Lynn Wilay - Plaster Relief
The Respiratory System
The organs of the respiratory system have two functions: they serve as an oxygen distributor and as a gas exchanger. In addition, the system also filters, warms, and humidifies the air that we breathe. Respiratory organs, like the sinuses, also affect speech and sound production and make possible the olfactory sense or the sense of smell.
The basic structure of this system is that of a tube with many branches ending in millions of microscopic thin-walled sacs called alveoli. The purpose of alveoli is to distribute air close enough to blood for a gas exchange to take place there. The respiratory membrane separates the air in the alveoli from the blood in surrounding capillaries.
The respiratory system is often divided into upper and lower tracts. The organs of the upper tract, the nose, pharynx, and larynx, are located outside of the chest cavity, where those in the lower tract, the trachea, bronchia, and lungs, are located within it.
Air enters the respiratory tract through the nostrils, flowing into the left and right nasal cavities. The surface of the nasal cavities is moist from mucus, and holds nerve endings responsible for our sense of smell.
The pharynx, or throat, is about five inches long. Air and food pass through here, with food moving to the esophagus and air flowing through the larynx, or voice box. The right and left Auditory or Eustachian tubes connect the middle ears with the pharynx, and allow for equalization of air pressure between the two.
The larynx, just below the pharynx, acts as the voice box and contains several pieces of cartilage, the largest being thyroid cartilage or the “Adam’s apple.” Two short fibrous bands, the vocal cords, stretch across the inside of the larynx. The epiglottis, cartilage that covers the opening of the larynx, acts as a trap door, closing during swallowing and preventing food from entering the trachea.
The trachea or windpipe is a tube about 4 ½ inches long. It extends from the larynx into the bronchi in the lungs. It is made of 15-20 C-shaped rings of cartilage placed one above the other with soft tissue between them. Think of the trachea as the main trunk of an upside-down tree. The first branches in each lung are the primary bronchi, branching into smaller or secondary bronchi, whose walls are kept open for air passage by rings of cartilage. These small passageways are called bronchioles, which subdivide into microscopic tubes called alveolar ducts, which end in alveolar sacs, which are made of many alveoli.
The right lung has three lobes and the left lung has two. A pleura (moist and slippery) membrane covers the outer surface of each lung and also lines the inner surface of the rib cage.
Breathing, or pulmonary ventilation, is the process that moves air into and out of the lungs. It makes possible the exchange of gases, called external respiration, between the air and lungs. Internal or cellular respiration, is the exchange of gases that occur between the blood and cells of the body.
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The Skeletal System The Muscular System The Nervous System The Digestive System The Respiratory System |
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