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Structure, blood supply and innervation of the pericardium.
Hi there! It’s Matt from Kenhub, and in this tutorial, we will be discussing the pericardium. The pericardium – seen here highlighted in green – is a double-walled sac that encloses the heart, the pericardial fluid and the roots of the great vessels, and is situated within the middle mediastinum. The pericardium has one layer made of fibrous tissue and one made of serous tissue. Its function is to lubricate the moving surfaces of the heart, and in this video, the anatomy of the pericardium will be discussed in detail.
The outer layer of the pericardium is known as the fibrous layer and consists of dense connective tissue. It is attached to the central tendon of the diaphragm via the pericardiacophrenic ligament whose fibers emerged with the tunica adventitia of the vessels which enter and exit the heart. The pericardial sac also attaches via ligamentous fibers to the sternum and, due to these attachments, it is affected by the movements of the heart, the great vessels, the sternum and the diaphragm. This fibrous exterior lining mechanically functions to prevent the heart from overfilling because the fibrous tissue as a whole is resilient and, although flexible, it does not stretch.
The inner layer of the pericardium is known as the serous layer or the parietal layer and is in direct contact with the pericardial fluid. It consist of a mesothelial layer, simple squamous epithelium which reflects onto the root of the great vessels and runs directly over the external surfaces of the heart as the epicardium or visceral pericardium.
The pericardial cavity is the potential space created by the pericardial reflection between the parietal and visceral layers of the serous pericardium, and this is where the thin film of pericardial fluid is kept allowing for the two surfaces to be lubricated and rub against one another without any friction.
Two sinuses exist within the pericardial cavity that include the transverse sinus and the oblique sinus. The transverse pericardial sinus extends transversely across the pericardium in between the roots of the great vessels (between the aorta and the pulmonary trunk), posterior to the ascending aorta and the pulmonary trunk, and anterior to the superior vena cava. The oblique pericardial sinus exists in the posterior part of the pericardium and is bordered laterally by the pulmonary veins which enter the heart and inferiorly by the inferior vena cava which is also returning to the heart, more specifically, between the right pulmonary veins and inferior vena cava and between the right pulmonary vein and the left pulmonary vein.
The blood supply of the pericardium comes from the pericardiacophrenic arteries and the internal thoracic arteries. The internal thoracic veins are responsible for the venous drainage of the area. The innervation of the pericardium is governed by several different branches including the phrenic nerves which give sensory fibers that control pain sensation and the sympathetic trunks which carry vasomotor fibers.
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