Topic 1 Part B Flashcards
Reabsorption – Proximal Tubule
__% of filtered load of sodium & water reabsorbed
-Cells of proximal tubule designed for ___ reabsorption capacity of ____ and ____
65% of filtered load of sodium & water reabsorbed
-Cells of proximal tubule designed for high reabsorption capacity of sodium and water
Reabsorption – Proximal Tubule
Little less percentage for _____
-Quantity can be __________
Little less percentage for chloride
-Quantity can be increased or decreased as needed
Proximal Tubule Cellular Ultrastructure
Contain large number of mitochondria to support
extensive active transport activity
Proximal Tubule Cellular Ultrastructure
Luminal (apical) brush border provides
huge surface area for rapid diffusion
Proximal Tubule Cellular Ultrastructure
Basolateral border contains
extensive number channels in between cells providing huge surface area
Proximal Tubule Cellular Ultrastructure
Luminal border contains extensive number of _____
-Co-transport of ______ and ______
-Counter-transport of ______ (move a large quantity of them against a small ________)
Luminal border contains extensive number of protein carrier molecules
- Co-transport of amino acids and glucose
- Counter-transport of hydrogen ions (move a large quantity of hydrogen ions against small hydrogen ion gradient
Proximal Tubule Cellular Ultrastructure
Basolateral border contains extensive amount of ____
N-K ATPase
Early vs. Late Proximal Reabsorption
First half of tubule:
Extensive co-transport of sodium with
glucose and amino acids
Early vs. Late Proximal Reabsorption
First half of tubule:
Sodium reabsorption carries ____, ____, ____ ions leaving _____ resulting in increasing [Cl-]
–____ mEq/L increases to _____ mEq/L
Sodium reabsorption carries glucose, bicarb, organic ions leaving chloride resulting in increasing [Cl-]
105 mEq/L increases to 140 mEq/L
Early vs. Late Proximal Reabsorption
Second half of tubule:
High chloride concentration favors _______
-Some movement may occur through specific ______
High chloride concentration favors chloride diffusion
-Some movement may occur through specific chloride channels
Early vs. Late Proximal Reabsorption
Second half of tubule:
Most ____ & _____ have been reabsorbed – ____ reabsorption drives _____ reabsorption
-_______ gradient
Most glucose & amino acids have been reabsorbed – sodium reabsorption drives chloride reabsorption
-Electrochemical gradient
Changes in Solute Concentrations
Total _____ of sodium in tubule changes but ____ does not change because ____ reabsorption matches sodium reabsorption
Total quantity of sodium in tubule changes but concentration does not change because water reabsorption matches sodium reabsorption
Changes in Solute Concentrations
Total osmolarity does not change for the same reason as sodium
-Proximal tubule _____ permeable to _____
Proximal tubule highly permeable to water
Changes in Solute Concentrations
____ & _____ concentrations decrease due to extensive ________
Glucose & amino acid concentrations decrease due to extensive reabsorption
Changes in Solute Concentrations
_____ & _____ are concentrated because they are not _______
Total amount of creatinine and urea in tubule does not ____
Creatinine & Urea are concentrated because they are not reabsorbed
Total amount of creatinine and urea in tubule does not change
Changes in Solute Concentrations
Total amount of Na+, Cl-, HCO3-, glucose, amino acids in tubule _______
decrease
Secretion of Organic Acids & Bases
Many end products of metabolism are secreted by proximal tubule (4)
Bile salts
Oxalate
Urate
Various catecholamines
Secretion of Organic Acids & Bases
Many drugs & toxins secreted (2)
Penicillin
Salicylates
Secretion of Organic Acids & Bases
Para-aminohippuric acid also secreted-
___% of PAH in renal blood flow is removed
Can be used to determine ____
90% of PAH in renal blood flow is removed
Can be used to determine renal blood flow
describe the Thin Descending & Ascending Segment of the Loop of Henle (4)
Thin epithelial membrane
No brush border
Few mitochondria
Minimal metabolic level
Thin Descending Segment of the Loop:
_____ permeable to water
_____ permeable to most solute
Highly permeable to water
Moderately permeable to most solute
Thin Descending Segment of the Loop:
Allows diffusion of water and solutes: No active ____
