As kids, we've always been listening to our parents reiterating the importance of proper digestion. But the question which always kept cropping is what is digestion? Digestion is defined as the mechanical and chemical breakdown of macro food particles into smaller and simpler forms, so as to facilitate the absorption of nutrients by the body. This is a definition of what is digestion, for kids in schools! Does the definition clear all doubts? No! In fact, it raises a few more. Let's take a look at the digestive system and try to find out what happens after the food goes into your mouth.
What is digestion and why is it necessary? Digestion is necessary to facilitate metabolism of food. The food that we eat contains various nutrients like proteins, vitamins, carbohydrates, minerals, etc. that provide energy, immunity, serve as building blocks, and nourishes the body. In the food that we eat, nutrients are in the form of large molecules that are physically and chemically bound together. Digestion breaks down this bond of complex molecules into simple nutrient molecules that can be absorbed by the body to support its day-to-day functions. For example the complex protein molecules are broken down into simple molecules of amino acids, which can be easily absorbed by the intestinal walls, and then can be diffused into the blood.
Several organs of the digestive system are involved in the digestion process. The process starts in the mouth and passes through the esophagus, stomach, small intestines, large intestines, rectum and ends with the anus. But, before we go further, it is important to know what controls the digestive system. There are hormones that control the functioning of the digestive system. These are produced by cells in the stomach and small intestine. Gastrin, secretin, and cholecystokinin (CCK) are the three hormones that mainly control digestion. Let us go step by step to see what happens after food enters the mouth.
The process of digestion begins in the mouth or the oral cavity. The mechanical process of cutting and chewing the food is the very basic step of digestion. This process also involves the mixing of food with saliva where the tongue is actively involved. There are certain enzymes in the saliva which softens the food and prepares it for digestion, before the core process starts in the stomach.
The next organ worth mentioning is the esophagus. It is a tunnel like organ that connects the mouth to the stomach and delivers the chewed food mixed with saliva to the stomach. It has a set of ring shaped muscles aligned parallel to each other that push the food towards the stomach. This is the reason why one can successfully swallow the food, even while in an upside down position (please, don't try this at home!).
The next organ in the functioning of the digestive system is the stomach. The stomach is the most important organ in the digestive system of mammals. Any disorder in the functioning of the stomach can cause digestion problems. The stomach is a small J-shaped pouch like organ, walls of which are made of highly elastic muscles. The inclusion of the stomach in the entire process of digestion is called the gastric phase of digestion. There are four parts into which the stomach is divided. The part that receives food from the esophagus is known as cardia. The food then passes on to the curvature of the stomach known as the fundus. The central part of the stomach breaks down the food particles. After the food molecules has been broken down, it is transferred to the antrum which passes it to the small intestine. When the food enters the stomach, the lining of the fundus (called the gastric fundal mucosa) produces hydrochloric acid (HCl). Basically, this acid does not directly contribute to the digestion process. It only optimizes the PH level required for the digestive enzymes produced by the liver and the pancreas for breaking down food.
The small intestine is the next organ that the food passes to in the process of digestion. It is the longest organ in the entire digestive system and can be as long as 7-8 meters. The small intestine is also divided into three parts. The duodenum is the part that connects the stomach to the rest of the intestine. In spite of being the shortest track in the small intestine, a lot of chemical digestion takes place here. In the duodenum, the digestive juices generated by the pancreas and liver mix to speed up the process. Here, the pH levels gradually change and turn into a base. The central part of the small intestine is known as the jejunum. This is the longest part of the small intestine and it is here that the absorption of nutrients take place. Here, the inner surface has small finger-like structures called villi. Each villi is covered with even smaller hair-like structures called microvilli. These improve the process of nutrient absorption by increasing the surface area of the intestine. Hepatic portal veins carry the blood containing the absorbed nutrients from the small intestine to the liver for filtering, removal of toxins, and nutrient processing. The remainder of the food is passed on to the ileum. The job of the ileum is to absorb the nutrients missed by the jejunum. Most vitamins are absorbed by the ileum.
After this, the remaining food particles and nutrients are transported to the large intestine, the next organ in the system. One of the large intestine function in digestion is fermentation, done by the gut bacteria, which breaks down the remaining nutrients after processing in the small intestine. There are three parts of the large intestine: the cecum, the colon and the rectum. The cecum is attached to the appendix and is also the connection between the small and the large intestines. The colon is responsible for the abrogation of water and salts from the digested foods. This is the final stage of digestion. The third and the final part of the large intestine is the rectum, and along with the anus, which allows for controlled elimination of stool. It is interesting to note that most digestion and absorption occurs before the food enters the large intestine but the food spends more time in the large intestine than anywhere else in the entire process.
It's interesting to know how long does digestion take. On an average, food takes ½ an hour to 2 hours to travels through the stomach, two to six hours to continue through the small intestine, and can spend six to 72 hours in the large intestine before being removed by defecation. So, in all the entire process of digestion can take anywhere between 24 to 72 hrs.
Digestion in humans is the process by which food is taken in, processed, and passed on through the body. Diet, water intake, and activity level can have a serious impact on digestion, and even healthy people can suffer from problems with digesting food. Symptoms like diarrhea, gas, constipation, indigestion, and other complaints are not serious in the short-term, but over an extended period of time, they can have harmful effects or even lead to serious illnesses. A few simple ways to improve the digestive process is to eat properly; consume more enzymes, fiber, and natural nutrients; drink plenty of water; and exercise often.
For most people, a balanced diet includes fruits, vegetables, carbohydrates, meat, dairy, and oils, and eating a healthy diet can improve digestion. Not only is it important to eat the right types of foods, but also to eat the food properly. For example, the digestive system runs more smoothly when food is eaten slowly; this allows the organs to work properly at a normal pace. Along the same lines, when too much food is consumed at one time, it cannot be digested as easily because it overloads the system, so to speak. Eating the right amount of food, slowly, will improve the body's digestive capabilities.
To aid digestion, the first place to begin is making changes in one's diet and enzymes are a helpful way to start. Enzymes help the digestive process because they increase nutrients and cause food to be more fully digested. Echinacea is one helpful enzyme, as are pepsin, spirulina, and milk protein, to name just a few. Many enzyme supplements can be purchased on the Internet or in most major drugstores.
Fiber is a carbohydrate that helps aid digestion, as it keeps things moving in the intestine, preventing toxic build up, which can lead to the aforementioned symptoms of digestive problems. Fiber can be found in raw fruits and vegetables, but it can also be purchased from major drug stores as a dietary supplement. Also helpful are natural nutrients that cleanse the intestine, such as aloe vera, beta carotene, senna pod, garlic, acidophilus, and rosehips.
Water is one of the most helpful aids to digestion. Drinking the recommended eight to ten glasses of clean water each day keeps the body hydrated and helps aid digestion in the intestinal tract. Some studies show that drinking cold fluids will actually slow down the digestive process, so many people choose to drink water at room temperature.
Aerobic exercise and stretching each day also contribute to healthier digestion, as the body as a whole will be in better working order. Many health care professionals recommend walking for ten minutes each day to avoid bloating or other uncomfortable symptoms of the digestive process. A variety of exercises, such as meditation, done after eating are believed to increase the rate of digestion.
Now, after understanding what is digestion, it is important to follow healthy practices like chewing food properly, avoiding alcohol and decreasing caffeine intake to keep your digestive system healthy and up and running.