Studied by 5 people
Tubular Reabsorption
Movement of substances from tubular fluid into blood.
Hyperosmolar Tubular Fluid
High solute concentration in renal medulla.
Proximal Convoluted Tubule (PCT)
Reabsorbs 65% of filtered Na+ and water.
Aquaporin
Channel protein facilitating water reabsorption.
Descending Loop of Henle
Permeable to water, impermeable to salts.
Ascending Loop of Henle
Reabsorbs salts, impermeable to water.
Active Transport
Requires ATP to move substances against gradients.
Primary Active Transport
Uses ATP for Na+, K+ ATP pumps.
Secondary Active Transport
Utilizes gradients created by primary transport.
Symport/Co-transport
Two substances move in the same direction. (e.g., Simultaneous transport of sodium with glucose/amino acids.)
Antiport/Counterparts
Two substances move in opposite directions. (e.g., Exchange of sodium with hydrogen ions.)
Osmolarity
Concentration of solutes in a solution.
Filtrate
Fluid in renal tubules before reabsorption.
Tubular Secretion
Movement of substances from blood into filtrate.
Transcellular Route
Substances move through tubular cells.
Paracellular Route
Substances move between tubular cells.
Isoosmotic Solution
Equal osmotic pressure of solute and solvent.
Dehydration Response
ADH increases water reabsorption in kidneys.
Capillary Proximity
Close contact between tubules and capillaries.
Sodium Reabsorption
Process of sodium uptake from tubular fluid.
Na+/K+ ATPase Pump
Active transport mechanism extruding 3 Na+ for 2 K+.
Chloride Reabsorption
Uptake of chloride alongside sodium in PCT.
Na+/H+ Counter Transporter
Exchanges sodium for hydrogen ions in PCT.
H+ Pumps
ATP-driven pumps moving H+ into tubular fluid.
Carbonic Anhydrase
Enzyme converting bicarbonate and H+ to carbonic acid.
Bicarbonate Reabsorption
80-90% of filtered bicarbonate is reabsorbed.
Saturation of Transporters
Maximum transport capacity reached at high solute levels.
Transport Maximum (Tm)
Maximum rate of substance reabsorption by transporters.
Renal Threshold for Glucose
Glucose appears in urine if blood >180 mg/dL.
Secondary Active Transport
Transport requiring energy indirectly via sodium gradient.
Filtered Glucose
Glucose filtered by glomerulus, reabsorbed in PCT.
Filtered Amino Acids
Amino acids filtered and completely reabsorbed in PCT.
Osmotically Active Particles
Particles that influence water reabsorption in kidneys.
Intracellular Sodium Concentration
Maintained low to favor sodium diffusion into cells.
Na+/HCO3- Cotransporters
Transporters moving sodium and bicarbonate into cells.
HCO3-/Cl- Countertransporters
Transporters exchanging bicarbonate for chloride ions.
Renal Handling of Ions
Processes managing ion concentrations in renal tubules.
Osmotic equilibrium
Water moves from lumen to interstitial fluid.
Transcellular pathway
Water movement through cell membranes.
Paracellular pathway
Water movement between cells.
Proximal convoluted tubule (PCT)
Site for solute-dependent water reabsorption.
Obligatory water reabsorption
Water leaving PCT is isotonic to plasma.
Secretion in PCT
Bile salts, creatinine, penicillin, aspirin secreted.
Descending Loop of Henle
Permeable only to water; reabsorbs water. // Permeable to water, not NaCl.
Ascending Loop of Henle
Reabsorbs sodium, potassium, chloride ions actively. // Reabsorb water, transport sodium to cortex.
Secondary active transport
Mechanism for ion reabsorption in ascending LOH.
Sodium-potassium pump
Decreases intracellular sodium in ascending LOH.
Principal cells
In distal tubule; regulate sodium and potassium.
Renin-aldosterone system
Regulates sodium reabsorption and potassium secretion.
Aldosterone
Steroid hormone; increases sodium channels and pumps.
HCO3-/Cl- counter transporters
Transporters in intercalated cells of late DCT.
Carbonic anhydrase
Enzyme producing bicarbonate and hydrogen ions.
Bicarbonate ion formation
New bicarbonate synthesized in late DCT.
pH buffering
Phosphate ions buffer excessive H+ secretion.
Renal clearance
Measurement of substance excretion in urine.
Glomerular filtration rate (GFR)
Rate at which substances are filtered by kidneys.
Plasma clearance
Varies based on kidney handling of substances.
Substance X excretion
Amount filtered equals amount excreted if not reabsorbed.
125 mL clearance
Volume of plasma cleared of substance X.
Plasma Clearance
Rate at which substance is cleared from plasma.
Creatinine
Endogenous waste product; estimates GFR.
Hyperosmotic Gradient
Concentration gradient in renal medulla for urine concentration.
Countercurrent Multiplier
System that enhances osmolarity in renal medulla.
Thick Ascending Limb
Pumps Na+, K+, and Cl-; creates hypotonic fluid.
Renal Medullary Interstitium
Fluid surrounding renal tubules; essential for concentration.
Tubular Fluid
Fluid within renal tubules; changes during filtration.
Urine Concentration
Kidney's ability to concentrate or dilute urine.
Osmolarity of Urine
Ranges from 50 to 1400 mOsm/L based on hydration. // Concentration of solutes in a solution.
Water Reabsorption
Process influenced by osmolarity and ADH levels.
Bicarbonate Ions
Synthesized in late distal convoluted tubules.
Kidney Disease Indicator
Creatinine clearance changes indicate kidney dysfunction.
Exogenous Substance
Substance not naturally produced by the body.
Filtration Process
Initial step in urine formation in kidneys.
Concentration Equilibrium
Reached when medullary osmolarity is 1200 mOsm/L.
Counter-current Exchange
Mechanism preserving renal medulla hyperosmolarity.
Vasa Recta
Blood vessels supplying the renal medulla.
Loop of Henle
Structure creating osmotic gradients in kidneys.
Hyperosmolarity
High solute concentration in renal medulla.
Urea Recycling
Reuses urea to maintain medullary osmolality.
Osmolality
Concentration of solutes in a solution.
ADH (Antidiuretic Hormone)
Hormone regulating water reabsorption in kidneys.
Dilute Urine (Hypotonic)
Urine with low osmolality, produced without ADH. // Urine with lower concentration than blood plasma.
Concentrated Urine (Hypertonic)
Urine with high osmolality, produced with ADH. // Urine with higher concentration than blood plasma.
Tubular Fluid Flow
Fluid movement through nephron's descending and ascending limbs.
Sodium Reabsorption
Active transport of Na+ from nephron to interstitium.
Water Permeability
Ability of tubules to allow water passage.
Collecting Duct
Final segment of nephron, adjusts urine concentration.
Filtrate
Fluid in nephron before it becomes urine.
Renal Medulla
Inner part of kidney, involved in urine concentration.
Proximal Convoluted Tubule
Site of significant reabsorption of water and solutes.
Distal Convoluted Tubule
Regulates electrolyte balance and water reabsorption.
Tubular Secretion
Process of removing substances from blood into nephron.
Osmotic Gradient
Difference in solute concentration across renal structures.
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