258 CLINICAL APPLIED ANATOMY. 



CONGENITAL DISEASE OF THE HEART. 



Lesions near the origin of the pulmonary artery from the 

 right ventricle are found in more than three-quarters of the 

 cases of congenital disease. The pulmonary trunk, the pulmonary 

 valves, or the infundibular part of the right ventricle may be 

 involved. It is necessary to point out that the infundibulum, or 

 that part of the right ventricle from which the pulmonary trunk 

 arises, is also known as the conus pulmonalis or the conus 

 arteriosus. The term bulbus arteriosus is applied to a segment 

 of the embryonic heart, which, becoming subdivided, not only 

 gives rise to the infundibulum of the right ventricle, but also to 

 the corresponding part of the left and to the stems of the aorta 

 and pulmonary artery. The bulbus, before this subdivision, is 

 looked upon by embryologists as consisting of two parts, one 

 part near the heart is the bulbus proper, and a more distal 

 portion is called by them the conus arteriosus. Since the latter 

 term is also applied to the infundibulum some confusion is 

 apt to arise. 



The right ventricle of the human heart is formed by the 

 fusion of two chambers, the infundibulum, which is a part 

 derived from the bulbus arteriosus, and the sinus, or body 

 of the ventricle, which is the right half of the foetal common 

 ventricle. The union of these constituent parts is indicated on the 

 wall of the ventricle by a muscular lip, which projects downwards 

 into the cavity and intervenes between the tricuspid and the 

 pulmonary orifices. This projecting lip is known as the supra- 

 ventricular crest. At the level of the crest a fibrous ring of 

 thickened endocardium is sometimes found, and this, when 

 much exaggerated, forms a diaphragm with a central perforation 

 of varying size. When this is the case, a heart with three 

 ventricles results, the infundibulum being sharply separated 

 from the sinus of the ventricle. (Fig. 29.) In other instances 

 the development of the infundibulum is arrested at an early 

 stage, and the chamber is represented by a small cavity or even 



