THE HEART 15
The anatomy of the Human Heart
The Flow Chart Showing the physiological function of the heart
An example of chronic condition that affects the Heart (Coronary Heart Disease)
Lifestyles the Can Cause Coronary Heart Disease
Preventive Measures to Coronary Heart Disease
Diagramof the Human Heart
Theheart is a muscular organ responsible for obtaining blood from allthe tissues and pumps it towards the lungs and reverses the sameprocess by pumping it to the tissues (Barker & Wilson, 2011). The location of the heart is on the posterior side of the sternum andthe costal cartilages, enclosed by the protective thorax, and held atthe base by the superior diaphragm. In thorax, the heart assumesaslanted position, with about two thirds leaning left side of themidline. The covering around it is referred the pericardium withinthe middle mediastinum (Barker & Wilson, 2011). The mediastinumis the space in between the pleura cavities formed when thepericardiumencloses to protect the heart. The pericardium isdouble-layered with a fluid between the layers to lubricate theheart. The lubrication facilitates sliding for the visceralpericardium.
Thereare four cavities in the heart with the ones on the upper side as theatria and the ones on the lower side as the ventricles. It also hasmuscles that enable it pump blood (cardiac muscles of the myocardium. The muscles in the ventricles are tougher hence their capability topump blood to tissues far in the body. The right atrium andventricle are the first receivers of blood, which they pump to thelungs. The left ventricle pumps blood to oxygen needing tissues inthe body. Blood flows through the heart in one complete stream beforeanother round follows. This made possible by the two pairs of valves.The first pair is called the atrioventricular valves. The two valvesare individually referred to as the tricuspid and bicuspid valves.The valves let blood into the heart from the atria to the ventricleswithout overflowing to other cavities. Due to pressure, blood mayflow back to the ventricles. However, this is blocked by both thesemilunar and pulmonary valves. The blood that gets into the heartdoes not nourish it, but through a different vascular supply which isonly meant for the heart. It arterial flow is through the base ofthe aorta that has coronary arteries while its venous flow takesplace via the cardiac veins.
Thepericardium is membrane with two layers that are differentiatedthrough a fluid called serous in between the layers(Weinhaus&Roberts, 2005). Before birth, the heart’s position is on theextreme end of the chest cavity, but transfers to the celomic cavityas the developmental stages that prepares the fetus for both. Thecelomic cavity produces the serous lubrication for the heart. Thelining encloses the heart almost instantaneously in the pericardiumas the heart is positioned in the cavity. One side of thepericardium is touches the heart: visceral pericardium. The parietalpericardium is on the outer side not in contact with the heart. Thevisceral pericardium has contact with the heart through itsmesothelium. The mesothelium produces the serous fluid forlubrication purposes. The visceral pericardium holds on mesotheliumthrough a specific connective tissue. It has another layer of fattytissue that connects it to the fibroblastic layer. The parietalpericardium contains a fibrous player that has elastin and collagenfibers the serve to make the surrounding tissues flexible.Inferiorly, it is linked to the diaphragm. It is attached to themanubrium and xiphoid process by the pericardiosternal ligaments. Laterally, it is connected to the parietal pleura a membrane thatcovers the lungs). The suspension of the heart in the pericardialcavity is possible through a phenomenon called the reflections.Arterial reflections are the pericardial enclosure of the aorta andthe pulmonary truck. Venous reflections is term used to denote theenclosure of the vena cava and the pulmonary veins in thepericardium.
Thecross section of heart shows three layers: the endocardium, theepicardium, and the middle myocardium (Weinhaus& Roberts, 2009).The endocardium is a sheet of epithelial cells found on the basementmembrane filled with connective tissue. The endocardium forms thesmooth layers in all the four chambers inside the heart and thevalves. The myocardium is an elastic layer on the inner walls of theheart that contracts. It has spiral-shaped cardiac muscles that thatsqueeze blood to the right direction (towards to atria inferiorly andthe ventricles superiorly). Cardiac muscles differ from other typesof muscles through their unique cardiac cells that branch. Cardiaccells are also enjoined to each at complex joints referred to asintercalated discs that form a broad network of cells. Cardiac cellsalso a unique location of nuclei at the center of each cell. Thediscskeep the cells held together. The gap junctions allow Calciumions to easily pass through the cells. The rapid movement of calciumions moves causes a transmission of electrical impulse throughout thenetwork of cardiac cells. The electric impulse triggers a wave ofcontraction throughout cardiac cells. The property is makes cardiacmuscles to be considered myogenic because the contraction emanatesfrom internal electrical impulses rather than from an external organ.
