22.1
Le système respiratoire
Le système respiratoire est composé des organes qui permettent de respirer. L’air pénètre dans les narines et la bouche, suivis par le pharynx (gorge)…
Le système respiratoire est composé ded'une série de passages et de conduitsqui apportent de l'air de l'extérieur du corpsdans les poumons à l'intérieur. L'air entre d'abord par les narineset dans la cavité nasale où les particules de matière,des débris potentiellement dangereuxcomme les bactéries et la saleté,sont filtrés par les poils et le mucuset de l'air plus propre est réchauffé et humidifié. L'air peut également circuler par la bouche,atteindre le pharynx et le larynx avant d'être canalisédans les voies respiratoires principales, la trachée,un tube cartilagineux composé de muscles lissesqui permettent la contractionet la relaxation nécessaire pendant la respiration.
Comme la trachée mène dans la cavité thoracique,puis se termine bifurquer en deux bronchescorrespondant aux poumons gauche et droitqui sont entourés de membranes pleuraleset lié par dessous par le diaphragme. Dans chaque poumon, une bronche se diviseen branches de plus en plus petites appelées bronchioles. Aux extrémités les plus petites sont les canaux alvéolairessubdivisés en petits sacs d'alvéoles,fines couches de cellules parenchymateuses.
Une telle organisation offre une grande superficie pour quel'échange gazeux se produise avec le système circulatoire.
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Q1: How does air travel through the respiratory system from the nostrils to the lungs?
Air enters through the nostrils into the nasal cavity where hairs and mucus filter out harmful particles like bacteria and dirt. The air is then warmed and humidified before traveling through the pharynx and larynx into the trachea. The trachea bifurcates into two bronchi that lead to the left and right lungs, where air continues through progressively smaller bronchioles to reach the alveoli for gas exchange.
Q2: What role do cilia and mucus play in keeping the lungs clean?
The bronchi and bronchioles are lined with cilia that beat upward to move mucus and trapped debris toward the throat for disposal through swallowing. This mucus traps foreign particles that pass through the nasal cavity defenses or enter via the mouth. Smoking damages cilia, making mucus removal difficult and increasing susceptibility to respiratory infections.
Q3: Why is the structure of alveoli important for lung function?
Alveoli are tiny sacs where gas exchange occurs between the lungs and the circulatory system. Each alveolar duct divides into approximately 100 alveolar sacs, each containing 20-30 alveoli. This grape-like structure maximizes surface area—the lungs contain 75 square meters of alveoli surface area, equivalent to a small apartment, enabling efficient oxygen uptake and carbon dioxide removal.
Q4: What is the function of the trachea and how does its structure support breathing?
The trachea is a 10-12 centimeter tube located in front of the esophagus that allows air to enter and exit the lungs. Its C-shaped hyaline cartilage keeps the trachea open during breathing. When smooth muscle in the trachea contracts, the diameter decreases and exhaled air is pushed out forcefully, as occurs during coughing.
Q5: How do the bronchi and bronchioles organize air distribution in the lungs?
As the trachea enters the thoracic cavity, it bifurcates into two bronchi corresponding to the left and right lungs. Each bronchus then splits into increasingly smaller branches called bronchioles. This branching pattern creates a tree-like structure that distributes air throughout the lungs while maximizing surface area for gas exchange.
Q6: What happens if the throat or mouth is blocked and breathing is obstructed?
In cases of damage to the throat or mouth that blocks breathing, a tracheostomy—a surgically-created hole in the trachea—can allow air to enter and exit the lungs, bypassing the obstruction. This procedure provides an alternative airway when normal breathing passages are compromised.
Q7: How does the nasal cavity prepare air before it reaches the lungs?
The nasal cavity filters, warms, and humidifies incoming air. Hairs and mucus in the nasal cavity trap particulate matter such as bacteria and dirt that could be harmful if inhaled. This initial processing ensures that cleaner, conditioned air reaches the lower respiratory tract and lungs.