reabsorboida

Reabsorboida is the Romanian term for reabsorption, the physiological process by which substances that have been filtered or secreted are taken back into the body's circulation, reducing their loss in excreta. This process is essential for conserving water, electrolytes, nutrients, and other needed solutes.

In the kidney, tubular reabsorption recovers most of the filtered load from the glomerular filtrate. The proximal tubule reabsorbs about two-thirds of filtered water and solutes, including glucose, amino acids, bicarbonate, and sodium, primarily via sodium-coupled transporters. The loop of Henle, distal tubule, and collecting duct continue selective reabsorption, with the amount and composition of reabsorbed material adjusted by hormones to regulate urine concentration and volume.

Mechanisms involve transcellular transport across tubular cells and paracellular diffusion between cells. Sodium reabsorption often drives the uptake of other solutes; water follows osmotically. Transport proteins and channels include SGLT transporters for glucose, bicarbonate transporters, various Na+-dependent exchangers, and aquaporin water channels. Hormonal regulation, notably aldosterone and antidiuretic hormone, fine-tunes reabsorption in the distal nephron and collecting ducts.

Reabsorption also occurs in the gastrointestinal tract, where nutrients and water are reclaimed from luminal contents, and in other systems such as the cerebrospinal fluid pathways, which can be reabsorbed into the venous circulation.

Clinical relevance: disturbances of reabsorption contribute to fluid and electrolyte disorders, and many diuretics act by inhibiting specific tubular reabsorption pathways to promote excretion. The term derives from Latin re- "again" and absorbere "to absorb."