Gross Anatomy of the Heart

Gross Anatomy of the Heart

• The heart is roughly the size and shape of a closed fist.
• It rests on the diaphragm near the midline of the thoracic cavity.
• It is located in the mediastinum, an anatomical region that extends from the sternum to the vertebral column, between the lungs.
• About two-thirds of the heart's mass lies to the left of the body's midline.
• It's shaped like an inverted cone.

Base and Apex of the Heart

• The base is opposite the apex and is its posterior aspect. Mainly formed by the atria, mostly the left atrium.
• The apex is the pointed end formed by the tip of the left ventricle. It rests on the diaphragm, angled anteriorly, inferiorly, and to the left.

Internal Structure of the Heart

• The right side pumps deoxygenated blood to the lungs.
• The left side pumps oxygenated blood to the body.
• Veins carry blood into the heart (vena cava, pulmonary vein). Arteries carry blood away from the heart (pulmonary artery, aorta).
• The heart has four chambers: right atrium, right ventricle, left atrium, left ventricle.
• Valves regulate blood flow between chambers (tricuspid, bicuspid/mitral, pulmonary, aortic).

Chambers of the Heart

• Right Atrium: Receives blood from the superior vena cava, inferior vena cava, and coronary sinus. Separated from the left atrium by the interatrial septum. Blood flows from the right atrium to the right ventricle through the tricuspid valve.
• Right Ventricle: Blood passes through the pulmonary valve into the pulmonary trunk, which branches into the pulmonary arteries. These carry blood to the lungs.
• Left Atrium: Receives blood from the lungs through four pulmonary veins. Blood flows from the left atrium to the left ventricle through the bicuspid (mitral) valve.
• Left Ventricle: The thickest chamber, forming the apex of the heart. Blood flows from the left ventricle through the aortic valve into the aorta, which branches to the coronary arteries and then to the systemic circulation, carrying oxygenated blood throughout the body. The left and right ventricles are separated by the interventricular septum.

Myocardial Thickness and Function

• The thickness of the myocardium (heart muscle) varies for different chambers—depending on their function.
• Atria have thin walls because they pump blood under low pressure to ventricles.
• Ventricles have thick walls because they pump blood under high pressure over greater distances.
• The right ventricle has a smaller workload than the left ventricle, pumping blood less distance.
• The left ventricle pumps blood a longer distance and against greater pressure.

Additional Details

• Additional detail about the heart's structure is available (slides and flashcards).
• Diagrams and illustrations help visualize the anatomy and function of the heart.