A group of cells with a similar structure and function working together. For example, muscular tissue contracts to bring about movement.
Organ
A collection of tissues working together to perform a specific function. For example, the stomach contains glandular, muscular and epithelial tissues.
Organ system
A group of organs working together to perform specific functions. For example, the digestive system contains organs such as the stomach, the small intestine and the large intestine.
