The Cardiovascular System

Question: How does structure Aid function of the human cardiovascular system? Answer: Introduction: Every living organism depends on interstitial fluid as a source of nutrients and oxygen and as a mode of disposal of waste materials. The blood plays a vital role in supplying oxygen to every organ of the body as well as carries away the waste materials from the organs. The continuous flow of blood is maintained by heart and it pumps the blood throughout a network of blood vessels. The human heart consists of four chambers that pump the blood to lungs in order to purify the deoxygenated blood and supplies oxygenated blood to the body (Nishikimi, 2011). The detail of the entire cardiovascular system is described below: 1. The structure and function of vascular system: There are three types of blood vessels in the human body and they are arteries, veins, and capillaries. The arteries carry oxygenated blood from the heart towards the target organs and they eventually decrease their size forming capillaries to the organ and the deoxygenated blood from the organs are carried away to the heart by the veins. However, the largest artery in the body is aorta and the largest vein is vena cava. The circulatory system is known as closed system as the blood in enclosed in the heart or in blood vessels and always following through one direction, i.e., Heart (ventricles) - Arteries - Capillaries - Organ- Veins - Heart (atrium) Source: (Nishikimi, 2011) The arteries and veins are made up of three layers known as inner epithelial tissue, middle smooth muscle, and outer connective tissue. These layers provide elasticity and strength to the vessels. The walls of the arteries are thicker that of veins and the three layers help to withstand the high blood pressure coming from the heart. The artery wall expands when the blood passes through it and relaxes to spring back to prevent backflow; this is known as secondary circulation and reduces the load of heart. The pulmonary arteries are the only arteries that carry deoxygenated blood (Mizuguchi, 2010). The arteries get branched to networks known as capillaries and they have very large surface area but very thin walls with only one epithelial layer. The capillaries are narrow and the blood pressure is also slow down allowing the diffusion to take place in the organs. The deoxygenated blood is then carried away to the heart by the veins and its path is through the skeletal muscles were the blood flow is restricted by valves so that the blood flow could occur against the gravity. 2. The Structure and function of human heart: The heart is cone shaped situated within the sternum and tilted to the left. The walls of the heart are made up of three tissues, outer and inner epithelial and middle cardiac muscle. The cardiac muscle respires aerobically and hence, ensures plenty of oxygen through coronary artery and consists of rich mitochondria. The heart is covered by a protective membrane known as pericardium that consists of pericardium fluid, which reduces the friction among the cardiac muscles (Fa-Po, 2015). Source: (Mizuguchi, 2010) The heart consists of four chambers, known as right atrium and right ventricle; and left atrium and left ventricle. The right side of the lungs receives deoxygenated blood from the body though the superior vena cava that brings blood from the head and arms and inferior vena cava from the rest of the body. The vena cava empties the deoxygenated blood to the right atrium when the heart relaxes and eventually when the heart contracts the right artrio-venticular (AV) valve opens and the blood moves from right atrium to the right ventricle. This value is known as tricuspid valve and makes the sound lub on closing and prevents the backflow of the blood when the heart relaxes as a result when the right ventricle contracts the pulmonary valve opens and the blood flows to the pulmonary artery to the lungs. The pulmonary valve prevents the backflow of the blood and makes a sound dup (Fa-Po, 2015). The oxygenated blood leaves the lungs and enters to the left atrium though the pulmonary vein that is the only vein to carry oxygenated blood. When the left atrium contract the blood flow to the left ventricle through the left AV valve known as bicuspid valve and it prevents the backflow of the blood. When the left ventricle contracts the blood flows to the aorta through the aortic valve that carries oxygenated blood throughout the body. When the blood enters aorta, its walls expands that helps to detect the pulse in the body (Kodani, 2015). 3. The Heartbeat: The heart rate is also known as pulse that is the number of times an individuals heart beats per minute. The heart beats depends on individual to individual from their body size, age and condition of heart and also whether the individual is moving, sitting or meditating in an even temperature. When an individual is resting the heart beat rate is between 60 and 80 times per minute. When an individual does vigorous exercise, heart beat rate increases due to the need of oxygen and glucose by the cells and also removal of generated carbon dioxide from the cells (Kodani, 2015). 4. The Cardiac Cycle: The cardiac cycle is the sequence of events that takes place in one heart beat and the contraction of both atrium followed by the contraction of both ventricles. The heartbeat consists of two phase systole and diastole. The systole derives contraction and this occurs when the ventricles contract that closes the AV valve and simultaneously opens the semi lunar valve and eventually pumps the blood to the heart. The diastole derives relaxation and it occurs when the ventricles relax allowing the blood pressure to close the semi lunar valve and opening AV valve (Nademanee, 2010). Source: (Nademanee, 2010) The heart consists of a single muscle but it does not contract at once. The contraction spreads eventually throughout the heart by specialised cells known as Sino Atrial Node (SA node) present in the right atrium. These cells are also called natural pacemaker of the heart. The impulse of SA node spread through the right and left atrium causing both atriums to contract simultaneously (Mizuguchi, 2010). References: Fa-Po, C. (2015). Current and state of the art on the electrophysiologic characteristics and catheter ablation of arrhythmogenic right ventricular dysplasia/cardiomyopathy. Kodani, E. (2015). Early detection of atrial fibrillation is the first step to prevent cardiogenic stroke: Usefulness of B-type natriuretic peptide, 65. Mizuguchi, Y. (2010). Concentric left ventricular hypertrophy brings deterioration of systolic longitudinal, circumferential, and radial myocardial deformation in hypertensive patients with preserved left ventricular pump function. Nademanee, K. (2010). Catheter ablation of atrial fibrillation guided by complex fractionated atrial electrogram mapping of atrial fibrillation substrate. Nishikimi, T. (2011). Current biochemistry, molecular biology, and clinical relevance of natriuretic peptides.