Stomach, saclike dilation in the gastrointestinal tract between the esophagus and the intestines, forming an organ of digestion. The stomach is present in virtually all vertebrate animals and ...

Pharynx, area of the gastrointestinal and respiratory tracts which lies between the mouth and the esophagus. In humans, the pharynx is a cone-shaped tube about 41/2 in. (11.43 cm) long. At its...

Thorax, body division found in certain animals. In humans and other mammals it lies between the neck and abdomen and is also called the chest. The skeletal frame of the thorax is formed by the...

Heartburn, burning sensation beneath the breastbone, also called pyrosis. Heartburn does not indicate heart malfunction but results from nervous tension or overindulgence in food or drink. The...

Enteritis, inflammation of the gastrointestinal tract. Acute enteritis is not usually serious except in infants and older people, in whom the accompanying diarrhea can cause dehydration throug...

Trachea or windpipe, principal tube that carries air to and from the lungs. It is about 41/2 in. (11.4 cm) long and about 3/4 in. (1.9 cm) in diameter in the adult. It extends from the larynx ...

Boerhaave, Hermann, 1668–1738, Dutch physician and humanist. One of the most influential clinicians and teachers of the 18th cent., Boerhaave spent almost his entire life in Leiden, which beca...

Parrotfish, common name for a member of the large family Scaridae, colorful reef fishes of warm seas, resembling the wrasses but of a larger size. Parrotfishes, also called pollyfishes, are so...

Digestive system, in the animal kingdom, a group of organs functioning in digestion and assimilation of food and elimination of wastes. Virtually all animals have a digestive system. In the ve...

Rotifera, phylum of predominantly free-living, microscopic, aquatic or semiterrestrial pseudocoelomates. Each rotifer has a head bearing a crown of cilia, the corona, at the anterior end; most...