Question

Left auricle receives pure blood from the
A. Pulmonary veins
B. Pulmonary artery
C. Superior vena cava
D. Inferior vena cava

Answer 1

Hint: Human heart is a muscular organ. Along with blood vessels and blood, the heart forms the human circulatory system. It is also called a blood vascular system. Blood vessels through which blood reaches the heart are called veins. Arteries are the blood vessels that carry blood from the heart to other body parts.

Complete answer: There are four chambers in the human heart. The upper chambers are called auricles and the lower ones are called ventricles. The heart pumps blood which reaches all the tissues in the body through blood vessels. Atria is further divided into two chambers by a partition called the interatrial septum and ventricles by the interventricular septum. The heart is derived from mesoderm. Atria and ventricles of the same side are also divided by fibrous tissue. It is called an atrioventricular septum. Walls of atria are thin while compared to walls of ventricles. It is because ventricles undergo vigorous contraction during ventricular systole so that blood is pumped outside and reaches all body parts. The valve present between the right atrium and right ventricle is the tricuspid valve. A bicuspid valve is present between the left atrium and left ventricle. The left auricle receives pure blood from the lungs through the blood vessel called the pulmonary vein. Impure blood is pumped out from the right ventricle to the lungs by the pulmonary artery. Blood reaches the right auricle from all parts of the body by superior and inferior vena cava.
Hence the correct option is A.

Note: Tricuspid and bicuspid valves prevent the possible back-flow which would happen to the atria during ventricular contraction. Other than these two, there is another valve called a semilunar valve that is present in the pulmonary artery and aorta.