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A complex process of digestion enables the nutrients to enter the body and its cells. Food contains all of the nutrients a person’s body needs for health, but large, complex compounds bind them. During digestion, the body breaks these compounds down into smaller parts. This enables them to enter cells, providing energy and Thisenefits. This article explains how the body digests food from when it enters the mouth to when it exits the body. It also suggests some tips for healthy digestion and how to identify problems. What is digestion Share on PinterestThe human gastrointestinal tract, also called the alimentary canal, is around 30 feet (9 meters) long in adults. It consists of the following: the mouth, or oral cavitythe esophagusthe stomachthe small intestinethe large intestine, or colonthe rectum In addition, the following organs support digestion, for example, by chewing or adding enzymes and other secretions that enable the body to absorb nutrients:the teeththe tonguethe salivary glandsthe liverthe pancreasthe gallbladder Together, these organs provide mechanical processing, the secretion of enzymes and bile to help break down compounds, and the excretion of waste. Some terms to describe these functions include:ingestion, which includes chewing and swallowingthe secretion of substances that enable food and nutrients to move through the body effectivelypropulsion, where muscles move the contents of the canal forwarddigestion, the breakdown of food, for example, through chewing and secretionsthe absorption of nutrients, which mainly occurs in the small intestinedefecation and urination, the removal of waste products through the rectum and the bladder, respectively The mouth Digestion begins even before the food enters the mouth. When a person smells or thinks of food or eating, the salivary glands begin producing saliva. Once the food is inside of the mouth: saliva moistens it.the teeth and tongue break it down mechanically.an enzyme in the saliva, salivary amylase, breaks it down into starch. Chewing and amylase digestion will convert the food into a small, round blob, or bolus. This enables a person to swallow it easily. The esophagus After swallowing, the bolus enters the esophagus, where gravity and muscle contractions help move it down to the stomach through a process called peristalsis. Peristalsis is the slow contraction of smooth muscles along and around the digestive system. As the bolus moves through the esophagus, these contractions push it toward the stomach. What is esophageal achalasia, and how does it affect digestion? The stomach The bolus enters the stomach through a ring-like muscle called the lower esophageal sphincter. This sphincter relaxes, allowing the bolus to enter the stomach. In the stomach, the following processes occur: The stomach stores the food temporarily. Cells in the stomach secrete gastric juices. These include hydrochloric acid, which maintains the pH of the stomach between 1.5–2.0.The stomach has three muscular layers that churn and mix its contents. These processes turn the food into a thick paste, known as chyme. Hydrochloric acid is essential for: destroying microorganisms, such as bacteriabreaking down proteins and plant fibersactivating pepsin, an enzyme that helps digest proteins The acid, however, can harm the stomach lining, so some cells produce mucus to protect the lining from damage. The stomach does not absorb many nutrients from the chyme into the bloodstream, so the chyme enters the small intestine through the pyloric sphincter. How can you increase stomach acid naturally? The small intestine The small intestine is around 20 ft (6 m) long and absorbs around 90% of the nutrients from food into the bloodstream. There are three sections: The duodenum: This receives chyme from the stomach and digestive enzymes from the liver and pancreas.The jejunum: Most of the chemical digestion and absorption occur here.The ileum: This contains the ileocecal valve, a sphincter through which food passes to the large intestine. Once the food is fully broken down, the villi absorb the nutrients, which enter the bloodstream. Villi are tiny, finger-like projections that line the walls of the small intestine. Within the villi are tiny capillaries called lacteals. By increasing their surface area, the villi maximize their absorption of nutrients. How do the intestines work? The large intestine Any unabsorbed food and nutrients now pass to the large intestine, or colon. The material is now feces. The large intestine is around 6 ft (2 m) long and consists of the:cecum, a pouch through which food enters from the small intestineascending colontransverse colondescending colonsigmoid colon From the large intestine, the body absorbs water and electrolytes. Food travels slowly through the colon to allow the body to absorb water, and trillions of gut bacteria break down any undigested food. Next, peristalsis moves the feces toward the rectum. The rectum As the digested food moves into the rectum, nerves in the wall of the rectum known as stretch receptors detect when the chamber is full and stimulate the desire to defecate. Defecation