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Nephron Reabsorption & Secretion - Overview

Nephron Reabsorption & Secretion - Overview

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Reabsorption and Secretion in the Nephron
Reabsorption
Removes solutes and water from the tubular fluid and returns them to the blood; much of the water, ions, and nearly all of the nutrients that are filtered are reclaimed.
Secretion
Moves solutes from the blood and nephron tubule cells into the tubular fluid; secretion is important for removal of substances that aren't filtered (such as drugs and metabolites) and for fine-tuning the final urine composition.
Transport in the Vasculature:
Efferent arteriole leaves glomerulus, gives rise to peritubular capillaries. Peritubular capillaries give rise to vasa recta of juxtamedullary nephrons. Vasa recta drains deoxygenated blood into the interlobular vein.
Reabsorption and Secretion by Segment
Reabsorbed from Proximal Tubule: Water Sodium Chloride Potassium Calcium Phosphate Urea Bicarbonate Glucose, amino acids, and other nutrients.
Secreted into Proximal Tubule: Hydrogen PAH (para-aminohippurate) Ammonium ions Certain drugs Organic acids and bases (such as creatinine)
Nephron loop: Concentrates or dilutes urine.
Reabsorbed from Thin Limb: Water
Secreted into Thin Limb: Urea
Reabsorbed from Thick Ascending Limb: Sodium Potassium Chloride Calcium Bicarbonate Magnesium (no water reabsorption) Distal Tubule reabsorption and secretion are hormonally regulated to fine-tune tubular fluid, to maintain ECF volume and osmolarity homeostasis.
Early Distal Tubule, aka, Diluting Segment: Sodium Chloride Potassium Calcium (no water reabsorption).
Reabsorbed from Late Distal Tubule: Water Sodium Chloride Bicarbonate Urea.
Secreted into Late Distal Tubule: Potassium
Secreted or Absorbed in Collecting Duct: Potassium Hydrogen Bicarbonate Ammonium ions

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