na+ reabsorption


 How does Parathyroid hormone (PTH) affect tubular reabsorption?

  • In proximal tubule decreases PO4 reabsorption
  • In thick ascending loop of Henle and distal tubule increases Ca++ reabsorption