The heart is a muscular organ that functions as a double pump to control blood flow. Like any other muscle in the human body, it contracts and expands. This pumping of the heart is called the Cardiac Cycle, which occurs about 72 times per minute. The heart is approximately the size of a human fist and it weighs about 300 grams. The heart is located in the chest cavity, between the lungs. ANATOMY The heart is surrounded by a fluid filled sac known as the pericardium. The pericardium is a double layered membrane that surrounds covers the heart.
The space between the two layers of the pericardium is filled with pericardial fluid. Pericardial fluid protects the heart from any kind of shock. There are two layers to the pericardial sac, the outer layer is known as fibrous pericardium and the inner layer is known as serous pericardium. The blood is pumped away from the heart through arteries and returns to the heart through veins. The major artery of the body is called the aorta and the major vein of the body is known as the vena cava. The heart is divided into two halves. The halves are then divided into chambers.
The upper two chambers of the heart are called the atria and the lower two chambers are called ventricles. The right atrium receives blood from the upper and lower body through systemic circulation and the left atrium receives blood from the lungs through pulmonary circulation. The heart wall is divided into three layers, the epicardium, myocardium, and endocardium. The epicardium is the outer protective layer of the heart. The myocardium is the muscular middle layer wall of the heart and the endocardium is the inner layer of the heart that is continuous with the innerl ining of blood vessels. In order to prevent blood from flowing backwards back into the heart, a system of one-way valves are located in the heart.
There two types of heart valves, the atrioventricular and semilunar valves. The atrioventricular valves are located in the middle of the heart between the atria and ventricles and only allow blood to flow from the atria into the ventricles. The atrioventricular valve on the right side of the heart is called the tricuspid valve and the atrioventricular valve on the left side of the heart is called the mitral valve or the bicuspid valve.
The semilunar valves are located between the ventricles and the arteries that carry blood away from the heart. The semilunar valve on the right side of the heart is the pulmonary valve and the semilunar valve on the left side of the heart is the aortic valve. CONDUCTION SYSTEM The heart is a muscle that works continuously. Each beat of a heart is set in motion by an electrical signal from within one’s heart muscle. Each beat of a heart begins with an electrical signal from the sinoatrial node. The sinoatrial node is located in the heart’s right atrium.
When the right atrium is filled with blood, the sinoatrial node sends an electrical signal to the left atria. Then the signal is sent to the left atria and the heart contracts. When the heart contracts, blood is pumped through the valves from the atria to the ventricles. As the electrical signal travels to the ventricles, it arrives at the atrioventricular node. Once here, the ventricles begin to fill up with blood. As the ventricles begin to fill with blood, the signal is released to the signal fibers. These fibers are divided into right and left bundles branches and they run through the hearts septum.
Then the electrical signal leaves the branches through the purkinje fibers, located on the walls of the hearts ventricles. As the signal spreads across the cells of the ventricle walls, the ventricles contract. ( The left ventricle contracts slightly before the right ventricle. ) The contraction of your heart’s right ventricle pushes blood through the pulmonary valve, to the lungs. The left ventricle pushes blood through the aortic valve, to the rest of your body. When the signal passes, the ventricles relax, until the next signal. The electrical activity is recorded using an electrocardiogram.
-4452737713800 Electrocardiogram P wave marks contraction of heart’s atria. 1 / 2 Segment between the P and Q wave shows the ventricles filling up with blood. Q wave marks the signal being transmitted through the signal fibers on the right and left bundle branches that run across the hearts septum. R wave marks contraction of heart’s left ventricle. S wave marks contraction of heart’s right ventricle. T wave marks the point when the ventricles are relaxing. POWERED BY TCPDF (WWW. TCPDF. ORG) g exposed to chemicals and dissection of the sheep and cat heart.