SECTION III 

 CIRCULATION 



LESSON XII 

 HEART 



I. Structure. 



(Drawings should be made of the various structures and a Text 

 Book of Anatomy may be consulted.) 



1. Use the sheep's heart supplied. Open the right auricle by a 

 horizontal cut. Open the right ventricle either by an inverted V 

 incision as demonstrated or by passing scissors down the pulmon- 

 ary artery into the ventricle and snipping through the anterior 

 wall. 



Examine the tricuspid valve and papillary muscles. 



Slit up the pulmonary artery and examine the semilunar valves. 



Open the left auricle and ventricle by a vertical antero -posterior 

 incision through the left auriculo- ventricular orifice and middle of 

 the aorta. This is best done by laying the heart on its anterior 

 surface and cutting from behind. Examine the mitral valve and 

 papillary muscles, the relations of the anterior cusp of the mitral to 

 the posterior aortic wall and the aortic semilunar valves and mouths 

 of the coronary arteries. 



On the septum between the ventricles note that a special band of 

 muscular fibres passes from the auricles to the ventricles. 



2. On the models of the thoracic organs, study the attachments 

 and relations of the heart to the anterior and posterior chest walls, 

 to the central tendon of the diaphragm and to the lungs. Note that 

 the lungs, heart and great vessels completely fill the thorax. 



3. In a boiled heart of a sheep, twist off the auricles, aorta and 

 pulmonary artery, and examine the auriculo -ventricular and 

 pulmonary fibrous rings from which the muscular fibres rise. 



Clear the visceral pericardium off the ventricles and study the 

 course of the muscle fibres. 



4. In the longitudinal section of the heart of a mouse under a 

 low power of the microscope, study the various parts. 



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