The heart consists of four chambers, four one-way valves, and a set of arteries and veins that regulate the normal flow of blood within the body.
smooth functioning of the circulatory system is maintained by a complex network of blood vessels that circulate blood throughout the body and back to the heart. Whereas veins bring deoxygenated blood back into the heart, those that carry oxygenated blood away from the heart to other tissues in the body are known as arteries. The two exceptions to these are the pulmonary arteries and pulmonary veins, as well as the umbilical artery and vein.
heart's two upper chambers are called the atria, with the atrial septum dividing the right and left atria. The superior and inferior are major veins that supply the right atrium with deoxygenated blood from the rest of the body.
superior brings deoxygenated blood into the right atrium from the upper limbs and head, whereas deoxygenated blood from the lower abdomen and limbs is brought into the heart through the inferior
pulmonary veins supply oxygenated blood from the lungs into the left atrium and are the only veins in the body to carry oxygenated blood. However, during pregnancy, the umbilical vein carries oxygenated and nutrient-rich blood from the placenta to the fetus.
Both atria contract and release blood into the ventricles when full, a process controlled by the atrioventricular valves. The flow of deoxygenated blood from the right atrium into the right ventricle is regulated by the tricuspid valve, while the mitral valve controls the flow of oxygenated blood from the left atrium to the left ventricle.
The two lower chambers of the heart are called the ventricles. The right ventricle receives deoxygenated blood that collects in the right atrium. This process occurs by systematically opening and closing the atrioventricular and semilunar valves.
The semilunar valve connecting the right ventricle to the lungs is the pulmonary valve. This valve remains closed while the tricuspid valve opens and releases bloodThe heart wall is composed of three layers,i⁸ncluding the outer middle myocardium (thick layer), and innermost endocardium (thin layer). The myocardium is made up of cardiac muscle fibers and is responsible for the contraction and relaxation that results in the pumping of the heart.
The two atria have a thinner myocardium layer than the ventricles, as the force required for atrial contractions is much less than that needed for ventricular contractions. The walls of the right ventricle are also thinner, as this ventricle only pumps blood a short distance to the lungs. Comparatively, the left ventricle, which has much thicker walls, must generate enough force to pump oxygenated blood throughout the rest of the body.
myocardium requires a constant supply of oxygen and nutrients to maintain the contractions and relaxations that keep the heart pumping. This blood supply is maintained through a set of coronary arteries and veins in the myocardium.
right and left coronary arteries, which branch off the first section of the aorta known as the ascending aorta between the left ventricle and aortic arch, supply blood to a network of capillaries in the myocardium. Deoxygenated blood from the myocardium is carried through a set of cardiac veins to the right atrium that is subsequently drained through the coronary sinus.
node is often referred to as the heart's pacemaker, as it sets the rhythm of the heartbeat. Additional components of the heart's electrical conduction system.
When full, the right and left atria contract together, thereby opening the atrioventricular valves and draining blood into the right and left ventricles, respectively. The electrical impulse from the SA node then proceeds through the conduction system that stimulates the contraction of the ventricles.
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