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Questions and Answers
All blood vessels have the same structure.
All blood vessels have the same structure.
False
What is the hollow space within blood vessels where blood flows?
What is the hollow space within blood vessels where blood flows?
Lumen
Which of the following is NOT a characteristic of arteries and arterioles?
Which of the following is NOT a characteristic of arteries and arterioles?
Which of the following layers of the blood vessel wall is responsible for maintaining the shape and structure of the vessel?
Which of the following layers of the blood vessel wall is responsible for maintaining the shape and structure of the vessel?
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Which type of artery contains a higher percentage of elastic fibers?
Which type of artery contains a higher percentage of elastic fibers?
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Arterioles are the site of greatest resistance to blood flow.
Arterioles are the site of greatest resistance to blood flow.
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Which of the following is NOT a type of capillary?
Which of the following is NOT a type of capillary?
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What is the function of metarterioles in the circulatory system?
What is the function of metarterioles in the circulatory system?
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Venules are very small veins that merge to form larger veins.
Venules are very small veins that merge to form larger veins.
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What mechanism helps to ensure one-way blood flow in veins?
What mechanism helps to ensure one-way blood flow in veins?
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What is the typical pattern of blood flow through the circulatory system?
What is the typical pattern of blood flow through the circulatory system?
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A venous anastomosis is a connection between two or more veins.
A venous anastomosis is a connection between two or more veins.
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The portal system is an important structure for connecting two capillary beds located in the same organ.
The portal system is an important structure for connecting two capillary beds located in the same organ.
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What is the main factor that influences the rate of blood flow?
What is the main factor that influences the rate of blood flow?
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If the resistance to blood flow increases, how does the body compensate to maintain flow?
If the resistance to blood flow increases, how does the body compensate to maintain flow?
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Blood pressure drives blood flow in the human body.
Blood pressure drives blood flow in the human body.
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What instrument is used to measure arterial blood pressure?
What instrument is used to measure arterial blood pressure?
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Which of the following is NOT a factor that contributes to blood flow resistance?
Which of the following is NOT a factor that contributes to blood flow resistance?
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Increased cardiac output leads to a decreased pressure gradient and flow rate.
Increased cardiac output leads to a decreased pressure gradient and flow rate.
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A lower blood volume, known as hypovolemia, can decrease the pressure gradient and flow rate.
A lower blood volume, known as hypovolemia, can decrease the pressure gradient and flow rate.
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What equation relates blood flow resistance to other factors?
What equation relates blood flow resistance to other factors?
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What is the effect of increased blood vessel length on resistance?
What is the effect of increased blood vessel length on resistance?
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Blood viscosity is inversely proportional to resistance.
Blood viscosity is inversely proportional to resistance.
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What is the most significant factor influencing resistance to blood flow?
What is the most significant factor influencing resistance to blood flow?
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A vessel with higher compliance has lower resistance to blood flow.
A vessel with higher compliance has lower resistance to blood flow.
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What is the correlation between obesity and higher blood pressure?
What is the correlation between obesity and higher blood pressure?
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Where are the baroreceptors located?
Where are the baroreceptors located?
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When blood pressure is too high, the parasympathetic nervous system is activated to decrease heart rate and cause vasodilation.
When blood pressure is too high, the parasympathetic nervous system is activated to decrease heart rate and cause vasodilation.
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What is the primary function of chemoreceptors in the circulatory system?
What is the primary function of chemoreceptors in the circulatory system?
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Low oxygen levels, high carbon dioxide levels, and low pH levels in the blood can trigger an increase in blood pressure.
Low oxygen levels, high carbon dioxide levels, and low pH levels in the blood can trigger an increase in blood pressure.
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Which of the following hormones is known to decrease blood pressure?
Which of the following hormones is known to decrease blood pressure?
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Most control pathways of the nervous and endocrine systems strive to decrease blood pressure.
Most control pathways of the nervous and endocrine systems strive to decrease blood pressure.
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What is autoregulation in the circulatory system?
What is autoregulation in the circulatory system?
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Which of the following does NOT contribute to vasodilation?
Which of the following does NOT contribute to vasodilation?
