The Diaphragm (PDF) - Gulf Medical University

The diaphragm January 23, 2025 www.gmu.ac.ae − It is a thin musculotendinous structure that separates the thoracic cavity from the abdominal cavity − It is pierced by the structures that pass between the chest and the abdomen. Shape of the Diaphragm: – The diaphragm curves up into r...

The diaphragm January 23, 2025 www.gmu.ac.ae − It is a thin musculotendinous structure that separates the thoracic cavity from the abdominal cavity − It is pierced by the structures that pass between the chest and the abdomen. Shape of the Diaphragm: – The diaphragm curves up into right and left domes or copulas. – The right dome reaches as higher than the left dome (because of the large size of the liver) – The domes support the right and left lungs, whereas the central tendon supports the heart. Origin: 1. A sternal part arising from the posterior surface of the xiphoid process. 2. A costal part arising from the deep surfaces of the lower six ribs & their costal cartilages. 3. A vertebral part (crura) arising from vertebral column and from the arcuate ligaments. a. The right crus arises from the bodies of the first 3 lumbar vertebrae and the intervertebral discs. b. The left crus arises from the bodies of the first 2 lumbar vertebrae and the intervertebral disc. − Lateral to the crura the diaphragm arises from the medial and lateral arcuate ligaments. ▪ The medial arcuate ligament extends from the body of the 2nd lumbar vertebra to the transverse process of the 1st lumbar vertebra. ▪ The lateral arcuate ligament extends from the transverse process of the 1st lumbar vertebra to the lower border of the 12th rib. ▪ The medial borders of the 2 crura are connected by a median arcuate ligament, which crosses over the anterior surface of the aorta. insertion: – It is inserted into a central tendon. – The superior surface of the tendon is partially fused with the inferior surface of the fibrous pericardium. − Some of the muscle fibers of the right crus pass up to the left and surround the esophageal orifice in a sling like loop. − These fibers act as a sphincter and assist in the prevention of regurgitation of the stomach contents into the thoracic part of the esophagus. Major Openings in the Diaphragm: 1. The aortic opening: at the level of the 12th thoracic vertebra between the crura. – It transmits the aorta, the thoracic duct, and the azygos vein (ATA). 2. The esophageal opening: at the level of the 10th thoracic vertebra to the left, in a sling of muscle fibers derived from the right crus. − It transmits the esophagus, the right and left vagus nerves. 3. The caval opening at the level of the 8th thoracic vertebra in the central tendon to the right. – It transmits the inferior vena cava and terminal branches of the right phrenic nerve. Relations of the diaphragm: i. Upper surface: is related to 3 membranes pleura on each side with pericardium in between which separate the diaphragm from the base of the lung on each side with the heart in between. ii. The lower surface: – The right cupola is related inferiorly to 3 right structures → right lobe of the liver, right kidney, and right suprarenal gland. – The left cupola is related to 3 left structures →left lobe of the liver, left kidney, and left suprarenal gland & the stomach and spleen. Nerve Supply of the Diaphragm: 1. Motor nerve supply: – The right and left phrenic nerves. 2. Sensory nerve supply: – The central part of the diaphragm (thoracic and abdominal surfaces are) supplied by the phrenic nerve and the periphery of the diaphragm is supplied from the lower six intercostal nerves. Blood supply of the diaphragm: 1. Inferior phrenic arteries (from abdominal aorta > inferior phrenic arteries). 2. Musculo-phrenic and pericardio- phrenic arteries (internal thoracic artery). Functions of the Diaphragm: 1. Muscle of inspiration: On contraction, it pulls its central tendon down and increases the vertical diameter of the thorax. The diaphragm is the most important muscle used in inspiration → ↑venous return in superior vena cava. 2. Muscle of abdominal straining: The contraction of the diaphragm assists the contraction of the muscles of the anterior abdominal wall in raising the intra- abdominal pressure for micturition, defecation, and parturition. 3. Assist weightlifting.