Reference > Anatomy of the Human Body > Page 535
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Henry Gray (1825–1861).  Anatomy of the Human Body.  1918.
 
  The aortic semilunar valves (Figs. 494, 497) are three in number, and surround the orifice of the aorta; two are anterior (right and left) and one posterior. They are similar in structure, and in their mode of attachment, to the pulmonary semilunar valves, but are larger, thicker, and stronger; the lunulæ are more distinct, and the noduli or corpora Arantii thicker and more prominent. Opposite the valves the aorta presents slight dilatations, the aortic sinuses (sinuses of Valsalva), which are larger than those at the origin of the pulmonary artery.
  The trabeculæ carneæ are of three kinds, like those upon the right side, but they are more numerous, and present a dense interlacement, especially at the apex, and upon the posterior wall of the ventricle. The musculi papillares are two in number, one being connected to the anterior, the other to the posterior wall; they are of large size, and end in rounded extremities from which the chordæ tendineæ arise. The chordæ tendineæ from each papillary muscle are connected to both cusps of the bicuspid valve.


FIG. 498– Section of the heart showing the ventricular septum. (See enlarged image)


Ventricular Septum (septum ventriculorum; interventricular septum) (Fig. 498).—The ventricular septum is directed obliquely backward and to the right, and is curved with the convexity toward the right ventricle: its margins correspond with the anterior and posterior longitudinal sulci. The greater portion of it is thick and muscular and constitutes the muscular ventricular septum, but its upper and posterior part, which separates the aortic vestibule from the lower part of the right atrium and upper part of the right ventricle, is thin and fibrous, and is termed the membranous ventricular septum. An abnormal communication may exist between the ventricles at this part owing to defective development of the membranous septum.

Strucutre.—The heart consists of muscular fibers, and of fibrous rings which serve for their attachment. It is covered by the visceral layer of the serous pericardium (epicardium), and lined by the endocardium. Between these two membranes is the muscular wall or myocardium.
  The endocardium is a thin, smooth membrane which lines and gives the glistening appearance

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