The Heart

The heart (myocardium) is an organ that forms part of the circulatory system. It is about the size of your fist and weights about 8 to 12 ounces. It pumps blood to send it to every single corner of the body because all the living tissues need oxygen and nutrients.

The heart muscle itself needs its own blood supply in order to function properly and it gets it from the two main coronary arteries. These two arteries originate from the ascending aorta which is the first section of the aortic artery. Complications of the aorta are aneurysms and aortic stenosis. See abdominal aortic aneurysm.

  According to research, this amazing   organ beats an average of 100,000   times each and every day and   about 3.5 billion times by the end of   a person’s entire life. It is a small     organ but yet it is a powerful   pumping machine.

  It is located in the middle of the   chest behind the breast bone   (sternum) and just to the left.

The Human Heart

The myocardium is surrounded by a double layered membrane called the pericardium. The pericardium’s outer layer surrounds the roots of the major vessels and it is attached to the spinal cord by ligaments, diaphragm, and other parts of the body.

The inner layer of the pericardium is attached to the entire heart muscle. The middle of the membranes is filled with fluid that serves as a coat to allow this organ to move freely.

See heart anatomy

The blood leaves the myocardium via the aorta and enters via the vena cavae; the superior vena cava and the inferior vena cava.

The myocardium has four chambers and four heart valves. The top chambers are called the right atrium and the left atrium. Note: pleural for atrium is atria. The bottom chambers are called the right ventricle and the left ventricle.

A wall of muscles that separates the right and left atria and the right and left ventricles is called the septum.

The myocardium (heart) generates its own electrical energy in the SA node which is responsible for regulating its own heart rate.