The human heart is located in the mediastinum, at the level of the fifth to eighth thoracic vertebrae. The heart is surrounded by a double-membrane sac called the pericardium that attaches the heart to the mediastinum.[17] The posterior surface of the heart is located near the spine, while the anterior surface is located behind the sternum and the cartilages of the ribs.[9] The upper part of the heart is the point of attachment to several large blood vessels, the superior vena cava, the aorta, and the pulmonary trunk. The upper part of the heart is located at the level of the third costal cartilage.[9] The apex of the heart is directed downwards and to the left of the sternum (about eight to nine centimeters from the midline) in the intercostal space between the fourth and fifth ribs, near the articulation of the ribs with their cartilages.[9]
The largest part of the heart is tilted to the left side of the chest (although in some cases it may be tilted to the right), and the left heart is stronger and larger than the right heart because it pumps blood throughout the body. Since the heart is located between the two lungs, the left lung is smaller than the right lung, and the left lung is distinguished by the presence of a cardiac notch at its edge to fit the heart.[9] The heart has a conical shape, its base is located at the top, and its end tapers at the bottom to form the apex.[9] The mass of an adult heart ranges from 250 to 350 grams. [18] The heart is usually the size of a fist: 12 cm long (5 inches), 8 cm wide (about 3.5 inches), and 6 cm thick (about 2.5 inches).[9] The hearts of well-trained athletes can be larger due to the effect of exercise on the heart muscle, similar to the response in skeletal muscles. [9]
