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Questions and Answers
What is the largest artery in the body?
What is the largest artery in the body?
In which vessel does the blood become deoxygenated?
In which vessel does the blood become deoxygenated?
What is the purpose of checking blood pressure at different points in the system?
What is the purpose of checking blood pressure at different points in the system?
What is the name of the large vein that collects deoxygenated blood?
What is the name of the large vein that collects deoxygenated blood?
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Where does the blood flow after leaving the capillary bed?
Where does the blood flow after leaving the capillary bed?
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What is the name of the artery that branches off from the aorta?
What is the name of the artery that branches off from the aorta?
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What happens to the blood as it passes through the capillary bed?
What happens to the blood as it passes through the capillary bed?
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How many vena cavas are there in the body?
How many vena cavas are there in the body?
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What is the average pressure in the aorta?
What is the average pressure in the aorta?
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What is the unit of pressure being referred to in the passage?
What is the unit of pressure being referred to in the passage?
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What is the equation that relates pressure, flow, and resistance?
What is the equation that relates pressure, flow, and resistance?
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What does the symbol ΔP represent in the equation?
What does the symbol ΔP represent in the equation?
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What is the term for the volume of blood flowing in a minute?
What is the term for the volume of blood flowing in a minute?
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What is the relationship between radius and resistance in vessels?
What is the relationship between radius and resistance in vessels?
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What is the term for the pressure at the beginning of a tube?
What is the term for the pressure at the beginning of a tube?
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What is the heart rate multiplied by in the equation for blood flow?
What is the heart rate multiplied by in the equation for blood flow?
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What is the pressure in the arteriole?
What is the pressure in the arteriole?
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What is the stroke volume for a 70 kilogram person?
What is the stroke volume for a 70 kilogram person?
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What is the total body resistance being referred to in the passage?
What is the total body resistance being referred to in the passage?
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What is the blood flow rate in liters per minute for the person in the example?
What is the blood flow rate in liters per minute for the person in the example?
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What is the relationship between resistance and radius in blood vessels?
What is the relationship between resistance and radius in blood vessels?
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What is the unknown variable being solved for in the equation?
What is the unknown variable being solved for in the equation?
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What is the pressure difference across the system?
What is the pressure difference across the system?
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What is the units of the total body resistance?
What is the units of the total body resistance?
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What is the purpose of the equation in this context?
What is the purpose of the equation in this context?
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What is the importance of knowing the weight of the person?
What is the importance of knowing the weight of the person?
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What is the flow rate of blood in the equation?
What is the flow rate of blood in the equation?
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What is the system being described in the example?
What is the system being described in the example?
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Study Notes
Blood Flow and Pressure
- The blood flow system starts with the heart and the largest artery, the aorta, which branches into smaller arteries, such as the brachial artery, and eventually reaches the capillary bed.
- The blood then flows from the capillary bed into venules and veins, collecting into a large vein called the vena cava.
Blood Pressure
- Blood pressure can be represented as a number, measured in millimeters of mercury (mmHg).
- The average pressure in the aorta is around 95 mmHg.
- The pressure falls dramatically as it flows through the system, reaching around 5 mmHg at the end.
Pressure at Different Points
- The pressure at the beginning of the system (aorta) is around 95 mmHg.
- The pressure at the brachial artery is around 90 mmHg.
- The pressure falls to around 80 mmHg as it enters the arteriole.
- The pressure drops dramatically to around 30 mmHg as it enters the capillary bed.
- The pressure is around 20 mmHg in the venule and 10 mmHg in the vein.
Resistance
- The total body resistance is the key question to be answered.
- The equation to solve for total body resistance is: ΔP = Q × R, where ΔP is the change in pressure, Q is the flow (blood flow), and R is the resistance.
- The flow (Q) can be calculated by knowing the stroke volume and heart rate.
- For a 70 kg person, the stroke volume is around 70 mL, and with a heart rate of 70 beats per minute, the flow is around 5 liters per minute.
- The resistance (R) is proportional to 1/R⁴, where R is the radius of the vessel.
Solving for Total Body Resistance
- Given the system, with the heart pumping blood into the aorta, the pressure at the beginning (95 mmHg) and end (5 mmHg), and the flow (5 liters per minute), the total body resistance can be calculated.
- The calculation yields a value of 18 mmHg·min/L for the total body resistance.
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Description
Learn about blood pressure, resistance, and flow as we explore the circulatory system, starting with the heart, aorta, and brachial artery.