The Heart Is A Muscular Organ In Both Humans And Other Animals

The heart is a muscular organ in both humans and other animals, which pumps blood through the blood vessels of the circulatory system.Blood provides the body with oxygen and nutrients, and alsoassists in the removal of metabolic wastes. The heart is located in the middle compartment of the mediastinum in the chest.

In humans, other mammals and birds the heart is divided into four 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. Fish incontrast have two chambers, an atrium and a ventricle, while reptiles have three chambers. In a healthy heart blood flows one way through the heart due to heart valves, which prevent backflow. Theheart is enclosed in a protective sac, the pericardium, which also contains a small amount of fluid. The wall of the heart is made up of three layers: epicardium; myocardium; and endocardium.

Theheart pumps blood through both circulatory systems. Blood low in oxygen from the systemic circulation enters the right atrium from the superior and inferior vena 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 theleft ventricle and is pumped out through the aorta to the systemic circulation−where the oxygen is used and metabolized to carbon dioxide. In addition the blood carries nutrients from the liver andgastrointestinal tract to various organs of the body, while transporting waste to the liver and kidneys.[citation needed] Normally with each heartbeat, the right ventricle pumps the same amount ofblood into the lungs as the left ventricle pumps out into the body. Veins transport blood to the heart, while arteries transport blood away from the heart. Veins normally have lower pressures than...