The heart (Lat. cor, Grk. kardia) is a muscle that maintains the circulation of blood. Deoxygenated blood flows into the right atrium of the heart from the superior vena cava and inferior vena cava, which drain blood from the upper and lower halves of the body respectively. After the blood is passed to the right ventricle, it exits via the to the lungs, where it receives oxygen. It then travels via the pulmonary veins into the left atrium, and then into the , which forces it through the aorta into the arteries that supply the body. The heart itself is supplied with oxygenated blood by the coronary arteries, and the deoxygenated blood is returned to the lungs via the cardiac veins.

By now you have already learned the major principles behind the formation of Latin-based vocabulary and can fully explain much of the terminology related to the heart. You know that pulmon- means “” and that the suffix -ary means “having to do with.” You know that the base ventr- and the suffix -cle combine to form a term literally meaning "little ” or “little pouch.” Likewise you can understand full Latin phrases such as inferior vena cava and superior vena cava. And even if you have not formally been introduced to phrases such as septum interventriculare cordis, you can use your knowledge of Latin nouns and adjectives to determine their meaning (here “division of the between the ventricles”; cf. septum nasi).

You also know that an atrium is a chamber, and you can further describe the ending of this word as a marker of the declension. More specifically, the atrium was the first large room in a Roman house. The source of the word atrium is unknown, but as commonly happened in antiquity various etymological explanations were set forward on the basis of function. It was suggested that atrium was linked to ater (“black”) because of the smoke that would be produced from fires lit in the room for the purpose of heat, light, or even cooking (a similar argument was advanced to explain the Greek word for “roof,” melathron, which is similar to the Greek root -).

Other terms will make sense after you have studied the Greek chapters. For example, “” is a Greek word meaing “tissue on the heart” and indicates the serous membrane that is the innermost part of the (Grk. “tissue around the heart”), the sac that surrounds the heart and the roots of the great vessels. “Aorta” is only very slightly changed from the Greek word aorte, which was used even in antiquity to denote the main artery in the human body. Meanwhile, “brachiocephalic” is a bilingual term derived from the Latin base brachi- (“”) and the Greek base cephal- (“”)—the two body parts supplied by this particularly branch of the aorta.