How do ventricles differ from atria in the heart?

Ventricles are larger, more muscular chambers in the heart that pump blood out, while atria are smaller chambers that receive blood.

In the human heart, there are four chambers: two atria (singular: atrium) and two ventricles. The atria are located on the upper half of the heart and their primary function is to receive blood that comes into the heart. The right atrium receives deoxygenated blood from the body through the vena cava, while the left atrium receives oxygenated blood from the lungs through the pulmonary veins. They have thin walls as they only need to pump blood a short distance to the ventricles.

On the other hand, the ventricles are located on the lower half of the heart. They are larger and have thicker, more muscular walls than the atria. This is because they need to pump blood out of the heart and into the body, which requires more force. The right ventricle pumps deoxygenated blood to the lungs through the pulmonary artery, while the left ventricle pumps oxygenated blood to the rest of the body through the aorta.

The difference in size and muscularity between the atria and ventricles is a result of the different roles they play in the circulatory system. The atria act as 'primer pumps', filling the ventricles with blood during the relaxation phase of the cardiac cycle. The ventricles, on the other hand, are the 'main pumps', pushing the blood out of the heart and into the circulatory system during the contraction phase.

In summary, while both atria and ventricles are crucial for the functioning of the heart, they differ in their size, muscularity, and function. The atria receive blood and have thinner walls, while the ventricles pump blood out and have thicker, more muscular walls.