The Human Breathing System This system includes the lungs, pathways connecting them to the outside environment, and structures in the chest involved with moving air in and out of the lungs.

 We inhale oxygen and exhale carbon dioxide  Breathing process involves inhalation and exhalation.

 What is Inhalation?  The process of breathing air into the lungs through the mouth and/ or nose  What is exhalation?  The movement of air out of the lungs to the external environment during breathing.

Oxygen Nose/ mouth WindpipeLungs

Carbon Dioxide LungsWindpipeNose/ mouth

 Air enters the body through the nose, is warmed, filtered, and passed through the nasal cavity  Air passes the pharynx and then to larynx. pharynx  Air enters the body through the nose, is warmed, filtered, and passed through the nasal cavity  Air passes the pharynx and then to larynx. pharynx

After passing the larynx, the air moves into the bronchi that carry air in and out of the lungs. bronchi Bronchi branch into smaller and smaller tubes known as bronchioles. After passing the larynx, the air moves into the bronchi that carry air in and out of the lungs. bronchi Bronchi branch into smaller and smaller tubes known as bronchioles.

Bronchioles terminate in grape-like sac clusters known as alveoli. alveoli Alveoli are surrounded by a network of thin- walled capillaries.capillaries

When you breath in: 1. The intercostals muscles contract. These pull the ribcage upwards. So the chest increase in volume. 2. The diaphragm contracts. This makes it flatten out, so the chest gets even larger. 3. As the chest gets larger internal air pressure in the lungs and thoracic cavity becomes less than outside atmospheric pressure. This pressure difference,forces air down the windpipe into the lung 3. Because the chest has got smaller, air pressure becomes more than outside, and air forced out of the lungs. When you breathe out: 1.The intercostal muscles relax, which lowers the ribcage. The chest decrease in volume. 2.The diaphargm relaxes, and buges upwards. This decreases the volume of the chest even more.

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