Human Anatomy: The Heart Structure
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Questions and Answers

What is the function of the myocardium in the heart?

  • To separate the left and right atria
  • To act as a smooth endothelial layer
  • To provide the contractile force for pumping blood (correct)
  • To receive oxygenated blood from the lungs

    • Which blood vessel is responsible for carrying deoxygenated blood from the upper body to the right atrium?

  • Inferior vena cava
  • Pulmonary vein
  • Superior vena cava (correct)
  • Aorta

    • What distinguishes the function of the left ventricle from the right ventricle?

  • It ejects oxygenated blood to the systemic circulation. (correct)
  • It has thinner walls than the right ventricle.
  • It ejects blood to the lungs only.
  • It receives blood exclusively from the superior vena cava.

    • Which structure aids in preventing backflow of blood into the atria during ventricular contraction?

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

    In the heart's anatomy, how many chambers receive blood directly from the body?

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

    What is the primary function of pulmonary circulation?

    <p>To move blood between the heart and the lungs</p> Signup and view all the answers

    Which side of the heart pumps oxygen-rich blood to the body?

    <p>Left ventricle</p> Signup and view all the answers

    What is the most direct impact of blood volume on blood pressure?

    <p>Increased blood volume increases blood pressure.</p> Signup and view all the answers

    During which cardiac phase do the ventricles fill with blood?

    <p>Ventricle diastole</p> Signup and view all the answers

    How does vascular resistance affect blood pressure?

    <p>Increased vascular resistance increases blood pressure.</p> Signup and view all the answers

    What leaves the heart via the aorta?

    <p>Oxygen-rich blood</p> Signup and view all the answers

    Which vessels are responsible for returning deoxygenated blood to the heart?

    <p>Vena cavae</p> Signup and view all the answers

    What happens to blood pressure as the distance from the left ventricle increases?

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

    What does the term 'cardiac output' refer to?

    <p>The amount of blood the heart pumps per minute</p> Signup and view all the answers

    Which factor has the least impact on blood pressure?

    <p>Heart rate</p> Signup and view all the answers

    What is the primary source of blood pressure in the cardiovascular system?

    <p>Contraction of ventricles</p> Signup and view all the answers

    Which part of the heart receives oxygen-poor blood from the body?

    <p>Right atrium</p> Signup and view all the answers

    What happens during ventricle systole?

    <p>The ventricles contract and pump blood out</p> Signup and view all the answers

    What type of blood does the right ventricle receive from the right atrium?

    <p>Deoxygenated blood</p> Signup and view all the answers

    What structure does the right ventricle pump deoxygenated blood into?

    <p>Pulmonary trunk</p> Signup and view all the answers

    Where does the left atrium receive oxygenated blood from?

    <p>Pulmonary veins</p> Signup and view all the answers

    Which structure does the left ventricle pump oxygenated blood into?

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

    What is the primary function of the inferior vena cava?

    <p>To return deoxygenated blood from the lower body</p> Signup and view all the answers

    How do the right and left ventricles compare in the volume of blood they eject?

    <p>They eject equal volumes of blood</p> Signup and view all the answers

    What is the characteristic pressure condition under which the right ventricle pumps blood?

    <p>Low pressure to the lungs</p> Signup and view all the answers

    Which arteries carry deoxygenated blood from the right ventricle to the lungs?

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

    What is the average cardiac output calculated from a stroke volume of 70 mL/beat and a heart rate of 75 beats/min?

    <p>5.25 L/min</p> Signup and view all the answers

    Which component of blood is responsible for the majority of its volume?

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

    Which process described contributes to the cessation of bleeding during haemostasis?

    <p>Vascular spasm</p> Signup and view all the answers

    Which is NOT a function of blood?

    <p>Production of hormones</p> Signup and view all the answers

    What is the primary function of red blood cells?

    <p>Transport oxygen and carbon dioxide</p> Signup and view all the answers

    Which type of white blood cell is primarily known for fighting infections?

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

    Which part of the blood composition contains the least amount in terms of percentage?

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

    What is the role of haemoglobin in red blood cells?

