Breathing is the process of moving fresh air into the lungs and removing waste air out of it. The organs and tissues that enable this process are collectively termed the respiratory system. The main components include the air passages (respiratory tract), the lungs and blood vessels that are intimately linked, and the muscles that enable breathing.
The airways or air passages are tubes through which air that is rich in oxygen reaches the lungs. In addition, through these tubes, carbon dioxide, a waste gas, is removed from the lungs. The airways include your:
Filtering, warming,and humidification of inhaled air begins at the entrance to the upper respiratory system and continues throughout the rest of the tract.By the time air reaches the depth of the lungs, most foreign particles and pathogens have been removed, and the humidity and temperature are within acceptable limits. The inhaled air is said to be 'conditioned' for acceptance by the body and this conditioning is due primarily to the respiratory mucosa - tissues that line the airways.
Contamination of the respiratory system is prevented by a series of filtration mechanisms. Hairs in nostril filter large particles. Specialized cells called Goblet cells as well as mucous glands in the lining of the tract produce a sticky mucous that bathes exposed surfaces. In the nasal cavity, hair-like structures called cilia, sweep that mucus and any trapped debris or microorganisms toward the pharynx, where it will be swallowed and exposed to the harsh conditions (acids and enzymes) of the stomach. In the lower respiratory system, that is, from the voice box and trachea downwards, there are also cilia present and they also beat toward the pharynx, moving a carpet of mucus upwards out of the system.
When irritants happen to reach the tract, they may produce local inflammation and so cause difficulty in breathing.
The lungs and linked blood vessels are so intertwined that oxygen is delivered to the body and carbon dioxide is removed. The lungs are located inside the rib cage.
Within the lungs, the airways branch into smaller passages called bronchi which themselves continue to branch into thousands of smaller, thinner tubes called bronchioles. These tubes end in bunches of tiny round air sacs called alveoli.
Each of these air sacs is covered in a mesh of tiny blood vessels called capillaries and the capillaries connect to the wider network of arteries and veins to move blood through the body.
The lungs are divided into five main sections called lobes. When one lobe is diseased, it may be removed. Adequate breathing can still be done using the remaining lobes.
There are muscles near the lungs that allow breathing when they expand and contract (tighten). These muscles include:
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