Résumé on the Circulatory System

Abstract

The study of the normal heart action is attracting an increasing amount of interest. Keith1 calls attention to the fact that the heart functionally consists of a central pump, the left ventricle, with three subsidiary loading pumps, the right and left auricles, and the right ventricle. Each chamber has a fulcrum, that of the auricle being applied through the fixation to the dorsal pericardial walls and through the pericardial extensions on the pulmonary vessels and lungs to the costal and diaphragmatic chest wall; the ventricles have two fulcrums, the fixed ascending stem of the aorta, and the movable fulcrum at the apex.With ventricular contraction the auricular base about the mitral and the tricuspid rings is reduced in size and through the action of muscles acting from the apical fulcrum is drawn down toward the apex, enlarging the auricles. This is the key to the venous pulse. The aortic base is unchanged and becomes the fulcrum from which the expelling musculature works. The muscles of the heart are arranged in groups of antagonistic muscles. In the left ventricle there is a circular expel¬ ling coat set between an outer and an inner spiral coat, the fixed axis passing from the mouth' of the aorta to the apex. In systole the muscles approach this axis. All of the muscular coats ultimately end in the fibers of the internal spiral coat of the left ventricle, each seg¬ ment narrowing or expanding on the principle of the iris diaphragm.The auriculoventricular bundle ends in the trabecular network of the apex where ventricular systole begins. The antagonist muscles are the internal muscles of the columnae carnae and the papillary muscles which extend from the apex to the base of the auricles and the aorta, and the external spiral muscles on the outside of the ventricle wall which end at the aortic and auricular bases. These groups are antag¬ onistic to lengthening of the heart chamber. In early systole when the auricular base descends, the circular fibers are more than antagon-1. Keith, Arthur: Brit. M. J. 1:361 (March 30) 1918. Downloaded From: http://archpedi.jamanetwork.com/ by a UCSF LIBRARY User on 06/13/2015ized, but in the later phase of systole the circular fibers become dominant, and raise the auricular base. The apico-aortic fibers are sustaining and do not change in length during systole.In the right ventricle, the pulmonary orifice is not fixed, the infundibular bands from the right base acting as the fulcrum. The septum really belongs to the left ventricle and is only passively a wall of the right, so that the internal musculature running from the apex to the base is more highly developed on the right, with the pectinate muscles forming an opponent set.Smith2 has an interesting study of the anatomy of the coronary arteries obtained by injecting the arteries with physiologic sodium chlorid solutions until the fluid returns clear and then injecting a solution consistng of 2 parts of barium suspended in 10 parts of water with a little tragacanth. Stereoscopic roentgenograms are made, and he finds studyi...