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Structure

Heart

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The heart is a four-chambered muscular pump that drives blood through the pulmonary and systemic circulations. It lies in the middle mediastinum, enclosed in the pericardium.

Terminologia Anatomica (Latin): Cor · Open in the 3D atlas

Location

Behind the sternum and the costal cartilages 2 to 6, about two thirds to the left of the midline. The apex points anteriorly, inferiorly and to the left, reaching the left fifth intercostal space near the midclavicular line.

Structure

The wall has three layers: endocardium, myocardium and epicardium (the visceral layer of the serous pericardium). A fibrous skeleton separates atria from ventricles and anchors the valves. The sternocostal surface is formed mainly by the right ventricle, the diaphragmatic surface mainly by the left ventricle.

Blood supply

Arterial supply comes from the right and left coronary arteries arising from the aortic sinuses. Venous blood drains mainly through the coronary sinus into the right atrium, with additional anterior cardiac veins and small Thebesian veins.

Innervation

The cardiac plexus receives sympathetic fibres from the cervical and upper thoracic (T1 to T4) segments, which raise rate and contractility, and parasympathetic fibres from the vagus nerve, which slow the rate. Cardiac pain travels in visceral afferents with the sympathetic nerves to T1 to T4.

Function

The right heart receives systemic venous blood and pumps it to the lungs; the left heart receives oxygenated blood and pumps it to the body. Valves enforce one-way flow and the conduction system coordinates the cardiac cycle. Atrial myocytes also secrete natriuretic peptide.

Clinical correlations

Coronary artery disease is the leading cause of myocardial infarction and heart failure. Fluid in the pericardial sac can cause tamponade, and pericardiocentesis is a recognised emergency route of drainage. Congenital septal and valvular defects are the commonest structural anomalies.

Common exam points

  • Apex beat: left 5th intercostal space, midclavicular line.
  • Wall layers: endocardium, myocardium, epicardium; the pericardium is fibrous plus serous (parietal and visceral).
  • Sternocostal surface is mostly right ventricle; diaphragmatic surface is mostly left ventricle; base is mostly left atrium.
  • The transverse sinus lies behind the aorta and pulmonary trunk and is used in surgery to clamp the great arteries.
  • Sympathetic supply T1 to T4; parasympathetic via the vagus; cardiac pain is referred to the chest and left arm.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Federative Committee on Anatomical Terminology (FCAT). Terminologia Anatomica: International Anatomical Terminology. Thieme (1998) — Tier 1 (standards / international bodies)
  4. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. Elsevier, 12th edition (2022) — Tier 3 (textbook)

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