organ

The adult human body has approximately 650 muscles, 100,000 km/60,000 mi of blood vessels and 13,000 nerve cells.

In biology, a part of a living body that has a distinctive function or set of functions. Examples include the oesophagus, liver, or brain in animals, or a leaf in plants. An organ is composed of a group of coordinated tissues. A group of organs working together to perform a function is called an organ system, for example, the digestive system comprises a number of organs including the oesophagus, stomach, the small intestine, the pancreas, and the liver. The tissues of a leaf include the epidermis, palisade mesophyll, and spongy mesophyll. The tissues of the oesophagus include muscle, and epithelium.