Heart Structure PDF

HEART STRUCTURE The heart is a strong muscular organ divided into the left and right side by a wall called the septum. It also has four “chambers” – two atria and two ventricles: The atria receive blood from veins and pump it to the ventricles Ventricles receive blood from the atria and pump...

HEART STRUCTURE The heart is a strong muscular organ divided into the left and right side by a wall called the septum. It also has four “chambers” – two atria and two ventricles: The atria receive blood from veins and pump it to the ventricles Ventricles receive blood from the atria and pump it to body tissues. The blood has further to travel from the ventricles so they are more muscular than the atria Valves in the heart prevent backflow of blood The coronary arteries lie on top of the heart and supply blood directly to the heart Tissues of The Heart Endocardium – epithelial tissue that lines the inside chambers. It has a smooth surface to allow for easy flow with little friction Myocardium – muscular walls of the heart that contract to move blood Nervous tissue – will increase/decrease heart rate Connective tissue – the outer layer of the heart that keeps it contained The Flow of Blood Through the Heart Every minute, 5 L of blood travels from the heart to the lungs, picks up oxygen and returns to the heart. The heart then pumps this oxygenated blood, along with nutrients, to the tissues of the body. This creates two circuits: Pulmonary Circuit The right side of the heart pumps blood into the lungs, then the left side of the heart (low pressure) Systemic Circuit The left side of the heart pumps oxygenated blood to the body (high pressure) How it Works The right atrium receives deoxygenated blood from the head and body via the superior and inferior vena cava Contraction of the right atrium forces the blood through the tricuspid valve into the right ventricle The ventricle contracts, forcing deoxygenated blood into the lungs (through the pulmonary artery past the pulmonary valve)  As this occurs, the left atrium receives oxygenated blood from the lungs The atrium contracts and pushes the blood through the bicuspid/mitral valve into the left ventricle. The left ventricle contracts and pushes the blood with a large amount of force into the aorta past the aortic valve to the head and body The heartbeat is a result of the coordinated contractions of the heart muscles. The rhythm is maintained by the sinoatrial node on the right atrium. This results in the continuous cycle of relaxation and contraction: Diastole – relaxation stage The valves are open and blood flows into the four chambers Lasts for about 0.4 seconds Ends with the contraction of atria Systole – contraction stage The ventricles contract and force blood out Lasts for about 0.3 seconds Valves are closed so blood does not flow back into atria The familiar “lub-dub” sound of the heart is a result of the cardiac cycle: Lub = state of systole in which the contractions cause the tricuspid and bicuspid/mitral valve to close Dub = at the end of systole, when the pulmonary valve and aortic valve fall back into place HEART STRUCTURE The heart is a strong muscular organ divided into the left and right side by a wall called the septum. It also has four “chambers” – two atria and two ventricles: The atria receive blood from __________ and pump it to the _____________ ___________ receive blood from the atria and pump it to body tissues. The blood has farther to travel from the ventricles so they are more ________________ than the atria _________ in the heart prevent backflow of blood The ___________________lie on top of the heart and supply blood directly to the heart Tissues of The Heart Endocardium – epithelial tissue that lines the ______________ chambers. It has a smooth surface to allow for easy flow with little friction Myocardium – _____________walls of the heart that contract to move blood Nervous tissue – will increase/decrease ___________________ Connective tissue – the ___________layer of the heart that keeps it ________________ The Flow of Blood Through the Heart Every minute, 5 L of blood travels from the heart to the lungs, picks up oxygen and returns to the heart. The heart then pumps this oxygenated blood, along with nutrients, to the tissues of the body. This creates two circuits: Pulmonary Circuit ____________________________________________ Systemic Circuit ____________________________________________ How it Works The right atrium receives ______________ blood from the head and body via the ______________ and _______________ vena cava Contraction of the right atrium forces the blood through the ______________ valve into the ________________ The ventricle contracts, forcing ______________ blood into the lungs (through the ________________ artery past the _________________ valve)  As this occurs, the left atrium receives _______________ blood from the lungs The atrium contracts and pushes the blood through the _________________ valve into the left ____________. The _______ ventricle contracts and pushes the blood with a large amount of force into the ____________ past the ______________ valve to the _________ and ______ The heart beat is a result of the coordinated contractions of the heart muscles. The rhythm is maintained by the sinoatrial node on the right atrium. This results in the continuous cycle of relaxation and contraction: Diastole – relaxation stage The valves are open and blood flows into the four chambers Lasts for about 0.4 seconds Ends with the contraction of atria Systole – contraction stage The ventricles contract and force blood out Lasts for about 0.3 seconds Valves are closed so blood does not flow back into atria The familiar “lub-dub” sound of the heart is a result of the cardiac cycle: Lub = state of systole in which the contractions cause the tricuspid and bicuspid/mitral valve to close Dub = at the end of systole, when the pulmonary valve and aortic valve fall back into place