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What does the word heart mean?

• An azygous muscle, of an irregularly pyramidal shape; situate obliquely and a little to the left side, in the chest ;-resting on the diaphragm by one of its surfaces :-suspended by its base from the great vessels; free and movable in the rest of its extent, and surrounded by the pericardium. The right side of the body of the heart is thin and sharp, and is called Margo acutus: the left is thick and round, and termed Margo obtusus. It is hollow within, and contains four cavities: two of which, with thinner and less fleshy walls, receive the blood from the lungs and the rest of the body, and pour it into two others, with thick and very fleshy parietes, which send it to the lungs and to every part of the body. Of these cavities, the former are called auricles, the latter ventricles. The right auricle and right ventricle form the Pulmonic or right or anterior heart. Cor venosum seu pulmonale, ( F.) Coeur du poumon. C. du sang noir, C. droit, C. anterieur: and the left auricle and ventricle, the systemic, corporeal, left, Dr aortic heart, Cor arteriosum seu aorticum, ( F.) Coeur du corps, C. gauche, C. aortique ou C. rouge. In the adult, these are totally distinct from each other, being separated by a partition ;-the septum cordis. Into the right auricle, the venae cavae, -superior and inferior, -and the coronary vein, open. The pulmonary artery arises from the right ventricle; the four pulmonary veins open into the left auricle, and the aorta arises from the left ventricle. The mean weight of the heart, in the adult, from the twenty-fifth to the sixtieth year, is, according to Bouillaud, from eight to nine ounces. The dimensions, according to Lobsteln and Bouillaud, are as follows: - Length, from base to apex, five inches six lines; breadth, at the base, three inches; thickness of the walls of the left ventricle, seven lines; at a finger's breadth above the apex, four lines; thickness of the walls of the right ventricle, two and a quarter lines; at the apex, half a line; thickness of right auricle, one line; of the left auricle, half a line. The heart is covered, externally, by a very thin, membranous reflection from the pericardium. The muscular structure of which it is constituted is much thicker in the parietes of the ventricle than in those of the auricles. Its cavities are lined by a very delicate membrane, the endocardium, which is continuous with the inner membrane of the arteries, as regards the left cavities, and with that of the veins, as regards the right. Its arteries- the coronary- arise from the commencement of the aorta. Its nerves proceed, chiefly, from the pneumogastric and the cervical ganglions of the great sympathetic. The heart is the great agent in the circulation. By its contraction, the blood is sent over every part of the body. Its action does not seem to be directly owing to nervous influence received from the brain or spinal marrow, or from both. The circulation may, indeed, be kept up, for some time, if both brain and spinal marrow be destroyed. When the ear is applied to the chest, a dull, lengthened sound is heard, which is synchronous with the arterial pulse. This is instantly succeeded by a sharp, quick sound, like that of the valve of a bellows or the lapping of a dog, and this is followed by a period of repose. The first sound appears to be mainly produced by the contraction of the ventricles; the second, by the reflux of the blood against the semilunar valves. These are what are called the Sounds of the Heart, ( F.) Bruits du Coeur. Dr. C. J. B. Williams thinks that the word lubb-dup conveys a notion of the two sounds. The Beating or Impulse of the heart, Heart-Stroke, Pulsus seu Ictus cordis, ( F.) Impulsion du Coeur, against the parietes of the chest, is mainly caused, perhaps, by the systole of the heart, which tends to project It forwards. It is doubted, however, by some, whether the impulsion be produced by the dilatation or the contraction of the ventricles. The following table exhibits the different actions of the heart, and their coincidence with its sounds and impulse. It presumes, that the period from the commencement of one pulsation to that of another is divided into eight parts; and if the case of a person, whose pulse beats sixty times in a minute, be taken, each of these parts will represent the eighth of a second. The heart is subject to different organic diseases; the chief of which are aneurism, contraction of the apertures, and rupture of its parietes.

• [ Latin] A hollow muscular organ which propels the blood into and through the arteries. It consists of two lateral halves( Right h., Left h.), each composed of an upper chamber( auricle) and a lower chamber( ventricle). In the left h. the auricle receives arterial blood from the lungs through the pulmonary veins and forces it into the ventricle, which in turn contracts, forcing the blood into the aorta and thus into the whole body. In the right h. the auricle receives venous blood from all parts of the body through the superior and inferior venae cavae and forces it into the ventricle which in turn sends it through the pulmonary artery to the lungs to be arterialized. At the orifice( auriculo-ventricular orifice) connecting each auricle with its ventricle, regurgitation is prevented by valves, a two-parted( mitral) valve on the left side and a three-parted( tricuspid) valve on the right. Semilunar valves, consisting of three cusps each, prevent the regurgitation of blood from the aorta and from the pulmonary artery into the ventricles. The h. consists of an inner layer of endothelium( endocardium), continuous with that of the vessels, and of muscular tissue( myocardium), composed of nucleated prismatic cells which show an obscure transverse striation, are destitute of sarcolemma, and are connected to the ends and to lateral processes of adjoining fibres by a cement substance. The fibres are imbedded in connective tissue, and the whole is invested by a serous membrane( pericardium). The valves consist of endothelium with a skeleton of connective tissue, and at the auriculo-ventricular orifices are checked and moved by tendinous cords( chordae tendineae) attached to muscular prominences( columnae carneae) in the ventricle.

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