The Right Atrium
Theright atrium has three demarcations: 1) the posterior portion with asmooth wall (the sinus venarum), 2) the anterior region with a liningof parallel, horizontal muscle bundles, and 3) the trail septum.
The right ventricle
Theright ventricle gets blood from the right atrium and impels to thelungs via the pulmonary trunk and other smaller arteries. Theanterior surface of the heart is covered by the rightventricularmuscles. The right ventricle’s walls have abundant,coarse trabeculae carnaea (Bateman, Russell, Chan, &Iaizzo,2010). Trabeculae carnaea are similar to the pectinate muscle in theright atrium. They resemble the myocardium with a bundle-likeappearance and are located on both the ventricles. Conus arteriosustransports blood from the anterior to superior direction from theright ventricle. Some parts of conus arteriosus extend to theinterventricular septum, which is found on the inferior part of boththe semilunar valves (Bateman, Russell, Chan, &Iaizzo, 2010). Therest of the outflow tract is separated from the right atrium by thesemicircular arch.
The tricuspid valve
Theventricle orifice is the passage of blood in the right chambers as itflows in from the rest of the tissues. The contraction rightventriclecan force blood back to the right atria, but this does not happenbecause the tricuspid valve blocks it. The tricuspid comprises of theannulus, three papillary muscles, three sets of chordae tendinae, aswell as three vulvular leaflets. The annulus makes theatrioventricular orifice to be firm to withstand the force andthrough its connection to the ventricular septum. The tricuspidvalve also comprises of three leaflets: the anterior, the posteriorand septal leaflets (Bateman, Russell, Chan, &Iaizzo, 2010).
The pulmonary semi-lunar valve
Theventricle systole causes enough force to push blood back to the leftventricle, but this does not happen due to the pulmonary semilunarvalve. It blocks it from flowing back to the ventricle during theventricular systole. It comprises of three semilunar shaped cusps(Bateman, Russell, Chan, &Iaizzo, 2010). Each of the semilunarcusps has the shape of a cup with a thin membrane, oriented to thepulmonary trunk. They let blood into the ventricle through their widelower parts. After filling the blood, they re-contact andsubsequently close. The cusps are linked to annulus through anorientation that opens into the lumen. The cusps on the wall ofright ventricle compress to allow blood to flow past the annulus.
The left atrium
Theleft atrium obtains oxygenated blood via pulmonary veins. The veinsthen join the left atrium as two veins that come in posteriorly andlaterally. Other smaller venous flows deoxygenated blood get intothe left atrium through the atrial myocardium. It is located at themidline, on the posterior side of the right atrium and the superiorside of the left ventricle. It glides over the coronary sulcus. Ithas the atrial appendage with pectinate walls (Weinhaus &Roberts, 2009). The walls are smooth true to their embryologicalorigin.
The left ventricle
Whenblood gets from the left atrium into the left ventricle, it pumps itto the rest of the body tissues through the aortic artery. The leftventricle forms the vast part of the lateral surface of the heart,including the posterior and anterior surfaces. The walls of the leftventricle also has trabeculae carnaea except that the muscular ridgesinside are finer than those in right ventricle. It has a thickermyocardium than that of the right ventricle (Weinhaus & Roberts,2009). The left ventricle is also barrel-shaped because theinterventricular septum appears bulging into the right ventricle.
