The heart is a muscular organ, Which is located between your lungs in the middle of your chest, behind and slightly to the left of your breastbone. It pumps blood through the blood vessels of the circulatory system. In humans, mammals, and birds It is divided into 4 chambers: upper left and right atria and lower left and right ventricles. Commonly the right atrium and ventricle are referred together as the right heart and their left counterparts as the left heart. It pumps blood with a rhythm determined by a group of pacemaking cells in the sinoatrial node. These generate a current that causes contraction of the heart, traveling through the atrioventricular node and along with the conduction system of the heart.
It receives blood low in oxygen from the systemic circulation, which enters the right atrium from the superior and inferior venae cavae and passes to the right ventricle. From here it is pumped into the pulmonary circulation, through the lungs where it receives oxygen and gives off carbon dioxide. Oxygenated blood then returns to the left atrium, passes through the left ventricle, and is pumped out through the aorta to the systemic circulation where the oxygen is used and metabolized to carbon dioxide. The heart beats at a resting rate close to 72 beats per minute.
Parts of Heart
It made up of 2 chambers:
- The upper two chambers are called auricles.
- The lower two chambers are called ventricles.
The heart wall is made of 3 layers:
- The outer layer is called the epicardium.
- The middle layer wall is called the myocardium.
- The inner layer wall is called the endocardium.
It consists of 4 valves:
- The aortic valve prevents the backflow of blood when it is pumped from the left ventricle to aorta.
- The mitral valve prevents the backflow of blood when pumped from the left atrium to the left ventricle.
- The pulmonary valve prevents the backflow of blood when it flows from the right ventricle to the pulmonary artery.
- The tricuspid valve prevents the backflow of blood when it is pumped from the right atrium to the right ventricle.
The arteries carry the blood rich in oxygen from the heart to different parts of the body. The pulmonary artery, being an exception, carries deoxygenated blood to the organs for purification.
The veins carry impure blood from different parts of the body to the heart for oxygenation. However, the pulmonary veins carry oxygenated blood to the heart.