Ingestion is the process of consuming something and taking it into the body. Usually, the word is used to describe taking food in through the mouth, as humans and many animals do. It can also be used to describe the absorption of materials or nutrients by a cell or organism. For example, a cell may ingest nutrients by absorbing them.
In human beings, ingestion most commonly occurs through the mouth. A person may ingest food and drink by chewing and swallowing or by swallowing alone. Additionally, human beings often ingest medicines through the mouth. For example, a human being may swallow a capsule, pill, or liquid medication. Some pills are also designed to be chewed rather than swallowed. There are even some medications that are in powder form and designed to be combined with food, such as applesauce, before ingestion.
When an individual ingests something, the substance begins to make its way through the gastrointestinal tract in a process called digestion. The food travels to the stomach, where stomach acids and enzymes act on it while the stomach's muscular lining squeezes and mixes the food. Eventually, the food moves on to the intestine. Most of digestion, the breaking down of food for use by the body, happens in the small intestine. Special juices and enzymes finish breaking the food down into nutrients, which the body uses, leaving the waste to travel into the large intestine and out of the body.
Unfortunately, food and drink aren’t the only things a person may ingest. The mouth can also be an entry point for microscopic organisms, viruses, and bacteria that make a person sick. Often, these things enter the body because they are in improperly prepared or stored food. Sometimes they enter the body when someone goes to the bathroom and then neglects to wash his hands before preparing, serving, or eating food. Ingestion of pathogens may sicken a person temporarily, but sometimes a pathogen is harmful enough to be deadly.
Sometimes human beings ingest foreign bodies, like buttons, coins, and batteries, by accident. Often, such things pass out of the body in bowel movements and do not cause harm. Swallowing batteries can lead to difficulty breathing, vomiting, and rashes, however.
Interestingly, there are some organisms that do not ingest food through a mouth. For example, amoebas, single-celled organisms, ingest food but do not need a mouth to do so. Instead, they absorb food into their bodies after wrapping themselves around a consumable item. Cells ingest in the same manner, absorbing food or other substances through the cell membrane, which is a protective barrier around the cell.