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Questions and Answers
What is the approximate weight of the human heart?
What is the approximate weight of the human heart?
How many times does the human heart beat in a day, on average?
How many times does the human heart beat in a day, on average?
Which system is responsible for the distribution of oxygenated blood to various parts of the body?
Which system is responsible for the distribution of oxygenated blood to various parts of the body?
What is the function of the capillary network in the cardiovascular system?
What is the function of the capillary network in the cardiovascular system?
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Which layer surrounds the heart and contains a sac of fluid?
Which layer surrounds the heart and contains a sac of fluid?
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What is the innermost layer of tissue that lines the chambers of the heart called?
What is the innermost layer of tissue that lines the chambers of the heart called?
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What is the primary function of the endocardium?
What is the primary function of the endocardium?
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Which type of muscle fibers are aligned in a way that allows the chambers of the heart to get smaller upon contraction?
Which type of muscle fibers are aligned in a way that allows the chambers of the heart to get smaller upon contraction?
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What is the basic rate at which action potentials are generated within the heart by autorhythmic cells?
What is the basic rate at which action potentials are generated within the heart by autorhythmic cells?
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Which type of valve has two leaflets instead of three?
Which type of valve has two leaflets instead of three?
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During which phase of the heartbeat does the heart muscle relax and allow the chambers to fill with blood?
During which phase of the heartbeat does the heart muscle relax and allow the chambers to fill with blood?
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From which structure do the left and right coronary arteries arise?
From which structure do the left and right coronary arteries arise?
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What is the approximate volume of plasma blood in an average adult?
What is the approximate volume of plasma blood in an average adult?
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Which type of cells are involved in the defense mechanisms of the body?
Which type of cells are involved in the defense mechanisms of the body?
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What are platelets?
What are platelets?
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Which part of the heart is responsible for the mechanical events of contraction and relaxation?
Which part of the heart is responsible for the mechanical events of contraction and relaxation?
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What is contained in plasma blood besides water?
What is contained in plasma blood besides water?
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Which component of plasma blood is vital for clotting?
Which component of plasma blood is vital for clotting?
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Where do platelets originate from?
Where do platelets originate from?
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Which part of the heart is responsible for the heart valves?
Which part of the heart is responsible for the heart valves?
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What is the main component of plasma blood that is responsible for transporting oxygen and carbon dioxide?
What is the main component of plasma blood that is responsible for transporting oxygen and carbon dioxide?
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Which type of cells are vital for the body's defense mechanisms and can include neutrophils, eosinophils, and lymphocytes?
Which type of cells are vital for the body's defense mechanisms and can include neutrophils, eosinophils, and lymphocytes?
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What is the function of platelets in the blood?
What is the function of platelets in the blood?
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Which part of the heart is primarily responsible for the mechanical events of contraction and relaxation?
Which part of the heart is primarily responsible for the mechanical events of contraction and relaxation?
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What is the approximate volume of plasma blood in an average adult?
What is the approximate volume of plasma blood in an average adult?
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Study Notes
Cardiovascular System (CVS)
- The CVS is a closed system that includes the heart, blood vessels, and blood.
Structure of the Heart
- The heart is a muscle that weighs around 300g and beats around 100,000 times a day, and around 3 billion times in a lifetime.
- It is surrounded by a sac of fluid contained within the pericardium.
- The heart has three layers: the pericardium, the myocardium (heart muscle), and the endocardium (innermost layer).
The Pericardium
- The pericardium is a sac of fluid that surrounds the heart.
The Endocardium
- The endocardium is a very fine layer of squamous epithelium resting on a thin layer of connective tissue.
- It lines the myocardium and valves and provides protection to the valves and heart chambers.
- If damaged, it can lead to thrombus formation.
The Myocardium (Heart Muscle)
- The myocardium is cardiac muscle that is striated like skeletal muscle but has features of smooth muscle.
- Muscle fibers are aligned in a way that when they contract, the chambers get smaller.
- Mitochondria are much larger (10x the size compared to skeletal muscle) and contain about 5000 mitochondria per cell.
- The left ventricle is thicker than the right ventricle.
Action Potential Initiation
- Action potential is initiated within the heart by autorhythmic cells that create minimal contraction.
- These cells spontaneously generate action potentials, acting as either pacemaker cells or conducting fibers.
- The basic rate is 80-100 bpm, but it can be reduced to 60-80 bpm by parasympathetic nervous system.
Valves
- Valves have three leaflets except the bicuspid, which has two leaflets.
- Atrioventricular valves are located between the chordae tendinae and papillary muscles.
- Semilunar valves are located in the aorta and pulmonary artery.
Action of Valves
- Atrioventricular valve action: chordae tendinae prevent valve cusps from billowing into the atria.
- Semilunar valve action: cusps are up during systole, and down during diastole.
Heart Muscle Contraction Mechanisms
- The heart muscle contraction mechanism has two phases: diastole and systole.
- Diastole is the phase when the heart muscle relaxes and allows the chambers to fill with blood.
- Systole is the phase when the heart muscle contracts and pumps blood from the chambers into the arteries.
Mechanical Events
- Diastole comprises three phases: isovolumetric ventricular relaxation, ventricular filling, and ventricular filling with atrial contraction.
- Systole comprises two phases: isovolumetric ventricular contraction and ventricular contraction with atrial relaxation.
The Coronary Circulation
- The coronary circulation is the heart's blood supply.
- It includes the left and right coronary arteries, which arise from the aortic sinus above the aortic semilunar valve.
- Coronary sinus is the cardiac vein that returns blood to the right atrium.
Vasculature
- Arteries/arterioles carry blood away from the heart.
- Veins/venules carry blood to the heart.
- Capillaries are the site of exchange of gases and nutrients with the tissues.
Arterial System
- Arteries contain large amounts of elastic and fibrous tissue.
- As arteries become smaller, the amount of elastic tissue decreases, and smooth muscle increases.
- The arterial system behaves as a pressure reservoir when stretched, and the elastic forces are stored until diastole.
Capillaries
- Capillaries are the smallest and thinnest-walled vessels (5-10 micrometers in diameter and 0.5 micrometers in wall thickness).
- They are the primary site for material exchange.
Venous System
- Veins serve as a volume reservoir for the ventricles of the heart.
- Walls are thinner than arterioles, with very little smooth muscle.
- Valves are present in peripheral veins but not in central veins.
Valves in Veins
- Valves serve to prevent blood from going backwards.
- They are assisted by the surrounding muscles acting as a pump.
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Description
Test your knowledge of the structure and function of the cardiovascular system with this quiz. Topics include the structure of the heart, the structure and function of blood vessels, and the mechanism of heart muscle contraction.
