Final answer:
The liver is involved in the metabolism and detoxification of various substances, including alcohol, nicotine, cortical hormones, and medications. Substances like ethanol and nicotine are metabolized into less harmful compounds, while cortical hormones are transformed and conjugated before excretion. The liver transforms drugs into excretable forms, but actual excretion primarily occurs through the kidneys.
Step-by-step explanation:
Detoxification and Excretion in the Liver
The liver is a central organ in the body's detoxification processes. It performs up to 500 functions, with drug metabolism being one of the crucial ones. Various substances, including alcohol, medications, and hormones, are broken down by liver enzymes to make them less harmful. For instance, ethanol is metabolized into carbon dioxide and water, while nicotine is extensively metabolized into various breakdown products like cotinine.
Drugs and hormones are modified in the liver by enzymes such as Catechol-O-Methyl-Transferase (COMT) and Mono-Amine Oxidase (MAO), leading to metabolites that are eventually excreted. Cortical hormones are another example of substances detoxified in the liver. They are reduced to tetrahydro derivatives and conjugated with glucuronic acid. Drug molecules that are water-soluble can be excreted in the urine, influenced by glomerular filtration, tubular secretion, and tubular reabsorption processes.
It is important to note that while the liver modifies these substances to make them less toxic, the excretion process itself mainly takes place through the kidneys. Thus, while the liver transforms substances to be more water-soluble or less harmful, it does not directly remove them from the body.