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Reabsorption and Secretion Along the Proximal Tubule - Anatomy & Physiology (view source)
Revision as of 15:17, 4 September 2008
, 15:17, 4 September 2008→THe Secretion of H<sup>+</sup> and the Reabsorption of HCO<sub>3</sub><sup>-</sup>
The secretion of these compounds occurs '''only in the proximal tubules'''. These molecules are mainly bound to plasma proteins with a small amount free in an active ionised form. It is only the free ions which are able to be transported. As the ionised molecules are transported into the blood more molecules are released from the plasma proteins to take their place. These can then be secreted etc etc. This allows a large amount of the substance to be secreted at one time. The mechanisms are not very selective and so many different substances are secreted at the same time. Secretion mechanisms are responsible for the secretion of drugs, hormones and things like food additives. Many unwanted or toxic organic molecules which enter the body are unionized. They therefore cannot be secreted so it falls to the liver to alter them into ionized forms to allow them to be disposed of.
The secretion of these compounds occurs '''only in the proximal tubules'''. These molecules are mainly bound to plasma proteins with a small amount free in an active ionised form. It is only the free ions which are able to be transported. As the ionised molecules are transported into the blood more molecules are released from the plasma proteins to take their place. These can then be secreted etc etc. This allows a large amount of the substance to be secreted at one time. The mechanisms are not very selective and so many different substances are secreted at the same time. Secretion mechanisms are responsible for the secretion of drugs, hormones and things like food additives. Many unwanted or toxic organic molecules which enter the body are unionized. They therefore cannot be secreted so it falls to the liver to alter them into ionized forms to allow them to be disposed of.
===THe Secretion of H<sup>+</sup> and the Reabsorption of HCO<sub>3</sub><sup>-</sup>===
===The Secretion of H<sup>+</sup> and the Reabsorption of HCO<sub>3</sub><sup>-</sup>===
[[Image:acidbaseflowkidap1.jpg|right|thumb|350px|<small><center>Secretion of H<sup>+</sup> and reabsorption of HCO<sub>3</sub><sup>+</sup> in the Proximal Tubule</center></small>]]
[[Image:acidbaseflowkidap1.jpg|right|thumb|350px|<small><center>Secretion of H<sup>+</sup> and reabsorption of HCO<sub>3</sub><sup>+</sup> in the Proximal Tubule</center></small>]]