Question

In humans, blood passes from the post caval to the diastolic right atrium of the heart due to
A.Pushing open of the venous valves
B.Suction pull only
C.Stimulation of the sino-auricular node
D.Pressure difference between the post caval and atrium and suction pull

Answer 1

Post caval refers to the inferior vena cava and the post caval refers to the superior vena cava. Post caval receives blood from the lower part of the body and transports to the right atrium of the heart.

Complete answer:
1.The blood from the abdominal organs and the lower limbs is carried by the post caval vein to the heart for purification of blood.
2.During relaxation of heart chambers which is known as the diastole the right, and the left atrium relaxes due to which the pressure inside the atrium decreases, and this pressure difference between the atrium and the postcaval veins leads to the entry of the blood to the right atrium.
3.The force that pulls the blood inside the right atrium of the heart due to the pressure difference between the right atrium and the postcaval vein is known as the suction pull.

Option D: The deoxygenated blood of the lower body is transported to the right atrium of the heart to oxygenate it. This transport of blood is facilitated by the suction pull and the pressure difference that exists between the post caval vein and the right atrium during diastole of the heart. Therefore, this is the correct option.

All other options are irrelevant.

Hence, the correct answer is option (D)

Note: 1)The postcaval vein consists of many other veins like hepatic veins, common iliac veins, inferior phrenic veins, right suprarenal veins, right gonadal veins, and the lumbar veins.
2)The right atrium receives blood from both the precaval and postcaval vein and the opening of these veins have valves which prevent the backward flow of the blood; the opening of the postcaval vein to the right atrium of the heart is guarded by Eustachian valve.