In physiology, reabsorption or tubular reabsorption is the flow of glomerular filtrate from the proximal tubule of the nephron into the peritubular capillaries, or from the urine into the blood. It is termed "reabsorption" because this is technically the second time that the nutrients in question are being absorbed into the blood, the first time being from the small intestine into the villi. This happens as a result of sodium transport from the lumen into the blood by the Na+/K+ ATPase in the basolateral membrane of the epithelial cells. Thus, the glomerular filtrate becomes more concentrated, which is one of the steps in forming urine. In this way, many useful solutes (primarily glucose and amino acids), salts and water that have passed in the proximal tubule through the Bowman's capsule, return in the circulation. These solutes are reabsorbed isotonically, in that the osmotic potential of the fluid leaving the proximal 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 out of the nephron.

Renin Angiotensin System:

1. The kidneys sense low blood pressure.

2. Release renin into the blood.

3. Renin causes production of Angiotensin I.

4. Angiotensin Converting Enzyme (ACE) converts Angiotensin I to Angiotensin II.

5. Angiotensin II stimulates the release of Aldosterone, ADH, and thirst.

6. Aldosterone causes kidneys to reabsorb sodium. ADH increases the uptake of water.

7. Water follows sodium.

8. Blood volume goes up, therefore blood pressure goes up.

Other articles related to "reabsorption":

Thiazide - Mechanisms of Action
... They control hypertension in part by inhibiting reabsorption of sodium (Na+) and chloride (Cl−) ions from the distal convoluted tubules in the kidneys by blocking the thiazide-sens ... Thiazide diuretics also increase calcium reabsorption at the distal tubule ... (In other words, less Ca++ in the cell creates a force for reabsorption from the lumen) ...
Renal Protein Reabsorption - Overview Table
... Characteristics of oligopeptide reabsorption Characteristic proximal tubule loop of Henle Distal convoluted tubule Collecting duct system S1 S2 S3 reabsorption (%) 99 reabsorption (mmoles ...
Renal Sodium Reabsorption - Overview Table
... Characteristics of Na+ reabsorption Characteristic proximal tubule loop of Henle Distal convoluted tubule Collecting duct system S1 S2 S3 descending limb ...
Aldosterone - Function
... This results in reabsorption of sodium (Na+) ions and water (which follows sodium) into the blood, and secreting potassium (K+) ions into the urine (lumen of collecting duct) ... secretion of K+ into the tubular lumen Aldosterone stimulates Na+ and water reabsorption from the gut, salivary and sweat glands in exchange for K+ ... Aldosterone is responsible for the reabsorption of about 2% of filtered sodium in the kidneys, which is nearly equal to the entire sodium content in human blood ...