Let’s take a look at the human body. The human body, like all living organisms, is made up of many different parts. Our bodies can be looked at as groups of working parts. Parts that work together to do a certain job are called a system. Can you name some systems of the human body?

Body Systems There are several different systems in the human body. The parts within each system work together to perform a certain job, or function. For example, the digestive system breaks down food to supply the body with nutrients, or fuel. What do you call the parts that make up a body system? Skeletal Nervous Digestive Circulatory Respiratory

OrgansBody Systems Organs are the parts that make up the body systems. Organs play important roles in helping the system function properly, but they cannot perform the job of the entire system by themselves. Here you can see a few different organs. Can you match the organs with the correct body systems? Heart Brain Nervous System Circulatory System

Body SystemsOrgansTissues Organs are made up of different types of material called tissues. Tissues are groups of specialized cells that work together to perform a certain job, or function. There are four basic types of tissue: epithelial, nervous, connective, and muscle. The tissue name may give you an idea of the types of organs where they are typically found. Can you name one organ that contains each type of tissue? Shown here are images of four different types of tissue found in the human body, as seen under a microscope. Epithelial tissue is found in the digestive tract. Connective tissue holds other tissues together. Neurons are part of the tissue of the nervous system. Skeletal muscle tissue is attached to bones.

Body SystemsOrgansTissuesCells The cell is the smallest individual working part of any living organism. The cell is often referred to as the basic unit of life. Cells are made of many parts, but these parts cannot work by themselves. They work together and rely on each other for the survival of the cell. Animal cell: human cheek cellPlant cells: onion cells

As you have seen, the human body is made up of many different parts. All of these parts are made of many cells, the basic unit of life. When an organism is made up of many cells, it is called a multicellular organism. Humans are multicellular organisms. Can you think of any other multicellular organisms? Cells, Cells, and More Cells

Some organisms are made up of only one cell. These organisms are called unicellular (meaning “one-celled”) organisms. Most unicellular organisms can be seen only with the help of a microscope. Would you like to know more about cells and microscopes? Cells Alone Amoeba (unicellular organism) Paramecium (unicellular organism)