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The myogenic mechanism is a local response of smooth muscle in arteriole walls that helps to regulate blood flow.
The myogenic mechanism is a local response of smooth muscle in arteriole walls that helps to regulate blood flow.
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The systemic circuit delivers oxygenated blood and nutrients to the tissues of the body.
The systemic circuit delivers oxygenated blood and nutrients to the tissues of the body.
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What structure divides to form the pulmonary arteries?
What structure divides to form the pulmonary arteries?
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The pulmonary veins carry deoxygenated blood from the lungs to the heart.
The pulmonary veins carry deoxygenated blood from the lungs to the heart.
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What is the largest artery in the body?
What is the largest artery in the body?
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The brachiocephalic trunk is a branch of the ascending aorta that supplies blood to the head, neck and upper limbs.
The brachiocephalic trunk is a branch of the ascending aorta that supplies blood to the head, neck and upper limbs.
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What is the name of the arterial circle that provides collateral circulation to the brain, protecting it from ischemic events?
What is the name of the arterial circle that provides collateral circulation to the brain, protecting it from ischemic events?
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The common carotid arteries branch to form the internal carotid artery and the external carotid artery.
The common carotid arteries branch to form the internal carotid artery and the external carotid artery.
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The celiac trunk, which branches from the abdominal aorta, supplies blood to the stomach, spleen, and liver.
The celiac trunk, which branches from the abdominal aorta, supplies blood to the stomach, spleen, and liver.
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Femoral, deep femoral, and popliteal arteries all supply blood to the lower limbs.
Femoral, deep femoral, and popliteal arteries all supply blood to the lower limbs.
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Venous blood is returned to the right atrium of the heart.
Venous blood is returned to the right atrium of the heart.
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The superior vena cava drains venous blood from the body above the diaphragm.
The superior vena cava drains venous blood from the body above the diaphragm.
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What are the veins called that drain blood from the thorax?
What are the veins called that drain blood from the thorax?
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The internal jugular veins drain blood from the brain and face.
The internal jugular veins drain blood from the brain and face.
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The primary method of capillary exchange is diffusion.
The primary method of capillary exchange is diffusion.
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Bulk flow refers to the movement of fluids through an endothelial cell via endocytosis and exocytosis.
Bulk flow refers to the movement of fluids through an endothelial cell via endocytosis and exocytosis.
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Blood hydrostatic pressure promotes filtration, while blood colloid osmotic pressure promotes reabsorption in capillary beds.
Blood hydrostatic pressure promotes filtration, while blood colloid osmotic pressure promotes reabsorption in capillary beds.
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Lymphatic capillaries help to prevent edema by absorbing excess interstitial fluid.
Lymphatic capillaries help to prevent edema by absorbing excess interstitial fluid.
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Cardiovascular centers located in the brain regulate blood pressure, distribution, and flow.
Cardiovascular centers located in the brain regulate blood pressure, distribution, and flow.
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Which part of the brain houses the cardiovascular centers?
Which part of the brain houses the cardiovascular centers?
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Cardioinhibitory centers are responsible for increasing heart rate and stroke volume.
Cardioinhibitory centers are responsible for increasing heart rate and stroke volume.
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Vasomotor centers control vascular tone by regulating vasoconstriction and vasodilation.
Vasomotor centers control vascular tone by regulating vasoconstriction and vasodilation.
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The sympathetic nervous system activates cardioacceleratory centers, while the parasympathetic nervous system activates cardioinhibitory centers.
The sympathetic nervous system activates cardioacceleratory centers, while the parasympathetic nervous system activates cardioinhibitory centers.
