The Renal system Flashcards
The renal system
Functions of the kidneys
Regulates blood volume and pressure
Regulates plasma concentrations of Na+, K+, chloride and other ions
Stabalises blood pH
Conserves valuable nutrients
Assists liver in detoxifing toxins and hormones
The renal system
General anatomical structure of the kidneys
Embedded in fat
Adrenals on upper surface
Nearly every sort of supply tube leaves via the hilus
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Cross section of kidney
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What supplies the kidney with blood?
Renal artery
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Renal blood supply flowchart
The renal system
Cortical nephron
Not really involved in the regulation of urine volume
Very small loop of Henlé
Involved in urine composition
Good lymphatic supply
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Juxtamedullary nephron
Distinct loop of Henlé
Have no lympatic drainage
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Blood flow of juxtamedullary nephron
Efferent arteriole gives rise to series of stright capillaries (vesa recta)
These run parallel with the loop of Henlé
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What’s the importance of the direction of blood flow in the juxtamedullary nephron?
In opposite direction to filtrate flow throught the loop of Henlé
Same direction as the flow of fluid through the collecting duct
Sets up a counter current
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Bowman’s capsule
Contains the glomerulus
Epithelium of the capsul invests the epithelium of the capillaries
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Glomerulus and it’s make up
Group of capillaries which the blood is filtered through
Afferent arteriole splits into 20-30 capillary loops aranged in 5-8 lobes
These recombine to form the efferent arteriole
These invaginate into the blind end of the tubule
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Juxtaglomerular Apparatus (JGA)
Produces renin
Contains baroceptors which regulate afferent and efferent arteriolar flow
Sensitive to concentration of NaCl in tubule
Can protect the nephron if it is failing
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How can the JGA protect the nephron if it is failing
Detects increase in NaCl
Reduces red blood flow and GFR
This reduces the filtering load
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What does GFR stand for?
Glomerular filtration rate
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Proximal tube structure in nephron
Cuboidal epithelium
Microvili form a brush border
Permeable to water and solutes
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What does the proximal tubule reabsorb?
60-70% of filtered load of ions
All organic solutes
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What is the site of obligatory reabsorbtion?
Proximal tubule
The renal system
Descending thin limb of the loop of Henlé
Flattened epithelium
Pars recta of the proximal tubule
Nucleus forms a bulge in the cell
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What is the descending limb of the loop of Henlé permeable to?
Water and solutes
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Ascending thick limbs of loop of Henlé
Cuboidal epithelium
Well developed tight junctions
Effectively impermeable to water
Well endowed with Na+, K+ and ATPase
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Distal convoluted tubule
Arises from the ascending limb of the loop of Henlé
Cells are columnar
No brush border
Forms macula densa where it makes contact with the afferent arteriole
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What is the site of facultative reabsorbtion?
The distal convoluted tubule
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The collecting duct
Arises from the distal convoluted tubule
Formed from several distal tubules
Site of regulation of urine volume
Some acidification of the urine
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Cell shape of the collecting duct
Cuboidal
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3 steps of urine formation
Ultrfiltration of plasma
Reabsorbtion of water and solutes
Secretion of selected solutes into tubules
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Why do large positively charged molecules most easily filtered by ultrafiltration?
Membranes of filtration unit negatively charged
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Why is tubular reabsorbtion important?
Kidney filters 160L of water a day
Reabsorbs more important molecules like glucose and amino acids than the body can store
Stops these from being lost
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GFR =
Kf (Pc + πt) - (Pt + πc)
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What is Pc in GFR?
Glomerular cappilary hydrostatic pressure
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What is πt in GFR?
Proximal tubule oncotic pressure
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What is πc in GFR?
Glomerular cappilary oncotic pressure
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What is Pt in GFR?
Tubular hydrostatic pressure
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What is Kf in GFR?
The permeability constant for the kidneys
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What mechanisms are responsible for regulating GFR?
Myogenic mechanism
Tubuloglomerular feedback
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How does the myogenic mechanism work in regulating GFR?
When vascular smooth muscle is stretched in contracts
This increases blood pressure in afferent arteriole
Arteriole contracts increasing resistance
GFR decreases
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How is most solutes transported across the tubular epithelium?
Na+/K ATPase pump
The renal system
How does the Na+/K ATPase pump drive solutes across the tubular epithelium?
Uses Na+ as it is going down it’s concentration gradient
Symporter molecules carry specfic soluteswith the Na+
Antiporter molecules move solutes in the opposite direction to Na+
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Where is 60-80% of all filtrate reabsorbed?
Proximal convoluted tubule
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What reabsorbs 100% of organic molecules?
Proximal convolted tubule
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Obligatory reabsorbtion in proximal convoluted tubule
- Na+
- HCO3
Na+ enters down electrochemical gradient via leak channels from the lumen
Antiport with H+
Symport with glucose (goes same way)
H+ combines with HCO3 and CO2 diffuses in
Process reversed so HCO3 absorbed H+ goes back to lumen
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What two things does the loop of Henlé do?
Absrobs about 50% of remaining water
Absorbs about 66% of remainging NaCl
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Which are the permeability properties of the loop of Henlé?
Thin limb - permeable to water and solutes
Thick ascending limb - impermeable to water
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How does the loop of Henlé create an osmotic gradient?
Na+ and Cl- pumped out of TAL into the peritubular fluid
Increases the osmotic pressure of the peritubular fluid
Causes water to flow of the the thin descending limb (TDL)
Causes increased solute concentration in fluid as it moves down TDL
Accelerates solute pumping in TAL
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What is the area of ccontrolled ion reabsorbtion?
Distal convulated tubule
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Reabsorbtion in distal convoluted tubule
Na+ enters with Cl- through Na+ channels
Na+ pumped out via the Na+/K+ ATPase
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What are the Na+ channels regulated by and why in the distal convoluted tubule?
Aldosterone
Prolonged Na+ reabsorbtion leads to K+ loss
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How does the distal convoluted tubule control it’s K+ levels?
Increased Na+ reabsorbtion increases K+ concentration
K+ then diffuses out via the K+ channels
Effectively diffusion
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How does the distal convoluted tubule secrete H+ and absorb HCO3?
The renal system
What causes the cycle of HCO3 formation to occur?
Cabronic anhydrase
