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Cardiovascular System The Heart Heart Facts • The cardiovascular system is composed of the heart and a _________system of vessels through which blood is circulated. • Hollow muscular organ • Tipped slightly so that a part of it sticks out and taps against the ______side of the chest (apex), which is what makes it seem as though it is located there. • During an average lifetime, the human heart will beat more than 2.5 billion times. • Beats over 100,000 times/day and 35 million times/year to pump blood around the body's 60,000 miles of blood vessels. • ____pints of blood pump throughout your entire body with one single heartbeat. External Structure of the Heart • Layers – Edocardium (inner layer) – Epicardium (outer layer) – Myocardium (middle layer) • _________________ - the protective membrane surrounding the heart • ____________arteries – supply blood to the outside of the heart External Structure Internal Structure • • • Atria and ventricles atria contract while the ventricles relax ventricles contract while the atria relax. • ____________________ (AV) Valves • Bicuspid (____________) Valve – between left atria and ventricle • Tricuspid Valve – between right atria and ventricle __________________(SL) Valves • Pulmonary SL Valve – between right ventricle and pulmonary artery • Aortic SL Valve – between left ventricle and aorta • • Ventricular ____________ - right and left ventricles are divided by a thick muscular wall – babies born with "hole in the heart“ – Why problematic? Septum connect papillary muscles to AV valves “heartstrings” The Cardiac Cycle • The events associated with one heartbeat. • A single cardiac cycle lasts ______ seconds • Described as the contraction and relaxation of the four heart chambers. – During relaxation, chambers fill with blood (_________________). – During contraction, chambers expel blood (_________________). Heart Sounds • The first heart sound (______) occurs during ventricular contraction when the tricuspid and bicuspid valves (___valves) close. • The second heart sound (________) occurs during ventricular relaxation when the pulmonary and aortic valves (___ valves) close. •The walls of the left ventricle are ________ as it has to pump blood to all the tissues, compared to the right ventricle which only pumps blood as far as the _____. Septum Blood Pressure • Blood moves through circulatory system from areas of high pressure to low pressure. (Contraction of the heart produces the pressure.) • Blood Pressure is a measurement of the _______ that blood exerts against the inner walls of ______________. • 120/80 is normal = systole/diastole – systolic pressure - The maximum pressure during ventricular contraction; systolic pressure is the peak arterial pressure. – diastolic pressure - The lowest pressure of blood in the arteries during ventricular relaxation (diastole); the arterial pressure drops. Blood Pressure vs. Distance From Left Ventricle Conduction System • Heart muscle cells contract without stimulation from the nervous system in a continuous, rhythmic pattern. • Contraction is initiated by the sinoatrial (SA) node (_______________________). – SA node is located in the right atrium – Cells of the SA node can reach threshold on their own – SA node initiates one action potential after another (~70-80 times/min) • Pathway of electrical impulse – Sinoatrial (SA) node – Atrioventricular (AV) node – Atrioventricular bundle (bundle of His) – Bundle branches – Purkinje fibers Electrocardiograms (ECG / EKG) • A recording of the electrical changes that occur within the myocardium as the heart contracts. R atr cont Electrocardiograms (ECG / EKG) Atria repolarized Ventricle depolarized Heart relaxed AV node and walls depolarize Atrial walls completely depolarized Atria repolarizes Ventricle depolarizes Ventricular walls repolarize