Podcast
Questions and Answers
What contributes to the blood-brain barrier in continuous capillaries within the central nervous system?
What contributes to the blood-brain barrier in continuous capillaries within the central nervous system?
Where are continuous capillaries predominantly found?
Where are continuous capillaries predominantly found?
In which organ are discontinuous (sinusoidal) capillaries commonly found?
In which organ are discontinuous (sinusoidal) capillaries commonly found?
What controls the dilation and constriction of blood vessels?
What controls the dilation and constriction of blood vessels?
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According to Poiseuille's law, what happens to resistance if one vessel has half the radius of another vessel?
According to Poiseuille's law, what happens to resistance if one vessel has half the radius of another vessel?
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Which type of resistance is greater: peripheral or pulmonary resistance?
Which type of resistance is greater: peripheral or pulmonary resistance?
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Which ventricle is responsible for moving blood through the pulmonary circuit at a lower pressure?
Which ventricle is responsible for moving blood through the pulmonary circuit at a lower pressure?
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What is the formula for calculating mean arterial blood pressure?
What is the formula for calculating mean arterial blood pressure?
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According to Pascal's principle, what happens when pressure is applied to an enclosed fluid?
According to Pascal's principle, what happens when pressure is applied to an enclosed fluid?
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What is the effect of total peripheral resistance on blood pressure?
What is the effect of total peripheral resistance on blood pressure?
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Which of the following is NOT a factor affecting blood pressure?
Which of the following is NOT a factor affecting blood pressure?
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Study Notes
Types of Capillaries
- Continuous capillaries are found in muscles, lungs, adipose tissue, and the central nervous system, where adjacent endothelial cells are closely joined together with no intercellular channels.
- The lack of intercellular channels in continuous capillaries contributes to the blood-brain barrier.
- An intercellular cleft is the space between adjacent cells, and a tight junction is where the lipid portions of the membranes of adjacent cells are bound together.
- Fenestrated capillaries are found in the kidneys, endocrine glands, and intestines.
- Discontinuous (sinusoidal) capillaries are found in the bone marrow, liver, and spleen, with a large distance between endothelial cells.
Physical Laws Describing Blood Flow
- Blood flow is directly proportional to the pressure difference (ΔP) between the two ends of the tube and inversely proportional to the frictional resistance to blood flow through the vessels.
- The pressure gradient can be determined mathematically by taking the difference in pressure between two locations and dividing it by the distance between the two locations.
- The resistance to blood flow through a vessel is directly proportional to the length of the vessel and to the viscosity of the blood.
- According to Poiseuille's law, a vessel with half the radius of another will have 16 times the resistance, resulting in 16 times less blood flow.
- The changes in diameter of veins do not contribute to resistance to blood flow.
Blood Vessel Regulation and Blood Pressure
- Dilation and constriction of blood vessels are controlled by the sympathetic nervous system.
- Decreasing the diameter of blood vessels, increasing the length of blood vessels, or increasing the viscosity of blood will increase peripheral resistance.
- Peripheral resistance is greater than pulmonary resistance, resulting in lower blood pressure in the pulmonary arteries than in the aorta.
- The right ventricle does not need to produce as high a pressure as the left ventricle to move blood through the pulmonary circuit.
Cardiac Output and Blood Pressure
- Cardiac output = heart rate X stroke volume = volume flow rate (ml/minute).
- Blood pressure is affected by total peripheral resistance, cardiac output, and blood volume.
- Mean arterial blood pressure = cardiac output X total peripheral resistance.
Pascal's Principle
- Pascal's principle states that a change in pressure applied to an enclosed fluid is transmitted undiminished to all portions of the fluid and to the walls of its container.
- Example: the pressure generated by the left ventricle is transmitted to the brachial artery, causing pulsations.
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Description
Explore the different types of capillaries in cardiovascular physiology, focusing on continuous capillaries. Learn about their structure, locations in the body such as muscles, lungs, adipose tissue, and the central nervous system, and their role in creating barriers like the blood-brain barrier.
