How the Digestive System Works | 3D Animation

Digestion of food starts in the mouth, the moment you take a bite. Teeth break down the food and mix it with the enzymes in saliva. Once the food entered the mouth, saliva moistens it. The teeth and tongue break it down mechanically. An enzyme in the saliva, called salivary amylase, breaks the food down into starch. Chewing in amylase digestion will convert the food into a small, round blob, or bolus. This enables a person to swallow it easily. 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 goes down through the esophagus, these contractions push it toward 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. The stomach stores the food temporarily. Cells in the stomach start to secrete gastric juices. These include hydrochloric acid, which maintains the pH of the stomach between 1.5 to 2.0. The stomach has three muscular layers that churn and mix its contents. These processes churn the food into a thick paste, known as chyme. The stomach does not absorb many nutrients from the chyme into the bloodstream. The chyme enters the small intestine through the pyloric sphincter. The small intestine is around 6 meters long and absorbs around 90% of the nutrients from food into the bloodstream. There are three parts of the small intestine, duodenum, jejunum, and ileum. Once the food is fully broken down, the villi absorb the nutrients, which enter the bloodstream. The liver digests food by producing bile to break down fats, removing toxins, and breaking down and storing some vitamins and minerals. The pancreas produces enzymes to help break down carbohydrates, fats, and proteins. The gallbladder stores the bile that is produced by the liver. When needed, bile passes into the small intestine, where it breaks down fat. Any unabsorbed food and nutrients now pass to the large intestine, or colon. The material is now feces. The large intestine is around 2 meters long. It consists of five parts. The cecum, ascending colon, transverse colon, descending colon, sigmoid 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. After that, peristalsis moves the feces toward 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. 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. It takes about 30 hours for food to move through the large intestine. The whole process from swallowing to defecation takes about 2-4 days. If you like this video, don't forget to subscribe our YouTube channel for more medical videos. Thanks for watching.