The vascular system is composed of arteries, veins and capillaries, which are a set of large and small tubes responsible for transporting blood from the heart to various tissues and organs throughout the body to meet the various nutrients required for the body’s activities, and for transporting metabolic end products (or waste products) back to the heart and out of the body through the lungs, kidneys and other organs. Although the vascular system is very large, here I will only describe the two parts of the blood vessels closest to the heart, the coronary arteries and the great vessels. The coronary arteries are the vascular system responsible for providing nutrition to the heart to ensure that the ventricles have sufficient strength to contract. The coronary arteries are named after the coronary vessels that resemble a crown around the surface of the heart, which start at the root of the aorta and are divided into two branches, the left and right coronary arteries. Among them, the beginning of the left coronary artery is called the “left trunk”, which travels a short distance and then divides into two branches, one of which travels forward to the front of the heart and is called the “anterior descending branch”; the other travels backward to the surface of the left ventricle and is called the “gyrus branch The other travels backward on the surface of the left ventricle and is called the “sulcus branch. An important branch from the right coronary artery is called the “posterior descending branch”. When the coronary arteries become narrowed due to atherosclerosis, it is often referred to as coronary heart disease. If the stenosis involves the anterior descending branch, the gyral branch and the right coronary artery, it is called a “triple lesion”, while if only one of them is involved, it is called a “single lesion”. The great vessels are those directly connected to the heart and include the aorta, pulmonary arteries, vena cava and pulmonary veins. The arteries are the tubes that carry blood away from the heart, and the veins are the tubes that carry blood back to the heart. The aorta is connected to the outlet of the left ventricle and sends oxygen-rich arterial blood throughout the body; the pulmonary artery is connected to the outlet of the right ventricle and is responsible for sending venous blood to the lungs for oxygenation. The vena cava is connected to the right atrium and is responsible for sending venous blood from the whole body back to the heart; the pulmonary vein is connected to the left atrium and is responsible for sending oxygenated arterial blood back to the heart. Because the arterial vessels are under higher pressure and have a more complex structure than the veins, they are far more likely to develop pathologies. For example, atherosclerosis, aneurysm, arteritis, and arterial vascular entrapment. The cardiac conduction system is the equivalent of the control circuit of the engine, which ensures that the heart beats at a normal frequency (heart rate) and rhythm (heart rhythm). The origin of the conduction system is a neuromuscular tissue called the sinus node, located in the upper right atrium, which sends regular impulses along a special pathway to the atria and ventricles, ensuring that the heart beats rhythmically. If the sinus node sends out abnormal impulses or the impulse conduction sequence is abnormal, the heart beats irregularly, which is called arrhythmia, such as tachycardia, bradycardia, irregular heart rate, premature beats, etc.