Question

Coronary sinus opens in the right atrium, receives blood from?
A. Coronary artery
B. Inferior vena cava
C. Superior vena cava
D. Coronary vein

Answer 1

Hint: Heart has a total of four chambers; two atria and two ventricles. The atrium receives blood from the veins from several parts of the body and is deoxygenated. The right atria pump blood into ventricles that flow into the lungs for oxygenation.

Complete step by step answer: The atrium receives blood from the veins from several parts of the body and is deoxygenated. The filling up of the atria by the blood from the veins is called the diastole and emptying it into the ventricles because of the contraction is called systole. The blood then is pumped out of the ventricles through arteries. The left atrium receives the blood from the pulmonary circulation/veins that are oxygenated and pumps to the left ventricle through the mitral valve, and then to the aorta for systemic circulation. The right atria receive the deoxygenated blood from the venous circulation and are pumped to the right ventricle through a tricuspid valve and then drawn out to pulmonary arteries for pulmonary circulation. The coronary sinus is a large vessel made up of small veins or the coronary vein that allows emptying the deoxygenated blood from the heart muscle to the right atrium between the inferior vena cava and tricuspid valve. The cardiac veins like the great cardiac vein, middle cardiac vein, small cardiac vein, a posterior vein of the left ventricle drain the blood into the coronary sinus. Inferior and superior vena cava empty blood directly into the right atrium. The coronary artery supplies oxygenated blood to the heart.
Hence, the correct answer is option D.

Note: Coronary sinus is covered by a thin semicircular endocardial fold also known as Thebesian valve and originates from the confluence of the oblique vein of the left atrium and great cardiac vein.