This spongy, pinkish organ looks like two upside-down cones in your chest. The right lung is made up of three lobes. The left lung has only two lobes to make room for your heart.

Bronchial tree

The lungs begin at the bottom of your trachea (windpipe). The trachea is a tube that carries the air in and out of your lungs. Each lung has a tube called a bronchus that connects to the trachea. The trachea and bronchi airways form an upside-down “Y” in your chest. This “Y” is often called the bronchial tree.

The bronchi branch off into smaller bronchi and even smaller tubes called bronchioles. Like the branches of a tree, these tiny tubes stretch out into every part of your lungs. Some of them are so tiny that they have the thickness of a hair. You have almost 30,000 bronchioles in each lung.

Each bronchiole tube ends with a cluster of small air sacs called alveoli (individually referred to as alveolus). They look like tiny grape bunches or very tiny balloons. There are about 600 million alveoli in your lungs. The small bubble shapes of the alveoli give your lungs a surprising amount of surface area — equivalent to the size of a tennis court. This means there’s plenty of room for vital oxygen to pass into your body.

Summary Each lung is divided into lobes. The bronchial tree running through your lungs is made up of the windpipe, bronchi, bronchioles, and alveoli.