A&P Heart Essay Questions

  • 1. 

    Damage to the__________ is referred to as heart block

    • A. 

    • B. 

    • C. 

    • D. 

  • 2. 

    Normal heart sounds are caused by which of the following events?

    • A. 

      Excitation of the SA node

    • B. 

      Closure of the heart valves

    • C. 

      Friction of blood against the chamber walls

    • D. 

      Opening and closing of the heart valves

  • 3. 

    The p wave of a normal electrocardiogram indicates_____________

    • A. 

      Ventricular repolarization

    • B. 

      Ventricular depolarization

    • C. 

    • D. 

  • 4. 

    Which of the following is not an age-related change affecting the heart?

    • A. 

    • B. 

      Decline in cardiac reserve

    • C. 

      Fibrosis of cardiac muscle

    • D. 

      Thinning of the valve flaps

  • 5. 

    Which of the following is not part of the conduction system of the heart?

    • A. 

    • B. 

    • C. 

    • D. 

  • 6. 

    Blood within the pulmonary veins returns to the

    • A. 

    • B. 

    • C. 

    • D. 

  • 7. 

    The left ventricular wall of the heart is thicker than the right wall in order to

    • A. 

      Acoommodate a greater volume of blood

    • B. 

      Expand the thracic cage during diastole

    • C. 

      Pump blood with greater pressure

    • D. 

      Pump blood through a smaller valve

  • 8. 

    Small muscle masses attached to the chordae tendineae are the

    • A. 

    • B. 

    • C. 

    • D. 

  • 9. 

    Which of the events below does not occur when the semilunar valves are open?

    • A. 

      Ventricles are in diastole

    • B. 

      Blood enters pulmonary artieries and the aorta

    • C. 

    • D. 

      Ventricles are in systole

  • 10. 

    The term for pain associated with deficient blood delivery to the heart that may be caused by the transient spasm of coronary arteries is

    • A. 

    • B. 

    • C. 

    • D. 

  • 11. 

    To auscultate the aortic semilunar valve, you would place your stethoscope in the

    • A. 

      Second intercostal space to the right of the sternum

    • B. 

      Second intercostal space to the left of the sternum

    • C. 

      Fifth intercostal space inferior to the left nipple

    • D. 

      Fifth right intercostal space

  • 12. 

    The source of blood carried to capillaries in the myocardium would be the

    • A. 

    • B. 

    • C. 

    • D. 

  • 13. 

    The fact that the left ventricle of the heart is thicker than the right ventricle reveals that it

    • A. 

      Pumps a greater volume of blood

    • B. 

      Pumps blood against a greater resistance

    • C. 

      Expands the thoracic cage

    • D. 

      Sends blood through a smaller valve

  • 14. 

    Hemrrhage with a large loss of blood causes

    • A. 

      A lowering of blood pressure due to change in cardiac output

    • B. 

      A rise in blood pressure due to change in cardiac output

    • C. 

      No change in blood pressure but a slower heart rate

    • D. 

      No change in blood pressure but a change in respiration

  • 15. 

    If cardiac muscle is deprived of its normal blood supply, damage would primarily result from

    • A. 

      Decreased delivery of oxygen

    • B. 

      A decrease in the number of available mitochondria for energy production

    • C. 

      A lack of nutrients to feed into metabolic pathways

    • D. 

      An inadequate supply of lactic acid

  • 16. 

    If the length of the absolute refractory period in cardiac muscle cells was the same as it is for skeletal muscle cells

    • A. 

      It would be much longer before cardiac cells could respond to a second stimulation

    • B. 

      Contractions would last as long as the refractory period

    • C. 

      Tetanic contractions might occur, which would stop the hearts pumping action

    • D. 

      It would be less than 1 2 ms

  • 17. 

    Norepinephrine acts on the heart by

    • A. 

      Decreasing heart contractility

    • B. 

      Causing a decrease in stroke volume

    • C. 

      Blocking the action of calcium

    • D. 

      Causing threshold to be reached more quickly

  • 18. 

    If the vagal nerves to the heart were cut, the result would be that

    • A. 

      The heart would stop, since the vagal nerves trigger the heart to contract

    • B. 

      The heart rate would increase by about 25 beats per minute

    • C. 

