The Heart is one of the most important organs in the human body, as well as being one of the most hardworking organs, since it starts beating the day we are born and continues that way until we die. The size of the heart is not so big, 12 cm long, 8-9 cm wide and 6 from front to back, and weighting from 9 to 10.5 ounces. It’s about the size of a human fist. The structure of the human heart can look rather complex, as well as its parts, but it’s actually very simple. It’s like a shell, with 4 open spaces called chambers that fill with blood. The ones from the top are called atria and the ones in the bottom are called ventricles. They are separated by the septum and a valve connects the atrium to the ventricle below it. The mitral valve connects the left atrium and ventricle and the tricuspid valve connects the right atrium and ventricle. The top of the heart connects to the blood vessels, the aorta being the biggest artery. It carries nutrient –rich blood away from the heart. The pulmonary artery connects the heart and lungs. And the superior and inferior vena cava, which carry blood into the heart. The heart is also conformed of 3 tissue layers; the first one is made of simple squamous epithetal cells and is called endocardium. The second one is the myocardium, which is composed of cardiac muscle tissue; this layer allows the heart to pump blood. And the last one is called the pericardium, and is composed of 2 layers that have a lubricant liquid between them.
The Human Heart