pericardium
noun
peri·car·di·um ˌper-ə-ˈkär-dē-əm 
plural pericardia ˌper-ə-ˈkär-dē-ə
1
: the conical sac of serous membrane that encloses the heart and the roots of the great blood vessels of vertebrates
2
: a cavity or space that contains the heart of an invertebrate and in arthropods is a part of the hemocoel
Example Sentences
Recent Examples on the Web In one passage, recommendations for a form of tracing paper included paper rubbed with linseed oil or pork fat, the amniotic membrane of a cow’s embryo, or the pericardium of an ox. 
Anthony Grafton, The New York Review of Books, 7 Sep. 2022 The branch on the pine log went far enough into my chest to perforate my pericardium—that’s the membrane surrounding my heart. Outside Online, 10 June 2022 Pericarditis is inflammation of the sac or pericardium around the heart. Kristen Jordan Shamus, Detroit Free Press, 2 July 2021 They are attached at the lower chest and abdomen and share their chest wall, diaphragm, pericardium and liver. Cnn Editorial Research, CNN, 26 May 2021 The goods news is that their hearts were separate as well, sharing only the lining around the heart – the pericardium. Carol Robinson | Crobinson@al.com, al, 22 Apr. 2021 Bleakley talked about an older dog that was referred to him by an oncologist for an abnormality with excess fluid in the pericardium around the dog’s heart. Georgann Yara, The Arizona Republic, 30 Oct. 2020 Gore-Tex fabric was used to place a patch over the holes in the pericardium around each of their hearts. Kristen Jordan Shamus, Detroit Free Press, 18 Sep. 2020 There’s a spot between the tendons—about two or three finger widths above the center of your inner wrist—called the pericardium 6 (PC6). Taylyn Washington-harmon, Health.com, 1 July 2020 See More
Anthony Grafton, The New York Review of Books, 7 Sep. 2022 The branch on the pine log went far enough into my chest to perforate my pericardium—that’s the membrane surrounding my heart. Outside Online, 10 June 2022 Pericarditis is inflammation of the sac or pericardium around the heart. Kristen Jordan Shamus, Detroit Free Press, 2 July 2021 They are attached at the lower chest and abdomen and share their chest wall, diaphragm, pericardium and liver. Cnn Editorial Research, CNN, 26 May 2021 The goods news is that their hearts were separate as well, sharing only the lining around the heart – the pericardium. Carol Robinson | Crobinson@al.com, al, 22 Apr. 2021 Bleakley talked about an older dog that was referred to him by an oncologist for an abnormality with excess fluid in the pericardium around the dog’s heart. Georgann Yara, The Arizona Republic, 30 Oct. 2020 Gore-Tex fabric was used to place a patch over the holes in the pericardium around each of their hearts. Kristen Jordan Shamus, Detroit Free Press, 18 Sep. 2020 There’s a spot between the tendons—about two or three finger widths above the center of your inner wrist—called the pericardium 6 (PC6). Taylyn Washington-harmon, Health.com, 1 July 2020 See More Word History
Etymology
Middle English, from Medieval Latin, from Greek perikardion, neuter of perikardios around the heart, from peri- + kardia heart — more at heart
First Known Use
15th century, in the meaning defined at sense 1
Medical Definition
pericardium
noun
peri·car·di·um ˌper-ə-ˈkärd-ē-əm
plural pericardia -ē-ə
: the conical sac of serous membrane that encloses the heart and the roots of the great blood vessels of vertebrates and consists of an 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 is closely adherent to the heart while the other lines the inner surface of the outer coat with the intervening space being filled with pericardial fluid