1. Respiratory System

2. Trapping Dust & Dirt Nose is lined with hair and mucus to trap dust / dirt. Trachea is lined with cilia (tiny hairs) and mucus for the same purpose.

3. Trachea (aka Windpipe) Trachea is a tube of soft tissue that is kept open by rings of cartilage Divides into left and right bronchi (singular = bronchus) to enter lungs Video clip

4. Trachea and Esophagus Trachea runs parallel to the esophagus (muscular food tube that connects to the stomach) Epiglottis is a flap of tissue that covers trachea when you swallow food and prevents food from entering the trachea

5. Alveoli (singular = alveolus) Air sacs at the end of the bronchioles –Each lung has 300-600 million alveoli Arranged in grape-like clusters Surrounded by capillaries

6. Alveoli and Gas Exchange Alveoli are the sites of gas exchange between the respiratory and circulatory systems Oxygen diffuses (high  low concentration) from alveoli to capillaries Carbon dioxide diffuses (high  low concentration) from capillaries to alveoli

7. Alveoli and Gas Exchange Red blood cells carry oxygen on hemoglobin

8. Control of Breathing A region in the brain stem (at the base of the brain, near the spinal cord) regulates breathing Monitors carbon dioxide levels in the bloodstream (NOT oxygen) & adjusts breathing rate