Block 3 The Heart Practice MCQ's The Cardiovascular System (I): The Heart

During the development of the fetal heart, the right horn of the sinus venosus contributes to the formation of the right atrium.

The muscular portion of the interventricular septum develops from the growth of the myocardium. This means that the muscle tissue in the septum is formed as the myocardium, which is the muscular layer of the heart, grows and develops. This process is essential for the proper functioning and structure of the heart, as the interventricular septum separates the left and right ventricles and helps to maintain the circulation of blood. Therefore, the statement is true.

The splanchnic mesoderm gives rise to the endocardial heart tubes. The endocardial heart tubes are the precursors to the heart and are formed during embryonic development. The splanchnic mesoderm is one of the three layers of the mesoderm, and it is responsible for forming the cardiovascular system, including the heart. The paraxial mesoderm gives rise to the somites, which eventually form the skeletal muscles, while the somatic mesoderm forms the dermis of the skin and the musculoskeletal system. The intermediate mesoderm gives rise to the urogenital system.

The truncus arteriosus gives rise to the pulmonary artery and the aorta. During embryonic development, the truncus arteriosus is a part of the primitive heart tube that eventually divides into two separate arteries, forming the pulmonary artery and the aorta. The pulmonary artery carries deoxygenated blood from the heart to the lungs, while the aorta carries oxygenated blood from the heart to the rest of the body.

The correct answer is transposition of the great vessels. Transposition of the great vessels is a congenital heart defect where the aorta arises from the right ventricle and the pulmonary trunk arises from the left ventricle. This causes the oxygenated blood to circulate back to the lungs instead of being pumped to the body, leading to cyanosis and failure to thrive in the newborn infant.

During the third week of development, the heart starts to beat. This is a crucial stage in embryonic development when the heart begins to form and starts contracting. It is an important milestone as it marks the beginning of the circulatory system and the functioning of the heart.

The left sinus horn becomes the coronary sinus. This is the correct answer because during embryonic development, the sinus venosus, a structure that forms part of the heart, gives rise to the sinus horns. The left sinus horn specifically becomes the coronary sinus, which is a large vein that collects deoxygenated blood from the heart muscle and delivers it to the right atrium. The other options listed do not accurately describe the fate of the left sinus horn during development.

The failure of the aorticopulmonary septum to undergo the 180-degree spiral during fetal development leads to the abnormal positioning of the aorta and pulmonary artery. In transposition of the great vessels, the aorta arises from the right ventricle instead of the left ventricle, while the pulmonary artery arises from the left ventricle instead of the right ventricle. This results in a complete reversal of the normal blood flow pattern and leads to severe circulatory problems after birth.

During the formation of the cardiac loop, the primitive atrium moves in a posterior and superior direction. This means that it moves towards the back and towards the top. This movement is part of the complex process of cardiac development and helps to establish the correct positioning and orientation of the heart within the developing embryo.

The aorticopulmonary septum does not contribute to the formation of the muscular interventricular septum. The muscular interventricular septum is formed by the growth and fusion of the muscular walls of the ventricles. The aorticopulmonary septum, on the other hand, divides the outflow channel of the ventricles into the aorta and the pulmonary trunk. It is largely derived from neural crest cells and undergoes a 180o spiral.

The sinus venarum is formed from tissue of the right sinus horn. This is because the sinus venarum is a smooth-walled portion of the right atrium, which is derived from the right sinus horn during embryonic development. The right sinus horn is one of the three sinus horns that contribute to the formation of the atria in the developing heart. Therefore, the correct answer is that the sinus venarum is formed from tissue of the right sinus horn.

The septum primum forms the valve of the oval foramen, which is a correct statement. The septum primum is a thin, membranous structure that grows from the roof of the atrium towards the endocardial cushions. It eventually fuses with the endocardial cushions to form the atrial septum. During development, the septum primum has an opening called the ostium primum, which allows blood to flow from the right to the left atrium. As the septum secundum forms, it grows to overlap the ostium primum, creating a valve-like structure called the valve of the oval foramen. This valve allows blood to flow from the right to the left atrium during fetal development.

Truncus Arteriosous becomes the AORTA

sinous horn associated with the ATRIUM not ventricle

formed from neural crest, specifically the cardiac neural crest

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