Lungs

• The trachea divides into two bronchi. One bronchus enters each lung.
• The trachea is the windpipe that connects the mouth and nose to the lungs, lined with goblet cells to produce mucus, and ciliated epithelial cells that have cilia to move mucus up to the mouth
• The bronchi are large tubes branching off the trachea with one bronchus for each lung, also lined with goblet cells and ciliated epithelial cells
• Alveoli are tiny moist air sacs where gas exchange takes place. Each alveolus is covered in capillaries
• Capillaries surround the alveoli in the lungs. Both the capillaries and alveoli walls are very thin - just one cell thick. They are made of semi permeable membranes which allow oxygen and carbon dioxide to pass through them