    <p>To carry oxygen and carbon dioxide</p> Signup and view all the answers

    Study Notes

    Layers of the Heart Wall

    • The heart wall is made of three layers:
      • Epicardium (outer)
      • Myocardium (middle)
      • Endocardium (inner)

    Heart Chambers

    • The heart has four chambers:
      • Two atria (superior)
      • Two ventricles (inferior)

    Right Atrium

    • Receives deoxygenated blood from:
      • Superior vena cava (from upper body)
      • Inferior vena cava (from lower body)
    • Pumps blood to the right ventricle

    Right Ventricle

    • Receives deoxygenated blood from the right atrium
    • Pumps deoxygenated blood into the pulmonary trunk
      • Pulmonary trunk branches into the left and right pulmonary arteries

    Left Atrium

    • Receives oxygenated blood from:
      • Pulmonary veins (from lungs)
    • Pumps oxygenated blood to the left ventricle

    Left Ventricle

    • Receives oxygenated blood from the left atrium
    • Pumps oxygenated blood to the aorta, which distributes it to the body.

    Left vs Right Ventricle

    • Both ventricles eject equal blood volumes.
    • The right ventricle pumps blood a short distance to the lungs at lower pressure.
    • The left ventricle pumps blood a longer distance to the body at a higher pressure.

    Systemic vs Pulmonary Circulation

    • Pulmonary circulation
      • Moves blood between the heart and lungs
      • Right side of the heart - leaves via pulmonary arteries
    • Systemic circulation
      • Moves blood between the heart and the body
      • Left side of the heart - leaves via the aorta

    Electrical Conduction System of the Heart

    • Enables coordinated heart contractions
    • Components:
      • Sinoatrial (SA) node (pacemaker)
      • Atrioventricular (AV) node
      • Bundle of His
      • Purkinje fibers
    • SA node initiates electrical impulses
      • AV node delays impulse
      • Bundle of His transmits impulse to ventricles
      • Purkinje fibers distribute impulse throughout ventricles

    Electrocardiogram (ECG)

    • A recording of the electrical activity of the heart
    • Components:
      • P wave: atrial depolarization
      • QRS complex: ventricular depolarization
      • T wave: ventricular repolarization

    Cardiac Cycle

    • Complete sequence of events in one heartbeat
    • Divided into two phases:
      • Diastole: Relaxation phase - ventricles fill with blood
      • Systole: Contraction phase - blood is ejected from ventricles

    Cardiac Output (CO)

    • Volume of blood ejected from the left ventricle per minute.
    • Calculated by: CO = Heart Rate (beats/min) x Stroke Volume (mL/beat)
    • Factors that influence cardiac output:
      • Preload: Amount of stretch of the ventricle before contraction
      • Afterload: Resistance the ventricle must overcome to eject blood
      • Contractility: Force of contraction of the ventricle
      • Autonomic nervous system: Sympathetic (increases HR & contractility) and parasympathetic (decreases HR)
      • Hormonal factors: Epinephrine, norepinephrine, thyroid hormones

    Functions of Blood

    • Transport:
      • O2 and CO2
      • Nutrients
      • Hormones
    • Regulation:
      • pH
      • Temperature
    • Protection:
      • Clotting
      • Antibodies and white blood cells

    Components of Blood

    • Plasma (55%)
      • Suspension medium for formed elements
    • Formed elements (45%)
      • Red blood cells (erythrocytes) (99%)
      • White blood cells (leukocytes)
      • Platelets

    Red Blood Cells (RBC)

    • Transport O2 and CO2
    • Biconcave disk shape:
      • Increases surface area
      • Promotes cell flexibility
    • Lack a nucleus and other organelles to maximize oxygen carrying capacity.
    • Contain hemoglobin: Oxygen-carrying protein

    White Blood Cells (WBC)

    • Function in immune defense: Combat invading microbes.
    • Contain a nucleus and organelles
    • Lack hemoglobin
    • Increased levels may indicate an infection

    Haemostasis

    • Sequence of responses that stop bleeding
    • Processes involved:
      • Vascular spasm: Smooth muscle in vessel walls contracts to reduce blood flow.
      • Platelet plug formation: Platelets adhere to exposed collagen and aggregate to form a plug.
      • Coagulation: Blood clotting to form a fibrin mesh to reinforce the platelet plug

    Blood Pressure

    • The pressure exerted by the blood on the walls of a blood vessel
    • Generated by ventricular contraction
    • Factors that influence blood pressure:
      • Blood volume
      • Cardiac output
      • Vascular resistance

    Vascular Resistance

    • Opposition to blood flow due to friction between blood and the walls of blood vessels.
    • Factors affecting vascular resistance:
      • Size of the lumen
      • Blood viscosity
      • Total vessel length

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    Description

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