___% of water reabsorption occurs in the loop of Henle
Allows diffusion of water and solutes: No active reabsorption
20% of water reabsorption occurs in the loop of Henle
Thin Ascending Segment of the Loop:
_______ to water
-Part of mechanism for _______
impermeable to water
-Part of mechanism for concentrating urine
Thick Ascending Segment
____ epithelial cells with high concentration of _______- High level of _______ activity
Thick epithelial cells with high concentration of mitochondria- High level of metabolic activity
Thick Ascending Segment
Able to reabsorb (6)
sodium chloride potassium (Approx 25% of filtered load) calcium bicarb magnesium
Thick Ascending Segment
_______ to water
As solute reabsorb ______ concentrations drop especially since water ____ reabsorbed – Fluid very ___
- Impermeable to water
- As solute reabsorb luminal solute concentrations drop especially since water NOT reabsorbed – Fluid very dilute
Sodium Reabsorption
Driven by _____ in ______ border of tubule cells
Driven by N-K ATPase in basolateral border of tubule cells
Sodium Reabsorption: how many transport mechanisms move sodium from tubular lumen
2 total
1 Na-2Cl-1K co-transport mechanism
Na-H counter-transport mechanism
Sodium Reabsorption
1 Na-2Cl-1K co-transport mechanism=
1. _____ means of moving sodium out of ____ into ____ cells
2. Potassium reabsorbed _____ potassium concentration gradient
3. Cl- & K+ diffuse out of cell into _______ via specific _______
- Primary means of moving sodium out of lumen into tubular cells
- Potassium reabsorbed AGAINST potassium concentration gradient
- Cl- & K+ diffuse out of cell into renal interstitial fluid via specific ion channels
Loop diuretics (furosemide, ethacrynic acid, bumetanide) inhibit the action of the
1Na-2Cl-1K co-transport mechanism
Loop Diuretics:
Less sodium reabsorption – less water reabsorption in
later segments of the nephron
Loop Diuretics:
Less sodium reabsorption – less potassium reabsorption with potential
loss of potassium
Na-Cl-K co-transport mechanism is isoelectric BUT K is able to diffuse back into lumen via potassium channels creating
+8 mV positive charge in tubule lumen
Electrical gradient drives diffusion of Na+, K+, Mg++ & Ca++ into the ________ via the tight junctions (paracellular diffusion)
renal interstitial space
Early Distal Tubule
Macula densa forms ______
-Part of _______ complex
-Provides feedback control for ____ and_____
Macula densa forms first part of tubule
- Part of juxtaglomerular complex
- Provides feedback control for GFR and blood flow (for this nephron)
Early Distal Tubule
Next segment is the _______
-____ reabsorption – no _____ reabsorption
-_______ segment of distal tubule
Next segment is the high convoluted
- Solute reabsorption – no water reabsorption
- Diluting segment of distal tubule
Early Distal Tubule
___% of filtered load for sodium & chloride reabsorbed
5%
Early Distal Tubule
Driven by ____ in _______ border of tubular cells
Driven by Na-K ATPase in basolateral border of tubular cells
Early Distal Tubule
Na-Cl co-transport mechanism moves Na+ and Cl- _____
–Chloride _____ out of cell via ______
Na-Cl co-transport mechanism moves Na+ and Cl- into cell down [Na+]
–Chloride diffuses out of cell via chloride specific channels
Early Distal Tubule
Thiazide diuretics inhibit this _______ mechanism
-Reduces sodium and chloride ______ and ultimately water reabsorption in _____segments of nephron
Thiazide diuretics inhibit this Na-Cl co-transport mechanism
-Reduces sodium and chloride reabsorption and ultimately water reabsorption in later segments of nephron
Functional Characteristics – Late Distal Tubule & Cortical Collecting Tubule:
Membranes _______ to urea
-All urea entering exits to _______ to be excreted
-Some reabsorption of urea will occur in ______
Membranes impermeable to urea
- All urea entering exits to collecting duct to be excreted
- Some reabsorption of urea will occur in medullary collecting ducts
Functional Characteristics – Late Distal Tubule & Cortical Collecting Tubule:
Sodium reabsorption controlled by various hormones but especially by
aldosterone
Functional Characteristics – Late Distal Tubule & Cortical Collecting Tubule:
Potassium secretion controlled by various hormones but especially by
aldosterone
Functional Characteristics – Late Distal Tubule & Cortical Collecting Tubule:
