Cardiovascular Anatomy
The Heart is made of four chambers, two atria (singular atrium) and two ventricles. When looking at an image of the four chambers of the heart the chambers on the right are referred to as the left atrium and ventricle while the chambers on the left are referred to as the right atrium and ventricle. This is because while inside a persons body the right atrium and right ventricle would correspond with their right side of the body, when looking at these images we are seeing a mirror image.
When looking at blood flow through the body we begin with oxygen-deprived blood entering the right atrium via the superior and inferior vena cavas. The blood then goes through the tricuspid valve, which is an atrioventricular valve, and enters the right ventricle. The right ventricle contracts, pumping the blood through the pulmanary valve, a semilunar valve, and through the pulmonary arteries to the lungs. In the lungs, oxygen diffuses into the blood which then returns to the heart's left atrium by way of the pulmonary veins. Contraction of the left atrium pushes the blood through the bicuspid (mitral) valve, also an atrioventrical valve, and into the left ventricle. The left ventricle is the largest chamber and is required to pump the blood through the semilunar aortic valve into the aorta which disperses the blood throughout the body.
Systemic Circulation is the route in which oxygenated blood is pumped from the left ventrical to all tissues in the body. This is responsible for delivering nutrients to the body cells and removes waste.
Pumonary Circulation brings deoxygenated blood from the right ventricle to the lungs for gas exchange in which the deoxygenated blood becomes oxygenated.
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Blood Vessels
Arteries are the largest blood vessels, followed by veins and then capillaries.
Arteries
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Three Layers, they are thick and elastic- Connective Tissue, a thick muscular layer and an endothelial layer. Strength required to support pressure
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Blood is pumped away from the heart
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Blood contains oxygen (except in the case of the pulmonary artery)
Veins
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Three Layers, they are thinner and less muscular.
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Valves prevent backflow of blood
Capillaries
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Single-celled layer, suitable for gas and nutrient exchange.
The heart walls are made of three layers:
Endocardium- the innermost layer. It is made of epithelial tissue and forms the lining of the entire circulatory system.
Myocardium- the middle layer. This layer is the thickest of the three and is made up of cardiac muscle.
Epicardium- the outer layer. The epicardium is the thin, external membrane.
The Cardiac Cycle
The cardiac cycle is the flow of blood through the heart. Electrical impulses of the heart cause the chambers to contract, forcing the blood through valves in a continuous cycle around the body.
In a regular cardiac cycle the process begins with the two atria simultaneously contracting and the ventricles are relaxed. As the atria relax, the ventricles contract. All four chambers remain relaxed and then the cycle repeats.
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Cardiac Muscle cells are either contractile cells or autorhythmic cells. The majority are contractile.
Examples of autorhythmic cells:
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Sinoatrial (SA), or Sinus, Node
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Atrioventricular (AV) Node
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Atrioventricular (AV) Bundle (occasionally referred to as the bundle of His)
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Right and Left Bundle Branches
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Purkinje Fibers
*Provided by MSN Encarta
**Provided by Eastern Kentucky University