      The av node would become the pacemaker of the heart

    • D. 

      Parasympathetic stimulation would increase, causing a decrease in heart rate

  • 19. 

    Foramen ovale

    • A. 

      Connects the two atria in the fetal heart

    • B. 

      Is a condition in which the heart valves do not completley close

    • C. 

      Is a shallow depression in the intreventricular septum

    • D. 

      Is a connection between the pulmonary trunk and the aorta in the fetus

  • 20. 

    Which vessel of the heart recieves blood during right ventricular systole?

    • A. 

    • B. 

    • C. 

    • D. 

  • 21. 

    Which of these vessels receives blood during ventricular systole?

    • A. 

    • B. 

    • C. 

    • D. 

      Both aorta and pulmonary trunk

  • 22. 

    The tricuspid valve is closed

    • A. 

      While the ventricle is in diastole

    • B. 

      When the ventricle is in systole

    • C. 

      While the atrium is contracting

    • D. 

      By the movement of blood from the atrium to ventricle

  • 23. 

    Which of the following factors does not influence heart rate

    • A. 

    • B. 

    • C. 

    • D. 

  • 24. 

    When viewing a dissected heart, it is easy to visually discern the right and left ventricles by

    • A. 

      Tracing out where the auricles connect

    • B. 

      Noticing the thickness of the venricle walls

    • C. 

    • D. 

      Finding the papillary muscles

  • 25. 

    Select the correct statement about the heart valves

    • A. 

      The mitral valve seperates the right atrium from the right ventricle

    • B. 

      The tricuspid valve divides the left atrium from the left ventricle

    • C. 

      Aortic and pulmonary valves control the flow of blood into the heart

    • D. 

      The AV valves are supported by chordae tendineae so that regurgitation of blood into the atria during ventricle contaction does not occur

  • 26. 

    Select the correct statement about the structure of the heart wall

    • A. 

      The fibrous skeleton forms the bulk of the heart

    • B. 

      Connective tissue in the heart wall aids in the conduction of the action potential

    • C. 

      The heart chambers are lined by the endomysium

    • D. 

      They myocardium is the layer of the heart that actually contracts

  • 27. 

    The second heart sound is heard during which phase of the cardiac cylce?

    • A. 

    • B. 

      Isovolumetric contraction

    • C. 

    • D. 

  • 28. 

    Select the correct statement about cardiac output

    • A. 

      A slow heart rate increases end diastolic volume, stroke volume, and force of contraction

    • B. 

      Decreased venous return will result in increased end diastolic volume

    • C. 

      If a semilunar valve were partially obstructed, the end systolic volume in the affected ventricle would be decreased

    • D. 

      Stroke volume increasees if end diastolic volume decreases

  • 29. 

    Isovolumetric contraction

    • A. 

      Refers to the short period during ventricular systole when the ventricles are completely

    • B. 

      Occurs while the AV valves are open

    • C. 

      Occurs immediately after the aortic and pulmonary valves close

    • D. 

      Occurs only in people with heart valve defects

  • 30. 

    Compared to skeletal muscle, cardiac muscle

    • A. 

      Has gap junctions that allow it to act as a functional syncytium

    • B. 

    • C. 

    • D. 

      Cells are larger than skeletal muscle cells

  • 31. 

    During the period of ventricular filling

    • A. 

      Pressure in the heart is at its peak

    • B. 

      Blood flows passively through the atria and the open AV valves into the ventricles

    • C. 

      The atria remain in diastole

    • D. 

      It is represented by the P wave on the ECG

  • 32. 

    The time of day most hazardous for heart attacks is

    • A. 

    • B. 

    • C. 

    • D. 

  • 33. 

    Select the correct statement about the function of myocardial cells

    • A. 

      The entire heart contracts as a unit or it does not contract at all

    • B. 

      Each cardiac muscle cell is nnervated by a sympathetic nerve ending so that the nervous system can increase heart rate

    • C. 

      The refactory period in skeletal muscle is much longer than that in cardiac muscle

    • D. 

      The influx of potassium ions from extracellular sources is the initiating event in cardiac muscle contraction.

  • 34. 

    During contraction of hear muscle cells

    • A. 

