pääreitistöstä

Pääreitistö refers to the main circulatory system in the human body, also known as the systemic circulation. It is responsible for transporting oxygenated blood from the left ventricle of the heart to all parts of the body and returning deoxygenated blood back to the right atrium. This vital pathway ensures that cells receive the nutrients and oxygen they need to function and that waste products are efficiently removed.

The journey begins as the left ventricle pumps oxygenated blood into the aorta, the body's largest artery. The aorta then branches into progressively smaller arteries, arterioles, and finally capillaries. Capillaries, with their thin walls, facilitate the exchange of oxygen and nutrients for carbon dioxide and waste products at the cellular level.

Following this exchange, deoxygenated blood collects in venules, which merge to form larger veins. These veins eventually lead back to the superior and inferior vena cava, the two largest veins in the body, which then empty into the right atrium of the heart. From the right atrium, the deoxygenated blood passes to the right ventricle, which pumps it to the lungs for reoxygenation, completing the pulmonary circulation. The continuous, cyclical nature of the pääreitistö is essential for sustaining life.