Heart of an Adult
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The adult human heat is about 5 inches long and 3.5 inches wide, weighing less than 1 pound. The importance of a healthy heart is to circulate blood throughout the body. When the heart stops beating, life stops as well. The heart is located in the thoracic cavity. This places the heart between the lungs, behind the sternum, in front of the thoracic vertebrae, and above the diaphragm. Although the heart symmetrically located, its axis of symmetry is not a long the midline.
The heart is a hollow, muscular, double pump that circulates the blood through the blood vessel to all parts of the body. Surrounding the heart is double layers of fibrous tissue call the pericardium. Between these two pericardial layers is a spaced filled with a lubricating fluid called pericardial fluid prevents the two layers from rubbing against each other and creating friction. The cardiac muscle tissue, also known as the myocardium, makes up the major portion of the heart. On the inner lining lies a smooth tissue call the endocardium. The endocardium covers the heart valves and lines the blood vessels providing smooth flowing of blood.
The human heart is separated into right and left halves by the septum. From the right heart, deoxygenated blood flows into the heart from the superior and inferior vena cava to the right atrium to the tricuspid valve to the right ventricle though the pulmonary semilunar valves to the pulmonary artery, which takes the blood to the lungs for oxygen. The left heart, where oxygenated blood flows into the heart from the lungs by the pulmonary veins to the left atrium through the bicuspid valves to the left ventricle to the aorta to the general circulation. So basically the pathway of the blood goes from 1) blood reaches the heart through superior vena cava and interior vena cava 2) then to the right atrium 3) then to the tricuspid valve 4) to the right ventricle 5) to the pulmonary semilunar valve 6) then to the main pulmonary artery 7) then to left pulmonary artery and right pulmonary artery 8) then to the lungs, this is where the blood receives oxygen 9) blood then flows from lungs to pulmonary veins 10) then into the left atrium 11) then into the bicuspid valve 12) then to the left ventricle 13) then to the semilunar veins 14) then to the aorta 15) and then blood with oxygen then goes to all cells of the body.
Each half is divided into two parts, thus creating four chambers. The two upper chambers are called the right atrium and the left atrium. The lower chambers are the right ventricle and the left ventricle.