Digestive and respiratory systems

Your body needs nutrients from food and oxygen from air to produce energy. Two body systems work together to supply these needs: the digestive system breaks down food, and the respiratory system takes in oxygen. Understanding both systems helps you make healthy choices every day.

The Digestive System

Digestion is the process of breaking food down into tiny molecules that can enter the bloodstream and reach every cell. The journey of food through your body follows a long, winding path called the digestive tract.

1. Mouth — Teeth chew food into smaller pieces and saliva begins breaking down carbohydrates.
2. Esophagus — A muscular tube that pushes food from the mouth down to the stomach.
3. Stomach — Churns food and mixes it with acid and enzymes to break it down further.
4. Small intestine — Absorbs nutrients (proteins, fats, carbohydrates, vitamins) into the bloodstream.
5. Large intestine — Absorbs water from the remaining material; the rest becomes waste.

The Respiratory System

Every cell in your body needs oxygen to work. The respiratory system brings oxygen in from the air and removes carbon dioxide, a waste gas produced by cells.

1. Nose/Mouth — Air enters the body; hairs and mucus in the nose filter dust and germs.
2. Trachea (windpipe) — A tube protected by rings of cartilage that carries air to the lungs.
3. Lungs — Two spongy organs that fill with air when you breathe in.
4. Alveoli — Tiny air sacs inside the lungs where oxygen passes into the blood and carbon dioxide passes out.
5. Diaphragm — A dome-shaped muscle below the lungs that contracts to make you inhale and relaxes to make you exhale.