Steffanie Reed, age 12, of Hattiesburg, Miss., for her question:
WHERE IS A PERSON'S DIAPHRAGM LOCATED?
Your diaphragm is the large muscle attached to your lower ribs that separates the chest from the abdomen. Here's how you pronounce the word: die uh fram.
The diaphragm is the chief muscle used in breathing. It is shaped like a dome. When you take a breath, the dome of the diaphragm moves downward. This increases the space in the chest. At the same time, the small muscles that are attached to the ribs cause these ribs to move outward, making the chest expand.
The expansion of the chest creates a slight vacuum inside the chest, which causes air from the outside to rush in. When air rushes in, you are taking a breath.
The action as air rushes in is called inspiration. Breathing out is expiration.
In expiration, the diaphragm relaxes and curves up toward the chest, and air is forced out of the lungs. In hard breathing, the abdominal muscles squeeze the abdominal organs upward against the diaphragm during expiration, helping force air out.
The phrenic nerve carries to the diaphragm the stimuli which make it work. This nerve arises in the neck area of the spinal cord and extends through the chest down to the diaphragm.
In addition to its work in breathing, the diaphragm of tens helps an animal support itself. If a person wants to pull or lift a heavy object, for example, he will usually take a deep breath and then hold it while he acts. This action "fixes" the ribs.
It is important in doing heavy work to "fix" your ribs because many large muscles of the back and abdomen pull against the ribs with great force.
The word diaphragm comes from two Greek words meaning across and fence.
A thick, vertical partition called the mediastinum or mediastinal septum, extends down the center of the chest, which is also called the thorax.
Enclosed within the mediastinal septum are the heart, the large blood vessels, the esophagus, the lower part of the windpipe and various glands and nerves. The lungs and their coverings are suspended on either side.
Only mammals, birds and crocodiles have a separate chest and abdomen.
You, as a human, have two lungs. These are large, pyramid shaped organs made up of masses of spongy tissue and suspended in the chest cavity. The lungs extend upward behind the collarbone. They rest on the powerful, muscular diaphragm.
The pleura is a continuous, thin, elastic membrane that covers the outside of the lungs and the inner walls of the chest cavity. Normally, there is no actual space between the portion of the pleura that covers the lungs and the portion that covers the inside of the chest cavity. These membranes are in constant contact.
But in certain diseases, blood, fluid or air may collect between the layer of the pleura. When this happens, a space develops between the membranes that compress the lung.