If the heart is the fun, exciting inside little bit of one orange, the pericardium could be contrasted to the peel approximately it. Prefer peel, it can seem vaguely unexciting – that is till you find out some that its really important (appeeling. Ahem.) physiological functions 1.
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In clinical terms, the pericardium is a fibro-serous, fluid-filled sack the surrounds the muscular human body of the heart and the root of the good vessels (the aorta, pulmonary artery, pulmonary veins, and the superior and inferior vena cavae).
This post will provide an overview of the functions, structure, innervation, and clinical meaning of the pericardium.
The pericardium is consisted of of two key layers: a tough external layer well-known as the fibrous pericardium, and a thin, inner layer recognized as the serous pericardium (to overextend the orange metaphor, the outer peel might be thought of together the fibrous layer, v the inside white stuff gift the serous layer).
Continuous with the central tendon that the diaphragm, the fibrous pericardium is make of challenging connective tissue and is relatively non-distensible. Its strictly structure stays clear of rapid overfilling of the heart, yet can contribute to serious clinical consequences (see cardiac tamponade).
Enclosed within the fibrous pericardium, the serous pericardium is itself divided into two layers: the outer parietal layer that lines the internal surface of the fibrous pericardium and also the internal visceral layer that forms the external layer of the heart (also well-known as the epicardium). Every layer is consisted of of a single sheet the epithelial cells, known as mesothelium.
Found between the outer and also inner serous layers is the pericardial cavity, which consists of a small amount of lubricating serous fluid. The serous fluid serves to minimize the friction produced by the heart as it contracts.
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Fig 1 – rundown of the class of the heart wall.
The stimulate of this layers have the right to be remembered making use of the acronym Fart Police Smell Villains:F – Fibrous great of the pericardiumP – Parietal great of the serous pericardiumS – Serous fluidV – Visceral class of the serous pericardium
The pericardium has numerous physiological roles, the most important of i m sorry are comprehensive below:Fixes the heart in the mediastinum and limits its motion. Continuous of the heart is feasible because the pericardium is attached to the diaphragm, the sternum, and also the tunica adventitia (outer layer) that the good vesselsPrevents overfilling of the heart. The relatively inextensible fibrous layer of the pericardium stays clear of the heart from enhancing in size too rapidly, for this reason placing a physical limit on the potential dimension of the organLubrication. A thin film of fluid in between the 2 layers of the serous pericardium to reduce the friction generated by the heart together it move within the thoracic cavityProtection indigenous infection. The fibrous pericardium serves as a physical obstacle between the muscular human body of the love and nearby organs susceptible to infection, such together the lungs.
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Fig 2 – Anterior watch of the pericardium. Keep in mind the attachments come the diaphragm, and also the roots of the good vessels.
Clinical Relevance: Transverse Pericardial Sinus
Formed together a an outcome of the embryological urgently of the heart tube, the transverse pericardial sinus is a passage through the pericardial cavity.
It is located:Posterior to the ascending aorta and also pulmonary trunk.Anterior to the superior vena cava.Superior to the left atrium.
In this position, the transverse pericardial sinus separates the heart’s arterial outflow (aorta, pulmonary trunk) native its venous inflow (superior vena cava, pulmonary veins).
The transverse pericardial sinus can be offered to identify and subsequently ligate the arteries of the heart during coronary artery bypass grafting.
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Fig 3 – The Transverse pericardial sinus, separating the significant arteries and also veins. Additionally note the close partnership of the fibrous pericardium and the diaphragm
The relatively inextensible fibrous pericardium can reason problems as soon as there is an build-up of fluid, known as pericardial effusion, in ~ the pericardial cavity.
The strict pericardium can not expand, and thus the heart is topic to the resulting enhanced pressure. The chambers can come to be compressed, hence compromising cardiac output.
Pericarditis, or inflammation of the pericardium, has myriad causes, including bacterial infection and myocardial infarction. The main symptom is chest pain, and also the condition can cause acute cardiac tamponade due to an accumulation of liquid in the pericardial cavity.
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By James Heilman, MD (Own work)
Fig 4 – Radiographic figure of pericardial effusion (note the enlarged heart shape).