involves two types of muscle movement. The first happens automatically, and a person cannot control it. This is a relaxation of the smooth muscles in the internal anal sphincter. The second, a person can control and is a conscious relaxation of the skeletal muscles in the external anal sphincter. If a person wishes to delay defection, they can avoid relaxing their muscles to move the feces back into the colon. The longer feces stay in the colon, the more water the body will absorb. This can lead to dry, hard feces, constipation, and possibly impaction. For this reason, a person should defecate as soon as is convenient. A person should seek medical advice if they are unable to defecate for about 3 days or if they have abdominal or rectal pain or bleeding What are some home remedies for constipation? Healthy digestion tips Ways of maintaining healthy digestion include:drinking plenty of waterfollowing a balanced diet with plenty of fruits, vegetables, fiber, and whole foodsavoiding delays when using the bathroom when possibleexercising regularlyfollowing food hygiene rules, such as handwashing and cooking meat, eggs, and fish well before eating themseeking medical help if a person’s usual digestive or toilet habits change When to see a doctor A person should seek medical help if they notice any of the following symptoms:persistent or recurring constipation, gas, vomiting, or diarrheasevere pain in any part of their digestive systempersistent or severe acid reflux or heartburnunexplained changes in their weight or appetiteblood in their stoolblood in their vomitdifficulty swallowing or feeling that food is stuck in their throatchanges in their bowel habits Which foods cause gas and bloating? Frequently asked questions Here are some answers to questions people often ask about digestion. What are the stages of the digestive system During digestion, food passes through the following stages: the mouththe esophagusthe stomachthe small intestinethe large intestine, or colonthe rectum How does digestion work step-by-step First, the teeth, tongue, and saliva turn food into a bolus, which is small and liquid enough to pass through the esophagus. Next, the bolus enters the stomach, where muscular action, acids, and enzymes turn it into a paste called chyme. The chyme enters the small intestine. Here, about 90% of absorption occurs. Nutrients enter the bloodstream through capillaries in villi. From there, the nutrients travel to various body cells. Any remaining food passes into the large intestine, or colon. The body absorbs water as the food passes through to the rectum, ready for defecation. How can I keep my digestion healthy Tips include: drinking plenty of watereating a varied diet with plenty of fresh vegetables and whole foodsestablishing regular bowel habitsseeking medical help for any unexplained changes in digestion or bowel habits Takeaway The digestive system moves food through the body, breaking it down so nutrients can absorb into the bloodstream, where cells can use them for energy, tissue growth and repair, and other purposes. Digestion involves multiple organs and systems, a range of chemicals, and peristalsis, automatic muscle movements, that move the food to the next stage. Anyone who notices changes to their usual digestive processes should seek medical advice, as this may indicate a health condition that requires treatment. Last medically reviewed on July 11, 2022ConstipationBiology / BiochemistryGastroIntestinal / Gastroenterology 7 sourcescollapsedMedical News Today has strict sourcing guidelines and draws only from peer-reviewed studies, academic research institutions, and medical journals and associations. We avoid using tertiary references. We link primary sources — including studies, scientific references, and statistics — within each article and also list them in the resources section at the bottom of our articles. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.Constipation: Frequently asked questions. (n.d.).https://www.uofmhealth.org/conditions-treatments/digestive-and-liver-health/constipation-frequently-asked-questionsDigestive system. (2022).http://www.diabetes.co.uk/body/digestive-system.htmlHow our digestive system works and keeping it healthy. (2020).https://www.gosh.nhs.uk/wards-and-departments/departments/clinical-specialties/gastroenterology-information-parents-and-visitors/how-our-digestive-system-works-and-keeping-it-healthy/Ogobuiro, I., et al. (2022). Physiology, gastrointestinal.https://www.ncbi.nlm.nih.gov/books/NBK537103/Quick anatomy lesson: Human digestive system. (2014).https://www.asge.org/home/about-asge/newsroom/media-backgrounders-detail/human-digestive-systemWhen to call the doctor about digestive problems. (n.d.).https://www.sutterhealth.org/services/gastroenterology/when-to-call-the-doctor-about-digestive-problemsYour digestive system & how it works. (2017).https://www.niddk.nih.gov/health-information/digestive-diseases/digestive-system-how-it-worksFEEDBACK:Medically reviewed by Cynthia Taylor Chavoustie, MPAS, PA-C — By Tim Newman — Updated on July 11, 2022 Latest newsWhat sets 'SuperAgers' apart? 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