Cells are the basic unit of structure and function of the human body organization as well as for any other living being. Not all cells in the body are equal, cells are specialized and each type carries a specific function.
Groups of cells of the same type form the tissues. There are four types of basic tissues:
- Connective tissue, is formed by cells with structural functions such as bones or cartilage, as well as blood.
- Epithelial tissue, is formed by cells that line the inner and outer body surfaces.
- Muscle tissue, is formed by cells that have the ability to contract.
- Nervous tissue, is formed by nerve cells, with the capacity of carrying electrical signals.
Two or more tissues form organs, which are structures that carry on specific functions.
And finally, the organ systems are formed by a group of organs that work together to perform complex functions.
So, without cell's activity, no body functions would be carried.