|Shier, David. Hole's Human Anatomy & Physiology [doc]. McGraw- Hill, 2002.||"Size = closed fist; 300g (adult)."||300 g|
|The Human Heart. Texas Heart Institute, June 2004.||"The Heart weighs between 7 and 15 ounces (200 to 425 grams) and is a little larger than the size of your fist."||200–425 g|
|Paulsen S, Vetner M, Hagerup LM. Relationship between heart weight and the cross sectional area of the coronary ostia. National Center for Biotechnological Information, September 1975.||"Sex variation in the area of the coronary ostia was studied in hearts with a normal weight (heart weight less than 400 g) and hypertrophic hearts (heart weight greater than or equal to 400 g)."||> 400 g|
|The Heart. The Franklin Institute Science Museum, 1996.||"The average adult heart is about the size of a clenched fist and weighs about 11 ounces (310 grams)."||310 g|
The heart is a relatively small (no bigger than a clenched fist), hollow, muscular organ which is in charge of pumping blood throughout the body and to other organs. It is made up of four chambers, and has a conical shape. The upper chambers are called the left and right atria, and the lower chambers are called the left and right ventricles. The left and right atria and left and right ventricles are separated by a wall of muscle known as the septum. The strongest and biggest chamber in the heart is the left ventricle. Its walls are only half-inch thick, and yet they are capable of pushing blood through a valve into your body. It is able to pump blood through blood vessels through small, recurring contractions.
The mass of a human heart is between 200–450 g, however approximately 300 g. However, this number can be extremely varied when the heart is diseased. A diseased heart can sometimes weigh as much as 1000 g; more than two pounds! The human heart is located between the lungs and in approximately the middle of the chest, slightly left of the breast bone. Approximately two thirds of its mass lies to the left of the body's midlines. In an average adult weighing approximately 80 kg, (approximately 175 pounds), the human heart is approximately 0.3% of the total mass. Although the heart is only a miniscule portion of a person's total weight, it plays the most important role in the entire body.
Stephanie Gambino -- 2006