The heart is a muscular organ located slightly left behind the breastbone and acts as the body’s circulatory pump. The heart pumps blood from the body, delivers it to the lungs before pumping it back to the body and help transport oxygen and various nutrients all over the body. The heart sits in the pericardial cavity which is filled with fluid. The walls of this cavity have a membrane lining called the pericardium which secretes a serous fluid that lubricates the heart and prevents friction when the heart is pumping. The pericardium also holds the heart in position and maintains a hollow space for the heart to expand when it is full. The pericardium has two layers which are the visceral layer that covers the outside of the heart and the parietal layer which forms a sac the outside of the pericardial cavity. The wall of the heart has three layers which are epicardium, myocardium, and endocardium layers. The epicardium is also known as the pericardium and protects the heart while lubricating it. Below this is the thicker myocardium layer which is responsible for helping the heart pump blood. Endocardium follows which is thin lining in the heart and helps the blood flow smoothly preventing it from clotting in the heart which might be fatal. The thickness of this wall varies with the different parts of the heart where the part that pumps blood to distant places in the body has a thicker myocardium while the one that pumps around ventricle near has a thinner myocardium. The heart has four chambers; right atrium, left atrium, right ventricle and left ventricle. The atria are small due to their function which is to receive blood from the body through a connection with veins and send it to the heart while ventricles are large since they have thick myocardium which allows them to pump blood from the heart to other parts of the body through a connection with arteries. The right side of the heart is always smaller than the left side due to their function. The right side pumps blood to the nearby organs while the left side pumps blood to all other parts of the body, hence the difference in the size of the myocardium. The heart has two kinds of valves; an atrioventricular valve located between atria and ventricles and allows blood to flow from atria to ventricles and semilunar valves located between ventricles and arteries. The valves function as doors that allow one-way passage of the blood and are well adapted to prevent backflow of blood (Taylor).
The heart operates in two states which are the systole and the diastole. Systole is the state in which cardiac muscles contracts in order to push blood out of the chamber. Diastole is the state in which cardiac muscles relax to allow chambers of the heart fill with blood. The cardiac cycle is all the things that happen during the heartbeat. The cycle has three phases which include, the atrial systole, ventricular systole, and the relaxation. Atrial phase is when atria contract and push blood into the ventricles. The atrioventricular valves stay open to allow entry of blood while semilunar valves remain closed to prevent blood from getting back to the heart. Because the atria are small, they only fill 25% of the ventricles. The ventricle at this phase is in diastole state. The next step is ventricular systole where the ventricles contract pushing the blood to the aorta and pulmonary trunk. The pressure felt here forces the semilunar valve to open forcing the atrioventricular to close and allows blood to flow to the arteries. The cardiac muscles of the arterial side automatically go to diastole state in this phase. The next step is the relaxation phase where all chambers of the heart are in relaxation state to allow blood flow into the heart from the veins. During this phase the ventricles fill up to 75% and the next 25% will only fill after the atria enter the systole phase. The atrioventricular valves open while the semilunar valves close to prevent backflow of blood from the arteries. Blood flows from the body to the heart through vena cava and enters the atrium. From here it is pumped through the tricuspid valve into the right ventricle. It is then pumped through pulmonary semilunar valve to the pulmonary trunk where it is taken to the lungs to release carbon dioxide and absorb oxygen. The blood then through pulmonary vein goes back to the heart to the left atrium which the contracts to push blood through bicuspid to the left ventricle. The blood is then pumped through the aorta semilunar valve to the aorta where the blood proceeds to circulate throughout the body and then returns to the heart through the vena cava and the cycle starts again (Taylor).
Rheumatic heart disease
Rheumatic heart disease is a condition that happens after one is infected with rheumatic fever. Rheumatic heart disease affects the mitral valve and the aortic valve causing them to leak or become narrow over time. The affected heart's valves might not be able to close properly and result to leak and in the long run low blood supply. The symptoms of this disease usually manifest themselves after an extended period of between 10 to 20 years. To prevent the disease from happening proper treatment of rheumatic fever is required. Signs and symptoms of rheumatic fever include fever, weight loss, rash, fatigue, joint swelling, small bumps under the skin, stomach pain, and redness over many joints. Rheumatic fever mostly affects children at the age of between 5 to 10 years but can also affect people of any age ("Rheumatic Heart Disease | Seattle Children’s Hospital").
Taylor, Tim. "Heart". InnerBody. N.p., 2016. Web. 16 July 2016.
"Rheumatic Heart Disease | Seattle Children’s Hospital". Seattlechildrens.org. N.p., 2016. Web.
16 July 2016.