Excretion And Elimination Of Toxicants And Their Metabolites :: essays research papers

Excretion and Elimination of Toxicants and their MetabolitesThe scratch line topic that was covered by this chapter was the excretion of wastesby the Renal system. The first step that occurs in the kidney deals with thenephron, which is the utilitarian unit of the kidney. In the glomerulus theformation of urine begins with the peaceable filtration of plasma through thepores that be found in the glomerulus. The plasma is forced through these poresby hydrostatic pressure. The only things that determines if a molecule exit imbibethrough the pores of the glomerulus is its molecular weight. The lower themolecular weight, the easier it will pass through the pores. An another(prenominal)determining reckon will be if a molecule is abjure to a large molecule. If thisis true then passage through the pores will be hindered by the coat of thelarger molecule.Reabsorbtion of the many ions, minerals and other nutrients that escaped inthe glomerular filtrate will need to be recovered.. Re absorbtion begins in thetubules of the nephron. Anywhere from 65% to 90% of reabsorbtion occurs inthese structures. Active reabsortion is used to recapture glucose, proteins,amino acids and other nutrients. Water and chloride ions are passivelyreabsorbed by the establishment of osmotic and electrochemical gradients. Boththe Loop of Henley and collecting duct are used to establish these osmolargradients. The tubule has a brush border that will absorb proteins andpolypeptides through pinocytosis. These molecules are sometimes catabolised andconverted into amino acids. and returned to the blood. sometimes theaccumulation of these proteins can lead to renal toxicityA second process that occurs in the tubules is tubular secretion. This isanother mechanism used to excrete solutes. discrimination may be either passive oractive. Secretions include organic bases, which occur in the pars recta of theproximal tubule. Secretions of weak bases and two weak acids occur passively. other mechanis ms involves the use of a mechanism that is called ion trapping. Ata certain pH the compounds are more ionized. Outside of the tubule thesecompounds are non-ionized and are lipophilic. Thus they are suitable to diffuseacross the membranes of the tubule. Once inside, the pH of the tubule willionize them and render then unable to pass across the cell membranes.The removal of xenobiotics is dependant on many factors. First is thepolarity of the xenobiotic. Polar compounds are soluble in the plasma water aremore easily removed by the kidneys through the use of glomerular filtration. Thefaster the rate of glomerular filtration , the faster the polar xenobiotics areExcretion And Elimination Of Toxicants And Their Metabolites essays research papers Excretion and Elimination of Toxicants and their MetabolitesThe first topic that was covered by this chapter was the excretion of wastesby the Renal system. The first step that occurs in the kidney deals with thenephron, which is the function al unit of the kidney. In the glomerulus theformation of urine begins with the passive filtration of plasma through thepores that are found in the glomerulus. The plasma is forced through these poresby hydrostatic pressure. The only things that determines if a molecule will passthrough the pores of the glomerulus is its molecular weight. The lower themolecular weight, the easier it will pass through the pores. Anotherdetermining factor will be if a molecule is bound to a large molecule. If thisis true then passage through the pores will be hindered by the size of thelarger molecule.Reabsorbtion of the many ions, minerals and other nutrients that escaped inthe glomerular filtrate will need to be recovered.. Reabsorbtion begins in thetubules of the nephron. Anywhere from 65% to 90% of reabsorbtion occurs inthese structures. Active reabsortion is used to recapture glucose, proteins,amino acids and other nutrients. Water and chloride ions are passivelyreabsorbed by the establishment of osmotic and electrochemical gradients. Boththe Loop of Henley and collecting duct are used to establish these osmolargradients. The tubule has a brush border that will absorb proteins andpolypeptides through pinocytosis. These molecules are sometimes catabolised andconverted into amino acids. and returned to the blood. Sometimes theaccumulation of these proteins can lead to renal toxicityA second process that occurs in the tubules is tubular secretion. This isanother mechanism used to excrete solutes. Secretion may be either passive oractive. Secretions include organic bases, which occur in the pars recta of theproximal tubule. Secretions of weak bases and two weak acids occur passively.Other mechanisms involves the use of a mechanism that is called ion trapping. Ata certain pH the compounds are more ionized. Outside of the tubule thesecompounds are non-ionized and are lipophilic. Thus they are able to diffuseacross the membranes of the tubule. Once inside, the pH of the tubule will ionize them and render then unable to pass across the cell membranes.The removal of xenobiotics is dependant on many factors. First is thepolarity of the xenobiotic. Polar compounds are soluble in the plasma water aremore easily removed by the kidneys through the use of glomerular filtration. Thefaster the rate of glomerular filtration , the faster the polar xenobiotics are