What is the process of blood circulation in the heart?

The heart is an important organ in the body, and the blood circulation in the heart is also related to the health of the body. If the blood circulation is slow, abnormalities will occur in the body. You can learn about the heart's blood circulation process or direction through the following introduction.

Heart blood circulation process

The cardiovascular system mainly includes the heart, arteries, capillaries and veins. The cardiovascular system is a completely closed system, and the heart is the engine of the system.

The heart is a hollow muscular organ that contracts and relaxes regularly, constantly sucking in and pushing out blood, ensuring that the blood flows forward in one direction along the blood vessels. Blood vessels are tubes that transport blood, including arteries, veins, and capillaries.

Arteries originate from the heart, branch repeatedly, and their diameter gradually becomes smaller and their number gradually increases. Finally, they are distributed to tissues throughout the body and become capillaries. Capillaries are network-like and are where the exchange of substances between blood and tissues takes place. Capillaries gradually merge into veins, small veins merge into large veins, and finally return to the heart, completing the blood circulation.

Types of heart blood circulation

The blood circulation in our body can be divided into two parts: small circulation and pulmonary circulation according to their circulation parts.

1. Systemic circulation (macrocirculation)

The blood vessels of the systemic circulation include the aorta and its branches that originate from the left ventricle of the heart, as well as the superior vena cava, inferior vena cava, coronary sinus and their branches that return to the heart.

The blood from the left ventricle is ejected into the aorta, along the arteries to the capillaries throughout the body, then merges into the small veins and large veins, and finally returns to the right atrium through the superior vena cava and inferior vena cava. The systemic venous circulation can be divided into three major systems: the superior vena cava system, the inferior vena cava system (including the portal vein system) and the cardiac venous system.

The superior vena cava system is a channel that collects venous blood from the head, neck, upper limbs, chest and back and returns it to the heart; the inferior vena cava system is a series of channels that collect venous blood from the abdomen, pelvis and lower limbs and returns it to the heart; the cardiac venous system is a channel that collects venous blood from the heart.

Venous blood return to the heart from lower extremities

2. Pulmonary circulation (small circulation)

The pulmonary circulation in our body mainly includes pulmonary artery circulation and pulmonary venous circulation. The blood in the pulmonary artery is mainly venous blood.

The blood in the right ventricle of the heart reaches the pulmonary capillaries through the pulmonary artery, where it exchanges gases with the gases in the alveoli, expelling carbon dioxide and inhaling oxygen. The blood then turns into bright red arterial blood and returns to the left atrium through the pulmonary veins.

The pulmonary veins are the only veins in the body that carry oxygen-rich blood. The body's neural regulation of cardiovascular activity is achieved through various cardiovascular reflexes. The efferent nerves that innervate the heart are the sympathetic nerves of the sympathetic nervous system and the vagus nerves of the parasympathetic nervous system.

3. Coronary circulation (small circulation)

The purpose of coronary circulation is to supply the heart with the nutrients and oxygen it needs and to carry away waste products. It is a circulation in which blood flows directly from the coronary artery at the base of the aorta to the capillary network inside the myocardium and finally flows back to the right atrium through the veins.

Blood circulation route

Blood circulation is divided into systemic circulation and pulmonary circulation

Pulmonary circulation

Right ventricle -- pulmonary artery -- capillary network in the lungs -- pulmonary vein -- left atrium.

Systemic circulation

Left ventricle -- aorta -- capillary network throughout the body -- superior and inferior vena cava -- right atrium.

Blood circulation route

Left ventricle → (now arterial blood) → aorta → arteries at all levels → capillaries (substance exchange) → (substance exchange) → (after substance exchange it becomes arterial blood) → pulmonary vein → left atrium → finally returns to the left ventricle and starts a new round of circulation.

Among them, the blood circulation from the left ventricle to the right ventricle is called the systemic circulation of blood, and the blood circulation from the pulmonary artery to the left atrium is called the pulmonary circulation of blood.