The larynx is the upper part of the trachea that allows the air to pass into the lungs. The nasopharynx opens through a slit-like aperture called the glottis of the larynx into the trachea. It bears a leaf-like cartilaginous flap called epiglottis. The function of the epiglottis is to close the glottis to check the entry of food during swallowing. The laryngeal skeleton is made up of nine cartilages. The larynx helps in sound production so is also called the voice box. They have vocal cords attached with the thyroid cartilage and the folds in those cords produce sound when air passes through it at the time of exhalation.

The trachea is also known as a windpipe. It is about a 10-11 cm long fibrocartilage tube of the lower respiratory tract. It is a thin-walled cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air. It extends up to the mid-thoracic cavity and passes air to the alveoli.

Each lung is covered by two membranes called pleura. The inner membrane is firmly bound to the surface of the lungs and is called the visceral pleura. The outer membrane is held to the thoracic wall and diaphragm by connective tissue and is called the parietal pleura. A pleural cavity exists between the two pleura, and it contains pleural fluid that reduces friction between the membrane while breathing.