The alveoli are surrounded by capillaries so oxygen and carbon dioxide diffuse between the air in the alveoli and the blood in the capillaries.ĭiffusion is the movement of gas from an area of high concentration to an area of low concentration. Gas exchange occurs at the alveoli in the lungs and takes place by diffusion. The respiratory system, in combination with the cardiovascular system, is responsible for providing this function. The human body is designed to take in oxygen and to remove carbon dioxide. Composition of the air we breathe Breathed in This decreases the size of the chest and increases the air pressure in the chest so air is forced out of the lungs. The intercostal muscles relax so the ribs move inwards and downwards under their own weight. The diaphragm relaxes and moves back to its domed shape. This increases the size of the chest and decreases the air pressure inside it which sucks air into the lungs. The intercostal muscles contract and move the ribs upwards and outwards. The diaphragm contracts and moves downwards. The intercostal muscles are found between the ribs and they control rib movement. The diaphragm is a sheet of muscle that separates the chest (or thoracic) cavity from the rest of the body. Two important structures for breathing are the diaphragm and intercostal muscles. At the end of the bronchioles, the air enters one of the many millions of alveoli where gaseous exchange takes place.īreathing is the term given to the process of taking air into and out of the lungs.Each bronchus branches out into smaller tubes called bronchioles.Air enters the body and is warmed as it travels through the mouth and nose.
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Respiratory system structure and function Passage of air into the lungs