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Bile is one of the integral parts when considering the human digestive system. Bile, also widely known as ‘gall’, is a dark greenish-yellow secretion usually produced by the liver, and is typically concentrated in a thinly situated muscular sac, called the gallbladder. The stored and concentrated bile, after the consumption of food, is later released into the opening of the small intestine, widely referred to as the duodenum. It is responsible for helping the breakdown of fat into fatty acids in the human digestive system.
Read Also: Symptoms of Liver Problem
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Key Takeaways: Bile, Gallbladder, Lipids, Duodenum, Bile salts, alkaline, Liver, small intestine.
What is Bile?
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Bile is a complex, alkaline, greenish-yellow fluid that is usually produced and secreted by the liver. It is responsible for aiding the process of absorption and digestion, assisting the breakdown of fats into fatty acids. In simple words, it helps in emulsifying fats into minuscule micelles.
Bile is a bitter secretion concentrated in the gallbladder that aids the breakdown within the small intestine, helping the body remove all the waste from the human body via the digestive tract. Once it reaches the gallbladder, the fluid can be 5 times as concentrated, sometimes even 18 times the original form of secretion.
Bile is continually secreted and stored in the gallbladder. It is usually released and discharged in the duodenum, the opening section of the small intestine, commonly situated between the stomach and the mid-portion of the jejunum. The discharge facilitates the process of digestion.
Biliary Tract
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Bile Composition
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There are several compounds that are responsible for the composition of bile, yet one of the most vital of all of them are bile acids, also typically known as bile salts. For humans to absorb fats, bile acids help combine lipids during the process of digestion. It is composed of various substances usually blended altogether, much like,
- Bile acids or Bile Salts.
- Cholesterol.
- water
- Pigments, like bilirubin, alongside others.
- Phospholipids, or phosphatides – which belong in the class of lipids, containing complex fats comprising phosphorus.
- Electrolytes, or simply, body salts – much like, sodium and potassium.
- Metals – Copper, to name one out of many.
One of the major, critically significant pigments present in bile is bilirubin – a yellowish orange substance – generally constituted during the breakdown of red blood cells. Once oxidized, bilirubin can be transformed into biliverdin – a pigment green in appearance. Adults commonly produce roughly about 400 to 800 milliliters of bile per day.
Function of Bile in Digestion
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Bile plays a pivotal role in the breaking down of lipids, especially fat into fatty acids to assist the process of digestion. It is a necessary step found in the human body that is responsible for emulsifying lipids for further absorption. It also commonly helps in the removal of waste substances the body cannot further use.
Bile also helps the absorption of fat-soluble vitamins, alongside discharging pigments highly toxic for the human body, such as bilirubin and cholesterol, if present in abundance.
It helps achieve complete digestion, especially due to the presence of bile salts. In the process of digestion, bile acts as an emulsifier that breaks larger fatty substances into smaller ones. In a nutshell, emulsified fats offer a larger room, helping lipase to act in harmony, helping expedite the process.
By and large, bile usually acts as a surfactant, aiding the emulsification of lipids quite faster. Bile salts carry anions that are hydrophilic and hydrophobic on either side. It shows readiness to surround droplets of liquids, like phospholipids, to compose micelles.
For the most part, the hydrophilic face of the micelles are found charged – which is partly necessary to intercept fatty droplets to begin shaping into larger particles of fat, generally found in a coat bile.
Bile also similarly helps in the activation of lipase. The increased amount of space helps lipase, a protein composed by the pancreas, to digest triglycerides and phospholipids, in the human body.
After the consumption of meals, the bile secreted by the liver flows to the small intestine. However, when the need to break down lipids minimizes, the bile flows into the gallbladder instead.
Bile Reflux
Read Further: Difference Between Small and Large Intestine
Things to Remember
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- Bile is a dark greenish-yellow substance, mostly alkaline in nature, that helps the breakdown of lipids, especially fat into fatty acids.
- Bile is composed of a few different compounds – like bile salts, cholesterol, water, pigments like bilirubin, body salts and metals.
- Bile also helps the absorption of fat-soluble vitamins, as much as it also helps discharging highly toxic pigments found in abundance in the human body – much like bilirubin and cholesterol.
- Once oxidized, bilirubin normally transforms into biliverdin – a pigment green in appearance.
- Adults commonly produce roughly about 400 to 800 milliliters of bile on average.
- Bile is secreted and stored in the gallbladder. Usually, it is released and discharged in the duodenum, the opening section of the small intestine.
- Bile doesn’t contain any digestive enzyme yet plays a major role in the process of digestion.
