NERVE SUPPLY 101 



The columnse carnae are columelliform projections of the myo- 

 cardium into the ventricular cavity. They consist of cardiac 

 muscle fibres, which are disposed in their long axis, and are cov- 

 ered by reflections and reduplications of the endocardium. The 

 irregular contour of the ventricular cavities appears to be entirely 

 due to the projecting columnae carnae. 



These muscular columns may present any one of three modes 

 of attachment to the myocardium : (1) They may be attached along 

 their entire extent ; (2) they may be attached only at their two 

 ends, the mid-portion being free ; (3) they may be attached to the 

 myocardium at one end only, the other end projecting into the 

 ventricular cavity as a papillary muscle, from whose apex chordae 

 tendinae pass to the auric ulo-ventricular valves. Either of the 

 last two forms may, in transections of the ventricles, appear as 

 isolated islands of muscular tissue surrounded by endocardium 

 and lying apparently free within the cavity of the ventricle. 



Blood vessels. The heart is supplied with blood through the 

 coronary arteries. The larger branches of these vessels pursue 

 their course beneath the epicardium in the superficial grooves of 

 the cardiac wall. From these large arteries, smaller branches are 

 distributed to the epicardium and to the muscular wall, the latter 

 vessels penetrating as far as the endocardium, in whose connective 

 tissue they form a meager capillary plexus. 



The capillaries of the myocardium are extremely abundant. 

 They form elongated meshes between the muscle fibres, the cir- 

 cumference of each muscle fibre being in relation with several 

 capillary vessels. The veins return the blood from these rich 

 capillary plexuses and pursue a course similar to that of the arter- 

 ies, the larger veins being always found in the broader connect- 

 ive tissue septa. 



NEEVE SUPPLY, The nerve supply of the vascular system 

 is by means of fine branches derived from the cerebro-spinal and 

 sympathetic systems. In the heart these minute nerve trunks end 

 in the various cardiac ganglia, most of which are found in the 

 connective tissue of the heart, e. g., the coronal plexuses about the 

 orifices of the aorta and pulmonary artery. From these ganglia 

 sensory nerve fibres are distributed to the endocardium and epicar- 

 dium, and motor fibres to the myocardium. The most of the former 

 are connected with the vagus, the latter with the sympathetic 

 trunks. 



From the cardiac ganglia branches pass to form a coarse plexus 



