The liver detoxifies numerous toxins. It also destroys drugs, such as alcohol, nicotine, and prescription medicines, because these things are not normal to the body.
Toxic substances are everywhere. The body is not only exposed to toxic chemicals in the environment, but also some toxins are produced in the body through normal body chemical reactions.How can our bodies cope? This module explains some of the ways that animals and humans combat and eliminate toxic chemicals. The organ systems involved include the lungs, the skin, and the digestive tract, but two organs are especially important: the liver and the kidneys.We call the process of eliminating toxins, “detoxication” or “detoxification,” which is the opposite of “intoxication.” Different tissues detoxify in varying ways.
Why It Matters
You would be sick all the time if your body did not have ways to detoxify all the bad things that you breathe, drink, eat, and get on your skin. In fact, you could not even live. The world is full of bad chemicals, even without man-made pollution.But toxins would still be a problem even if we lived in a clean environment. Our own body makes toxic chemicals. For example, did you know that one product the body makes as a by-product of its normal chemical reactions is ethyl alcohol (the kind found in alcoholic drinks)? And the body changes alcohol into an even more toxic compound, acetaldehyde!Have you heard all the advertisements for Vitamin E and C as substances needed to combat free radicals? Free radicals are normal chemical breakdown products and they are very toxic. Sometimes, these radicals cause cancer and contribute to aging.See these sites for more information:
How We Find Out
We learned earlier that kidneys detoxify by secreting toxins or filtering toxins out of the blood into urine. But how do we know this?The best way to learn what kidneys do is to examine the product of their function- urine. Examining the urine is also a good way to know if anything is wrong with kidney function. Medical technicians in hospitals and clinics routinely examine urine (“urinalysis”) looking for any abnormalities. Any abnormalities could signal kidney disease. Examples of diseases that can be detected by urinalysis include diabetes, kidney stones, and chronic infections of the urinary tract.Kidneys stones, after they have been concentrated and removed from urine. Such stones in the urine can block urine formation and cause severe pain.Urine is analyzed in three ways:
What We Know
Obviously, loss of kidney function will lead to death. Inability to reabsorb water would lead to severe dehydration. Inability to secrete potassium can actually cause death because build up of potassium would stop the heart. Fortunately, two kidneys provide excess capacity. Only one kidney is actually essential. However, the loss of both kidneys is fatal. The only cure if both kidneys failed would be to get a transplant or to have the blood cleaned by machine (a process called kidney dialysis).
To be effective in cleaning blood, the kidneys must have a rich flow of blood. About 23% of the blood pumped by the heart over the course of a minute goes to the kidneys. So, within a few minutes, all of the blood in the body gets swept through the filtering system of the kidney.
GF = glomerulus filtering. TR = tubular reabsorption. TS = tubular secretion. So, you see that blood is filtered, giving up much of the water and dissolved substances it contains. Then, much of the water and some of the dissolved substances are reabsorbed into blood. Finally, some dissolved substances in blood are actually secreted into the urine. See Animations of Kidney Function
How do you suppose any organ could specialize to detoxify? One approach is taken by the kidney. The liver takes a different approach, involving two steps. If we examine the liver under a microscope, we see rows of liver cells with small spaces in between that act as a filter to remove dead cells, microorganisms, and chemicals as the blood flows slowly through the liver. This filter includes cells that engulf (“eat”) the sludge that is left trapped in the filter. Once inside the Kuppfer cells, the sludge must be broken down. There are two phases of detoxification in the liver. Phase one includes an enzyme, cytochrome p-450, to detoxify the bad stuff. This means that the harmful chemical gets broken down into smaller parts that are not harmful to the body. Phase two detoxification is when the Kuppfer cells add materials to the chemical to be broken down, and this new chemical is not harmful to the body. This addition of materials to a harmful substance is called conjugation. Once phases one and two have been performed, the sludge is ready to be added back to the regular blood stream and secreted as waste, and it never harms the body. We have a wonderful, life-saving detoxification plant.
