Renal - High Yield Information Flashcards
The functional unit of the kidney is the…
Nephron
The nephron consists of…
Glomerulus
Proximal Tubule
Loop of Henle
Distal Tubule
Collecting Duct
What effect do Starling forces have in the nephron?
Starling forces across the glomerular capillaries provide the driving force for the ultrafiltration of plasma from the glomerualr capillaries into Bowman’s capsule
Glomerular filtrate is devoid of/has very little…
Devoid = entirely lacking
cellular elements - red/white blood cells and platelets
protein
Filtrate is otherwise identical to plasma
What is the purpose of autoregulation in the kidney?
it allows GFR and RBF to remain contant depsite fluctuations in arterial blood pressure between 80 and 180 mmHg
Define
Juxtaglomerular Apparatus (JGA)
What is it? What does it do?
important feedback mechanism
regulates renal blood flow and GFR
What structures make up the JGA?
Macula Densa
Extraglomerular Mesangial Cells
Granular Cells
Granular cells produce renin
What can be used to measure GFR?
Creatinine and inulin
Plasma Creatinine concentration is used to measure GFR Clinically
The clearance of PAH is equal to…
the effective renal plasma flow
Renal Blood Flow is about ____% of CO
25%
What does Renal Blood Flow do?
indirectly determines GFR
Modifies the rate of solute and water reabsorption by the proximal tubule
Delivers O2, nutrients, and hormones to the cells of the nephron
Returns CO2 and reabsorbed fluid and solutes to general cirulation
Delivers substrates for excretion in the urine
What are the major hormonal regulators of GFR and RBF?
Sympathetic Nerves
Angiotensin II
prostaglandins, NO, endothelin, natriuretic peptides, bradykinin, and adenosine affect GFR and RBF too
The major body fluid compartments are…
Extracellular Fluid (ECF)
Intracellular Fluid (ICF)
Na+ is confined to the…
ECF
What is the result of Na+ being confined to the ECF?
the amount of Na+ in the body determines the volume of the ECF
_ of the volume of total body water is in the ICF
2/3
_ of the volume of total body water is in the ECF
1/3
Plasma volume makes up _ of the ECF
1/4
Why are plasma and interstitial fluid nearly identical in composition?
Most plasma constituents are freely exchanged across the capillary wall
except for the lack of plasma proteins in IF
What causes the significantly different compositions between the ECF and ICF?
Cell membrane barrier
Fluid balance is controlled by…
Regulation of ECF volume by maintaining salt balance
Regulation of ECF osmolarity by maintaining water balance
Changes in ECF volume occur by…
changing Na+
Because of the osmotic holding power of Na+, changing a body’s total Na+ content changes ECF volume
alters arterial blood pressure in the same direction
What is the major cation in the ECF?
Na+
How is salt intake and output controlled?
Intake is uncontroled
Output is closely regulated by the kidney by changing urine concentration of Na+
How do blood pressure regulating mechanisms vary GFR and amount of Na+ filtered/reabsorbed?
GFR and Na+ filtered are varied by adjusting the caliber of the afferent arterioles supplying the glomeruli
Na+ reabsorption is varied by varying secretion of aldosterone which promotes Na+ reabsorption in renal tubules
T or F
Varying Na+ filtration and reabsorption has no effect on ECF Volume?
False
varying Na+ filtration/reabsorption alters ECF volume
Changes in ECF osmolarity occur by…
changing H2O balance
Why is varying H2O balance important?
It is vital in avoiding osmotic shifts between the ECF and ICF cells
What occurs in the ECF when there is excess H2O?
ECF solutes are diuted
H2O is driven into the cells due to ECF hypotonicity
What occurs in the ECF when H2O is deficit?
ECF solutes are concentrated
H2O is driven out of the cells and into hypertonic ECF
What helps prevent the fluxes of excess/deficit H2O?
ADH (primarily) and thirst (lesser extent) stimulated by hypothalamic osmoreceptors
Volume concentration and expansion refer to…
ECF volume
Define
Isosmolar Volume Expansion or Contraction
If ECF volume changes and the solute concentration remains the same
Define
Hyperosmolar Expansion or Contraction
If ECF volume changes but the solute concentration increases
Define
Hypo-osmolar Expansion or Contracton
If the ECF volume changes but the solute concentration falls
What is the overall function of the four major segments of the nephron?
Proximal Tubule, LoH, Distal Tubule, Collecting Duct
Determine the composition and volume of the urine by the processes of selective reabsorption of solutes and water and secretion of solutes
Define
Tubular Reabsorption
allows the kidney to retain the substances that are essential and regulate their levels in the plasma by altering the degree to which they are reabsorbed
What are the major solutes/ions reabsorbed by the nephron?
Na+
Cl-
K+
HCO3-
Ca2+
PO4-3
organic anions and cations
water
The nephron reabsorbs _ % of filtered water, _ % of filtered sugar, and _ % of filtered salt
99% filtered water
100% filtered sugar
99.5% filteres salt
How do the distal segments of the nephron participate in reabsorption?
They have a more limited reabsorptive capacity
The final adjustments in the comosition and volume of urine and most of the regulation by hormones occur in these segments
Tubular Secretion
Secretion of substances into tubular fluid is a means for excreting various byproducts of metabolism, exogenous organic anions and cations (i.e. drugs), and toxins from the body
What regulates NaCl reabsorption in the kidneys?
Various hormones (Angiotensin II, Aldosterone, ADH, Natriuretic Peptides)
Sympathetic Nerves
Starling forces
What is the major hormone that regulates water reabsorption?
ADH
How is K+ homeostasis maintained by the kidneys?
They adjust K+ excretion to match dietary K+ intake, and by the hormones insulin, epinephrine, and aldosterone which regulate the distribution of K+ between the intracellular fluid and ECF
What regulates K+ secretion by the distal tubule and collecting duct?
Na+ reabsorption
plasma [K+]
aldosterone
changes in tubular fluid
acid base disturbaces
What regulates Ca2+ reabsorption by the thick ascending limb and distal tubule?
Primarily PTH and Vitamin D (calcitriol)
both stimulate Ca2+ reabsorption
What inhibits PO43- reabsorption by the proximal tubule?
PTH
How do the kidneys maintain acid-base balance?
Through excretion of H+
How do the kidneys prevent the loss of the HCO3- in the urine?
By reabsorbing virtually all the HCO3- filtered at the glomeruli
Both the reabsorption of filtered HCO3- and the excretion of acid are accomplished by…
The secretion of H+ by the nephrons
The thick ascending limb is _ to water.
impermeable
How does the thick ascending limb reabsorb Na+ in the apical membrane?
via a Na+-K+-2Cl- cotransporter
How does the thick ascending limb reabsorb Na+ in the basolateral membrane?
via a Na+-K+ ATPase
The distal convoluted tubule is _ to water
impermeable
How does the distal tubule reabsorb Na+?
via a thiazide-sensitive apical membrane NaCl cotransporter
Cortical collecting duct principal cells reabsorb _ and secrete _.
Reabsorb Na+
Secrete K+
The kidneys return _ to the body and produce urine with a total solute concentration greater than…
water
plasma
What is the purpose of the countercurrent multiplication system?
To return water to the body via the blood stream
What does it mean that the Loops of Henle are countercurrent multipliers?
They create an osmotic gradient in the kidney medulla
What does it mean that the vasa recta are countercurrent exchangers?
They passively help maintain the medullary gradient
The collecting ducts have a low _ , which can be increased by _.
Low water permeability
increased by ADH
