per·i·car·di·um   (pěr'ĭ-kär'dē-əm)    n.   pl. per·i·car·di·a (-dē-ə) The membranous sac filled with serous fluid that encloses the heart and the roots of the aorta and other large blood vessels. [New Latin, from Greek perikardion, from perikardios, around the heart : peri-, peri- + kardiā, heart; see kerd- in Indo-European roots.] per'i·car'di·al (-dē-əl), per'i·car'di·ac' (-dē-āk') adj.

pericardium 

Main Entry: peri·car·di·um
Pronunciation: "per-&-'kärd-E-&m
Function: noun
Inflected Form: plural peri·car·dia /-E-&/
: the conical sac of serous membrane that encloses the heart and the roots of the great blood vessels of vertebrates and consists ofan outer fibrous coat that loosely invests the heart and is prolonged on the outer surface of the great vessels except the inferior vena cava and a double inner serous coat of which one layer isclosely adherent to the heart while the other lines the inner surface of the outer coat with the intervening space being filled with pericardial fluid

pericardium per·i·car·di·um (pěr'ĭ-kär'dē-əm)
n. pl. per·i·car·di·a (-dē-ə)
The fibroserous sac enclosing the heart and the roots of the great vessels, consisting of two layers: the visceral layer or epicardium, immediately surrounding the heart; and the outer parietal layer, which forms the sac and is lined with a serous membrane. Also called heart sac, theca cordis.

---

per'i·car'di·al (-dē-əl) or per'i·car'di·ac' (-dē-āk') adj.