Body Systems Overview

The human body is made up of many systems that work together to keep us alive and healthy. Each system has a specific job. In Grade 3 we focus on five major body systems: the skeletal system, muscular system, digestive system, nervous system, and circulatory system.

The Five Major Body Systems

• Skeletal System — all the bones in your body. It gives your body shape and support, protects organs, and allows movement at joints. Adults have 206 bones.
• Muscular System — all the muscles in your body. Muscles pull on bones to create movement. You have over 600 muscles.
• Digestive System — breaks down the food you eat into nutrients your body can use. Includes the mouth, esophagus, stomach, and intestines.
• Nervous System — your brain, spinal cord, and nerves. It sends and receives messages to control everything your body does, including thinking, feeling, and moving.
• Circulatory System — the heart, blood vessels (arteries, veins, capillaries), and blood. The heart pumps blood that carries oxygen and nutrients to every cell in the body.

How the Systems Work Together

• When you run: your muscular system moves your legs, your skeletal system provides the frame, your circulatory system delivers oxygen, your nervous system controls coordination, and your digestive system provides the energy from food.
• Body systems never work alone — they always cooperate to keep you healthy.