Blood Vessels: Structure and Function
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Questions and Answers

Which blood vessel type carries blood away from the heart?

  • Arterioles (correct)
  • Veins
  • Capillaries
  • Venules

    • Capillaries have thick walls to facilitate efficient exchange of materials.

    False

    What are the three layers of blood vessels called?

    tunics

    The large elastic arteries serve as a pressure ___________ during ventricular diastole.

    <p>reservoir</p> Signup and view all the answers

    Match the following blood vessel types with their functions:

    <p>Arteries = Carry blood away from the heart Capillaries = Facilitate exchange between blood and tissues Veins = Return blood to the heart Venules = Merge into larger veins</p> Signup and view all the answers

    What is the primary component of the tunica externa?

    <p>Collagen</p> Signup and view all the answers

    Vasodilation is the increase in lumen diameter due to the contraction of smooth muscle fibers.

    <p>False</p> Signup and view all the answers

    What type of blood vessel merges into venules?

    <p>capillaries</p> Signup and view all the answers

    The __________ anchoring endothelium to underlying tissues provides tensile strength.

    <p>basement membrane</p> Signup and view all the answers

    What is the main function of arterioles?

    <p>Regulate blood flow to tissues</p> Signup and view all the answers

    What is the primary function of capillaries?

    <p>Nutrient exchange with tissues</p> Signup and view all the answers

    Muscular arteries have a thicker layer of smooth muscle compared to elastic arteries.

    <p>True</p> Signup and view all the answers

    What are the small blood vessels called that regulate blood flow into capillaries?

    <p>arterioles</p> Signup and view all the answers

    Block to circulation through end arteries can lead to tissue death or _______.

    <p>necrosis</p> Signup and view all the answers

    Match the types of capillaries to their characteristics:

    <p>Continuous capillaries = Smooth endothelial structure Fenestrated capillaries = Have pores for increased permeability Sinusoids = Twisted with large openings</p> Signup and view all the answers

    Which type of arteries are known as distributing arteries?

    <p>Muscular arteries</p> Signup and view all the answers

    Veins contain valves to prevent backflow of blood.

    <p>True</p> Signup and view all the answers

    What is the name of the points where multiple blood vessels join together?

    <p>anastomoses</p> Signup and view all the answers

    The diameter of an erythrocyte is _______ μm.

    <p>8</p> Signup and view all the answers

    What regulates the vessel diameter of arterioles?

    <p>Nerves in the tunica externa</p> Signup and view all the answers

    Capillaries have tunica externa and tunica media layers.

    <p>False</p> Signup and view all the answers

    What term describes blood flow that bypasses capillaries through a direct channel?

    <p>throughfare channel</p> Signup and view all the answers

    The largest recorded blood volume in muscular venules is _______%.

    <p>360</p> Signup and view all the answers

    Which type of capillaries would you find in the kidneys?

    <p>Fenestrated capillaries</p> Signup and view all the answers

    Which of the following results from hypovolemic shock?

    <p>Decreased blood volume</p> Signup and view all the answers

    Pulmonary blood vessels dilate in response to low oxygen levels.

    <p>False</p> Signup and view all the answers

    What term describes persistently elevated blood pressure?

    <p>hypertension</p> Signup and view all the answers

    The _____ carries blood between two capillary networks.

    <p>portal vein</p> Signup and view all the answers

    Match the types of shock with their causes:

    <p>Hypovolemic shock = Excessive dehydration Cardiogenic shock = Damage to the heart Anaphylactic shock = Excessive histamine production Septic shock = Bacterial toxins</p> Signup and view all the answers

    What is the primary function of systemic circulation?

    <p>Distribute oxygenated blood to body tissues</p> Signup and view all the answers

    Which of the following factors increases vascular resistance (VR)?

    <p>Longer vessel length</p> Signup and view all the answers

    The ductus arteriosus allows blood to flow from the lungs into the aorta in a fetus.

