A four-chambered muscular pump about the size of a closed fist. Its right side sends blood through the lungs to collect oxygen; its left side drives that blood out to every tissue in the body.
Key facts
- Size
- About 12 × 8 × 6 cm
- Weight
- ≈ 250–350 g in adults
- Daily
- ≈ 100,000 beats, ≈ 7,000 L of blood
- Output
- ≈ 5 L per minute at rest
Location
Middle mediastinum, behind the sternum and between the lungs, resting on the diaphragm. About two-thirds of it lies to the left of the midline, with the apex pointing down and to the left near the 5th intercostal space.
Functions
- Pumps deoxygenated blood to the lungs (pulmonary circulation).
- Pumps oxygenated blood to the body (systemic circulation).
- Keeps blood moving one way with four valves.
- Sets its own rhythm through a built-in electrical conduction system.
Structure
Two atria receive blood and two ventricles eject it. The wall has three layers: endocardium (inner lining), myocardium (cardiac muscle) and epicardium (outer layer), all enclosed in the pericardial sac.
Blood supply
Right and left coronary arteries, the first branches of the aorta. Venous blood returns mainly through the coronary sinus into the right atrium.
Related structures
Clinical significance
- Coronary artery disease and myocardial infarction.
- Heart failure — the pump cannot meet the body's needs.
- Valvular heart disease (stenosis or regurgitation).
- Arrhythmias such as atrial fibrillation.
For the medical student
The heart has an anterior (sternocostal) surface formed mainly by the right ventricle, a diaphragmatic (inferior) surface formed by both ventricles, and a base formed chiefly by the left atrium. The atrioventricular (coronary) groove separates atria from ventricles; the anterior and posterior interventricular grooves mark the septum and carry the major coronary vessels.
Worth knowing
The heart begins beating about three weeks after conception.
Cardiac muscle never rests for longer than the pause between two beats.
References
- Standring S, ed. Gray's Anatomy: The Anatomical Basis of Clinical Practice. 42nd ed. Elsevier; 2020 — Heart and great vessels.
- Netter FH. Atlas of Human Anatomy. 8th ed. Elsevier; 2022 — Thorax: heart plates.
- Dalley AF, Agur AMR. Moore's Clinically Oriented Anatomy. 9th ed. Wolters Kluwer; 2022 — Thorax.
- National Library of Medicine, StatPearls — Anatomy, Thorax, Heart (NCBI Bookshelf).
- 3D geometry: BodyParts3D, © The Database Center for Life Science, licensed under CC Attribution 4.0 International (Mitsuhashi N, et al. Nucleic Acids Res. 2009).
Educational model. Values are typical adult figures and vary between people. Not for diagnosis or treatment decisions.