      The action potential is initiated by voltage-gated slow calcium channels

    • B. 

      Some calcium enters the cell from the extracellular space and triggers the release of larger amounts of calcium from intracellular stores

    • C. 

      The action potential is prevented from spreading from cell to cell by gap junctions

    • D. 

      Calcium is prevented from entering cardiac fibers that have been stimulated

  • 35. 

    Commotio cordis is heart failure due to a

    • A. 

      Mild electrical shock to the heart itself

    • B. 

      Severe electrical shock to the body

    • C. 

      Relatively mild blow to the chest that occurs during a vulnerable interval (2 ms) when the heart is repolarizing

    • D. 

      Loss of blood from an artery

  • 36. 

    Which statement best describes arteries

    • A. 

      All carry oxygenated blood to the heart

    • B. 

      All carry blood away from the heart

    • C. 

      All contain valves to prevent the backflow of blood

    • D. 

      Only large arteries are lined with endothelium

  • 37. 

    If we were able to artificially alter the membrane permeability of pacemaker cells so that sodium influx is more rapid

    • A. 

      Threshold is reached more quickly and heart rate would increase

    • B. 

      Potassium channels compensate and no change in heart rate would occur

    • C. 

      Heart rate would decrease, but blood pressure would rise due to the excess sodium present

    • D. 

      Tetanic contraction would occur due to the short absolute refractory period of cardiac muscle

  • 38. 

    Which tunic of an artery is most responsible for maintaining blood pressure and continous blood circulation?

    • A. 

    • B. 

    • C. 

    • D. 

  • 39. 

    Which of hte following chemicals does not help regulate blood pressure?

    • A. 

    • B. 

      Atrial natriuretic peptide

    • C. 

    • D. 

  • 40. 

    Which tunic of an artery contains endothelium?

    • A. 

    • B. 

    • C. 

    • D. 

  • 41. 

    Aldosterone will

    • A. 

      Promote an increase in blood pressure

    • B. 

      Promote a decrease in blood volume

    • C. 

      Result in a larger ouput of urine

    • D. 

      Decrease sodium reabsorption

  • 42. 

    Brain blood flow autoregulaton

    • A. 

      Is less sensitive to pH than to a decreased oxygen level

    • B. 

      Causes constriction of cerebral blood vessels in response to a drop in systemic blood pressure

    • C. 

      Is abolished when abnormally high CO2 levels persist

    • D. 

      Is controlled by caridac centers in the pons

  • 43. 

    Permitting the exchange of nutrients and gases between the blood and tissue cells is the primary function of

    • A. 

    • B. 

    • C. 

    • D. 

  • 44. 

    The circulatory route that runs from the digestive tract to the liver is called

    • A. 

      Hepatic portal circulation

    • B. 

    • C. 

    • D. 

  • 45. 

    The arteries that are also called distributing arteries are the

    • A. 

    • B. 

    • C. 

    • D. 

  • 46. 

    Which of the following signs of hypovolemic shock is a relatively late sign?

    • A. 

    • B. 

    • C. 

    • D. 

      Rapildy falling blood pressure

  • 47. 

    Which of the following is likely during vigorous exercise?

    • A. 

      Blood will be deverted to the digestive organs

    • B. 

      The skin will be cold and clammy

    • C. 

      Capillaries of the active muscles will be engorged with blood

    • D. 

      Blood flow to the kidneys increases

  • 48. 

    Which of the following is not one of the three main factors influencing blood pressure?

    • A. 

    • B. 

    • C. 

    • D. 

  • 49. 

    Which of the choices below explains why the artreioles are known as resistance vessels?

    • A. 

      Their prime function is the exchange of nutrients and wastes between the blood and tissue cells

    • B. 

      The contraction and realxation of the smooth muscle in their walls can change their diameter

    • C. 

      They distribute blood to various parts of the body

    • D. 

      They contain a large quantity of elastic tissue

  • 50. 

    Which of the following processes provides a long-term response to changes in blood pressure?

    • A. 

    • B. 

      Baroreceptor-initiated reflexes

    • C. 

      Chemoreceptor-initiated reflexes

    • D. 

  • 51. 

    The form of circulatory shock known as hypovolemic shock is

    • A. 

