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The Structure and Functioning’s of the Human Heart
By Shil Patel and Daivik Gandhi
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Contents
• Basic facts• Layers• Vessels• Chambers• Cardiac Cycle• Cardiac Muscle Cells• Electrical Impulses• Calcium ions for contraction
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Basic Facts
• Size of a fist.• Roughly between 250 to 350 grams.• Slightly left of the middle of the Chest.• Anterior to the Vertebral Column.• Posterior to the Sternum.• Enclosed in the Pericardium.• The Pericardium is a double walled sac which
protects the Heart.
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Layers
• 3 main layers of the Heart.• Epicardium – the inner wall of the Pericardium, made
up of connective tissues and produces Pericardium Fluid for lubrication.
• Myocardium – which is the layer of cardiac muscle, which causes the contractions. Muscle cells contain filaments of proteins, mainly actin and myosin.
• Endocardium – it is the inside layer and it is biologically and embryologic ally very similar to endothelial cells.
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Vessels
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Chambers
• 4 Chambers of the Heart. • Two Superior Atria. • Two Inferior Ventricles.• The right hand side of the Heart has a thicker
Myocardium because it needs to pump blood at a higher pressure.
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The Cardiac Cycle
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Cardiac Cycle
• Atrial Systole – Atria contract and the blood flows into the Ventricles. The Semi-Lunar valves are closed.
• Ventricular Systole – Ventricles contract and the blood is forced into the Pulmonary Artery and Aorta. The Atrioventricular Valves are forced shut.
• Diastole – resting phase, all chambers are relaxed and the blood is filling in the Atria.
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Cardiac Cycle
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Cardiac Muscle Cells
• Found on the walls of the heart.• It is resistant to fatigue.• Coronary arteries refresh and supply oxygen
to the cells.
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Electrical Impulses
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Electrical Impulse (II)
• The Cardiac muscles need to be able to depolarise without using the nervous system as a source.
• The depolarisation must be very quick!
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Calcium ions for Contraction
• During a contraction, many cross-bridges are continuously made and broken causing them to slide past thick filaments and so shorten the sarcomere.
• Tropomyosin (a rod shaped protein) subunits cover myosin head groups on actin fibres.
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