OIA1004 (TERMS) URINARY SYSTEM II

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.