THORACIC DIAPHRAGM BY ATIBA P.M GROSS ANATOMY OF THORAX ANA 202 INTRODUCTION It is a double- domed sheet of skeletal muscle, located at the inferior-most aspect of the rib cage. It acts in partition and respiration. ANATOMICAL POSITION AND ATTACHMENT The diaphragm is located at the inferior-most aspect of the ribcage, filling the inferior thoracic aperture. It acts as the floor of the thoracic cavity. It has peripheral and central attachment PERIPHERAL ATTACHMENT It has three peripheral attachment; Lumbar vertebrae and arcuate ligament. Costal cartilages of the ribs 7-10. Xiphoid process of the sternum. Crura of Diaphragm The tendinous parts of diaphragm arise from the vertebrae, they are left and right crura. Right crus: L1-L3 and their intervertebral discs. Left crus: L1-L2 and their intervertebral discs. Central Tendon of diaphragm It’s muscle fibres combine to form the central tendon. The tendons ascend to fuse with the inferior surface of the fibrous pericardium. The diaphragm ascends form left and right domes, at either side of the pericardium. Diaphragm Hiatus There are three opening that act as conduit for structure from thorax to the abdomen. • Caval hiatus • Oesophageal hiatus • Aortic hiatus ACTIONS The diaphragm is the primary muscle of respiration. During inspiration, it contracts and flattens, increasing the vertical diameter of the thoracic cavity. This produces lung expansion, and air is drawn in. ACTIONS During expiration, the diaphragm passively relaxes and returns to its original dome shape. This reduces the volume of the thoracic cavity. INNERVATION AND VASCULATURE The halves of the diaphragm receives motor innervation from a phrenic nerve. The left half of the diaphragm is innervated by the left phrenic nerve and vice versa. The phrenic nerve is formed in the neck within the cervical plexus, and contains fibres from spinal roots C3-C5. INNERVATION AND VASCULATURE The majority of the arterial supply to the diaphragm is delivered via the inferior phrenic arteries, which arise directly from aorta. INNERVATION AND VASCULATURE The remaining supply is from the superior phrenic, pericardicophrenic, and musculophrenic arteries. The draining veins follows corresponding arteries. CLINICAL RELEVANCE Diaphragmatic paralysis is due to an interruption in its nervous supply. This can occur in the phrenic nerve, cervical spinal cord, or the brainstem. It is due to a lesion of the phrenic nerve. It produces paradoxical movement of diaphragm.