    <p>False</p> Signup and view all the answers

    What does the hepatic portal circulation carry?

    <p>blood from gastrointestinal organs to the liver</p> Signup and view all the answers

    Skeletal muscle contraction decreases the rate of venous return to the heart.

    <p>False</p> Signup and view all the answers

    The _____ vein carries oxygenated blood to the liver.

    <p>hepatic artery</p> Signup and view all the answers

    What physiological change occurs in the thoracic cavity during inhalation?

    <p>Increases thoracic cavity volume</p> Signup and view all the answers

    Match the following arteries to their locations:

    <p>Common Carotid Arteries = Head Vertebral Arteries = Neck and Spinal Column Basilar Artery = Base of the brain Internal Carotid Arteries = Skull</p> Signup and view all the answers

    Vascular resistance is affected by the _____ of vessel lumen.

    <p>diameter</p> Signup and view all the answers

    Match the following hormones with their effects on blood pressure:

    <p>Renin-angiotensin-aldosterone system = Increases blood volume and blood pressure Epinephrine = Stimulates vasoconstriction Anti-diuretic hormone (ADH) = Increases water reabsorption Atrial natriuretic peptide (ANP) = Decreases blood volume and blood pressure</p> Signup and view all the answers

    Which nervous system response is stimulated to help restore oxygen delivery during shock?

    <p>Sympathetic</p> Signup and view all the answers

    Idiopathic hypertension has an identifiable cause.

    <p>False</p> Signup and view all the answers

    Which hormone is secreted in response to dehydration to help regulate blood pressure?

    <p>Anti-diuretic hormone (ADH)</p> Signup and view all the answers

    Blood viscosity is not a factor affecting vascular resistance.

    <p>False</p> Signup and view all the answers

    What prevents maternal and fetal blood from mixing?

    <p>placenta</p> Signup and view all the answers

    What mechanism prevents backflow of blood in veins?

    <p>Venous valves</p> Signup and view all the answers

    Blood that is _____ in oxygen flows from the right ventricle to the lungs.

    <p>deoxygenated</p> Signup and view all the answers

    The _____ system regulates blood flow by allowing vessels to change their own physiology.

    <p>autoregulation</p> Signup and view all the answers

    Which of the following correctly describes blood velocity?

    <p>Inversely proportional to total cross-sectional diameter</p> Signup and view all the answers

    During sleep, the skeletal muscle pump is inactive.

    <p>False</p> Signup and view all the answers

    What happens to the pressure at the entry to the right atrium?

    <p>It is 0 mmHg</p> Signup and view all the answers

    Increasing blood volume typically leads to _____ blood pressure.

    <p>increased</p> Signup and view all the answers

    What happens when the diaphragm contracts during inhalation?

    <p>Increases thoracic cavity volume</p> Signup and view all the answers

    What is the primary mechanism of capillary exchange that involves the movement of substances through fenestrations or intercellular clefts?

    <p>Diffusion</p> Signup and view all the answers

    Movement from blood into interstitial fluid is called reabsorption.

    <p>False</p> Signup and view all the answers

    What term describes the study of forces that affect blood flow in the body?

    <p>Hemodynamics</p> Signup and view all the answers

    The pressure exerted by solutes and proteins in blood is known as _________.

    <p>Blood colloid osmotic pressure</p> Signup and view all the answers

    What percentage of fluid filtered from capillaries is typically reabsorbed?

    <p>85%</p> Signup and view all the answers

    Net filtration pressure (NFP) is calculated by the difference between blood flow and vascular resistance.

    <p>False</p> Signup and view all the answers

    What happens to the remaining 15% of fluid that is not reabsorbed from capillaries?

    <p>It is taken up by lymph vessels.</p> Signup and view all the answers

    Blood pressure is measured in __________.

    <p>millimeters of mercury (mmHg)</p> Signup and view all the answers

    What pressure is known to contribute to filtration in capillaries?

