Trachea: Often referred to as the windpipe, the trachea is a tube that extends from the larynx (voice box) down to the chest, where it divides into the left and right bronchi. It serves as the main airway, allowing air to travel from the throat to the lungs.

Bronchi: The trachea divides into two primary bronchi (one for each lung). These bronchi further subdivide into smaller branches within each lung. The bronchi are responsible for directing air into the lungs and are lined with mucus and tiny hair-like structures called cilia, which help to filter out particles and pathogens.

Bronchioles: These are smaller branches of the bronchi that spread throughout the lungs. They continue to divide into even smaller tubes and lead air to the alveoli. Bronchioles do not have cartilage like the larger bronchi; instead, they are made of smooth muscle that can constrict or dilate to regulate airflow.

Alveoli: These are tiny, balloon-like structures at the end of the bronchioles where gas exchange occurs. The alveoli are surrounded by capillaries, and it’s here that oxygen from the air is transferred into the blood, and carbon dioxide from the blood is expelled into the air to be exhaled. The large surface area and thin walls of the alveoli facilitate efficient gas exchange.