Nursing 5th Note-1 PDF - Circulatory System

Circulatory System I A. Taha Demirbaş, Assis Prof Anatomy Functions of the Circulatory System The circulatory system consists of the heart, blood vessels, and blood The term cardiovascular system refers only to the heart and blood vessels The fundamental purpose of the circulatory sy...

Circulatory System I A. Taha Demirbaş, Assis Prof Anatomy Functions of the Circulatory System The circulatory system consists of the heart, blood vessels, and blood The term cardiovascular system refers only to the heart and blood vessels The fundamental purpose of the circulatory system is to transport substances from place to place in the blood Blood is the liquid medium in which these materials travel Blood vessels ensure the proper routing of blood to its destinations And the heart is the pump that keeps the blood flowing The Pulmonary and Systemic Circuits The cardiovascular system has two major divisions: A pulmonary circuit, which carries blood to the lungs for gas exchange and returns it to the heart and, A systemic circuit, which supplies blood to every organ of the body, including other parts of the lungs and the wall of the heart itself  The right half of the heart supplies the pulmonary circuit It receives blood that has circulated through the body and pumps it into a large artery, the pulmonary trunk From there, the oxygen poor blood is distributed to the lungs, where it unloads carbondioxide and picks up a fresh load of oxygen It then returns to the left side of the heart by way of the pulmonary veins  The left half of the heart supplies the systemic circuit It pumps blood into the body’s largest artery, the aorta The aorta gives off branches that ultimately deliver oxygen to every organ of the body and pick up their carbon dioxide and other wastes After exchanging gases with the tissues, this blood returns to the heart by way of the body’s two largest veins—the superior vena cava, which drains the upper body, And the inferior vena cava, which drains everything below the diaphragm The pulmonary trunk, pulmonary veins, aorta, and the two venae cavae are called the great vessels (great arteries and veins) because of their relatively large diameters Position, Size, and Shape of the Heart The heart is located in the thoracic cavity in the mediastinum, between the lungs and deep to the sternum From its superior to inferior midpoints, it is tilted toward the left, so about two-thirds of the heart lies to the left of the median plane The broad superior portion of the heart, called the base, is the point of attachment for the great vessels The inferior end tapers to a blunt point, the apex of the heart, immediately above the diaphragm The pericardium The heart is enclosed in a double-walled sac called the pericardium. The outer wall, called the pericardial sac (parietal pericardium), has a tough, superficial fibrous layer of dense irregular connective tissue and a deep, thin serous layer The serous layer turns inward at the base of the heart and forms the epicardium (visceral pericardium) of the heart surface The space between the parietal and visceral membranes of serous layer is called the pericardial cavity The Heart Wall The heart wall consists of three layers A thin epicardium covering its external surface, A thick muscular myocardium in the middle, and A thin endocardium lining the interior of the chambers The chambers The heart has four chambers, best seen in frontal section The two at the superior pole (base) of the heart are the right and left atria (singular, atrium) They are thin-walled receiving chambers for blood returning to the heart by way of the great veins The two inferior heart chambers, the right and left ventricles They are the pumps that eject blood into the arteries and keep it flowing around the body The valves The atrioventricular (AV) valves regulate the openings between the atria and ventricles The right AV valve is also called the tricuspid valve The left AV valve is also known as the mitral valve The semilunar valves (pulmonary and aortic valves) regulate the flow of blood from the ventricles into the great arteries The pulmonary valve controls the opening from the right ventricle into the pulmonary trunk The aortic valve controls the opening from the left ventricle into the aorta The Pathway of Blood Flow Through the Heart The pathway from 4 to 6 is the pulmonary circuit And the pathway from 9 to 11 is the systemic circuit Violet arrows indicate oxygen- poor blood, and orange arrows indicate oxygen-rich blood Coronory circulation Immediately after the aorta leaves the left ventricle, it gives off a right and left coronary artery The coronary sinus, a large transverse vein on the posterior side of the heart, collects blood from all veins as well as some smaller ones and it empties blood into the right atrium The conduction system The cardiac conduction system, which controls the route and timing of stimulation to ensure that the four heart chambers are coordinated with each other