The Bicuspid valve
Bloodis pumped to the left ventricle via the atrioventricular orifice. Blood is prevented from flowing back to the left atrium by bicuspidowing to the contraction of the left ventricle. It is made up of twoleaflets: the mural wall and aortic. The mural leaflet has the shapeof a trapezoid
The aortic semilunar valve
Theaortic semilunar valve makes it impossible for blood to flow back tothe left ventricle when it relaxes in diastole. The aortic valve hasthree cusps which contact with each other to prevent blood flow.
Flow Chart for the Heart’s physiological functions
Heads and Arms
Stomach and Intestines
Lower body and legs
A chronic condition that affects the heart
Anexample of a heart condition that affects the physiological functionsof the heart is the coronary heart disease (CHD). CHD occurs when aplaque accumulates in the lumen of the coronary arteries (Cohen&Hasselbring, 2007).Coronary arteries take oxygenated blood tothe cardiac muscle cells. The accumulation of plaque in the coronaryarteries leads to atherosclerosis. The accumulation occurs for a longa time till the plaque reduces the amount of oxygenated blood gettingto the heart. Sometimes, the plaque raptures, forming a clot insidethe coronary artery. The raptured plaque becomes hard over time as aresult of the accumulation of cholesterol on it. The enlargement ofthe raptured plaque and the clot eventually reduce the rumen of theartery, significantly reducing the amount of oxygenated bloodreceived by the right atrium.
Health issues and lifestyles that may cause adverse changes in circulatory system
Someof the health issues and lifestyles that are likely to increase therisk of coronary disease are:
Cigarette smoking- Smoking increases the risk of coronary disease through the chemicals in tobacco. They destroy blood cells along blood vessel linings and also the structure of the heart. The result is an increased risk of atherosclerosis, which is a direct cause of coronary disease.
Stress- People reacting negatively to stress are more likely to suffer ischemia, and their coronary arteries are likely to remain constricted for a longer time than those who stay calm during stress
Being overweight and obese-. Being overweight overworks the heart, raises blood pressure levels, lowers good HDL cholesterol, increases blood cholesterol and triglycerides, and increases the risk of developing diabetes, another risk factor for CHD.
Lack of physical exercises- Avoiding a sedentary lifestyle is one way of reducing cardiovascular disease by bringing down chances of suffering from myocardial infraction. There is sufficient evidence that supports the importance of aerobic physical activity, especially when it is done at modest intensity, in protecting against heart attack. The two substances that cause the formation of plaques in coronary arteries are the low density lipoproteins (LDP-C) and the triglycerides. When a person exercises more frequently, they low the two substances, therefore, reducing the chances of suffering a stroke. Considering that Diabetes is also a risk factor of coronary heart disease, exercises increases the body’s sensitivity to insulin, bringing the down the possibility of diabetes-linked coronary disease. Physical exercises reduce the amount of high density lipoproteins (HDL-C), and also reduce the pressure levels of blood in the arteries. All these factors combined show the exercising is a preventive lifestyle aspect in reducing the risk of CHD.
Preventive measures include lifestyle changes and medicine such as:
Adhering to a healthy diet
Engaging in physical activity
Quitting smoking and voiding second hand smoking
Dealing with stress
Exercising to keep fit and less weight.
Barker,T. A., & Wilson, I. C. (2011).Surgical anatomy of the mitral andtricuspid valve. InMitral valve surgery(pp. 3-19). Springer London.
Bateman,M. G., Russell, C. E., Chan, B. Y., &Iaizzo, P. A. (2010). Adetailed anatomical study of the papillary muscles and chordaetendineae of the left ventricle in perfusion fixed human hearts. TheFASEB Journal,24(1_MeetingAbstracts),446-4.
Cohen,B. M., &Hasselbring, B. (2007). Coronaryheart disease: A guide to diagnosis and treatment.
Weinhaus,A. J., & Roberts, K. P. (2005).Anatomyof the human heart.In Handbook of Cardiac Anatomy, Physiology, and Devices (pp. 51-79).Humana Press.
Weinhaus,A. J., & Roberts, K. P. (2009).Anatomyof the Human Heart.I n Handbook of Cardiac Anatomy, Physiology, and Devices (pp. 59-85).Humana Press.