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Key Terms - Heart

Key terms ofor the heart on page 344.
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Pericardium
encloses the heart and the proximal ends of the large blood vessels to which it attaches.
Epicardium
the visceral pericardium, protects the heart by reducing friction.
Myocardium
the thick middle layer which consists mostly of cardiac muscle tissue that pumps blood out of the heart chambers.
Endocardium
the inner layer which consists of epithelium and connective tissue that contains many elastic and collagenous fibers.
Atria
upper chambers whihch have thin walls and recieve blood returning to the heart.
Ventricles
the lower chambers which recieve blood from the atriaand contract to force blood out of the heart into the arteries.
Tricuspid Valve
a large valve with three cusps which lies between the right atrium and the right ventricle.
Papillary Muscles
small mounds of cardiac muscle tissue.
Pulmonary Valve
a valve with three cusps.
Bicuspid Valve
a valve through which blood passes from the left atrium into the left ventricle.
Aorta
the exit of the heart and a large artery.
Aortic Valve
the base of the aorta which has three cusps
Coronary Arteries
the first two branches of the aorta
Cardiac Veins
veins of the heart whose paths roughly arallel to those of the coronary arteries which drain blood that has passed through myocardial capillaries
Coronary Sinus
an enlarged vein on the hearts posterior surface which empties into the right atrium
Cardiac Cycle
the actions which take place in the heart in a cycle
Functional Syncytium
a mass of merging cells that funtion as a unit
Cardiac Conduction
clumps and strands of specialized cardiac muscle tissue whose fibers contain only a few fibrils.
Sinoatrial Node
a key portion of the cardiac conduction which is a small elongated mass of specialized cardiac muscle tissue just beneath the epeicardium
pacemaker
a machine used to generate the heart's rhythmic contractions
Atrioventricular Node
a mass of specialized cardiac muscle tissue
Electrocardiogram
a recording of the electrical changes in the myocardium during a cardiac cycle
Arteriole
thinner tubes within the arteries
Vasoconstriction
the reuction of the diameter of the blood vessel
Capillary
the smallest diameter blood vessels
Venule
microscopic vessels that continue from the capillaries and merge to form veins
Systole
contracting ventricles which squeeze blood out and into the pulmonary trunk and aorta
Disatole
the arterial pressure drops
Cardiac Output
the volume discharged from the left ventricle per minute
Pulmonary Circut
consists of vessels that carry blood from the heart to the lungs and back to the heart
Systemic Circut
carries blood from the heart to all other parts of the body and back again.