The heart has an important musculature and an even more important function, that of maintain blood flow on which the functioning of the whole organism depends. It is a biological pump, coupled to a very delicate and complex system of veins and arteries, but its functions are very clear from the beginning. Do not stop pumping blood.
In this article we will talk about the different parts that make up the human heart, also briefly describing their different functions and peculiarities.
The 18 parts of the human heart and how they work
The human heart has a curious morphology.. Located behind our sternum, slightly to the left, it is protected by the ribs and attached to the lungs, which have their own network of circulation with the heart, through which the blood is enriched with oxygen and releases its carbon dioxide before returning to circulate through the heart to the rest of the body.
It’s a muscular and not entirely symmetrical organbecause the muscles on the left side of the heart are stronger and bulkier (because they send blood through the whole body, rather than just through the pulmonary circulatory system). It is surrounded by protective tissue, blood vessels, and specialized cells that help keep your rhythmic contractions going.
Below we list the different parts of the heart, as well as a brief description of their functions and peculiarities:
1. Myocardium
Myocardium is the contractile muscle layer which performs the mechanical action of pumping blood into the body. It is a muscle that functions involuntarily, that is, without the need for a nervous impulse coming from the nervous system. The contractile signal is generated in the heart itself.
The myocardium is more abundant in the lower part of the heart, the ventricles, than in the upper part, the atria. It is also more present on the left side than on the right side of the heart.
2. Endocardium
The endocardium is the lining of the different chambers of the heart. It consists mainly of endothelial cells, similar to the rest of the blood vessels, as well as a layer of lax connective tissue.
3. Pericardium
The pericardium is a fibrous membrane that surrounds the heart and the great blood vessels that connect to it, as isolation and protection. We can think of the pericardium as a large bag, made up of two layers: Serous pericardium and fibrous pericardium.
Its viscosity and protective capacity allow the heart to move freely without being affected by nearby structures.
4. Right Auricle
The right atrium is the cavity in the upper-right part of the heart, above the right ventricle. It is reached by the superior vena cava and the inferior vena cava. carry to the heart the blood that has already circulated through the bodyrich in carbon dioxide and poor in oxygen. The blood reaches the right atrium before going down into the right ventricle.
5. Right ventricle
The right ventricle is attached to the right atrium, from which it receives blood. The right ventricle is also connected to the pulmonary artery, which will be responsible for carrying blood from the right ventricle to the lungs, where gas exchange will occur. It contracts slightly before the left ventricle.
6. Tricuspid valve
Between the atria and the ventricles, as well as between the ventricles and the arteries, we find the valves. They are made up of connective tissue and their main function is that of avoid blood reflux and isolate both the atria and the ventricles.
They open only when blood is pumped through them, and close immediately by the contractile action of the myocardium.
The tricuspid valve is the one lies between the right ventricle and the right atrium. It is called tricuspid because it is made up of three sheets of connective material, attached to the right ventricle through tendons and small papillary muscles.
7. Pulmonary valve
The pulmonary valve is the one that connects the right ventricle to the pulmonary artery. It opens when the right ventricle contracts, allowing blood to flow into the artery.
8. Left Auricle
The left atrium receives blood from the pulmonary veins (there are 4, 2 coming from the right lung and 2 coming from the left lung). From the left atrium, blood flows into the left ventricle through the mitral valve.
9. Left ventricle
The left ventricle contains the strongest muscles in the whole heart. From this ventricle, blood is pumped into the aortic artery, which divides to water the rest of the body’s blood. The blood pressure generated by this ventricle must be much higher than that generated by the right ventricle.
10. Mitral valve
The mitral valve separates the left atrium from the left ventricle. Like the tricuspid valve, it is also attached to the ventricle through tendons and papillary muscles, which prevent its opening when the ventricle is empty as well as its opening when the ventricle contracts.
11. Aortic valve
The aortic valve is the valve that separates the aortic artery from the left ventricle. It has to be able to withstand high blood pressures.
12. Tendon cords
Tendon cords are connective tissue structures that connect mitral and tricuspid valves to papillary muscles.
13. Papillary muscles
The papillary muscles are found in the wall of the ventricles. They have the shape of a cone and their main function is that of keep the valves closed to prevent blood reflux, i.e., blood flowing backwards into the heart circuit.
14. Sinus node
The sinoatrial node is an accumulation of cells that function as the natural pacemaker of our heart, indicating when it must be contracted. The electrical signal begins in the sinoatrial node, but travels through specialized structures from the top to the bottom of the heart, causing muscle contraction.
15. Atrioventricular node
The atrioventricular node is located close to the sinoatrial node. Also has the ability to function as the heart’s pacemaker, but will only do so in the event that the sinoatrial node fails. The impulses of the atrioventricular node are less frequent than those of the sinoatrial node.
16. Atrioventricular fascicule
The atrioventricular fascicule, also known as the bundle of His, is a cord-shaped muscular structure that functions as the cable through which the excitatory impulse from the nodes travels from the atria to the ventricles.
17. Coronary arteries
The coronary arteries envelop the heart, providing nutrients to the entire structure. These branch into left and right coronary arteries, each nourishing mainly the respective halves of the heart. Diseases of the coronary arteries are the most common type of heart condition.
18. Coronary veins
It is the coronary veins that return oxygen-poor blood from the heart and surrounding tissues back to the heart. Curiously, these veins drain directly into the right atrium in a very efficient and elegant manner.
Bibliographic references
- Susan Standring; Neil R. Borley; et al., eds. (2008). Gray’s anatomy : the anatomical basis of clinical practice (40th ed.). London: Churchill Livingstone. ISBN 978-0-8089-2371-8.
- Anderson, Robert H.; Mori, Shumpei (2016). “Wilhelm His Junior and his bundle.” Journal of Electrocardiology. doi:10.1016/j.jelectrocard.2016.06.003. ISSN 0022-0736.
- Csepe, T., Zhao, J., Hansen, B., Li, N., Sul, L., & Lim, P. et al. (2016). Human sinoatrial node structure: 3D microanatomy of sinoatrial conduction pathways. Progress In Biophysics And Molecular Biology, 120(1-3), 164-178. doi:10.1016/j.pbiomolbio.2015.12.011.