Structure and Location

  • The heart is a muscular organ in most animals.
  • It pumps blood through the blood vessels of the circulatory system.
  • The heart is approximately the size of a closed fist.
  • It is located between the lungs, in the middle compartment of the chest.
  • The heart is divided into four chambers in humans, other mammals, and birds.
  • The human heart is situated in the mediastinum.
  • It is located at the level of thoracic vertebrae T5-T8.
  • The heart has its apex pointing to the left.
  • The largest part of the heart is usually slightly offset to the left side of the chest.
  • The heart is cone-shaped, with its base positioned upwards and tapering down to the apex.

Chambers and Valves

  • The heart has four chambers: two upper atria and two lower ventricles.
  • The atria open into the ventricles via the atrioventricular valves.
  • The right atrium and ventricle are referred to as the right heart.
  • The left atrium and ventricle are referred to as the left heart.
  • The ventricles are separated from each other by the interventricular septum.
  • The heart has four valves that separate its chambers.
  • The valves between the atria and ventricles are called the atrioventricular valves.
  • There is one valve between each atrium and ventricle.
  • The valves at the exit of each ventricle are called semilunar valves.
  • The valves ensure one-way blood flow through the heart.

Function and Cardiac Cycle

  • The heart pumps blood with a rhythm determined by pacemaker cells.
  • Deoxygenated blood enters the heart through the right atrium and passes to the right ventricle.
  • From the right ventricle, it is pumped into the pulmonary circulation to the lungs.
  • Oxygenated blood returns to the left atrium, passes through the left ventricle, and is pumped out through the aorta into systemic circulation.
  • The heart beats at a resting rate close to 72 beats per minute.
  • The cardiac cycle is the sequence of events in which the heart contracts and relaxes.
  • Systole is the period when the ventricles contract and diastole is the period when the ventricles relax.
  • The atria and ventricles work in concert to efficiently pump blood.
  • Blood fills the ventricles during diastole and is ejected during systole.
  • The mitral and tricuspid valves open and close to regulate blood flow.

Arterial and Venous Supply

  • Coronary circulation supplies the heart with oxygen, nutrients, and removes metabolic wastes.
  • It includes arteries, veins, and lymphatic vessels.
  • Blood flow through the coronary vessels is influenced by the relaxation or contraction of the heart muscle.
  • The left main coronary artery and the right coronary artery are the main arteries that supply blood to the heart.
  • The left anterior descending artery supplies the front, outer side, and septum of the left ventricle, while the left circumflex artery supplies the back and underneath of the left ventricle.
  • The coronary sinus is a large vein that drains into the right atrium.
  • It receives blood from the great cardiac vein, the posterior cardiac vein, the middle cardiac vein, and small cardiac veins.
  • The anterior cardiac veins drain the front of the right ventricle and directly into the right atrium.
  • Small lymphatic networks called plexuses exist beneath each layer of the heart.

Nerve Supply and Development

  • The heart receives nerve signals from the vagus nerve and nerves from the sympathetic trunk.
  • These nerves influence the heart rate and the force of heart contraction.
  • The vagus nerve, part of the parasympathetic nervous system, decreases the heart rate.
  • Nerves from the sympathetic trunk, part of the sympathetic nervous system, increase the heart rate.
  • These nerves form a network called the cardiac plexus.
  • The heart is the first functional organ to develop and starts beating at around three weeks into embryogenesis.
  • It derives from splanchnopleuric mesenchyme in the neural plate.
  • The heart tube forms and undergoes further development, including the formation of septa and valves.
  • Before the fifth week, there is an opening in the fetal heart called the foramen ovale.
  • The embryonic heart rate accelerates and reaches a peak rate of 165-185 bpm before slowing down.

Heart Mentions


Heart Data Sources

Reference URL
Glossary https://www.alternix.com/blogs/glossary-of-terms/heart
Wikipedia http://en.wikipedia.org/wiki/Heart
Wikidata https://www.wikidata.org/wiki/Q1072
Knowledge Graph https://www.google.com/search?kgmid=/m/07gdl1