MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Y.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

CHAPTER 5. THE PROCESS OF BLOOD AND LYMPH CIRCULATION. ITS PATHOLOGY

SYSTEMIC AND PULMONARY CIRCULATION

At the beginning of the 17th century, the eminent scientist William Harvey proved that The Cardiovascular system consists of the systemic and pulmonary circuits. Thus, the arterial and venous systems are not isolated, but interconnected as a single vascular network.

The Heart of mammals, including humans, is a hollow, four-chambered muscular organ divided into two atria and two ventricles.

The systemic Circulation begins in the left ventricle and ends in the right atrium (Fig. 5.9). When the left ventricle contracts, it pumps arterial Blood into the aorta; from there, flowing through the Arteries, arterioles, and capillaries of the entire body, the blood enters venules. The venules converge into small Veins and subsequently merge into large ones, finally emptying into the superior and inferior venae cavae, which deliver venous blood to the right atrium. From a physiological standpoint, the systemic circulation serves as an exchange or metabolic pathway, because as blood circulates through it, it supplies essential nutrients to the Cells and removes Metabolic waste products from them.

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Fig. 5.9. Diagram of Blood Circulation

The Pulmonary Circulation begins in the right ventricle and ends in the left atrium. From the right ventricle, venous blood flows through the pulmonary artery into the lung capillaries, and from there, oxygenated arterial blood returns via the Pulmonary veins to the left atrium. From a physiological perspective, the pulmonary circulation Functions as a gas-exchange pathway, because as blood passes through the pulmonary capillaries, it releases carbon dioxide and becomes saturated with oxygen.

The Coronary Circulation starts from the aortic bulb (its ascending part) and ends in the right atrium; it supplies blood to the heart tissue and drains it via cardiac veins.

The hemocirculatory bed mediates the transition of blood from arteries to veins and facilitates metabolic exchange. It consists of arterioles, pre-capillary arterioles, capillaries, post-capillary venules, and venules.