The first place that blood from the stomach and intestines goes is to the liver. But then the blood leaving the liver goes to the heart and is pumped directly to the kidneys. Kidneys regulate the balance of water and salts in the body, but they also have a very important role in detoxication. With about 200 quarts being pumped through the kidneys every day, they do a big job for such a small organ! The main job is to take all of the blood in the body and clean it. This means:
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All substances that are absorbed in the digestive tract enter the veins that drain the gut and are carried in this venous blood to the liver. Think of the liver as the gatekeeper between the intestines and the general blood circulation. This is one of the few cases where venous blood comes INTO an organ. Because you have been told that the liver detoxifies chemicals, do you see why the liver gets its input of blood from the blood that drains from the gut? Relation of the liver to other organs in the abdomen. The liver lies just under the diaphragm and on top of the stomach. It is attached by a large vein to the stomach and small intestines. The liver detoxifies numerous toxins. It also destroys drugs, such as alcohol, nicotine, and prescription medicines, because these things are not normal to the body. Some medicines have the bad side effect of damaging liver cells. It is like a war between liver cells and the medicine, because the liver is programmed to destroy foreign chemicals and cannot know that medicines are supposed to be good for the body nor know which medicines may damage the liver cells in the process of destroying the drug.
Many products of bodily metabolism are waste products that the body either does not need or cannot use. The body may even be damaged by some of metabolism’s products. Thus, mechanisms exist to rid the body of these damaging chemicals. In addition, many chemicals in our environment are damaging to the body and such products need to be eliminated or destroyed. Three organ systems act in indirect ways to detoxify.
Story Time
Claude Bernard, 1813-1878
Experimenting on animals is a controversial practice. Many people think that animals have rights and should not be subjected to experimentation. Medical researchers, however, hold the view that animal research is necessary to human welfare and is certainly more defensible than eating animals. Experimenting on animals, also known as vivisection, was established as acceptable scientific practice by Claude Bernard. It was he who showed how much could be learned and applied to medical practice through vivisection.
In defending biomedical research on animals, the American Medical Association says:
“In fact, virtually every advance in medical science in the 20th century, from antibiotics and vaccines to antidepressant drugs and organ transplants, has been achieved either directly or indirectly through the use of animals in laboratory experiments.”
Claude Bernard was born near Villefranche (20km north of Lyons-see photo on right of his birthplace, now a museum), where his father worked the Chevalier de Quincieux estate. His father was a winemaker and Claude helped him tend the vineyards and process the harvest. His mother, Jeanne Saulnier, had a peasant background. His father went broke in a wine-marketing venture, and the family was poor. Claude studied Latin with a local priest and was taken in as a student in a Jesuit school at Villefranche. That school taught no science, and it is amazing that Claude developed an early interest in science. He studied at the middle school in Thoissey, but he quit school, without a diploma, and apprenticed to a chemist named Millet in a Lyon suburb. His work there was apparently boring, but he did enjoy the errands he ran to the nearby veterinary school.
While at Lyon, Claude developed an interest in medicine, perhaps in part because of his exposure to the veterinary school. Claude left Lyon to study medicine in Paris between 1834 and 1843. Claude was not a particularly good student, but then he had a very poor school background. Of 29 students passing the examination for the internship, Bernard ranked 26th. He failed the examination that would have qualified him to teach in the medical school, so he began collaborating with others in research projects.
Claude Bernard worked with François Magendie the leading physiologist of his time. For a while, Claude worked in Magendie’s shadow, but it soon became clear that Claude could hold his own with the best, even Magendie. In 1854 a chair of general physiology was created for Claude in the Sorbonne, and he was elected to the Academy of Sciences. When Magendie died in 1855, Bernard succeeded him as full professor before succeeding him to the experimental medicine chair at the Ollège de France in 1855.
Claude did not have his own laboratory at first, but his fame was such that he had a personal interview with Emperor Napoleon who made sure that a lab was constructed for him.
