If you are unfamiliar with this song, a version is available on At this stage, the emphasis is on performing high-quality chest compressions, rather than providing artificial respiration. Current standards call for compression of the chest at least 5 cm deep and at a rate of 100 compressions per minute, a rate equal to the beat in “Staying Alive,” recorded in 1977 by the Bee Gees. This is particularly critical for the brain, as irreversible damage and death of neurons occur within minutes of loss of blood flow. By applying pressure with the flat portion of one hand on the sternum in the area between the line at T4 and T9 ( Figure 19.3), it is possible to manually compress the blood within the heart enough to push some of the blood within it into the pulmonary and systemic circuits. The position of the heart in the torso between the vertebrae and sternum (see Figure 19.2 for the position of the heart within the thorax) allows for individuals to apply an emergency technique known as cardiopulmonary resuscitation (CPR) if the heart of a patient should stop.

The slight deviation of the apex to the left is reflected in a depression in the medial surface of the inferior lobe of the left lung, called the cardiac notch. It is important to remember the position and orientation of the heart when placing a stethoscope on the chest of a patient and listening for heart sounds, and also when looking at images taken from a midsagittal perspective. The right side of the heart is deflected anteriorly, and the left side is deflected posteriorly. The inferior tip of the heart, the apex, lies just to the left of the sternum between the junction of the fourth and fifth ribs near their articulation with the costal cartilages. The base of the heart is located at the level of the third costal cartilage, as seen in Figure 19.2. The great veins, the superior and inferior venae cavae, and the great arteries, the aorta and pulmonary trunk, are attached to the superior surface of the heart, called the base. The dorsal surface of the heart lies near the bodies of the vertebrae, and its anterior surface sits deep to the sternum and costal cartilages. Within the mediastinum, the heart is separated from the other mediastinal structures by a tough membrane known as the pericardium, or pericardial sac, and sits in its own space called the pericardial cavity. Figure 19.2 shows the position of the heart within the thoracic cavity. The human heart is located within the thoracic cavity, medially between the lungs in the space known as the mediastinum. In order to understand how that happens, it is necessary to understand the anatomy and physiology of the heart. Over one year, that would equal 10,000,000 liters or 2.6 million gallons of blood sent through roughly 60,000 miles of vessels. This would be equal to 5.25 liters of fluid per minute and approximately 14,000 liters per day. Each of the major pumping chambers of the heart ejects approximately 70 mL blood per contraction in a resting adult. If one assumes an average rate of contraction of 75 contractions per minute, a human heart would contract approximately 108,000 times in one day, more than 39 million times in one year, and nearly 3 billion times during a 75-year lifespan. The vital importance of the heart is obvious. Trace the pathway of oxygenated and deoxygenated blood thorough the chambers of the heart.Identify the veins and arteries of the coronary circulation system.Compare systemic circulation to pulmonary circulation.Relate the structure of the heart to its function as a pump.Identify the tissue layers of the heart.Describe the internal and external anatomy of the heart.Describe the location and position of the heart within the body cavity.By the end of this section, you will be able to:

Heart blood flow diagram