Renal Flashcards
How much blood every hour do the kidneys recieve?
120 pints
What is the main function of the kidneys? (Name 6)
Bones: activate vitamin D by 1-alpha-hydroxylation
Plasma sodium: renin released from kidney is the first step in RAA axis for sodium conservation
BP: low arterial pressure stimulates RAA axis to increase plasma volume
Disposal: toxin, nitrogenous compounds - filtered from plasma into urine
Blood oxygen: erythropoetin is produced by the kidney and is necessary for red blood cell synthesis
Blood pH: excretion of H+ is controlled in distal convoluted tubule
Describe the microstructure of the kidney?
Consist of many nephrons that span across the cortex and into the medulla and then back. The nephrons contain bowmans capsule, proximal convoluted tubule, ascending and descending limb (of the loop on henle) and the collecting duct
How does the final filtrate leave?
It leaves the kidney via the ureter and drains into the urinary bladder. Urine is excreted via urethra.
Urine can be used to investigate the imbalances and functionality of the kidney
What does the glomerulus allow to be filtered?
Blood is filtered to remove excess fluid, waste products and regulate ion levels, such as H+, Na+ and K+
What does the glomerular filtrate barrier consist of?
endothelium, basement membrane and podocytes
How does the glomerular filtration barrier ensure the correct molecules are being filtered?
Mainly based on size, but also shape and charge. The endothelial cells only allow a certain size, similar to a sieve. Finally the podocytes spacing is determined by an actin skeleton
What sizes are permitted to be filtered?
> 50kDa are absent. Size of albumin (68kDa) and larger are prevented from entering the lumen.
negatively charged proteins are retained in blood.
What is the function of the proximal convoluted tubule?
Bulk reabsorption of electrolytes from filtrate into circulation
What electrolytes are reabsorbed? and does it require ATP?
active: Na+
passive: glucose, amino acids, bicarbonate, potassium, phosphate
What is secreted into the lumen of the distal convoluted tubule and why?
H+ -> important stabiliser of the acid/base balance and used to reabsorb things like bicarbonate via the use of carbonic anhydrase.
organic anions & organic cations - indirectly aid in passive transport by producing an electrochemical gradient
What does the loop of henle consist of?
Ascending and descending limbs
What is the function of the loop of henle?
to create a hyperosmolar medulla - necessary for the production of a concentrated urine
Describe the system allow for dilute or concentrated urine?
Counter current multiplication system: Forms dilute urine after H2O load (via ADH) and concentrated after H2O restriction.
In simple, the play between the vasa recta and loop of henle
The blood vessel runs opposite to the flow of filtrate in the loop of henle. This produces an osmotic gradient.
The ascending limb is impermeable to water but instead pumps out NaCl (via co transporters) to the blood vessel running the opposite direction. The blood carries the NaCl into the medulla (making it hyperosmotic).
The blood then moves opposite direction of the descending limb. Where water is permeable. Water moves back into the blood reducing the osmotic tension of the blood.
How can water in highly dilute urine be reabsorbed?
Via the release of ADH, which act on the collecting duct. This causes aquaporins to move into the impermeable membrane
What is the function of the distal convoluted tubule?
fine tuning of electrolyte reabsorption or secretion - mainly Na, K and H
What hormone controls the function of the distal convoluted tubule?
aldosterone
What are the osmotic states of medulla and cortex?
medulla - hyperosmotic
cortex - hyposmotic
Name all electrolytes that are being secreted or absorbed in the proximal convoluted tubule?
Proximal convoluted tubule:
Absorbed - glucose, amino acid, phosphate, Na, Cl, bicarbonate, water
Secrete: H+
Name all electrolytes that are being secreted or absorbed in the loop of henle?
Descending limb: K and water reabsorbed
Ascending limb: Ca and Mg absorbed, Na, Cl absorbed
Name all electrolytes that are being secreted or absorbed in the distal convoluted tubule?
Fine-tuning absorption of Na, K and some secretion of H+ to reabsorb HCO3
- One Na leaves and one K enters lumen
- Cl is also reabsorbed
- Ca2+ reabsorbed
Name all electrolytes that are being secreted or absorbed in the collecting duct
absorbed: water (ADH dependent), bicarbonate, Na, Cl
secreted: K, H, NH3
Note: NH3 absorbed when ADH acts on it
Match the following. (E=excreted and R=reabsorbed) A. Descending limb B. Ascending limb C. Distal convoluted tubule D. Proximal convoluted tubule E. Collecting duct
- R: Magnesium, NaCl
- R: H2O, NH3, Na, Cl, HCO3. E: K, H, NH3
- R: H2O, K
- R: AA, PO4, Glu, Na, H2O, K, Cl, HCO3.
- R: HCO3, Na, K. E: H, organic anions and cations
B1 D4 A3 E2 C5
What is the countercurrent multiplier?
A. Forms concentrated urine after H2O load (via ADH) and dilute after H2O restriction
B. Forms dilute urine after H2O load (via ADH) and dilute after H2O restriction
C.Forms dilute urine after H2O load (via ADH) and concentrated after H2O restriction
D. Forms concentrated urine after H2O load (via ADH) and concentrated after H2O restriction
C
How does angiotensin II affect the proximal convoluted tubule?
A. Decrease Na-H exchange to increase urine pH
B. Decrease water reabsorption
C. Increase K-Na transport
D. Increase Na-H exchange to reabsorb Na
D
- Leads to shift of fluid into the blood volume and ECF. Increases arterial pressure
How does aldosterone affect the renal reabsorption?
A. Increased sodium uptake in collecting duct
B. Increased sodium uptake in distal tubule and collecting duct
C. Decreased reabsorption of sodium
D. Increased sodium in uptake in distal tubule
B
- Act by stimulating insertion of Na channels and Na-K ATPase proteins
What is the main function of RAA?
A. Regulate rate of renal blood flow
B. Increase urine concentration
C. Decrease filtration size
D. Increase filtration size
A. RAA works to primarily regulate the rate of renal blood flow using renin, aldosterone II and aldosterone
How is intracellular accumulation of Na avoided?
Na is only actively reabsorbed. Maintained by Na+/K+-ATPase. Also absorption of glucose and AA is coupled with Na
How is the high medullary osmolality maintained?
By the vasa recta removing any water that is reabsorbed in the descending limb
Difference in tubular fluid between ascending and descending limbs?
Descending is more permeable to water, thus, fluid is more concentrated.
Ascending is impermeable to water so fluid is more dilute
