Heart MCQs

Angiogenic cell clusters appear in mesoderm only. The heart arises as two bilateral tubes that eventually fuse into one heart tube that begins to beat around the 21st day. When the aortic arches develop, they do so in a cephalic to caudal direction. Reference - Textbook of Langman's, 12th Edition, Cardiovascular System Embryology Page number - 185

Myocardium or heart muscle arises from the splanchnic mesoderm near the heart tubes in the cardiogenic region. Endocardium is also from this cardiogenic splanchnic mesoderm, from angiogenic cell clusters forming the heart tubes. Epicardium or visceral pericardium is from splanchnic mesoderm lining the intraembryonic coelom. Reference - Textbook of Langman's, 12th Edition, Cardiovascular System Embryology Page number - 185

In the placenta, there is no anastomosis between the maternal and fetal vessels. Maternal blood from the spiral arteries enters the cotyledons, where it bathes the villi from the fetus. This all occurs without anastomosis. Reference - Textbook of Langman's, 12th Edition, Cardiovascular System Embryology Page number - 185

The right sinus horn of the sinus venosus enlarges and forms the fetal right atrium. The left sinus horn regresses to form the main vein draining the heart muscle, the coronary sinus. The original right atrium becomes the right auricle and also part of right atrium anterior to the crista terminalis. Reference - Textbook of Langman's, 12th Edition, Cardiovascular System Embryology Page number - 170

Ans. is 'c' i.e., Sinus venosus [Ref Essentials of human embryology p. 873] The Coronary sinus develops from the Sinus venosus segment of embryonic heart. Left horn of sinus venosus retrogresses to form part of coronary sinus

The structure marked is the membranous part of the interventricular septum. It is derived from endocardial cushions. Endocardial cushions are soft tissue masses that protrude in the atrioventricular and conotruncal regions. Atrioventricular cushions are derived from overlying endocardial cells. The conotruncal cushions are derived from the neural crest cells. Endocardial cushions contribute to the formation of: Atrial septa Ventricular septa (membranous portion) Atrioventricular canals Atrioventricular valves Aortic and pulmonary channels Reference - Textbook of Langman's, 12th Edition, Cardiovascular System Embryology Page number - 171

Early in heart development, the heart tubes are suspended within the intraembryonic coelom by the dorsal mesocardium. The rupture of this membrane and the folding of the heart tubes brings the outflow tract and inflow tract close together, producing the transverse pericardial sinus. Reference - Textbook of Langman's, 12th Edition, Cardiovascular System Embryology Page number - 170

Remember that ventricular systole is the period when the ventricles are contracting. This contraction forces blood out of the heart, which pushes the aortic and pulmonary valves open. During systole, the tricuspid and mitral valves are closed. They are prevented from prolapsing (being pushed back into the atrium) by the chordae tendinae and papillary muscles Reference: Textbook of Gray's Anatomy for students, 3rd Edition, Thorax, Page number - 235