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During most of the 1800s, France was the world leader in medicine, and Claude Bernard grew up in that culture where advances in medicine were being driven by the scientific method. Claude became a leader in using the scientific method and, in fact, is generally considered the founder of modern experimental physiology. One of the lasting contributions he made was his demonstration of the value of hypothesis-driven research. Claude’s experiments began with a hypothesis, and tests were designed that would either support or refute the hypothesis, and that in turn guided the next steps in experimentation. Claude had three guiding principles for his own research; he believed that 1) the notion of “vital force” does not explain life; (2) animal research (vivisection) is indispensable for physiological research; and (3) life is mechanistically determined by physic-chemical forces.
Of the many lasting discoveries made by Claude, one stands out because it is such a fundamental principle. The principle (called a scientific law in Physics) is that the internal workings of warm-blooded animals are more or less constant, and that physiological mechanisms resist external forces that would alter this state. This is the principle of homeostasis, which was further advanced by his successor Walter Cannon.
Among his many other discoveries were experimental demonstrations of many of the functions of the liver. He showed that secretions of the pancreas contained digestive enzymes. He showed that certain parts of the pancreas were involved in diabetes. He also showed that the contraction and relaxation of small blood vessels were regulated by nerves. In addition, he demonstrated that there was a functional junction between nerves and muscle and that curare blocks this junction. If they had been awarding Nobel Prizes in those days, Claude would have won several. His contemporary, Louis Pasteur, called him “physiology itself.”
Ironically, the organ systems that Claude spent so many years studying were the very ones that caused his own illness and death. Claude apparently developed chronic enteritis, with disease affecting the pancreas and the liver.
Biography of Claude Bernard, 1813-1878
1810-1820 1820-1830 1830-1840 1840-1850 1850-1860 1860-1870 1870-1880 1813 Born on 12th July at St Julien, Rhône, France 1827 Pupil at the college in Villefranche 1831 Leaves the college in Thoissey
1832 Apprentice in Millet’s Pharmacy in Vaise, then a suburb of Lyon
1833 Leaves St Julien for Paris
1834 Obtains his baccalaureate
1837 Appointed extern of the Paris hospitals
1939 Appointed intern of the Paris hospitals 1843 Doctor of Medicine. Thesis on gastric juices. Discovers the glycogenic function of the liver.
1844 Fails the aggregation exam
1845 Marries Françoise Marie (Fanny) Martin
1846 Birth of a son Louis-Henri (dies at three months)
1847 Birth of a daughter, Jeanne-Henriette (Tony), died in 1923. Appointed substitute professor for Magendie at the Collège de France. Death of his father, Pierre Bernard.
1849 Naissance de Marie (meurt en 1922). Chevalier de la Légion d’honneur. 1853 Doctor of Natural Science
1854 Elected member of the French Academy of Sciences. Occupies the chair of General Physiology in the Paris Faculty of Science (Sorbonne)
1855 Appointed professor of medicine at the Collège de France
1856 Birth of Claude-Henri (died in 1857) 1861 Elected Member of the French Academy of Medicine
1865-1867 Convalescence after an illness (a sort of enteritis). Publication of his Introduction to the study of experimental medicine
1867 Death of his mother, Jeanne Saunier Appointed Commander of the French Legion of Honour
1868 Elected to the French Academy to the chair left vacant by the death of Flourens. His chair of General Physiology transferred to the French Museum of Natural History
1869 Officially separated from his wife. First letter to Madame Raffalovitch. Appointed Senator of the French Empire 1876 Chief administrator of the Paris Universal Exhibition
1877 Last lecture at the Collège de France
1878 Dies on 10th February at 40 rue des Ecoles, Paris.
National funeral takes place on 16th February at the church of Saint-Sulpice, Paris. He is buried in the Père-Lachaise cemetery, Paris, France
References: Bayliss, L.E. Living Control Systems, English University Press, London, 1966
LaFollette, Hugh and Niall Shanks. “Animal Experimentation: The Legacy of Claude Bernard”. http://www.etsu.edu/philos/faculty/hugh/bernard.htm
The Claude Bernard Museum. http://www.claude-bernard.co.uk/page20.htm
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