The blood always flows through the vessels in a certain way and how does flow once it leaves heart?

How blood flows through the vessels:

Blood flows through the vessels in a continuous circuit, starting from the heart and returning to the heart. This circuit is divided into two main parts: the pulmonary circulation and the systemic circulation.

1. Pulmonary circulation: The pulmonary circulation is the part of the circulatory system that carries blood from the heart to the lungs and back to the heart. It serves to oxygenate the blood. The process starts when the heart's right atrium receives deoxygenated blood from the body through two large veins called the superior vena cava (which carries blood from the upper body) and the inferior vena cava (which carries blood from the lower body). This blood is then pumped from the right atrium to the right ventricle. The right ventricle contracts, pumping the deoxygenated blood into the pulmonary artery, which carries it to the lungs. In the lungs, the blood picks up oxygen and releases carbon dioxide through the process of gas exchange. The oxygenated blood then returns to the heart via the pulmonary veins, which empty into the left atrium.

2. Systemic circulation: The systemic circulation is the part of the circulatory system that carries oxygenated blood from the heart to the rest of the body and back to the heart. It serves to supply oxygen and nutrients to the body's tissues and remove waste products. From the left atrium, the oxygenated blood flows into the left ventricle. The left ventricle contracts, pumping the oxygenated blood into the aorta, the largest artery in the body. The aorta branches into smaller arteries that deliver the blood to various organs, tissues, and cells in the body. In the tissues, the blood releases oxygen and nutrients and picks up carbon dioxide and other waste products. The deoxygenated blood is then collected by small veins, which merge into larger veins and eventually return the blood to the right atrium of the heart, completing the systemic circulation.

The heart's pumping action and the elastic recoil of the blood vessels maintain the continuous flow of blood throughout the circulatory system. This ensures that oxygen, nutrients, and waste products are transported efficiently between the heart, the lungs, and the rest of the body.