Previous Year Questions
- The characteristic that is shared by urea... [KCET 2009]
- The primary dentition in humans differs from... [NEET 2015]
- Stool of a person contain whitish grey colour due to... [NEET 2002]
- Food is moved along the alimentary canal by the contraction known as... [JIPMER 2003]
- A baby boy aged two years is admitted to play school and passes through a dental check - up. The dentist observed that the boy had twenty teeth. Which teeth were absent?… [NEET 2017]
- Which cells of "Crypts of Lieberkuhn" secrete antibacterial lysozyme?... [NEET 2017]
- Secretin and cholecystokinin are digestive hormones. They are secreted in….[NEET 2005]
- Which of the following statements is not correct?... [NEET 2015]
- If for some reason the parietal cells of the gut epithelium become partially non-functional, what is likely to happen?... [NEET 2010]
- Jaundice is a disorder of... [NEET 2010]
- Duodenum has characteristic Brunner's gland which secrete two hormones called...[NEET 2004]
- A healthy person eats the following diet-5 gm raw sugar,. 4 gm albumin, 10 gm pure buffalo ghee adultrated with 2 gm vegetable ghee (hydrogenated vegetable oil) and 5 gm lignin. How many calories he is likely to get?...[NEET 2013]
- A person who is eating boiled potato, his food contains the component...[NEET 2000]
- Anxiety and eating spicy food together in an otherwise normal human, may lead to...[NEET 2012]
- Calcium deficiency in the body occurs in the absence of...[NEET 1994]
- Choose the correct enzyme - substrate pair... [NEET 1996]
- Continuous bleeding from an injured part of body is due to deficiency of...[NEET 2002]
- Duct leading from parotid gland and opening into vestibule is...[NEET 1998]
- During prolonged fastings, in what sequence are the following organic compounds used up by the body...[NEET 2003]
- Emulsification of fat is carried out by...[NEET 1990]
Sample Questions
Ques. What is Bile? (2 marks)
Ans.Bile is a very significant part when considering the human digestive system. Bile, also widely known as ‘gall’, is an alkaline, dark greenish-yellow fluid that is commonly produced by the liver, and is typically stored and concentrated in the gallbladder. Bile, a complex fluid secretion of the liver, is responsible for aiding the process of absorption and digestion in the human body, assisting the breakdown of lipids, especially fats into fatty acids.
Ques. What is the function of bile? (2 marks)
Ans. Bile facilitates the process of digestion in the human body. Bile is also equally responsible for the removal of waste materials the body cannot further use. It also helps the absorption of fat-soluble vitamins, besides discharging pigments highly toxic for the human body, such as bilirubin and cholesterol, if present in abundance. It helps achieve complete digestion, especially due to the presence of bile salts. In general, bile acts as a surfactant, aiding the emulsification of lipids quite faster.
Ques.What is the pH value of Bile? Name and define the organ responsible for its secretion. (3 marks)
Ans. The pH value of the bile juice is around 7.5 to 8.5, which is typically more than the pH value found in the gallbladder. Bile is a complex, alkaline, greenish-yellow fluid that is usually produced and secreted by the liver. The liver is the largest gland in the human body and secretes bile – a digestive fluid – responsible for the emulsification of lipids, especially fats. It facilitates the removal of toxins from the blood as well. Bile, the fluid liver secretes, is also equally responsible for aiding the process of absorption and digestion, assisting the breakdown of fats into fatty acids. In simple words, it helps in emulsifying fats into minuscule micelles.
Ques. Define the role of the liver in the human body. (4 marks)
Ans. The liver is the largest gland in the human body, typically found in the shape of a muscular spongy mass with multiple lobes. It is responsible for more than one function. The liver helps regulate several chemical levels found in the blood and also similarly secretes a greenish-yellow fluid, bile. The liver assists, breaks down and also balances the nutrients found in the human body. It helps the metabolization of fats, proteins and carbohydrates – besides enzyme activation as well.
Ques. What are the contents of Bile? (5 marks)
Ans. For humans to absorb fats, bile acids help combine lipids during the process of digestion. It is composed of different substances usually blended altogether, much like,
- Bile acids or Bile Salts (0.7 per cent). - Cholesterol, Lecithin and fatty acids as well (0.51 per cent). - Water (97 to 98 per cent). - Pigments, like bilirubin (0.2 per cent), alongside others. - Phospholipids, or phosphatides – which belong in the class of lipids, containing complex fats comprising phosphorus. - Electrolytes, or simply, body salts (200 meq/l) – much like sodium and potassium. - Metals – Copper, to name one out of many.
Ques. What is the working mechanism of bile in human beings? (3 marks)
Ans. After the consumption of food, bile is stored and gradually also concentrated in the gallbladder, and quite a tiny amount flows into the intestine. The fat that enters the duodenum, the opening section of the small intestine, incites the nerve signals that consequently result in the contraction of the gallbladder. There are several hormones that are responsible for navigating this process, much like Cholecystokinin, Secretin, Gastrin, and Somatostatin. Usually after the hormonal and nerve signals, the bile tends to flow into duodenum, blending with the food, stomach acids and several digestive secretions produced by the pancreas, during the process. It helps the intestines subsequently absorb the nutrients, flowing them back to the bloodstream.
Ques. Define why bile salts play a significant role in the digestion process? (3 marks)
Ans. The liver is the largest gland found in the human body, usually in the shape of a muscular spongy mass with multiple lobes and looks reddish-brown in appearance. The pH value of the bile juice is roughly about 7.5 to 8.5, which is typically more than the pH value found in the gallbladder. Bile also contains bile salts which are very significant for aiding digestion, especially because they are the fundamental components of bile. Bile salts are responsible for the digestion of fats. They also equally play a pivotal role in absorbing fat-soluble vitamins, like vitamin A, D, E and K.
Ques. “Bile juice does not have any digestive enzyme but is yet considered equally important in aiding digestion.” Justify why. (2 marks)
Ans. Bile juice is a digestive secretion produced by the liver. And, even though it has no digestive enzyme content, it still plays a vital role in aiding digestion. The major reason behind it is because it contains bile salts, like bilirubin and biliverdin. These pigments typically assists the breakdown of large fat globules into several smaller micelles, such that the pancreatic enzymes can easily include them in the process of digestion. This process is usually widely known as the ‘emulsification of fat.’
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