The Genitourinary System Flashcards

Question

What are theideal properties of a molecule to practically measure GFR? Which is the ideal molecule that could be used to practically measure GFR? What is the common molecule used practically to measure GFR?

Answer 1

Ideal properties = measure a freely filtered molecule in the urine that is neither secreted nor reabsorbed in the kidneys (as GFR = OE). So GFR can be measured by measuring renal clearance of this molecule Ideal = inulin Common = creatinine

Answer 2

Creatinine does not need to be infused, muscles are continuously producing it - large volumes of urine can be collected over long periods of time. However, muscle wasteage raises creatinine levels and a small amount of creatinine is secreted in the nephron Because it it freely filtered

Answer 3

Renal plasma flow (RPF) rate - volume of plasma delivered to the kidneys per unit time Para aminohippurate (PAH) - all the PAH is removed from the plasma passing through the kidneys through filtration and secretion Because all of the PAH that enters the kidney is excreted, so the renal clearance of PAH must equal RPF

Answer 4

Filtration fraction (FF) - usually calculated as a percentage and represents the proportion of the fluid reaching the kidneys that passes into the renal tubules FF = [GFR] / [RPF] x 100 Between 15 - 20%

Answer 5

1. Passive transport, 2. Active transport Passive = diffusion, osmosis, electrochemical gradient Active: primary = pumps, endocytosis; secondary = movement of one solute along its electrochemical gradient provides energy for the movement of another solute against the oncentration gradient - symport (bring something else with it), antiport (pump something out in the opposite direction) Electrochemical gradient only exists due to pumps creating that different in electrical potential

Answer 6

All 3 passive mechanisms take place in the nephrons Both, primary and secondary active mechanisms are in the nephrons. Na⁺/K⁺ ATPase pump = lowers Na+ concentration in the cell, so Na+ moves down the concentration gradient, the movement can be used to bring something else in / pump something else out

Answer 7

Substances, other than travelling through cells, also go between cells, known as the paracellular pathway. Often water uses the path, and with it other solutes also use this pathway Transcellular = through the cell. As the membrane is made of lipids, water requires a protein channel (e.g. aquaporin) to travel through cells. Most of the Na+ reabsorption requires Na⁺/K⁺ ATPase

Answer 8

PCT - around 70%, including water as it follows the substances via osmosis Reabsorbed = 67% Na+, 67% Cl-, 90% HCO3-, 100% glucose, 67% water, 100% amino acids, 50% urea Secreted = drugs, ammonia, bile salts, prostaglandins, vitamins (folate and ascorbate)

Answer 9

Carbonic anhydrase is present in the tutbular fluid - it converts H⁺ and HCO₃^- into H₂O and CO₂so CO₂can diffuse into the cells Inside the cells carbonic anhydrase then coverts back the H₂O and CO₂into H⁺ and HCO₃^-. The H⁺ is then exhcanged for an Na⁺ molecule via an antiportar, so H⁺ exits the cell whilst Na⁺ enters it To prevent HCO₃^- build up, it is goes through a symporter where both, Na⁺ and HCO₃^- leave the cell ---- Increasing the number of Na⁺/H⁺antiportars

Answer 10

When there is low Na⁺ levels in the blood, or low blood volume, renin is secreted. This causes angiotensin II secretion, which increases the number of antiportars, so more Na⁺ is pumped out into the tubular fluid and water follows. This causes greater Na⁺ and water reuptake Glucose reabsorption dependent on the Na⁺/glucose symporter. Na⁺ is pumped out of the other side of the cell into the blood, causing Na⁺ to move down the electrochemical gradient from the tutbular fluid into the cell, bringing with it a glucose molecule. As the glucose concentration in the cell is higher than in the blood, it diffuses through a glucose transporter (GLUT 2)

Answer 11

Reabosorbed = 25% Na⁺, 25% Cl^-. 15% H₂O Descending limb = impermeable to NaCl, permeable to water Ascending limb = impermeable to water, permeable to NaCl Put in A level notes on the counter current system More salts are reabsorbed than water, so the fluid coming in down the descending limb is hyper-osmolar, and the fluid going out of the ascending limb is hypo-osmolar

Answer 12

In the thick ascending limb there is Na+ and Cl- reabsorption Na⁺/K⁺ ATPase pump exchanges one Na+ out of the cell for one K⁺ entering the cell There is also an Na⁺/K⁺/Cl^-symporter, than brings in those salts into the cell The K⁺ and Cl^- go travel through a symporter into the blood, down the electrochemical gradient There is also a paracellular pathway for the cations

Answer 13

Reabsorbed = Na⁺, Cl^-, Ca²⁺ For Na⁺ and Cl^- reabsorption, the Na⁺/K⁺ ATPase pump pushes out one Na⁺ into the blood and brings in one K⁺ into the cell. Na⁺ and Cl^- enter the cell from the tubular fluid via the Na⁺/Cl^-symporter. The K⁺/Cl^- symporter then pushes out a K⁺ and Cl^- into the blood Active calcium reabsorption occurs using the Na⁺/K⁺ ATPase pump that pushes out an Na⁺ into the blood and brings in one K⁺ into the cell. Na⁺ and Ca²⁺ enter the cell from the tubular fluid via the Na⁺/Ca²⁺symporter. Then via an Na⁺/Ca²⁺antiporter, the Ca²⁺exits the cell into the blood, and an Na⁺ enters

Answer 14

Principal cell = Na⁺ reabsorption, H₂O reabsorption, K⁺secretion Intercalacted cell = maintains acid base balance

Answer 15

Reabsorbed = Na⁺, water, HCO₃^-, and H⁺; Secreted = HCO₃^-, and H⁺ Na⁺ and water are reabsorbed as the Na⁺/K⁺ ATPase pump pushes out one Na⁺ into the blood and brings in one K⁺into the cell. This lowers the concentration of Na⁺ in cell, so Na⁺ moves into the cell from the tutbular fluid, and K⁺ moves into the tubular fluid as there is a higher concetraion of K⁺inside the cell than in the tutbular fluid. Water follows behind the Na⁺, travelling from the tubular fluids through aquaporins into the cell, and through more aquaporins into the blood

Answer 16

Aldosterone - regulates Na⁺reabsorption by changing the number of Na⁺channels and Na⁺/K⁺ ATPase pumps ADH - regulates water by altering the number of aquaporins

Answer 17

Using a proton (H⁺) pump and a Cl^- antiporter Alpha = HCO₃^-reabsorption, H⁺ secretion Beta = HCO₃^-secretion, H⁺reabsorption