The respiratory system is a set of organs and structures that allow gas exchange between the environment (oxygen loaded) and the human body (whose blood is loaded with carbon dioxide). The functioning of the respiratory system is therefore closely related to the functioning of the circulatory system.
What is the respiratory system?
The organs of the respiratory system allow the gaseous exchanges between the external environment and the organism. The respiratory system consists of the nose, pharynx, larynx, trachea, lungs, pleura, bronchi and bronchioles.
The nose is in the centre of the face, in the middle position, and forms the first part of the respiratory tract. Involved in respiratory and olfactory, the nose consists of bone and cartilage that form the external structure, which is protruding relative to the plane of the face. Inside there are the fronts of the nasal cavity consisting of two long and winding channels lined with mucosa that open to the outside of the body, into the nostrils.
The pharynx is a channel that connects the throat with the oesophagus. Comprised of musculo-mucosal, it represents the first graduation section of the digestive tract – receives the food bolus from the mouth through swallowing – and it is a part of the upper airway: the air from the nose enters the pharynx and then moves into the larynx.
The larynx is presented as a hollow cylinder. Besides being the organ responsible for excellence in speech, it allows the passage of the inhaled air (from the nose and mouth to the bronchi) and exhaled air (from the bronchial tubes to the nose and mouth). It is provided with a closure device, which prevents the entry chewed food (bolus) coming from the mouth during swallowing.
The trachea connects the larynx with the initial portion of the bronchi, where it splits at the fifth thoracic vertebra, sharing in both left and right bronchial trees.
The bronchi have a cylindrical shape and they are located between the bifurcation of the trachea and bronchioles. Their job is to allow and ensure the passage of air from the trachea to the bronchioles and the alveoli. In the human body there are two main bronchi: right bronchus and left bronchus.
The bronchioles represent the small terminal branches of the bronchi within the lungs characterized by a diameter of less than one millimetre; these branch out further towards the pulmonary alveoli which, in turn, branch off into sacks (or infundibula), non-cellular small structures in the form of a bag arranged in a cluster which represent the terminal part of the respiratory breathing. Through the walls of the sacs the gas exchange process is performed. The walls of the bronchioles are characterized by a cubic epithelium cell (the presence of smooth muscle and elastic connective tissue).
The lungs are the two organs involved in the supply of oxygen to the body and the removal of carbon dioxide from the blood as well as the gas exchange between the environment and the blood (a process known as the gas exchange). Located in the chest cavity, the lungs are surrounded by a serous membrane, the pleura, which is essential for the performance of their functions.
The lungs are separated by a space between the spine and the sternum, the mediastinum, which also includes the heart, oesophagus, trachea, bronchi, thymus gland and great vessels. Each of the two lungs at the upper end has an apex that extends upward to the base of the neck, and rests on the diaphragmatic muscle at the lower end. Their main task is to get the blood load of carbon dioxide and waste products from the bloodstream and clean it up: once cleaned, blood is then sent to the heart, from where it is delivered to all the organs and tissues. The lungs have a high degree of elasticity, which promotes the expulsion of air during exhalation. As in the case of kidneys, only one lung is sufficient to ensure the functioning of the whole breathing process.
The pleura is the serous membrane that covers the lungs. It consists of two layers, called pleural layers: the parietal pleural leaflet (also called "parietal pleura") is located outside the lungs and separates them from the chest wall; while the visceral pleural leaflet (also called "visceral pleura"), adheres to the inner surface of the lung. The task of the pleura is to allow the lungs to slide on the walls of the lung cavity (the space of the thorax, that is, within which they are located) and to allow the expansion of the lungs during inhalation.
What function does the respiratory system serve?
The function of the respiratory system is to allow the gas exchange, or the process that allows oxygen supply to all organs and tissues by means of blood oxygenation.