Respiratory System – a Group of Respiratory Organs

The respiratory system is a group of organs and structures that helps us breathe. It is composed of the lungs, airways, muscles, and associated blood vessels. The airways, which transport oxygen-rich air to the lungs and remove carbon dioxide, include the nose and connected air passages (nasal cavities), the mouth, the larynx (or voice box), the trachea (windpipe), tubes (bronchial tubes or bronchi) and branches. Upon entering through the nose or mouth, the air is both warmed and moistened to prevent irritation from cold, dry air.

The air travels through the larynx, down the trachea, and splits into two bronchial tubes that lead into the lungs. Another integral part of the respiratory system is the lungs, coupled with the blood vessels, which deliver oxygen to the body and assist in the removal of carbon dioxide. The lungs lie on either side of the breastbone and fill the inside of the chest cavity. Within the lungs, bronchi branch into thousands of smaller, thinner tubes called bronchioles, each one ending in alveoli, clusters of tiny, round air sacs. Each alveolus is enveloped by a mesh of tiny blood vessels called capillaries, connected to a network of veins and arteries that circulate the blood throughout the body.

Oxygen drawn from the air is absorbed into the bloodstream through the capillaries, then travels through the pulmonary vein and its branches to the heart, subsequently circulating throughout the body. Once the body's cells utilize the oxygen, they produce the waste gas known as carbon dioxide. This gas then travels back up to the heart through the pulmonary artery and its branches, returning to the capillaries that surround the alveoli. When the lungs exhale, the carbon dioxide is expelled from the body for other organisms to use.

The muscles involved in breathing include the diaphragm, intercostal muscles, abdominal muscles, and the muscles in the neck and collarbone area, which work in conjunction to expand and contract the lungs, thus enabling respiration. The dome-shaped diaphragm, the principal muscle in breathing and located just below the lungs, separates the abdominal cavity from the chest cavity. The ribs, which protect and support the chest cavity, also shift slightly to accommodate the expansion and contraction of the lungs during respiration.

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