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Study Notes
Blood Vessel Overview
- Blood flows through the body via bulk flow through blood vessels
- Flow is proportional to the pressure gradient, needing to overcome resistance
- Arteries carry blood away from the heart, branching into arterioles
- Capillaries are the sites of exchange with tissues, primarily via diffusion
- Venules and veins carry blood back toward the heart
Blood Vessel Histology
- Blood vessels share general characteristics, varying slightly in structure
- Lumen is the hollow space blood flows through
- Arteries and arterioles have a thicker wall than veins and venules, for withstanding high pressure
- Veins and venules have thinner walls and larger lumens
Blood Vessel Anatomy
- Blood vessel walls are composed of tunics
- Tunica intima (interna) is the innermost layer, including endothelium and basement membrane
- Tunica media is the middle layer, largely composed of smooth muscle
- Tunica externa is the outermost layer, mainly collagen and elastic fibers
Arteries
- Elastic arteries have a high percentage of elastic fibers, helping propel blood during ventricular diastole
- Muscular arteries have a higher percentage of smooth muscle, controlling blood distribution
- Arterioles are microscopic arteries leading to capillaries
- All three tunics are very thin in arterioles
- Arterioles are the main point of resistance, controlling blood flow through capillaries
Capillaries
- Thin-walled vessels enabling exchange of substances with tissues
- Three types exist: continuous, fenestrated, and sinusoidal capillaries, each with varying degrees of permeability
- Continuous capillaries have a complete lining, suited for smaller molecules
- Fenestrated capillaries have pores, allowing for greater exchange of fluid and larger molecules
- Sinusoidal capillaries have large gaps, allowing for the exchange of plasma proteins
Metarterioles and Capillary Beds
- Metarterioles regulate blood flow into capillary beds using precapillary sphincters
- Sphincters contract or relax to control flow through capillaries
Venules
- Extremely small veins that merge to form veins
- Walls consist of endothelium and few smooth muscle bands.
Veins
- Carry blood toward the heart
- Thinner walls than arteries, with larger lumens, and low pressure
- Veins contain valves to prevent backflow
Blood Flow and Pressure
- Blood flow is the movement of blood through the body, influenced by pressure gradients and opposed by resistance
- Blood pressure is necessary to overcome the resistance to maintain blood flow
- Blood pressure is measured via a sphygmomanometer, recorded as a ratio of systolic and diastolic pressures
- Pulse pressure is the difference between systolic and diastolic pressures
- Mean arterial pressure (MAP) is the average pressure over a cardiac cycle
Variables Affecting Blood Flow and Pressure
- Cardiac output, blood volume, and vessel compliance influence pressure gradient
- Blood vessel length, viscosity, and radius affect resistance
- Compliance is a vessel's ability to expand; higher compliance reduces resistance
- Blood velocity is inversely related to cross-sectional area of vessels. Capillaries have the largest cross-sectional area, leading to slowest blood velocity.
Blood Flow Circuits
- Systemic circuit delivers oxygenated blood to tissues and nutrients, returning deoxygenated blood
- Pulmonary circuit sends deoxygenated blood to lungs for gas exchange, returning oxygenated blood
Vascular Pathways
- Arterial anastomoses are multiple arteries supplying a common capillary bed, offering alternate routes
- Venous anastomoses occur where multiple veins drain into a common vein
- Portal systems link two capillary beds between an artery and vein
Regulation of Blood Flow
- Neural Regulation - The cardiovascular centers in the brain regulate blood pressure, distribution, and flow via the cardioaccelerator and cardioinhibitory centers, and vasomotor centers
- Chemical signals in tissues mediate local changes to blood flow
- Endocrine regulation - Hormones like epinephrine increase blood pressure via increased cardiac output & vasoconstriction
- Chemoreceptors and baroreceptors communicate with control centers to maintain blood flow and pressures
- Autoregulation permits local adjustments in blood flow by opening or closing precapillary sphincters
Capillary Exchange
- Diffusion, the most common method for exchange, occurs with molecules moving from areas of high to low concentration.
- Transcytosis involves substances crossing endothelial cells, frequently via endocytosis and exocytosis
- Bulk flow is the movement of fluid between blood and tissues, driven by hydrostatic and osmotic pressures.
- Hydrostatic pressure pushes fluid out, while osmotic pressure draws fluid in.
- Net filtration occurs when filtration exceeds reabsorption
Lymphatic Capillaries
- Excess interstitial fluid is absorbed and returned to the bloodstream by lymphatic capillaries to eliminate edema
Other details
- Blood flow through a vessel is affected by its radius, which has more influence on resistance than vessel length or blood viscosity. The walls of arteries and veins have three layers: tunica intima, media, and externa.
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