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Cardiovascular system (Anatomy of the heart (Aorta- transports oxygenated…
Cardiovascular system
Anatomy of the heart
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Atrioventicular node- is located on the floor of the right atrium between the right AV valve and the opening for the coronary sinus
Atrioventricular bundles extends from the AV node and function in transmitting cardiac action potentials through the heart
Coronary sinus- a wide channel that receives blood from the coronary veins and empties into the right atrium of the heart
Bicuspid valve- located between the right atrium and right ventricle. It keeps blood flowing in one direction.
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Fossa ovalis- small oval depression in the right atrium that occupies the spot of the foramen ovale, which holds function during fetal development
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Myocardium- is the thickest of the three heart wall layers. Contraction of cardiac muscle composing the myocardium creates the needed force to pump blood. (Thicker in left ventricle)
Papillary Muscle- anchor thin strands of collagen fibers to the antrioventricular valves. contraction of these muscles prevents inversion of the valves
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Tricuspid valve is located between the right atrium and right ventricle. It keeps blood flowing in one direction
Superior and Inferior Vena Cava - brings deoxygenated blood from the body and drains it into the right atrium
Sinoatrial node- located in the posterior wall of the right atrium. These cells initiate the heartbeat and are also referred to as the pacemaker of the heart
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Purkinhe fibers- carries the contraction impulse from the bundle branches to the myocardium of the ventricles
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The cardiac cycle
- Before atrial contraction: all four chambers are at rest, blood is returned to the right atrium via the vena cava, the AV valves are open and the semilunar valves are closed.
- Atrial contraction is initiated by the stimulation of the cardiac muscle cells of the atrial wall, this is done by the SA node, this moves the blood from the atrium into the ventricles (ventricular filling)
- Atrial contraction ends and ventricular filling is complete
- Ventricular contraction is then initiated by the purkinje fibers causing a pressure increase in the ventricles which forces the AV valves to close.
- As the ventricles continue to contract the pressure exceeds the pressure within the arterial trunks and the semilunar valves open and blood is ejected from the ventricles and into their associated arterial trunk
- The ventricles begin to relax, expand back to resting size and the pressure begins to decrease causing an initial back flow of blood that is stopped when the semilunar valves shut.
- The final phase is distinguished by the continued relaxation and pressure decrease in the ventricles. This decrease in pressure causes the AV valves to open and the cycle starts over!
Electrical Conduction
- The SA node creates an action potential.
- The action potential is fired, and is spread between cardiac muscles cells in the atria and the muscle cells in the atrial wall are excited, resulting in both atria contracting simultaneously.
- The conduction rate is then slowed at the AV node to allow the atria to finish contracting and to complete ventricular filling
- The action potential then travels from the AV node through the AV bundles and to the purkinje fibers
- The action potential has now reached the ventricle and is spread between ventricular cardiac muscle cells allowing for the contraction of the ventricles
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