The Body’s Structural Hierarchy
The body is sort of like a factory: It has an organizational hierarchy and different systems that accomplish different tasks:
- The most basic unit of the body is a single cell.
- When groups of cells work together on a similar job, they are called tissues. There are all sorts of tissues in your body, such as skin, muscles, and nerves.
- When tissues work together to accomplish a bigger job, they are called organs. Your kidneys, heart, liver, and intestines are all organs.
- Even organs can work together--to form organ systems. Organ systems are made of a number of different organs working together to accomplish a task. For example, the circulatory system is an organ system that circulates blood, oxygen, and nutrients throughout your body.
Tissue Types
- Epithelial Tissue: Epithelial tissue is the outer layer of tissue on your body (in other words, your skin) and also the tissue that lines some of your body’s inner surfaces.
- Connective Tissue: Connects tissues. Ligaments are a connective tissue that connects bones. Connective tissue also fills in spaces. The cartilage in your ears and nose is connective tissue.
- Muscular Tissue: Tissue that can contract and expand, creating movement.
Nervous Tissue: Tissue that relays messages throughout your body.