Section 13: Key Points
What We've Covered
This section made the following main points:
What We've Covered
This section made the following main points:
- Excretion, as used in ToxTutor, pertains to the elimination of a xenobiotic and its metabolites by specific excretory organs.
- The primary organ systems involved in excretion are the:
- Urinary system, which involves:
- Filtration in the glomerulus.
- Secretion in the proximal tubule section of the nephron to transport certain molecules out of the blood and into the urine.
- Reabsorption in the proximal convoluted tubule of the nephron to reenter nearly all of the water, glucose, potassium, and amino acids lost during filtration back into the blood.
- Gastrointestinal system, which occurs from two processes:
- Biliary excretion — generally active secretion by the liver into the bile and then into the intestinal tract, where it can be eliminated in the feces or reabsorbed.
- Intestinal excretion — an important elimination route only for xenobiotics that have slow biotransformation or slow urinary or biliary excretion.
- Biliary excretion — generally active secretion by the liver into the bile and then into the intestinal tract, where it can be eliminated in the feces or reabsorbed.
- Respiratory system, which is important for xenobiotics and metabolites that exist in a gaseous phase in the blood:
- Excreted by passive diffusion from the blood into the alveolus.
- Urinary system, which involves:
- Minor routes of excretion occur including breast milk, sweat, saliva, tears, and semen.