Kidney: producer, regulator, excretor Flashcards
What are the synthetic functions of the kidney?
Production of EPO, active form of vitamin D
Explain the mechanism and result of EPO production
Fall in oxygen level in renal tissues causes EPO to be secreted in kidney, stimulates RBC precursors in bone marrow
Explain the mechanism and result of vitamin D production-include chemical symbols of products
Skin+UV: cholecalciferol produces from dietary precursors (D3)
Liver: converted to 25-hydroxycholcalciferol (25-OHD3)
Kidney: converted to 1, dihydroxycholecalciferol (1,25-(OH)2D3) known as calcitriol
What cells produce EPO?
peritubular cells
What are tight junctions?
Fusion of adjacent cells to create a barrier to passage of water and dissolved particles
Describe the tight junctions in the PCT, DCT and collecting duct
PCT=loose DCT=tight CD=very tight
What is the main role of the glomerulus?
Producing filtrate
What is the mechanism of glomerulus function?
High pressure filtration of blood
Podocytes covering the ball of glomerular capillaries have very small negatively charged filtration channels
What are the properties of a marker used for GFR measurement?
Readily filtered, not metabolised, reabsorbed or secreted
What is the equation for GFR? What is the value to be found?
Filtrate flow (unknown) x filtrate concentrate (plasma concentration) = urine flow x urine concentration
What are three markers that can be used for GFR?
Creatinine: product of muscle metabolism, minor tubular secretion, results will be overestimated
Cystatin C: protein produced by mast cells
Inulin: Plant extract
If creatinine production is constant what can be used to give a GFR estimate?
Plasma creatinine concentration
What two different mechanisms of autoregulation in a broad sense?
1: Afferent arteriole dilates, improving renal blood flow at lower arterial pressure
2: Efferent arteriole constricts, improving GFR at a lower renal blood flow
What are the three tubulo-glomerular feedback mechanisms?
1) Adenosine-Produced when we are hydrated, constricts afferent arteriole, inhibits renin release, inhibited by low filtrate flow
2) Angiotensin II-RAAS system, constricts efferent
3) PGE2-Produced in DCT in response to low filtrate flow, dilates afferent arteriole, cytoprotective to tubule, antagonist to ADH
What is the main role of the proximal convoluted tubule?
Conservation of majority of useful filtrate components
What transporters are on the side of the tubule lumen in the PCT?
Na+/H+ Antiporter
Na+/Glucose symporter
What are the transporters on the side of the interstitial fluid in the PCT?
Na+/HCO3- cotransporter
Na+/K+ pump
How is H+ and HCO3- produced in the PCT?
H20 and CO2 enter cell through leaky junctions, forms H2CO3, forms H+ and HCO3-
What is the main role of the loop of henle?
Producing hypotonic tubular fluid and hypertonic interstitial fluid, and ion reabsorption
How does the loop of henle achieve it’s mechanisms?
Selective permeabilities to ions and H20 in each limb, plus countercurrent multiplier
What is reabsorbed in the descending limb of the loop of Henle? Through which channels?
H20 through AQP1 by osmosis
What is reabsorbed in the ascending limb of the loop of henle?
Ions
What transporters are on the tubular side in the ascending LoH?
K+ Na+ 2Cl- co-transporter
What is on the side of the interstitial fluid in the ascending LoH?
K+ channels, K+/Na+ active pump
