The body is classified into Cell (e.g Red blood cells, hepatocytes etc) - tissue (epithelial etc) - organ (heart, liver etc) - system (circulatory etc) - organism (human etc) So, Cardiac muscle is a...
Tissues- group of cells that perform a specific function(ex. muscle tissue) Organs- a group of tissues(ex. stomach) Organ system- a group of organs(ex. digestive system)