Organ

An organ is a collection of tissues that provide a function or functions. In conventional terms the organ contains tissues that are in such close proximity to one another that the organ can be taken out from one place.

However a functional definition of an organ would include things like the immune system where the cells that make up the organ are widely scattered throughout the body.

Examples of organs include

• Heart
• Brain
• Lung
• Liver
• Kidney
• Bladder
• Spleen
• Gut

Organs may be subdivided into `solid' and `hollow'. Solid organs are organs like the liver and hollow organs would be parts of the gastro-intestinal tract. Another name for a `hollow' organ would be a viscus.