How the Heart Receives Its Blood: Key Pathways & Clinical Relevance
The heart is a major organ of the human body which is responsible for the circulation of the blood. Blood circulation in the body ensures that every cell of the organ receives nutrients and oxygen supply to perform its metabolism. To understand the blood supply of the heart it is important to understand the location of the heart, anatomy of the heart, the vasculature of the nerve which answers questions like which artery supplies blood to the heart. This article dwells with the intricacies of blood supply of heart anatomy and functioning, which arteries supply blood to heart, the circulation system of the heart known as coronary circulation.
Heart
The location of the heart can be defined by understanding the cavity it is present in. The heart is present in the thoracic cavity, which is posterior to the sternum, inferior to the diaphragm. It is located in between the lungs. The heart is made up of myocardium muscle, this muscle has exceptionally high thickness thus the heart can not work with the normal vasculature of the circulation. The blood supply of the heart is also known as coronary circulation and the artery that supplies blood to the heart is known as the coronary artery. The heart is the four-chambered organ. It is divided into two atria and two ventricles.
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Valves
There are four major valves present in the heart they are called, atrioventricular valve and the semilunar valve. Each of these valves is prest in pair thus forming 4 valves.
The atrioventricular valve is also known as the mitral valve, they are present in the left and right atrioventricular junction. The left atrioventricular valve has two openings that are bicuspid and the right atrioventricular valve is known as the tricuspid valve because of three openings. It is important to note that the valves of the heart open in only one direction, thus allowing the blood to flow into a singular direction of circulation.
The semilunar valves guide the movement of blood during ventricular relaxation. They are present at the junction between the ventricle and outflow vessel. The outflow blood vessels are aortic and pulmonary vessels.
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Heart Wall
The heart wall can be defined as the muscular structure of the heart. The heart wall has 4 layers pericardium, epicardium, myocardium, and endocardium. The pericardium is the outermost layer of the heart wall, it is the layer in which arteries supply blood to the heart. It has a fibrous sac-like structure from the outside and the inner surface is generally parietal. Epicardium is the layer just below the pericardium, between both these layers there is a presence of the cavity; this cavity is known as the pericardial cavity. It is a fluid filled cavity. This layer, the epicardium, is also known as the visceral layer of the pericardium. The myocardium is the layer that is responsible for the contraction and relaxation of the atrium and ventricle, thus ensuring the blood supply of the heart. It has a modification known as an intercalated disk, which is specialized to the cardiac muscle only, it ensures the connection between the left and right ventricle and similarly left and right atrium. It is important to note that valves lack this intercalated disk. The blood vessels responsible for the blood supply of heart protrudes into this layer.
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Coronary Arteries
The blood supply of the heart is mediated by the arteries that specialized for circulation according to the blood supply of heart anatomy, it is because of the thickness of the cardiac muscle. Now the question arises which artery supplies blood to the heart. The answer to this question is coronary arteries. The blood supply of the heart is mediated by the coronary artery; these arteries are divided into two main classes: the left coronary arteries and the right coronary arteries. This complete circulation including the venous supply of the heart is known as coronary circulation.
The left coronary artery divides into the left anterior descending and circumflex branches, Both the arteries originate from the coronary Ostia. Coronary Ostia is the opening of the base of the aorta, they are located behind the aortic valve leaflets. The coronary arteries because they surround the epicardium are known as epicardial coronary vessels. These coronary vessels have a special feature of low vascular resistance as compared to normal blood vessels. The microcirculation of the blood is achieved at the level of small arteries and arterioles. They are the region that performs maximum exchange of oxygen and nutrients, thus they are the vital site of regulation, regulation of the blood flow is primarily achieved here.
