Heart Anatomy and Physiology Review
Heart Lab Study Notes
External Anatomy of the Heart
General External Features
Apex: The inferior, pointed end of the heart, typically directed towards the left hip.
Base: The superior, broad portion of the heart, where the great vessels emerge.
Left Atrium: One of the superior chambers, receives oxygenated blood from the pulmonary veins.
Right Atrium: The other superior chamber, receives deoxygenated blood from the body via the vena cavae.
Left Auricle: A small, ear-like appendage extending from the left atrium, increasing its volume.
Right Auricle: A similar appendage extending from the right atrium.
Left Ventricle: The inferior left chamber, pumps oxygenated blood into the aorta.
Right Ventricle: The inferior right chamber, pumps deoxygenated blood into the pulmonary trunk.
Ligamentum Arteriosum: A fibrous remnant of the ductus arteriosus, which connected the pulmonary trunk and aorta in the fetal heart. It connects the aortic arch and pulmonary trunk in adults.
Great Vessels of the Heart
Superior Vena Cava: Large vein that carries deoxygenated blood from the upper body (head, neck, upper limbs, thorax) to the right atrium.
Inferior Vena Cava: Large vein that carries deoxygenated blood from the lower body (abdomen, pelvis, lower limbs) to the right atrium.
Pulmonary Trunk: A large artery that emerges from the right ventricle and quickly bifurcates into the pulmonary arteries, carrying deoxygenated blood to the lungs.
Pulmonary Veins: Typically four veins (two from each lung) that carry oxygenated blood from the lungs back to the left atrium.
Pulmonary Arteries: Formed from the bifurcation of the pulmonary trunk, these arteries carry deoxygenated blood to the lungs.
Aorta: The largest artery in the body, originating from the left ventricle and distributing oxygenated blood to all parts of the body.
Ascending Aorta: The initial portion of the aorta, rising superiorly from the left ventricle.
Aortic Arch: The curved portion of the aorta that gives off major arteries to the head, neck, and upper limbs.
Descending/Thoracic Aorta: The portion of the aorta that descends through the thorax, posterior to the heart.
Coronary Circulation
Coronary Arteries (supply oxygenated blood to the myocardium):
Right Coronary Artery: Originates from the ascending aorta; supplies blood to the right atrium, most of the right ventricle, and parts of the left ventricle and interventricular septum.
Left Coronary Artery: Originates from the ascending aorta; typically branches into the circumflex artery and the anterior interventricular artery (LAD).
Circumflex Artery: A branch of the left coronary artery; encircles the heart in the coronary sulcus, supplying the left atrium and posterior left ventricle.
Anterior Interventricular Artery (also known as Left Anterior Descending or LAD artery): A branch of the left coronary artery; runs down the anterior interventricular sulcus, supplying the anterior walls of both ventricles and the interventricular septum. It is often called the
External Anatomy of the Heart
General External Features
Apex: The inferior, pointed end of the heart, formed by the muscular walls of the left ventricle. It is typically directed towards the left hip and rests on the diaphragm, usually located in the fifth intercostal space, about 9 cm to the left of the midline. Function: Serves as the point of maximal impulse (PMI) of the heart, where the strongest beat can be felt or heard.
Base: The superior, broad portion of the heart, formed primarily by the left atrium and a small part of the right atrium. It is the site where the great vessels (aorta, pulmonary trunk, vena cavae, and pulmonary veins) emerge from or enter the heart. Function: Serves as the attachment point for the great vessels and is key for venous return and arterial outflow.
Left Atrium: One of the superior chambers, located posteriorly. Function: Receives oxygenated blood from the lungs via typically four pulmonary veins and pumps it into the left ventricle.
Right Atrium: The other superior chamber, located anteriorly and to the right. Function: Receives deoxygenated blood from the body via the superior and inferior vena cavae and from the heart wall itself via the coronary sinus. It pumps blood into the right ventricle.
Left Auricle: A small, muscular, ear-like appendage extending from the left atrium. Function: To increase the capacity of the left atrium, allowing it to hold a larger volume of blood, especially during periods of high venous return.
Right Auricle: A similar ear-like appendage extending from the right atrium, also containing pectinate muscles. Function: To increase the capacity of the right atrium, serving a similar volume-increasing function as the left auricle.
Left Ventricle: The inferior left chamber and the most muscular chamber of the heart. Function: Pumps oxygenated blood with great force into the aorta to be distributed throughout the systemic circulation. Its walls are significantly thicker than those of the right ventricle to generate higher pressure.
Right Ventricle: The inferior right chamber. Function: Pumps deoxygenated blood into the pulmonary trunk, which carries blood to the lungs for oxygenation. Its walls are thinner than the left ventricle, reflecting the lower pressure required for pulmonary circulation.
