Question

ln which chamber of heart does oxygen-rich blood first enter?
A. Right atrium
B. Right ventricle
C. Left ventricle
D. Left atrium

Answer 1

Birds like mammals exhibit double circulation and closed circulatory systems. Due to the presence of four-chambered heart oxygenated and deoxygenated blood does not mix with deoxygenated blood and efficiency of double circulation increases.

Complete answer:
In birds a closed circulatory system is present. In birds a four-chambered heart is present. Which includes two auricles and two ventricles.
Double circulation- Double circulation is a process in which blood passes through the heart twice in one complete cycle.
Double circulation involves two circulations:
-Systemic circulation
-Pulmonary circulation
Systemic circulation- In systemic circulation oxygenated blood passes from the left ventricle to aorta it is then circulated to the tissues by network of arteries and capillaries then deoxygenated blood from the tissues is emptied into the right auricle through network of veins, venules and vena cava.
Pulmonary circulation-In pulmonary circulation deoxygenated blood from the right ventricle move to the pulmonary artery pulmonary artery then carries the blood to the lungs. In Lungs oxygenation of blood occurs Now oxygenated blood transferred to the left atrium by pulmonary veins. Blood circulates in body tissues through the systemic circulation and circulates in the lungs through the pulmonary circulation.

Hence, the correct answer is option (D).

Note: In Aves only right aortic (systematic) arch persists in the adults. The renal portal system is vestigial. Erythrocytes are minute, oval and nucleated. The blood of the birds may be called the richest blood in the animal kingdom. It has more RBC per cubic mm of blood than in any other animal.
-Study of birds is termed as ornithology.
-African ostrich is the largest living bird. Eggs of ostrich are the largest living bird.
-Columbia has the world's richest diversity of birds.
-Four chambered hearts of mammals and birds actually evolved from three chambered hearts.