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Selective reabsorption is the process whereby certain molecules (e.g. ions, glucose and amino acids), after being filtered out of the capillaries along with nitrogenous waste products (i.e. urea) and water in the glomerulus, are reabsorbed from the filtrate as they pass through the nephron. [1]
Selective reabsorption of useful molecules by the canal cells occurs as the solutes pass down the tubule. Protonephridia are generally found in basal organisms such as flatworms. Protonephridia likely first arose as a way to cope with a hypotonic environment by removing excess water from the organism (osmoregulation). Their use as excretory and ...
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.
For example, bicarbonate (HCO 3 −) does not have a transporter, so its reabsorption involves a series of reactions in the tubule lumen and tubular epithelium. It begins with the active secretion of a hydrogen ion (H + ) into the tubule fluid via a Na/H exchanger :
Secretion and reabsorption of various substances throughout the nephron. Reabsorption is the transport of molecules from this ultrafiltrate and into the peritubular capillary network that surrounds the nephron tubules. [33] It is accomplished via selective receptors on the luminal cell membrane. Water is 55% reabsorbed in the proximal tubule.
Fig.3) Secretion and reabsorption of various substances throughout the nephron. The nephron uses four mechanisms to convert blood into urine: filtration, reabsorption, secretion, and excretion. [5]: 395–396 These apply to numerous substances. The structure and function of the epithelial cells lining the lumen change during the course of the ...
Renal corpuscle showing glomerulus and glomerular capillaries Figure 2: (a) Diagram of the juxtaglomerular apparatus: it has specialized cells working as a unit which monitor the sodiujuxtaglomerular apparatus: it has three types of specm content of the fluid in the distal convoluted tubule (not labelled - it is the tubule on the left) and adjust the glomerular filtration rate and the rate of ...
Although only a fragment of total reabsorption happens here, it is the main part of intervention. This is e.g. done by endogenous production of aldosterone, increasing reabsorption. Since the normal excretion rate of sodium is ~100mmoles/day, then a regulation of the absorption of still more than 1000 mmoles/day entering the collecting duct ...