Heart Anatomy: Chambers and Location

Heart Anatomy Overview

• The heart is located within the thoracic cavity, specifically in the mediastinum.
• The heart is shifted about 2/3 to the left of the midsternal line.
• The apex of the heart points towards the left hip.
• The base of the heart points towards the right shoulder.
• The heart weighs approximately 200-300 grams and is about the size of a fist.

Heart Chambers

• The two upper chambers of the heart are called the atria (right and left).
• The right atrium receives blood from three major vessels:
  • Inferior vena cava (IVC) brings blood from below the diaphragm.
  • Superior vena cava brings blood from the head, neck, and upper limbs.
  • Coronary sinus receives blood from the myocardium.
• The fossa ovalis is a scar tissue in the right atrium, a remnant of the foramen ovale in the fetus.
• The left atrium receives oxygenated blood from the pulmonary veins.
• The left pulmonary veins bring blood from the left lung.
• The right pulmonary veins bring blood from the right lung.

Heart Valves

• Valves prevent backflow and ensure one-way blood flow.
• The tricuspid valve (or right atrioventricular valve) separates the right atrium from the right ventricle.
• The bicuspid valve (mitral valve or left atrioventricular valve) separates the left atrium from the left ventricle.
• Valves consist of layers called the Zona fibrosa, Zona spongiosa, and Zona ventricularis, with an endothelial lining.
• Chordae tendineae are collagen cords attaching to the valve cusps, anchoring the valves.
• Papillary muscles attach to the chordae tendineae and anchor them, preventing valve prolapse.
• Ischemia or damage to the papillary muscles (e.g., during myocardial infarction) can cause valve regurgitation.

Ventricles and Septa

• The right ventricle is the pumping chamber on the right side of the heart.
• The left ventricle is the pumping chamber on the left side of the heart.
• The interventricular septum separates the right ventricle from the left ventricle.
• Ventricular septal defect, a congenital disorder, involves a hole in this septum.
• The interatrial septum separates the left atrium and the right atrium

Pulmonary and Aortic Valves and Vessels

• The pulmonary semilunar valve separates the right ventricle from the pulmonary trunk.
• The aortic semilunar valve separates the left ventricle from the aorta.
• The pulmonary trunk splits into the left and right pulmonary arteries leading to the lungs.
• Blood flows through the ascending aorta, then the aortic arch.
• Three important vessels branch off the aortic arch:
  • Brachiocephalic trunk (which splits into the right common carotid artery and the right subclavian artery).
  • Left common carotid artery.
  • Left subclavian artery.

Heart Layers

• The layers of the heart, from innermost to outermost, are:
  • Endocardium: Innermost layer made of endothelial tissue.
  • Myocardium: Middle muscular layer made of cardiac muscle tissue; thicker in the left ventricle.
  • Epicardium (or visceral layer of the serous pericardium): Outer layer.
• The pericardial cavity contains pericardial fluid, which reduces friction during heartbeats.
• The parietal layer of the serous pericardium is continuous with the visceral layer (epicardium).
• The fibrous pericardium is the outermost layer, made of dense irregular connective tissue.
  • Anchors the heart to surrounding structures.
  • Protects the heart.
  • Prevents the heart from overfilling with blood.