    <p>Blood hydrostatic pressure</p> Signup and view all the answers

    Match each type of capillary exchange mechanism with its description:

    <p>Diffusion = Movement through fenestrations and clefts Transcytosis = Bulk uptake of large molecules Bulk flow = Mass movement due to pressure gradients Reabsorption = Movement from interstitial fluid into blood</p> Signup and view all the answers

    What is edema?

    <p>An increase in interstitial fluid volume.</p> Signup and view all the answers

    Blood flows from areas of low pressure to areas of high pressure.

    <p>False</p> Signup and view all the answers

    What is the term for the volume of blood flowing through a given tissue at a particular time?

    <p>Blood flow</p> Signup and view all the answers

    The highest blood pressure occurs during __________.

    <p>cardiac systole</p> Signup and view all the answers

    Study Notes

    Blood Vessels: Structure and Function

    • Five major types of blood vessels interconnected to form a loop: arteries, arterioles, capillaries, venules, and veins.
    • Arteries and arterioles carry blood away from the heart. Large elastic arteries exit the heart, followed by muscular medium-sized arteries, which branch to form arterioles.
    • Capillaries facilitate exchange between blood and tissues, enabling the transfer of essential nutrients and elimination of waste. Arterioles narrow into capillaries. Capillaries have thin walls for efficient exchange.
    • Venules and veins return blood to the heart. Capillaries merge into venules, which merge into larger veins. Veins are responsible for the return of blood to the heart.

    Blood Vessel Tunics

    • Blood vessel walls have three layers called tunics.
    • Tunica interna: innermost layer, an endothelial lining in direct contact with blood; facilitates diffusion with a smooth surface for blood flow. Endothelium secretes nitric oxide (NO). The basement membrane anchors endothelium, providing tensile strength and a surface for cell migration. A thin sheet of elastic fibers lies above the basement membrane. Large pores in the tunica interna allow large molecules to pass through by diffusion.
    • Tunica media: middle layer of smooth muscle and connective tissue; important for vasoconstriction (decreasing lumen diameter) and vasodilation (increasing lumen diameter) in response to various signals. Smooth muscle contraction during vasoconstriction and relaxation during vasodilation. Another layer of elastic fibers follows the smooth muscle, adding extensibility and elasticity.
    • Tunica externa: outermost layer, composed mainly of collagen and elastic fibers; contains nerves and tiny vessels called vasa vasorum, which supply nutrients to the blood vessels themselves. The vasa vasorum are more prominent in large vessels like the aorta.

    Elastic and Muscular Arteries

    • Elastic arteries, enriched with elastic fibers, act as pressure reservoirs pushing blood from the heart during diastole. This elasticity of the aorta allows it to handle the high pressure generated during ventricular systole. These arteries are called conducting arteries because they carry blood from the heart.
    • Muscular arteries have a thicker smooth muscle layer than elastic arteries; their looser tunica externa allows for more vasodilation and vasoconstriction and thus act as distributing arteries.

    Arterioles and Capillary Beds

    • Arterioles are microscopic arteries with thin walls, primarily smooth muscle, regulating blood flow into capillaries. They narrow to form metarterioles, culminating in precapillary sphincters, which regulate the flow into capillary beds. Nerves in the tunica external contribute to regulatory mechanisms of the arterioles' diameter.
    • Capillaries are the smallest blood vessels with single-cell thick walls for efficient diffusion. They branch extensively forming capillary beds. There are three main capillary types: continuous, fenestrated and sinusoids distinguished by the density of their endothelial cell junctions.
    • Continuous capillaries are prevalent in the nervous system, muscle, and skin.
    • Fenestrated capillaries have pores, increasing permeability to proteins, are found in the kidneys, intestines, and endocrine glands.
    • Sinusoids have wider lumens, lack a complete basement membrane, and are most often found in liver, spleen, anterior pituitary, and adrenal glands. These sinusoids enable the transport of larger molecules and cells like reticulocytes.

