Foreign bodies

# Overview
In physiology, a foreign body (Latin: corpus alienum) is any object originating outside the body. In machinery, it can mean any unwanted intruding object.

# Foreign bodies in humans
Foreign bodies typically become lodged in the eyes, ears, nose, airways, and rectum which are the main orifices of human beings. Foreign bodies can be in hollow organs (like swallowed batteries) or in tissues (like bullets). They can be inert or irritating. If they irritate they will cause inflammation and scarring. They can bring infection into the body or acquire infectious agents and protect them from the body's immune defenses. They can obstruct passageways either by their size or by the scarring they cause. Some can be toxic.
Both children and adults experience problems caused by foreign objects getting stuck in their bodies. Young children, in particular, are naturally curious and may intentionally put shiny objects, such as coins or button batteries, into their mouths. They also like to stick things in their ears and up their noses. Adults may accidentally swallow a non-food object or inhale a foreign body that gets stuck in the throat. Airborne particles can lodge in the eyes of people at any age. These foreign bodies often result in allergies which are either temporary or even turn into a chronic allergy. This is especially evident in the case of dust particles.
Most objects that are swallowed will, if they have passed the pharynx, pass all the way through the gastrointestinal tract. Rarely an object becomes arrested (usually in the terminal ileum or the rectum) or a sharp object penetrates the bowel wall. If the person who swallowed the foreign body is doing well, usually a x-ray image will be taken which will show any metal objects, and this will be repeated a few days later to confirm that the object has passed all the way through the digestive system. Also it needs to be confirmed that the object is not stuck in the airways, in the bronchial tree. If the foreign body causes problems like pain, vomiting or bleeding it must be removed. Also swallowed mercury batteries should be removed as soon as possible as they are very dangerous especially to small children.

# Foreign bodies in animals
Foreign bodies are common in animals, especially dogs and cats.  Dogs will readily eat toys, bones, and any object that either has food on it or retains the odor of food.  Unlike humans, dogs are susceptible to gastrointestinal obstruction due to their ability to swallow relatively large objects and pass them through the esophagus.  Foreign bodies most commonly become lodged in the stomach because of the inability to pass through the pyloric sphincter, and in the jejunum.  Symptoms of gastrointestinal obstruction include vomiting, abdominal pain, and depression due to dehydration.  Peritonitis results if either the stomach or intestine has ruptured.  Foreign bodies in the stomach can sometimes be removed by endoscopic retrieval or if necessary by gastrotomy.  Foreign bodies in the jejunum are removed by enterotomy.
Certain foreign bodies in animals are especially problematic.  Bones or objects with sharp edges may cause tearing of the wall of the esophagus, stomach, or small intestine and lead to peritonitis. Pennies swallowed in large numbers may cause zinc poisoning, which in dogs leads to severe gastroenteritis and hemolytic anemia.  Linear foreign bodies can especially be dangerous.  A linear foreign body is usually a length of string or yarn with a larger object or clump of material at either end.  One end is usually lodged in the stomach or proximal small intestine and the other end continues to travel through the intestines.  The material becomes tightly stretched and the intestines may be lacerated by it.  This is especially common in cats who may enjoy playing with a ball of string or yarn.  Sometimes the linear foreign body anchors in the mouth by catching under the tongue. Pantyhose is a common linear foreign body in dogs.

# Gallery
- Foreign Bodies.  With permission of Dermatology Atlas
- Foreign Bodies.  With permission of Dermatology Atlas
- Foreign Bodies.  With permission of Dermatology Atlas