Atherosclerosis is one of the leading causes of stroke and heart disease and causes around 50% of deaths. Fibrous tissues and plagues in artery walls block blood flow in the heart, which results in a heart attack. Arteries carry blood rich in oxygen to the capillaries where there is an exchange of carbon dioxide and oxygen. The capillaries carry deoxygenated blood to the veins and back to the heart and lungs. In a closed circulatory system, the heart pumps blood through various vessels separated by interstitial fluids. The paper discusses how the blood pumps describe the functions of arteries, capillaries, veins, and the circulatory system.
The heart functions as an organized pump composed of the thick myocardium, inner endocardium, and outer epicardium. The muscles provide the desired force to pump blood during each contraction. Moreover, the epicardium serves as a connective and fatty tissue layer between the visceral pericardium and the heart. These four chambers contain two ventricles and two atria (Onwuka et al., 2018). Inferior vena cava provides deoxygenated blood straight into the right atrium while the superior vena cava supplies it to the right ventricle where the pulmonary artery sends it into the lung for oxygenation. Pulmonary vein conveys oxygenated blood into the left atrium in addition to the left aorta receives the blood through the left ventricle, which supplies it to the body.
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Atherosclerosis refers to build-up of cholesterol fats and other substances in the walls of the artery. The formation of fatty deposits in the arteries' inner layers commences by cholesterol crystal deposition in the smooth muscles. The proliferation of plagues in the fibrous tissues bulges within the arteries, hence reducing blood flow (Rafieian-Kopaei, 2014). The collection of plague in artery walls burst, triggering the formation of blood clots, which blocks the flow of blood in the heart, causing a heart attack.
Arteries carry blood rich in oxygen from the heart to the capillaries, where the exchange of carbon dioxide and oxygen occurs. Capillaries transport blood rich in waste to the veins, which drain blood from limbs and organs and send it to the heart (Pappano & Wier, 2018). Arteries are then divided into muscular arteries, elastic arteries, and arterioles. The elastic arteries are the biggest, are close the heart, and have thick walls. On the other hand, muscular arteries deliver blood to various body parts, while arterioles have a single muscle layer around the endothelial lining. Capillaries have thin walls or around 1 millimeter and are just large enough to allow red blood cells to pass through (Pappano & Wier, 2018). The uniting of capillaries forms venules that are highly porous to allow the movement of blood cells and water across the walls. Venules form veins that have elastin smooth muscles containing longitudinal collagen bundle fibers.
The circulatory system is a network of veins, arteries, and capillaries emanating from the heart. This closed-loop system does not allow blood to flow freely in the cavity is present in vertebrates and invertebrates. All vertebrates have a single heart and closed circulatory system. Invertebrates like the annelid earthworm have a fluid called hemolymph, pumped through the vessels into the body cavity (Starr, Evers, &Starr, 2016). The closed circulatory system distributes fluids faster than the open systems and provides a higher degree of distribution of materials in the various parts of the body as the vessels can be easily narrowed or widened when needed.
Heart valves provide a coordinated flow of blood during the cardiac cycle. Fibrous tissues and plagues in vessels block blood flow, leading to atherosclerosis, which causes a heart attack. Arteries convey oxygenated blood straight from the heart into the capillaries to facilitate the interchange of oxygen and nutrients across the cells. Capillaries then carry deoxygenated blood into the veins and back into the heart. The vertebrates and some invertebrates use a closed circulatory system where blood is pumped from the heart into the veins. The closed circulatory system has more advantages than the open system as it facilitates the faster distribution of blood.
References
Starr, C., Evers, C., & Starr, L. (2016). Biology: Concepts and applications . Boston, MA: Cengage Learning
Onwuka, E., King, N., Heuer, E., & Breuer, C. (2018). The Heart and Great Vessels. Cold Spring Harbor perspectives in medicine , 8 (3), a031922. https://doi.org/10.1101/cshperspect.a031922
Pappano, A. J., & Wier, W.G. (2018). Cardiovascular Physiology. Philadelphia, PA: Elsevier Health Sciences
Rafieian-Kopaei, M., Setorki, M., Doudi, M., Baradaran, A., & Nasri, H. (2014). Atherosclerosis: process, indicators, risk factors, and new hopes. International Journal Of Preventive Medicine , 5 (8), 927–946.