      The form of shock caused by anaphylaxis

    • B. 

      Any condition in which blood vessels are inadequately filled and blood cannot circulate normally

    • C. 

      Shock that results form large-scale loss of blood volume, or after severe vomitting or diarrhea

    • D. 

  • 52. 

    Peripheral resistance

    • A. 

      Decreases with increasing length of the blood vessel

    • B. 

      Increases as blood vessel diameter increases

    • C. 

      Increases as blood viscostiy increases

    • D. 

      Is not a major factor in blood pressure in healthy individuals

  • 53. 

    Blood flow to the skin

    • A. 

      Is controlled mainly by decreasing pH

    • B. 

      Increases when environmental temperature rises

    • C. 

      Increases when body temperature drops so that the skin does not freeze

    • D. 

      Is not an important source of nutrients and oxygen for skin cells

  • 54. 

    The pulse pressure is

    • A. 

      Systolic pressure plus diastolic pressure

    • B. 

      Systolic pressure minus diastolic pressure

    • C. 

      Systolic pressure divided by diastolic pressure

    • D. 

      Diastolic pressure plus 1/3 (systolic pressure plus diastolic pressure)

  • 55. 

    Which of the following do not influence arterial pulse rate?

    • A. 

    • B. 

    • C. 

    • D. 

      The vessel selected to palpate

  • 56. 

    Which of the following is true about veins?

    • A. 

      Venous valves are formed from the tunica media

    • B. 

      Up to 35% of total body blood is in venous circulation at any given time

    • C. 

      Veins have a small lumen in relation to the thickness of the vessel wall

    • D. 

      Veins are called capacitance vessels or blood reservoirs

  • 57. 

    Which of the choices belwo reflects the balance (or imbalance) between the direction and amount of luid that flows across the capillary walls?

    • A. 

      Hydrostatic and osmotic pressure

    • B. 

      Hydrostatic pressure only

    • C. 

      Blood volume and viscosity

    • D. 

      Plasma and formed element concentration

  • 58. 

    The influence of blood vessel diameter on peripheral resistance is

    • A. 

      The only factor that incfluences resistance

    • B. 

      Significant because resistance is inversely proportional to the fourth power of the vessel radius

    • C. 

      Significant because resistance is directly proportional to the blood vessel diameter

    • D. 

      Insignificant because vessel diameter does not vary

  • 59. 

    Histologically, the _________  is squamous epithelum supported by a sparse connective tissue layer

    • A. 

    • B. 

    • C. 

    • D. 

  • 60. 

    In the dynamics of blood flow through capillaries, hydrostatic pressure

    • A. 

      And ostmotic pressure are the same

    • B. 

      Is the same as capillary blood pressure

    • C. 

      Generally forces fluid from the interstitial space into the capillaries

    • D. 

      Is completley canceled out by osmotic pressure

  • 61. 

    Mechanisms that do not help regulate blood prssure include

    • A. 

      Nervous control that operates via reflex arcs involving baroreceptors, chemoreceptors and higher brain centers

    • B. 

    • C. 

      Renal regulation via the renin-angiotensin system of vasoconstriction

    • D. 

      Chemical controls such as atrial natriuretic peptide

  • 62. 

    The term ductus venosus refers to

    • A. 

      A fetal shunt that bypasses the lungs

    • B. 

      Damage to the valves in the veins, leading to varicose veins

    • C. 

      A conditon of the aged in which the arteries lose elasticity

    • D. 

      A special fetal vessel that allow umbilical blood to bypass the liver

  • 63. 

    Which of the following is a type of circulatory shock?

    • A. 

      Hypovolemic, caused by increased blood volume

    • B. 

      Cardiogenic, which results from any defect in blood vessels

    • C. 

      Vascular, due to extreme vasodilation as a result of loss of vasomotor tone

    • D. 

      Circulatory, where blood volume is normal and constant

  • 64. 

    Which of the choices below does not involve tissue perfusion?

    • A. 

      Delivery of oxygen and nutrients to, and removal of wastes from, tissue cells

    • B. 

      Gas exchange in the lungs

    • C. 

      Absorption of nutrients form the digestive tract

    • D. 

  • 65. 

