How many can honestly say they understand the diaphragm? If someone were to ask you to picture the diaphragm as you take a deep breath in, what do you picture?
Have you ever payed attention to your breath?
Lets get some anatomy clear so your picture gets a little less fuzzy. The diaphragm is a dome shaped muscle that separates the thoracic cavity from the abdominal cavity. There are essentially three parts, costal, sternal and crural. The costal portion attaches to the lower 6 ribs, sternal portion to the back of the xiphoid process and the crural part to the upper bodies of L1, L2 and L3, anterior longitudinal ligament and IV discs. The crural part attach by a right and left crus.
The three parts converge to form what is called the central tendon. This tendon has no bony attachments. There are also fascial connections to the psoas major and quadratus lumborum.
So that's the anatomy, now how about picturing the function. 70-80% of inspiration is performed by the diaphragm. As you breath in, the diaphragm contracts, which lowers and flattens its dome. Now remember, the diaphragm is between the thoracic and abdominal cavity. So as it lowers, the thoracic cavity gets bigger and the abdominal cavity gets compressed. This compression builds up and resists the diaphragm coming lower. So now you have intra abdominal pressure. This pressure expands the lower ribs laterally. Now because the intra abdominal pressure stabilizes the diaphragm, if it continues to contract the costal part of the diaphragm elevates the middle and lower ribs. (ribs 6-12)
The thoracic cavity gets larger as mentioned earlier. This allows the lungs to expand to take up the now available space.
So now hopefully you can picture what takes place when you take a nice deep breath! The next post I'll cover what happens when proper breathing goes awry, what to look for and the dysfunction it can create in your body.
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