The circulatory system is comprised of blood vessels that supply oxygen and nutrients to the body while removing carbon dioxide (CO 2 ) and water (H 2 O). The heart is one of the core organs of the circulatory system. It pumps blood through the rests body as well as through itself (Goodwill et al., 2011). However, the heart does not acquire nutrients as blood flows through its chambers; it relies on coronary circulation to function properly. This paper is composed of two parts. The first part of this paper will delve into discussing what is unique about the delivery of nutrients and the delivery of wastes to and away from the heart. In particular, the paper will describe coronary circulation and explain what happens as blood flows to the heart and away from the heart. In the second part of this paper, three flow charts will be created to illustrate how blood flows through various blood vessels.
Part 1: The Deliver of Nutrients to the Heart and Delivery of Wastes from the Heart
The Delivery of Nutrients to the Heart
The heart is considered as the main or central organ in the circulatory system. Its tissue is called myocardium. The heart is mainly responsible for pumping blood. Thus, the heart is basically a pump, and like any other pump, the heart requires fuel to function properly. Since it is muscle tissue, the myocardium requires oxygen and nutrients in order to facilitate the supply of blood throughout the body. However, it is important to note that although blood flows through the heart's chambers, it does not supply the heart with nutrients. The big question is: how does the heart receive oxygen and nutrients? How are wastes substances removed from the heart?
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The heart relies on coronary circulation to function properly. Like any other muscle in the body, the myocardium needs constant oxygen and blood supply. The myocardium receives nutrients from the blood it receives from unique blood vessels called coronary arteries, which are located outside of the heart. These blood vessels branch off of the aorta and deliver oxygenated blood into the myocardium itself (Goodwill et al., 2011). During systole, the heart's ventricle contracts, forcing blood into coronary arteries.
The coronary arteries are main responsible for regulating the supply of oxygen and nutrients to the myocardium. The amount of blood supplied depends on how much oxygen and nutrients the hearts need at the time (King & Lowery, 2017). This is influenced by several factors, including the heart rate and blood pressures (King & Lowery, 2017). For example, the higher the heart rate, the more oxygen and nutrients the heart needs.
Two coronary arteries, which lie to the outside of the heart, stem from aorta. The LCA branches into the left anterior descending artery and circumflex artery. The former is responsible for supplying blood to the “anterior wall, anterolateral way, top of the left ventricle, and interventricular septum” (Rehman et al., 2020). The latter is responsible for supplying blood to the “lateral wall” and “lower and back portions of the left ventricle.” The RCA is mainly responsible for supplying oxygen and nutrients to the “inferior wall” and “posterior wall of the left ventricle.”
During diastole, the aorta gets filled with blood from the left and right atria. The heart’s conducting system creates cycles that feeds the aorta with blood. The primary function of the conducting system is to keep the heart beating in coordinated and normal rhythm, helping circulate the blood throughout the body and into the coronary arteries. The result is the continuous supply of oxygenated blood into the heart, which is necessary to keep an individual alive. If there is a problem with coronary arteries, the myocardium will not get enough oxygen and blood, and the heart will not function properly.
The coronary arteries are also comprised of small blood vessels called collateral coronary arteries. When the heart is functioning properly, collateral coronary arteries play only a minor role. However, suppose there is a problem with the coronary arteries, for example, when they become obstructed. In that case, these vessels help increase the supply of oxygen and nutrients to the myocardium. Although they are small, collateral coronary arteries succeed in supplying sufficient nutrients to the heart muscle. This, in turn, helps prevent major damage to the myocardium.
The Delivery of Wastes away from the Heart
The heart and blood vessels work together to deliver wastes away from the heart. Cardiac veins are mainly responsible for removing metabolic waste and deoxygenated blood from the myocardium. The great, middle and small cardiac vein removes blood from the heart's anterior aspect, posterior interventricular septum, and right ventricle, respectively. The left posterior and oblique vein remove blood from the “inferior wall of the left ventricle and posterior wall of the left atrium,” respectively. These blood vessels do not collect occlusive material that has the potential to block the flow of blood. The blood capillaries in the kidneys also act as mechanisms to filter blood. Blood that reaches the kidneys is comprised of nutrients and wastes. The nutrients are absorbed back into the blood. On the other hand, the wastes are removed in the form of urine.
Coronary Circulation
Coronary circulation is the part of the systematic circulatory system that facilitates the circulation of blood from the aorta to and from the heart through the coronary arteries and cardiac veins. Simply put, coronary circulation supplies blood and provide drainage from the myocardium (Bagaswoto et al., n.d). The heart is comprised of two coronary arteries, which branch off of the aorta. During diastole, blood is forced into the coronary arteries, which then delivers oxygenated blood into the myocardium. Deoxygenated blood from the heart muscle is then transported back to the chambers of the heart via coronary veins.
There are two arteries that are responsible for the delivery of blood from the aorta to the myocardium are the left and the right coronary artery. The former is further subdivided into two branches: circumflex and anterior interventricular artery. The former is mainly responsible for supplying blood to the left atrium, and the latter supplies blood to the “interventricular septum.” The right coronary artery is also subdivided into two branches: “the right marginal and the posterior interventricular artery” (Villa et al., 2016). The former is mainly responsible for supplying blood to the lateral side of the heart, while the latter supplies blood to the interventricular septum.
Once the myocardium is supplied with blood, the deoxygenated blood has to be delivered away from it. Cardiac veins retrieve deoxygenated blood from the heart muscle. The great, middle, and small cardiac vein and the left posterior and oblique vein are the cardiac veins that deliver deoxygenated blood from the myocardium. More specifically, the great, middle and small cardiac vein remove blood from the anterior aspect of the heart, posterior interventricular septum, and right ventricle, respectively. The left posterior and oblique vein remove blood from the inferior wall of the left ventricle and posterior wall of the left atrium, respectively.
References
Bagaswoto, H. P., Maharani, E., & Setianto, B. Y. Coronary Circulation and Hemodynamics. ACI (Acta Cardiologia Indonesiana) , 2 (1).
Goodwill, A. G., Dick, G. M., Kiel, A. M., & Tune, J. D. (2011). Regulation of coronary blood flow. Comprehensive Physiology , 7 (2), 321-382.
King, J., & Lowery, D. R. (2017). Physiology, cardiac output. https://www.ncbi.nlm.nih.gov/books/NBK470455/
Rehman, I., Kerndt, C. C., & Rehman, A. (2020). Anatomy, thorax, heart left anterior descending (LAD) artery. StatPearls [Internet] . https://www.ncbi.nlm.nih.gov/books/NBK482375/
Villa, A. D., Sammut, E., Nair, A., Rajani, R., Bonamini, R., & Chiribiri, A. (2016). Coronary artery anomalies overview: the normal and the abnormal. World journal of radiology , 8 (6), 537.