    A patient with essential hypertension might have pressures of 200/120 mm Hg. This hyperstensive state could result in all of the following changes except

    • A. 

      Increased work of the left ventricle

    • B. 

      Increased incidence of coronary artery disease

    • C. 

      Increased damage to blood vessel endothelium

    • D. 

      Decreased size of the heart muscle

  • 66. 

    Arteriole blood pressure increases in response to all but which of the following?

    • A. 

    • B. 

    • C. 

    • D. 

    • E. 

  • 67. 

    Which of the following are involved directly in pulmonary circulation?

    • A. 

      Superior vena cava, right atrium, and left ventricle

    • B. 

      Right ventricle, pulmonary artery, and left atrium

    • C. 

      Left ventricle, aorta, and inferior vena cava

    • D. 

      Right atrium, aorta, and left ventrilce

  • 68. 

    Fenestrated capillaries

    • A. 

      Are not more permeable than continous capillaries

    • B. 

      Are not common in endocrine oragns and in areas ewhere capillary absorption is an imprtant function

    • C. 

      Do not occur in the glomerular capillaries of the kidneys

    • D. 

      Are not found in the brain

  • 69. 

    The hepatic portal vein

    • A. 

    • B. 

      Carries nutrient-rich blood to the liver

    • C. 

      Carries oxygen-rich blood from the liver to the viscera

    • D. 

      Carries blood from the liver to the inferior vena cava

  • 70. 

    Factors that aid venous return include all except

    • A. 

      Activity of skeletal muscles

    • B. 

      Pressure changes in the thorax

    • C. 

    • D. 

  • 71. 

    Select the correct statement about blood flow

    • A. 

      It is relatively constant through all body organs

    • B. 

    • C. 

      It is greatest where resistance is highest

    • D. 

      Blood flow through the entire vascular system is equivalent to cardiac output

  • 72. 

    What do the ductus  arteriousus and the foramen ovale become at birth?

    • A. 

      Ligamentum teres; fossa ovalis

    • B. 

      Fossa ovalis; ligamentum arteriosum

    • C. 

      Ligamentum arteriosum; ligamentum teres

    • D. 

      Ligamentum arteriosum; fossa ovails

  • 73. 

    Which of the following blood pressue readings would be indicative of hypertension?

    • A. 

      120/80 in a 30 year old man

    • B. 

      140/90 in a 70 year old woman

    • C. 

      170/96 in a 50 year old man

    • D. 

      110/60 in a 20 year old woman

  • 74. 

    The velocity of blood flow is

    • A. 

      In direct proportion to the toal cross-secitonal area of the blood vessels

    • B. 

      Slower in the arteries than in capillaries because arteries possess a realtively large diameter

    • C. 

      Slower in the veins than in the capillaries because veins have a large diameter

    • D. 

      Slowest in the capillaries because the total cross-secitonal area is the greatest

  • 75. 

    A throumbus (blood clot) in the first branch of the arch of the aorta would affect the flow of blood to the

    • A. 

      Left side of the head and neck

    • B. 

    • C. 

    • D. 

      Right side of the head and neck and right upper arem

  • 76. 

    Cerebral blood flow is regulated by

    • A. 

    • B. 

    • C. 

      Intrinsic autoregulatory mechanisms

    • D. 

      The hypthalamic "thermostat"

  • 77. 

    Normal average blood pressure for a newborn baby is

    • A. 

    • B. 

    • C. 

    • D. 

  • 78. 

    Modified capillareis that are lined with phagocytes are called

    • A. 

    • B. 

    • C. 

    • D. 

  • 79. 

    Select the correct statement about factors that influence blood pressure

    • A. 

      An incrase in cardiac ouput corresponds to a decrease in blood pressure, due to the increased delivery

    • B. 

      Systemic vasodilation would increase blood pressure, due to diversion of blood to essential areas

    • C. 

      Excess protein production would decrease blood pressure

    • D. 

      Excess red cell production would cause a blood pressure increase

  • 80. 

    The baroreceptors in the carotid sinus and aortic arch aresitive to which of the following?

    • A. 

      A decrease in carbon dioxide

    • B. 

      Changes in arterial pressure

    • C. 

      A decrease in oxygen levels

    • D. 

      An increase in oxygen levels

  • 81. 

