The anatomy of the lungs can be broken down into the structures that compose the airway. The main units of the airway include the larynx, trachea, bronchi, bronchioles and alveoli. Inside lung tissue, the circulatory system and the respiratory system meet and conduct an oxygen and carbon dioxide exchange. For this reason, we inhale oxygen and exhale carbon dioxide.
Larynx
The larynx is the top-most point of the airway. As a covering for the airway, the epiglottis prevents food particles from descending toward the lungs. The larynx contains the structure responsible for speaking sound, called vocal cords. These two bands vibrate to deliver tone, pitch and loudness. The vocal cords are protected by a cartilage encasing. During a yawn, the larynx slides down the trachea.
Trachea
The trachea is a tubular structure that is parallel to the esophagus, according to the American Lung Association. C-shaped cartilage contributes to the trachea's structure. Several vertical C-shaped rings keep the airway open. The esophagus, which lies parallel to the trachea, does not have structures that provide a definitive shape. When food passes through the esophagus, the opening of the C-shaped rings provide room for the food to pass through this tube. The airway divides at the bottom of the trachea.
Bronchi and Bronchioles
According to the American Lung Association, bronchi and bronchioles are extensions of the larynx. Like the branches of a tree, the bronchi divide into the bronchioles, which further divide. With each division the diameter of the airway gets smaller. Alveoli are at the end of the bronchioles. The smallest diameter of the airway is at the end of the bronchioles.
Alveoli
The alveoli are the main unit of the lung. An exchange of gases occurs at the alveoli. The American Lung Association states that the circulatory system brings blood without oxygen to the alveoli. This blood contains carbon dioxide, a by-product of creating energy. The bronchiole contains high quantities of oxygen. At the alveoli, the circulatory system exchanges carbon dioxide for oxygen. Blood with oxygen is delivered to the body and carbon dioxide is exhaled.
Breathing
There are two processes that occur during breathing. These processes are inspiration and exhalation. Inspiration brings air into the lungs by creating a vacuum in the air passages. This vacuum is created by flattening the diaphragm and expanding the rib cage, creating a negative pressure inside the airway. Exhalation squeezes air out of the lungs by collapsing the rib cage and pressing the diaphragm underneath the lungs.
