The Pericardium: An Examination of Structure, Function, and Disease


The pericardium is a vital structure for most organisms that have a heart that pumps blood. The pericardium encapsulates the heart and it is a flexible and thin, yet durable membranous sack that contains the fluid that surrounds the heart. The pericardium has the membranous ability to regulate the fluid that it contains, and this function is what separates it from most of the membranous sacks in organisms that surround other organs, i.e. the kidney.

The pericardium is anchored to the human body by its connection to the blood vessels surrounding the heart, the diaphram, and the sternum.
The pericardium consists of two layers as seen in the following diagram:


heartpericardium.jpg
ws


This diagram clearly portrays the continuity of the visceral pericardium and the parietal pericardium and the point of their intersections are where major blood vessels connect with the heart. Conceptually, it is not incorrect to picture that the parietal pericardium has two parts, the fibrous outer layer, and the serous inner layer. The serous layer and the visceral pericardium are smooth and are the perimeter of the pericardial cavity. The pericardial cavity is also known as the intermembranous space. The arrows denote this space in the following image:


external image C511.jpghttp://www.bmc.cardiologydomain.com/images/dynamic/C511.jpg



This intermembranous space is the primary example of how structure meets function in the pericardium. The fact that the pericardium consists of two smooth layers allows it to contain, and be filled with lubricating fluid. This fluid maintains the position of the heart in the ribcage no matter of the respiration cycle. When these dual layers are healthy they prove to protect the heart from infection and keep the heart at a constant size without unwanted stretching or enlargement. Refer to the bottom of the page to examine an unhealthy, aka diseased, pericardium.

The pericardium in the human body is remarkably similar to that in the pig body. There is little diversity between the human and pig in respect to the pericardium.


Examine the pericardium in a fetal pig:

PIG_WIKI.JPG


Considering that this is a picture of a pig that is dead, most of the intermembranous fluid that is usually found in the pericardium is not there. The absence of fluid shows how thin the actual layers of the pericardium are, and it is surprising how durable and flexible the pericardium is considering the thin visceral and parietal layers.


Diseases of the Pericardium:

In terms of quantity, there are very few diseases that tend to be diagnosed in the pericardium. Benign and malignant tumors can grow in the pericardium, but this is a very rare occurence. In contrast, pericarditis is overwhelmingly more common. True to its nature as a suffix, "itis" means swelling, and most people recognize this suffix (i.e. appendicitis). Pericarditis is the swelling of the pericardium.

In a patient that has pericarditis both layers of the pericardium, visceral and parietal, swell, and there are many potential factors that can cause the swelling. The most common root of pericarditis is due to a viral infection. The pericardium is most susceptible to viral infection during or after a respiratory infection, or in severely compromised immune systems, such as patients with the AIDS virus. Bacterial infections of the pericardium are far less likely to occur than viral infections, however, bacteria has been isolated from pericardiums with pericarditis. It is believed that the bacteria must have been from another source of infection in the body, or can cause direct infection after open heart surgery, as the pericardium is opened to the environment. Other causes of pericarditis are not unique to the pericardium as these problems can cause inflammation in many different parts of the body, and do. For example, trauma, kidney failure, hypothyrodism, and medication all can cause inflammation many places in the body, including the pericardium.

Patients with pericarditis complain of chest pain and fever, and is made significantly worse by deep breathing. The pain is located in the center or the left of the chest. When a patient complains of these symptoms she or he is given an EKG, and patients with pericarditis' EKG are irregular. If the EKG is not normal, then a X-Ray, MRI, or CT scan, or a combination of all three will be used.

The treatment procedure is called pericardiocentisis. Essentially a surgeon will inject a catheter into the pericardium and extract the unwanted fluid that is the cause of the swelling.

pericarditis.jpg
ws


http://en.wikipedia.org/wiki/Pericardium
http://www.americanheart.org/presenter.jhtml?identifier=4683
http://www.heart-vessels.com/cardiovascular-diseases/cardiac-tamponade.php
http://www.nlm.nih.gov/medlineplus/ency/imagepages/18081.htm
http://www.medterms.com/script/main/art.asp?articlekey=9128
http://www.metrohealth.org/body.cfm?id=1487&oTopID=1479




[[josh pics|]]