    The arterise that direcetly feed into the capillary beds are called

    • A. 

    • B. 

    • C. 

    • D. 

  • 82. 

    The short term controls of blood pressure, mediated by the nervous sytem and bloodborne chemicals, primarily operate via all but which of the following?

    • A. 

      Reflex arcs involving baroreceptors

    • B. 

    • C. 

      Reflex arcs associated with vasomotor fibers

    • D. 

  • 83. 

    Where in the body would you find low oxygen levels causing vasoconstrition and high levels causing vasodilation?

    • A. 

    • B. 

    • C. 

    • D. 

  • 84. 

    If blood pressure is almost normal in a person who has lost blood, doos that mean the tisssues are receiving adequate blood flow?

    • A. 

    • B. 

    • C. 

  • 85. 

    Which of the following would not result in the dilation of the feeder arterioles and opening of the precapillary sphincters in systemic capillary beds?

    • A. 

      A decrease in lical tissue oxygen content

    • B. 

      An increase in local tissue carbon dioxide

    • C. 

      A local increase in histamine

    • D. 

  • 86. 

    Secondary hypertension can be caused by

    • A. 

    • B. 

    • C. 

    • D. 

  • The almost continuous traffic into and out of a busy factory at rush hour occurs at a snails’ pace compared to the endless activity going on within our bodies. Like the bustling factory, the body must have a transportation system to carry its various cargos back and forth, and this is where the cardiovascular system steps in.

    Contents

    Functions of the Heart

    The functions of the heart are as follows:

    1. Managing blood supply. Variations in the rate and force of heart contraction match blood flow to the changing metabolic needs of the tissues during rest, exercise, and changes in body position.
    2. Producing blood pressure. Contractions of the heart produce blood pressure, which is needed for blood flow through the blood vessels.
    3. Securing one-way blood flow. The valves of the heart secure a one-way blood flow through the heart and blood vessels.
    4. Transmitting blood. The heart separates the pulmonary and systemic circulations, which ensures the flow of oxygenated blood to tissues.

    Anatomy of the Heart

    The cardiovascular system can be compared to a muscular pump equipped with one-way valves and a system of large and small plumbing tubes within which the blood travels.

    Heart Structure and Functions


    The modest size and weight of the heart give few hints of its incredible strength.

    • Weight. Approximately the size of a person’s fist, the hollow, cone-shaped heart weighs less than a pound.
    • Mediastinum. Snugly enclosed within the inferior mediastinum, the medial cavity of the thorax, the heart is flanked on each side by the lungs.
    • Apex. It’s more pointed apex is directed toward the left hip and rests on the diaphragm, approximately at the level of the fifth intercostal space.
    • Base. Its broad posterosuperior aspect, or base, from which the great vessels of the body emerge, points toward the right shoulder and lies beneath the second rib.
    • Pericardium. The heart is enclosed in a double-walled sac called the pericardium and is the outermost layer of the heart.
    • Fibrous pericardium. The loosely fitting superficial part of this sac is referred to as the fibrous pericardium, which helps protect the heart and anchors it to surrounding structures such as the diaphragm and sternum.
    • Serous pericardium. Deep to the fibrous pericardium is the slippery, two-layer serous pericardium, where its parietal layer lines the interior of the fibrous pericardium.

    Layers of the Heart


    The heart muscle has three layers and they are as follows:

    • Epicardium. The epicardium or the visceral and outermost layer is actually a part of the heart wall.
    • Myocardium. The myocardium consists of thick bundles of cardiac muscle twisted and whirled into ringlike arrangements and it is the layer that actually contracts.
    • Endocardium. The endocardium is the innermost layer of the heart and is a thin, glistening sheet of endothelium hat lines the heart chambers.

    Chambers of the Heart


    The heart has four hollow chambers, or cavities: two atria and two ventricles.

    • Receiving chambers. The two superior atria are primarily the receiving chambers, they play a lighter role in the pumping activity of the heart.
    • Discharging chambers. The two inferior, thick-walled ventricles are the discharging chambers, or actual pumps of the heart wherein when they contract, blood is propelled out of the heart and into the circulation.
    • Septum. The septum that divides the heart longitudinally is referred to as either the interventricular septum or the interatrial septum, depending on which chamber it separates.

