Layers of the Heart
1.) pericardium - encloses the heart and the proximal ends of the large blood vessels attached to the heart 2.) epicardium - protects the heart by reducing friction - consists of connective tissue beneath epithelium - also contains adipose tissue, which holds arteries and veins 3.) myocadium - thick middle layer that consists of cardiac muscle tissue that helps to pump blood through the heart - muscle tissue is separated by connective tissue which holds capillaries and nerve fibers 4.) endocardium - inner layer that consists of connective and epithelium tissue that contains elastic and collagenous fibers - contains blood vessels and cardiac muscle fibers |
Around 7,000 liters of blood are pumped throughout the body every day. In a lifetime, an individual heart contracts about 2.5 billion times. The heart is a hollow, muscular pump, responsible for the circulation of blood throughout the body. It is located between the lungs, behind the sternum. The ribs serve as the protection to the heart and lungs within the thoracic cavity. The average size of an adult human's heart is 14 centimeters long and 9 centimeters wide. However, this varies depending on the size of an individual's body. Heart Chambers 1.) Right Atrium - receives blood from the superior vena cava and the inferior vena cava - blood is drained into the right atrium from the myocardium of the heart 2.) Left Atrium - receives blood from the lungs through four pulmonary veins, two from each lung 3.) Right Ventricle - pumps blood to lungs against a weakly resisting blood flow 4.) Left Ventricle - forces blood to all other parts of the body against a strongly resisting blood flow |
Heart Valves
1.) Tricuspid valve - prevents blood from moving from right ventricle into right atrium as the ventricles contract 2.) Pulmonary Valve - prevents blood from moving from the pulmonary trunk into the right ventricle as the ventricles relax 3.) Mitral (bicuspid) valve - prevents blood from moving from left ventricle into left atrium as the ventricles contract 4.) Aortic valve - prevents blood from moving from aorta into left ventricle during ventricular relaxation |