Ligamentum Arteriosum: A fibrous remnant of the ductus arteriosus, a shunt found in the fetal heart. In adults, it connects the inferior surface of the aortic arch to the superior aspect of the pulmonary trunk. Function: In adults, it is a non-functional remnant; in the fetus, the ductus arteriosus shunted blood from the pulmonary trunk to the aorta, bypassing the lungs.
Great Vessels of the Heart
Superior Vena Cava: A large systemic vein that drains deoxygenated blood from all structures superior to the diaphragm (head, neck, upper limbs, and thorax). Function: Delivers deoxygenated blood from the upper body and head to the right atrium.
Inferior Vena Cava: The largest vein in the body, carrying deoxygenated blood from all structures inferior to the diaphragm (abdomen, pelvis, and lower limbs). Function: Delivers deoxygenated blood from the lower body and trunk to the right atrium.
Pulmonary Trunk: A large artery emerging from the right ventricle. Function: Carries deoxygenated blood from the right ventricle towards the lungs. It quickly bifurcates into the right and left pulmonary arteries just superior to the heart.
Pulmonary Veins: Typically four veins (two from each lung – superior and inferior from the right lung, superior and inferior from the left lung). Function: Carry oxygenated blood from the lungs back to the left atrium.
Pulmonary Arteries: The right and left pulmonary arteries are formed from the bifurcation of the pulmonary trunk. Function: Carry deoxygenated blood to the capillaries of the respective lungs for gas exchange (oxygenation).
Aorta: The largest artery in the body, originating from the left ventricle. Function: Distributes oxygenated blood to all parts of the systemic circulation.
Ascending Aorta: The initial portion of the aorta, rising superiorly from the left ventricle. Function: Gives rise to the right and left coronary arteries, supplying the heart muscle itself, and connects the left ventricle to the aortic arch.
Aortic Arch: The curved portion of the aorta that passes over the superior aspect of the heart. Function: Gives off three major arteries (brachiocephalic trunk, left common carotid artery, left subclavian artery) that supply the head, neck, and upper limbs with oxygenated blood.
Descending/Thoracic Aorta: The portion of the aorta that continues inferiorly through the thorax, posterior to the heart, before passing through the diaphragm. Function: Distributes oxygenated blood to the thoracic organs and wall, and continues on to supply the lower body.
Coronary Circulation
Coronary Arteries (supply oxygenated blood to the myocardium):
Right Coronary Artery (RCA): Originates from the right aortic sinus of the ascending aorta. It typically runs in the coronary sulcus (atrioventricular groove) between the right atrium and right ventricle. Function: Supplies oxygenated blood to the right atrium, most of the right ventricle, the sinoatrial (SA) node (in about 60\% of people), the atrioventricular (AV) node (in about 90\% of people), and the posterior one-third of the interventricular septum (via its posterior interventricular artery branch). Key branches include the right marginal artery and the posterior interventricular artery (PDA).
Left Coronary Artery (LCA): Originates from the left aortic sinus of the ascending aorta. It is a short, wide vessel that quickly bifurcates into two main branches (or sometimes three with an intermediate branch). Function: Primary supplier of oxygenated blood to the majority of the left ventricle and interventricular septum.
Circumflex Artery (Cx): A branch of the left coronary artery; it encircles the heart in the coronary sulcus to the left. Function: Supplies oxygenated blood to the left atrium and the posterior and lateral walls of the left ventricle. It often gives off an obtuse marginal artery.
Anterior Interventricular Artery (also known as Left Anterior Descending or LAD artery): The other major branch of the left coronary artery; it runs down the anterior interventricular sulcus towards the apex of the heart. Function: Supplies oxygenated blood to the anterior two-thirds of the interventricular septum and the anterior walls of both ventricles, particularly the left. It is often critically important, earning it the nickname "widowmaker" due to the extensive damage caused by blockages.
Coronary Veins (drain deoxygenated blood from the myocardium):
Coronary Sinus: The main venous structure of the heart, located on the posterior surface of the heart in the coronary sulcus. Function: Receives most of the venous blood from the myocardium and empties directly into the right atrium, returning deoxygenated blood from the heart muscle itself.
Great Cardiac Vein: Follows the anterior interventricular artery (LAD) and then the circumflex artery. Function: Drains deoxygenated blood from the anterior aspects of the ventricles and left atrium, eventually entering the coronary sinus.
Middle Cardiac Vein: Travels with the posterior interventricular artery (PDA) in the posterior interventricular sulcus. Function: Drains deoxygenated blood from the posterior aspects of both ventricles, and empties into the coronary sinus.
Small Cardiac Vein: Accompanying the right marginal artery and then runs in the coronary sulcus alongside the right coronary artery. Function: Drains deoxygenated blood from the right atrium and right ventricle, typically emptying into the coronary sinus or directly into the right atrium.
Anterior Cardiac Veins: Several small veins that drain directly from the anterior surface of the right ventricle into the right atrium. Function: Drain deoxygenated blood from select parts of the right ventricle, bypassing the coronary sinus to empty directly into the right atrium.