    Venules and Veins

    • Veins and venules have thin walls and cannot withstand high pressure. Venules accumulate large volumes of blood, acting as blood reservoirs. Veins contain valves to prevent backflow of blood, and their thick tunica externa aids in distensibility.

    Capillary Exchange

    • Capillary exchange: the movement of substances between blood and interstitial fluid. Three mechanisms:
      • Diffusion: movement of substances down pressure gradients across capillaries.
      • Transcytosis; using pinocytosis to transport larger molecules.
      • Bulk flow: movement of large volumes of water and solutes, regulated by pressure differences (filtration and reabsorption).
    • Net filtration pressure (NFP) = (BHP + IFOP) – (BCOP + IFHP); where: BHP = blood hydrostatic pressure, IFOP = interstitial fluid osmotic pressure, BCOP = blood colloid osmotic pressure, and IFHP = interstitial fluid hydrostatic pressure.
    • Excess interstitial fluid is collected by lymphatic vessels and returned to the circulatory system.

    Hemodynamics

    • Hemodynamics: the study of forces that affect blood flow.
    • Blood flow: volume of blood per unit time. Perfusions: delivery of blood to particular areas. The rate of blood flow depends on blood pressure and vascular resistance.
    • Blood pressure: the hydrostatic pressure exerted by blood against vessel walls driven by ventricular contraction, highest in the arteries and lowest in the veins. Blood pressure is measured in mmHg.
    • Vascular resistance: the opposition to blood flow due to friction between blood and vessel walls; dependent on vessel diameter, blood viscosity, and vessel length. Increased vessel diameter decreases resistance and increases blood flow.
    • Venous return: movement of blood from capillaries to the heart, aided by the skeletal muscle and respiratory pumps. The skeletal muscle pump relies on muscle contraction compressing and preventing backflow in valves, while the respiratory pump relies on pressures changes in the thoracic cavity to propel blood back to the heart.

    Control of Blood Pressure and Flow

    • The cardiovascular center regulates heart rate, contractility, and vasoconstriction/vasodilation.
    • Hormones, such as the renin-angiotensin-aldosterone system (RAAS), epinephrine/norepinephrine, ADH, and ANP, influence blood pressure and flow.
    • Autoregulation allows blood vessels to adjust their diameter in response to local metabolic demands.

    Homeostatic Imbalances

    • Shock: inadequate tissue perfusion due to low blood pressure or inadequate blood flow. Various types exist (hypovolemic, cardiogenic, anaphylactic, neurogenic, septic, obstructive).
    • Hypertension: persistently elevated blood pressure increases the risk of cardiovascular disease.

    Circulatory Routes

    • Systemic circulation: carries oxygenated blood from the left ventricle to the body and returns deoxygenated blood to the right atrium. Major systemic circuits include coronary, cerebral, and hepatic portal circulations.
    • Cerebral circulation: the circle of Willis is a network of anastomoses supplying blood to the brain.
    • Hepatic portal circulation: carries nutrient-rich, but deoxygenated, blood from the digestive tract and spleen to the liver for processing.
    • Pulmonary circulation: carries deoxygenated blood from the right ventricle to the lungs for oxygenation, and then oxygenated blood to the left atrium.

    Fetal Circulation

    • Fetal circulation is unique; oxygen and nutrients are exchanged through the placenta; the foramen ovale connects the atria, bypasses the fetal lungs, and the ductus arteriosus connects the aorta and pulmonary arteries directly to shunt blood from the right ventricle into the aorta. Blood drains into the umbilical artery from the internal iliac arteries to return to the placenta.

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    Description

    Explore the five major types of blood vessels: arteries, arterioles, capillaries, venules, and veins. Understand the intricate structure of blood vessels, including the three tunic layers and their crucial roles in circulation. This quiz will test your knowledge on how these vessels interconnect and function together.

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