Left coronary artery- according to the pattern of blood supply of heart anatomy, the left coronary artery divides into two main branches. One of the branches is named as circumflex artery while the other is named as Left Anterior Descending artery (LAD). left coronary arteries are comparatively larger than the right coronary arteries, they arise from the left aortic sinus. It appears in the mid between the pulmonary trunk and the left auricle. At this, it bifurcates to give an interventricular branch. The circumflex artery is the farther artery. From the interventricular point, it runs to the anterior coronary sulcus. It finally terminates by anastomosing by the right coronary artery. According to blood supply of heart anatomy, the left artery covers the regions of the left atrium, ventricles, (the greater part of the left ventricle and a smaller part of the right ventricle), anterior part of the interventricular septum, and AV bundle.
Blood Supply of Heart Diagram:
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Right coronary arteries further bifurcate into the right marginal artery and posterior descending artery. They are distributed in ventricles but to be noted that they are majorly present in the right ventricle and comparatively less in the left ventricle. They do not provide blood to the SA node, the SA node is supplied with the left coronary artery.
FAQs on Blood Supply of Heart: Coronary Arteries, Valves & Functions
1. What is meant by the blood supply of the heart, and why is it important?
The blood supply of the heart refers to the network of vessels, known as the coronary circulation, that provides the heart muscle (myocardium) with oxygenated blood and removes deoxygenated blood. Although the heart's chambers are filled with blood, the heart wall is too thick to be nourished by this blood. It requires its own dedicated supply to function continuously, as it is one of the most metabolically active organs in the body.
2. What are the main arteries that supply oxygenated blood to the heart muscle?
The heart muscle is primarily supplied by two main arteries that arise from the aorta just above the aortic valve. These are:
- Right Coronary Artery (RCA): Supplies blood to the right atrium, right ventricle, and the bottom portion of the left ventricle.
- Left Main Coronary Artery (LMCA): A short vessel that quickly divides into two major branches, the LAD and the LCX, to supply the rest of the heart.
3. Can you explain the key branches of the left coronary artery, like the LAD and LCX?
The Left Main Coronary Artery (LMCA) is crucial as it branches into two significant arteries:
- The Left Anterior Descending (LAD) artery supplies blood to the front and bottom of the left ventricle and the front of the septum.
- The Left Circumflex (LCX) artery encircles the heart muscle, supplying oxygenated blood to the outer side and back of the heart.
4. How is deoxygenated blood drained from the heart tissue after use?
After the heart muscle uses the oxygen from the blood, the deoxygenated blood is collected by a network of cardiac veins. These veins run alongside the coronary arteries. Most of these veins merge to form a large vessel called the coronary sinus, which then drains this deoxygenated blood directly into the right atrium to be sent to the lungs for re-oxygenation.
5. How does the coronary circulation (blood supply to the heart) differ from the blood flowing through the heart's chambers?
This is a key distinction. The blood flowing through the heart's chambers (atria and ventricles) is part of the pulmonary and systemic circuits, destined for the lungs and the rest of the body. The coronary circulation is a separate, dedicated system that originates from the aorta to specifically nourish the heart muscle itself. The heart does not draw its own oxygen supply from the blood passing through its chambers.
6. What is unique about the timing of blood flow into the coronary arteries?
Unlike most other arteries in the body that receive blood during heart contraction (systole), the coronary arteries receive the majority of their blood flow during heart relaxation (diastole). This is because during systole, the powerful contraction of the heart muscle compresses the coronary arteries, temporarily reducing blood flow. When the heart relaxes, the pressure is released, allowing blood from the aorta to fill them effectively.
7. What is the consequence if the blood supply to a part of the heart muscle is blocked?
An interruption or blockage in a coronary artery deprives the corresponding area of the heart muscle of oxygen and nutrients, a condition called ischemia. If this blockage is prolonged, the affected heart tissue begins to die. This event is known as a myocardial infarction, or more commonly, a heart attack. The severity depends on which artery is blocked and how much muscle tissue is affected.
8. What is the role of the mitral valve in the heart's overall function?
The mitral valve is an atrioventricular valve located between the left atrium and the left ventricle. Its primary role is to ensure one-way blood flow. It opens to allow oxygenated blood to pass from the left atrium into the left ventricle and closes tightly when the ventricle contracts to prevent blood from flowing back into the atrium, ensuring it is all pumped into the aorta.
