Cardiovascular System The cardiovascular system is a system that provides an overview of the circulation processes that occur in the organs of the human body. Good circulation processes can be seen in the components that are functioning well, where the size of the heart in adults is between 250 - 360 grams which is located in the left mediastinal cavity, behind the sternum, in front of the spine, and above the diaphragm and is surrounded by the right and left lungs. The structure of the cardiovascular system consists of the heart and blood vessels which are responsible for distributing blood and other substances it contains throughout the body. The structure of the heart consists of muscle striations, an ultra pattern whose structure is similar to muscle striations, which when viewed microscopically will clearly show branching cells that are freely interconnected and form a 3-dimensional complex network. In order to ensure that blood can reach all parts of the body consistently, the heart must always beat. Heart rate is regulated by the autonomic nervous system (SSO) without control so it cannot be regulated at will or according to our wishes. In the cardiovascular system, blood is transported in the heart and blood vessels so it is sometimes also called a closed system. Blood vessels are grouped into 2, namely arteries, where blood vessels leave the heart, and veins, where blood vessels flow to the heart. Based on their size, blood vessels are divided into several groups, namely large blood vessels (aorta, common iliac artery, superior vena cava, inferior vena cava), medium blood vessels (tibial artery, radial artery) and small blood vessels (arteriole, venule). In small blood vessels there are capillaries that connect the arteries and veins which have a certain histological structure. The heart is located on the left side of the chest cavity (thorax). The heart organ consists of heart muscle (myocardium) and the outer layer of the heart that is coatedpericardium. The heart is composed of 4 chambers separated by partitions, namely the right and left ventricles, and the right atrium and left. Separating these parts is important because part of the right heart receives and also pumps blood that contains low oxygen, whereas the left heart contains high oxygen. The interventricular and atriventricular septum form the left ventricle of the heart. On the bpartitionatrioventricularThere are two heart valves, namely valvestricuspidalis(3 valve plates) and valves bicuspidalis(2 valve plates). The right ventricle and left ventricle are the same size with the right atrium and left atrium. The ventricle is limited by the heart muscle and septum interventricularwhile the atrium is limited by the heart muscle and a thin septum. The four chambers of the heart are lined by several layers, namely layersendothelium, endocardium, myocardiumAnd pericardium (visceral and parietal). Heart valves consist of fibrous connective tissue which is coated on both sidesendothelium. Blood flows in the heart from the right side to the left side in one direction, this is due to the presence of valves to prevent backflow of blood. Blood will flow from the right atrium to the right ventricle which contains low oxygen and contains CO2tall. After that the blood flows through the arteriespulmonaryto the lungs for oxygenation, then returns to the left atrium via the oxygen-rich pulmonary vein, then flows to the left ventricle and continues throughout the body via the aorta. Functions : Several functions of the cardiovascular system include: (1) Transporting substances needed by cells such as oxygen, glucose, and carrying waste materials such as CO2, and urea for disposal; (2) Delivering hormones to target organs, and playing a role in temperature regulation (3) Plays a role in the body's immune system and blood clotting. Each part of the heart works together to fulfill its task of carrying around 14,000 liters of blood every day. The following is an explanation of the functions of the heart. Pericardium  The heart is always beating so there is a big potential for rubbing against other organs. Therefore, apart from being a support for the heart, the pericardium is needed to minimize friction by producing a fluid called serous to lubricate the heart.  One part of the heart is the chambers (right ventricle and left ventricle), which are located on the lower side of the heart. Its function is to pump clean blood from the heart to the lungs (by the right ventricle) and to all parts of the body (by the left ventricle). Porch  The atrium (heart porch) is located at the top of the heart. Its function is to receive dirty blood originating from the whole body (right atrium function) and receive dirty blood originating from the lungs (left atrium function) which is carried through the blood vessels. Valve  In the heart, there are 4 valves which function to keep blood flowing in one direction. The tricuspid valve regulates blood flow from the right atrium to the right ventricle. The pulmonary valve regulates blood flow from the right ventricle to the pulmonary artery. The mitral valve regulates the flow of oxygen-rich blood from the lungs to the left atrium and then to the left ventricle. The aortic valve regulates oxygen-rich blood from the left ventricle to the aorta. Cardiac muscle  Heart muscle plays an important role when pumping blood to the lungs and other parts of the body. The heart muscle itself has a cylindrical shape with light and dark lines. When carrying out its function, the heart muscle has two cycles, namely systole which is the cycle when the heart muscle contracts to pump blood and diastole, which is the condition when the heart muscle relaxes during the process of blood entering the heart. Blood vessel  Arteries function to carry oxygen-rich blood from the heart to the rest of the body.  Veins function to carry oxygen-poor blood from throughout the body back to the heart. Capillaries  function as a connection between small arteries and small veins.