Hey there! It’s Matt from Kenhub, and in this tutorial, we will discuss the diaphragm. The diaphragm is a skeletal muscle that resides in the trunk of the body and separates the thoracic and abdominal cavities from one another. Its function occurs during breathing when it contracts to enlarge the thoracic cavity and reduce the intrathoracic pressure so that the lungs may expand and fill their alveoli with air.
The diaphragm’s superior origin is continuous from the xiphoid process anteriorly to the lower six costal cartilages of the thorax laterally and the first 2/3 lumbar vertebrae posteriorly. The musculoskeletal fibers radiate from all angles towards the center of the body and converged into a central tendon which is the inferior attachment or muscular insertion point. It is innervated by the phrenic nerve which arises from the fibers of the 3rd to the 5th cervical spinal root ganglia. It draws the central tendon anteriorly and inferiorly during inspiration.
The diaphragm has several openings in its dome which allows structures to pass between the thoracic and abdominal cavities. There are 3 major openings and 5 minor openings. The major openings are named after the largest structures that run through them and are the aortic hiatus which allows the aorta, the azygos vein, and the thoracic duct to pass from the thoracic cavity into the abdomen; the esophageal hiatus which contains the esophagus and the esophageal arteries as well as the anterior and posterior vagal trunks, and the vena caval foramen which of course encircles the inferior vena cava as well as some of the branches of the right phrenic nerve.
The minor openings and their structures are: The lesser aperture of the right crus that houses the greater and lesser right splanchnic nerves, the lesser aperture of the left crus contains the greater and lesser left splanchnic nerves and the hemiazygos vein, the sympathetic trunk runs behind the diaphragm under the medial lumbocostal arches, the Foramen of Morgagni which is found in the areolar tissue between the sternal and costal parts of the diaphragm contains the superior epigastric branch of the internal thoracic artery and the lymphatics of the abdominal wall that sit on the convex surface of the liver, and the medial and lateral lumbocostal arches contain areolar tissue that when present separates the superior and posterior surface of the kidney from the pleura.
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