Through digestion is probably not the first thing on your mind when sinking your teeth into a warm slice of veggie pizza, it is an important part of getting the nourishment you need. During digestion, your body breaks food down into nutrients that your body can absorb. The food moves through several different organs until it eventually leaves your body as waste -- a process that takes 40 hours, on average. Your digestive system is made up of the gastrointestinal tract, which includes the mouth, esophagus, stomach, small intestine and large intestine, and secondary, or accessory organs, which include the liver, gallbladder and pancreas.
Mouth and Esophagus
Digestion starts in your mouth. Your teeth break down food by mashing and grinding it into smaller pieces. This is called mechanical digestion. Glands in the mouth -- the salivary glands -- release an enzyme called salivary amylase that also begins to break down the food chemically. After you swallow the broken down food -- which is now called a bolus -- the muscles in your esophagus contract to move the bolus to your stomach. This process is called peristalsis. It takes the bolus abut 8 seconds to travel through the esophagus.
The stomach produces hydrochloric acid, enzymes and mucus that help break down food. The stomach churns and the muscles contract to mix food with these digestive juices to get it ready to enter your small intestine. By the time the food leaves the stomach, it is a semi-liquid substance called chyme.
Most digestion and nutrient absorption happens in the small intestine. Much like the esophagus, the small intestine goes through peristalsis to mix enzymes from the liver, gallbladder and pancreas with partially digested food. It is also here that the nutrients enter into your bloodstream through small finger-like structures, which are called villi and microvilli. By the time food reaches your large intestine, it has been almost completely digested. The large intestine does absorb water and electrolytes, however. The large intestine also forms the waste that will eventually leave your body.
The liver makes bile, a liquid that helps break down the fat you eat. Bile, which is a mixture of water, bile acids, cholesterol and phospholipids, breaks up large fat molecules into smaller ones. This helps your body digest and absorb fat better. Bile also helps mix fat with water so that it can enter your bloodstream correctly. The liver makes 500 to 1,000 milliliters of bile each day.
The gallbladder, which is attached to the liver, is where your body stores bile after it's made by the liver. The gallbladder can store 30 to 50 milliliters of bile at a time. When there is fat in your small intestine, the gallbladder releases bile so that can digest the fat properly.
The pancreas produces and releases enzymes that help break down protein, fat and carbohydrates. The pancreas also makes two hormones -- insulin and glucagon -- that help metabolize sugar and control blood sugar levels.
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