the highest rate of tubular reabsorption occurs in the kidneys.
the highest rate of tubular reabsorption occurs in the kidneys.
where does the highest rate of tubular reabsorption occur?
kidneys
a decrease in volume or pressure is a nonosmotic stimulus for antidiuretic hormone production in the hypothalamus, which exerts its effect in the medullary collecting duct for water reabsorption. through unknown mechanisms, activation of the sympathetic nervous system leads to enhanced proximal tubular reabsorption of salt and water, as well as urea (bun), calcium, uric acid, and bicarbonate. the net result of these 4 mechanisms of salt and water retention is decreased output and decreased urinary excretion of sodium (< 20 meq/l). the increased reabsorption of na leads to increased water and urea reabsorption from the proximal tubules of the kidney back into the blood. in contrast, creatinine is actually secreted in the proximal tubule. this generally leads to a bun:cr ratio  20 and a fractional excretion of na of  1% and an elevated urine osmolarity.
azotemia
in renal physiology, reabsorption or tubular reabsorption is the process by which the nephron removes water and solutes from the tubular fluid (pre-urine) and returns them to the circulating blood. it is called "reabsorption" (and not "absorption") both because these substances have already been absorbed once (particularly in the intestines) and because the body is reclaiming them from a postglomerular fluid stream that is well on its way to becoming urine (that is, they will soon be lost to the urine unless they are reclaimed). substances are reabsorbed from the tubule into the peritubular capillaries. this happens as a result of sodium transport from the lumen into the blood by the na/katpase in the basolateral membrane of the epithelial cells. thus, the glomerular filtrate becomes more concentrated, which is one of the steps in forming urine. reabsorption allows many useful solutes (primarily glucose and amino acids), salts and water that have passed through bowman's capsule, to return to the circulation. these solutes are reabsorbed isotonically, in that the osmotic potential of the fluid leaving the proximal convoluted tubule is the same as that of the initial glomerular filtrate. however, glucose, amino acids, inorganic phosphate, and some other solutes are reabsorbed via secondary active transport through cotransport channels driven by the sodium gradient.
reabsorption