The Heart

External Features

• Sternocostal (anterior) surface - formed mainly by the right ventricle, with a narrow strip of left ventricle and the right atrium/auricle at its border. The anterior interventricular sulcus separates the ventricles and carries the anterior interventricular (LAD) artery and vein.
• Diaphragmatic (inferior) surface - formed chiefly by the left ventricle and part of the right ventricle, separated from the atria by the coronary sulcus (containing the coronary sinus) and from each other by the posterior interventricular sulcus.
• Right pulmonary surface - formed by the right atrium.
• Left pulmonary surface - formed by the left ventricle.

Arterial Supply (Coronary Arteries)

• Right coronary artery (RCA): arises from the right aortic sinus, runs in the coronary sulcus (initially covered by the right auricle), gives the right marginal artery, and continues posteriorly to give the posterior interventricular (posterior descending) artery in most people (right-dominant circulation). It supplies the right atrium, most of the right ventricle, the posterior part of the interventricular septum, and usually the SA and AV nodes.
• Left coronary artery (LCA): passes between the pulmonary trunk and left auricle, then divides into the anterior interventricular artery (left anterior descending, LAD), running in the anterior interventricular sulcus, and the circumflex artery, running posteriorly in the coronary sulcus. It supplies most of the left ventricle, the anterior interventricular septum, part of the right ventricle anteriorly, and the left atrium.

Venous Supply

• Great cardiac vein (continuation of the anterior interventricular vein, in the anterior interventricular sulcus and left coronary sulcus)
• Middle cardiac vein (in the posterior interventricular sulcus)
• Small cardiac vein (right side of the heart)

Nerve Supply

• Sympathetic supply: superior, middle, and inferior cervical cardiac nerves (from the cervical sympathetic ganglia) and thoracic cardiac branches (from upper thoracic ganglia) carry postganglionic fibers (preganglionic cell bodies in the upper thoracic spinal cord) plus visceral pain afferents. Sympathetic stimulation increases heart rate, contractility, and AV conduction velocity.
• Parasympathetic supply: cervical and thoracic cardiac branches of the vagus nerve carry mostly preganglionic fibers that synapse in cardiac ganglia near the heart; afferents mainly relay baroreceptor/stretch information. Vagal stimulation decreases heart rate and contractility and slows AV conduction.
• The cardiac plexus has superficial (below the aortic arch, anterior to the right pulmonary artery) and deep (behind the aortic arch, anterior to the tracheal bifurcation) parts, which give branches following the coronary arteries to supply the whole heart.
• Visceral afferents (pain fibers) travel with the sympathetic cardiac nerves back to spinal segments T1-T7 (and C3-C4), which is why cardiac ischemic pain is referred to the left shoulder, neck, and the ulnar border of the left arm (Color Atlas of Human Anatomy Vol. 2, p. 63-64).

Applied Aspects (Clinical Correlations)

• Myocardial infarction ("heart attack"): over 90% follow acute thrombosis on a ruptured atherosclerotic plaque occluding a coronary artery. Because coronary arteries are functional end arteries, occlusion causes irreversible ischemic damage to the dependent myocardial territory; the size/site of infarct depends on which vessel and how proximal the occlusion is, and whether collaterals exist.
• Referred cardiac pain: due to convergence of visceral afferents with somatic afferents at T1-T7 spinal segments, ischemic cardiac pain (angina/MI) is classically referred to the left arm, shoulder, neck, and jaw.
• Coronary artery disease and angina: progressive atherosclerotic narrowing causes exertional chest pain; complete thrombotic occlusion causes MI.
• Interventional and surgical correlations: percutaneous coronary intervention (angioplasty/stenting) via femoral, radial, or brachial artery access can relieve stenosis; coronary artery bypass grafting (using the internal thoracic artery, radial artery, or great saphenous vein) is used for severe/multivessel disease.
• Valvular disease: mitral and aortic valve stenosis/incompetence (often post-rheumatic or degenerative/calcific) leads to chamber hypertrophy, dilation, and eventually pulmonary edema or heart failure; right-sided (tricuspid/pulmonary) valve disease is more often due to infection (e.g., IV drug use-related endocarditis).
• Clinical naming: the left coronary artery's main stem is called the "left main," the anterior interventricular artery is the LAD, and the RCA's terminal branch is the posterior descending artery (PDA) - terminology used routinely in angiography reports.
• Coronary dominance variation: in right-dominant hearts (most common) the RCA gives the posterior interventricular branch; in left-dominant hearts this branch arises from an enlarged circumflex artery instead - relevant when planning revascularization.