    Associated Great Vessels


    The great blood vessels provide a pathway for the entire cardiac circulation to proceed.

    • Superior and inferior vena cava. The heart receives relatively oxygen-poor blood from the veins of the body through the large superior and inferior vena cava and pumps it through the pulmonary trunk.
    • Pulmonary arteries. The pulmonary trunk splits into the right and left pulmonary arteries, which carry blood to the lungs, where oxygen is picked up and carbon dioxide is unloaded.
    • Pulmonary veins. Oxygen-rich blood drains from the lungs and is returned to the left side of the heart through the four pulmonary veins.
    • Aorta. Blood returned to the left side of the heart is pumped out of the heart into the aorta from which the systemic arteries branch to supply essentially all body tissues.

    Heart Valves


    The heart is equipped with four valves, which allow blood to flow in only one direction through the heart chambers.

    • Atrioventricular valves. Atrioventricular or AV valves are located between the atrial and ventricular chambers on each side, and they prevent backflow into the atria when the ventricles contract.
    • Bicuspid valves. The left AV valve- the bicuspid or mitral valve, consists of two flaps, or cusps, of endocardium.
    • Tricuspid valve. The right AV valve, the tricuspid valve, has three flaps.
    • Semilunar valve. The second set of valves, the semilunar valves, guards the bases of the two large arteries leaving the ventricular chambers, thus they are known as the pulmonary and aortic semilunar valves.

    Cardiac Circulation Vessels


    Although the heart chambers are bathed with blood almost continuously, the blood contained in the heart does not nourish the myocardium.

    • Coronary arteries. The coronary arteries branch from the base of the aorta and encircle the heart in the coronary sulcus (atrioventricular groove) at the junction of the atria and ventricles, and these arteries are compressed when the ventricles are contracting and fill when the heart is relaxed.
    • Cardiac veins. The myocardium is drained by several cardiac veins, which empty into an enlarged vessel on the posterior of the heart called the coronary sinus.

    Blood Vessels


    Blood circulates inside the blood vessels, which form a closed transport system, the so-called vascular system.

    • Arteries. As the heart beats, blood is propelled into large arteries leaving the heart.
    • Arterioles. It then moves into successively smaller and smaller arteries and then into arterioles, which feed the capillary beds in the tissues.
    • Veins. Capillary beds are drained by venules, which in turn empty into veins that finally empty into the great veins entering the heart.

    Tunics


    Except for the microscopic capillaries, the walls of the blood vessels have three coats or tunics.

    • Tunica intima. The tunica intima, which lines the lumen, or interior, of the vessels, is a thin layer of endothelium resting on a basement membrane and decreases friction as blood flows through the vessel lumen.
    • Tunica media. The tunica media is the bulky middle coat which mostly consists of smooth muscle and elastic fibers that constrict or dilate, making the blood pressure increase or decrease.
    • Tunica externa. The tunica externa is the outermost tunic composed largely of fibrous connective tissue, and its function is basically to support and protect the vessels.

    Major Arteries of the Systemic Circulation


    The major branches of the aorta and the organs they serve are listed next in sequence from the heart.

    Arterial Branches of the Ascending Aorta

    The aorta springs upward from the left ventricle of heart as the ascending aorta.

    • Coronary arteries. The only branches of the ascending aorta are the right and left coronary arteries, which serve the heart.

    Arterial Branches of the Aortic Arch

    The aorta arches to the left as the aortic arch.

    • Brachiocephalic trunk. The brachiocephalic trunk, the first branch off the aortic arch, splits into the right common carotid artery and right subclavian artery.
    • Left common carotid artery. The left common carotid artery is the second branch off the aortic arch and it divides, forming the left internal carotid, which serves the brain, and the left external carotid, which serves the skin and muscles of the head and neck.
    • Left subclavian artery. The third branch of the aortic arch, the left subclavian artery, gives off an important branch- the vertebral artery, which serves part of the brain.
    • Axillary artery. In the axilla, the subclavian artery becomes the axillary artery.
    • Brachial artery. the subclavian artery continues into the arm as the brachial artery, which supplies the arm.
    • Radial and ulnar arteries.

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