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
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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 |