at the end of a normal exhalation the diaphragm is
Exhalation The main reason for exhalation is to rid the body of carbon dioxide, which is the waste product of gas exchange in humans. Air is brought in the body through inhalation. During this process air is taken in through the lungs. Diffusion in the alveoli allows for the exchange of O2 into the pulmonary capillaries and the removal of CO2 and other gases from the pulmonary capillaries to be exhaled. In order for the lungs to expel air the diaphragm relaxes, which pushes up on the lungs. The air then flows through the trachea then through the larynx and pharynx to the nasal cavity and oral cavity where it is expelled out of the body.[1] Exhalation takes longer than inhalation since it is believed to facilitate better exchange of gases. Parts of the nervous system help to regulate respiration in humans. The exhaled air isnâ€™t just carbon dioxide; it contains a mixture of other gases. Human breath contains volatile organic compounds (VOCs). These compounds consist of methanol, isoprene, acetone, ethanol and other alcohols. The exhaled mixture also contains ketones, water and other hydrocarbons.[2][3]
Pharynx The laryngopharynx, (Latin: pars laryngea pharyngis), also known as hypopharynx, is the caudal part of pharynx; it is the part of the throat that connects to the esophagus. It lies inferior to the epiglottis and extends to the location where this common pathway diverges into the respiratory (larynx) and digestive (esophagus) pathways. At that point, the laryngopharynx is continuous with the esophagus posteriorly. The esophagus conducts food and fluids to the stomach; air enters the larynx anteriorly. During swallowing, food has the "right of way", and air passage temporarily stops. Corresponding roughly to the area located between the 4th and 6th cervical vertebrae, the superior boundary of the laryngopharynx is at the level of the hyoid bone. The laryngopharynx includes three major sites: the pyriform sinus, postcricoid area, and the posterior pharyngeal wall. Like the oropharynx above it, the laryngopharynx serves as a passageway for food and air and is lined with a stratified squamous epithelium. It is innervated by the pharyngeal plexus.