- Able to secrete _____ ions against large concentration gradient of _____
- Proximal tubule moves hydrogen ions against ____ gradient of _____
- Able to secrete hydrogen ions against large concentration gradient (1000:1)
- Proximal tubule moves hydrogen ions against small gradient (4 to 10:1)
Functional Characteristics – Late Distal Tubule & Cortical Collecting Tubule:
Water permeability controlled by concentration of _____
-No ADH - no ____ permeability – excrete ____ urine
-Increased concentrations of ADH increase permeability of ____ and decrease the volume of ____and increase the ________ of the urine
Water permeability controlled by concentration of antidiuretic hormone (ADH, aka vasopressin)
- No ADH - no water permeability – excrete dilute urine
- Increased concentrations of ADH increase permeability of water and decrease the volume of urine and increase the concentration of the urine
Late Distal Tubule & Cortical Collecting Tubule
two types of cells
Principal cells
Intercalated cells
Late Distal Tubule & Cortical Collecting Tubule
principal cells=
Reabsorb sodium & water
Secrete potassium
Late Distal Tubule & Cortical Collecting Tubule
intercalated cells=
Reabsorb potassium
Secrete hydrogen
Principal Cell Activity
_____ in _____ borders of tubule cells drives activity
Na-K ATPase in basolateral
Principal Cell Activity
Sodium follows _______ gradient – _____ through sodium specific channels
Sodium follows concentration gradient – diffuses through sodium specific channels
Principal Cell Activity
Potassium follows ______ gradient out of cell into _______ via potassium specific channels
Potassium follows concentration gradient out of cell into tubular lumen via potassium specific channels
Potassium Sparing Diuretics (Aldosterone antagonists):
What type of antagonist
Mineralocorticoid receptor
Potassium Sparing Diuretics (Aldosterone antagonists)
Compete with aldosterone receptor sites which inhibits
sodium reabsorption & potassium secretion
Potassium Sparing Diuretics (Aldosterone antagonists) drug names
Spironolactone & eplerenone
Potassium Sparing Diuretics (Sodium Channel Blockers)
Inhibit entry of sodium into cell which reduces amount of
sodium transported by Na-K ATPase
Potassium Sparing Diuretics (Sodium Channel Blockers)
reduces secretion of potassium as action of Na-K ATPase
decreases
Potassium Sparing Diuretics (Sodium Channel Blockers):
drug names
Amiloride & triamterene
Intercalated Cell Activity – Hydrogen Ions:
Secretion controlled by
H-ATPase transporter
Intercalated Cell Activity – Hydrogen Ions:
Presence of carbonic anhydrase allows conversion of
CO2 and H2O to hydrogen ions and bicarb ions
Intercalated Cell Activity – Hydrogen Ions:
Chloride also secreted following
electrochemical gradient
Intercalated Cell Activity – Hydrogen Ions:
Bicarb reabsorbed using Cl-HCO3- counter-transport mechanism following the
Cl- gradient into the cell
Intercalated Cell Activity – Hydrogen Ions:
- _____moved freely between cell and interstitial fluid
- ______ is also reabsorbed
- CO2 moved freely between cell and interstitial fluid
- Potassium is also reabsorbed
Meduallary Collecting Ducts:
Reabsorb ___% of filtered water and sodium
<10%
Meduallary Collecting Ducts:
Determine final concentration of
solutes and urine concentration
Meduallary Collecting Ducts:
Epithelial cells smooth with few
mitochondria
Meduallary Collecting Ducts:
Water permeability controlled by
ADH
Meduallary Collecting Ducts:
Urea is reabsorbed via specific urea transporters which moves urea into the
interstitial spaces thus affecting osmolarity
Meduallary Collecting Ducts:
Secretes
hydrogen ions (like cortical collecting tubule)
Solute Concentrations:
Change in solute concentration depends on rate of
reabsorption (secretion) versus rate of water reabsorption
Solute Concentrations:
Y-axis: Ratio of
[tubular] / [plasma]
Solute Concentrations:
Items highly concentrated are
not needed by body
Solute Concentrations:
Inulin neither secreted or reabsorbed provides indication of
water reabsorption
Solute Concentrations:
- Inulin conc of 3 means that
- Inulin conc of 125 means that
- Inulin conc of 3 means that 1/3 of water remains in tubule (2/3 has been reabsorbed)
- Inulin conc of 125 means 1/125 of water remains while 124/125 has been reabsorbed
