Blood Supply and Gas Exchange in Lungs
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Questions and Answers

What is a potential consequence of chronic pulmonary hypertension?

  • Decreased pulmonary blood flow
  • Reduced vascular resistance
  • Right ventricular heart failure (correct)
  • Increased oxygen uptake

    • In the upright position, what causes greater hydrostatic pressure in the lung's lower vessels?

  • Gravity (correct)
  • Decreased cardiac output
  • Increased blood viscosity
  • Constricted blood vessels

    • What happens to capillary transit time during exercise?

  • It remains constant at 1 second
  • It increases to 2 seconds
  • It becomes unpredictable
  • It decreases to approximately 0.3 seconds (correct)

    • What is the primary factor that prevents pulmonary oedema under normal conditions?

    <p>Low capillary pressure (A)</p> Signup and view all the answers

    What can cause pulmonary oedema if left atrial pressure rises significantly?

    <p>Mitral valve stenosis (C)</p> Signup and view all the answers

    How much of the total body mass does the brain roughly account for compared to its percentage of cardiac output?

    <p>2% body mass, 15% cardiac output (C)</p> Signup and view all the answers

    What is the main role of diuretics in the treatment of pulmonary oedema?

    <p>Relieve symptoms by reducing fluid overload (B)</p> Signup and view all the answers

    What could lead to increased capillary pressure and subsequent fluid filtration?

    <p>High left atrial pressure (A)</p> Signup and view all the answers

    How much does the oxygen consumption of grey matter account for total body consumption at rest?

    <p>20% (D)</p> Signup and view all the answers

    What is the normal range for pulmonary capillary pressure?

    <p>9 - 12 mmHg (C)</p> Signup and view all the answers

    What is the primary purpose of pulmonary circulation?

    <p>Delivers blood to the alveoli for gas exchange (A)</p> Signup and view all the answers

    What characteristic of pulmonary circulation contributes to its low resistance?

    <p>A large number of capillaries arranged in parallel (C)</p> Signup and view all the answers

    What is the mean arterial pressure in the pulmonary circulation?

    <p>12-15 mmHg (C)</p> Signup and view all the answers

    Which mechanism primarily regulates pulmonary vascular tone?

    <p>Hypoxic pulmonary vasoconstriction (C)</p> Signup and view all the answers

    What is the impact of chronic hypoxic vasoconstriction on the heart?

    <p>Right ventricular failure (B)</p> Signup and view all the answers

    Which feature of alveoli facilitates efficient gas exchange?

    <p>Short diffusion distance between gases and blood (B)</p> Signup and view all the answers

    How does the bronchial circulation primarily serve the lungs?

    <p>To meet the metabolic requirements of lung tissue (C)</p> Signup and view all the answers

    What is the primary function of a high density of capillaries in the alveolar wall?

    <p>Enhance gas exchange efficiency (D)</p> Signup and view all the answers

    What is the effect of pulmonary artery pressure during normal functioning of the lungs?

    <p>Low pressure to facilitate gas exchange (A)</p> Signup and view all the answers

    What is the primary role of the ventilation-perfusion ratio?

    <p>To balance air and blood distribution in the lungs (C)</p> Signup and view all the answers

    What is the primary role of high capillary density in active muscle?

    <p>It provides a large surface area for gas exchange. (A)</p> Signup and view all the answers

    What occurs in the capillaries at rest regarding perfusion?

    <p>Approximately half of the capillaries are perfused at any time. (B)</p> Signup and view all the answers

    Which agent is NOT thought to act as a vasodilator?

    <p>Norepinephrine (D)</p> Signup and view all the answers

    How does adrenaline affect blood vessels in skeletal muscle?

    <p>It acts as a vasodilator through β2 receptors. (C)</p> Signup and view all the answers

    What is the main purpose of cutaneous circulation?

    <p>To regulate the core temperature. (A)</p> Signup and view all the answers

    What is the primary function of arteriovenous anastomoses (AVAs) in apical skin?

    <p>To regulate heat loss from the skin. (C)</p> Signup and view all the answers

    Under what control are arteriovenous anastomoses primarily regulated?

    <p>Neural sympathetic control (C)</p> Signup and view all the answers

    What happens to AVAs when the core temperature increases?

    <p>They dilate to allow increased heat loss. (B)</p> Signup and view all the answers

    What adaptation is typical of circulatory structures associated with specialized functions?

    <p>Alterations in elasticity and permeability. (D)</p> Signup and view all the answers

    What effect does a decrease in core temperature have on sympathetic tone in AVAs?

    <p>It decreases sympathetic tone, leading to vessel dilation. (D)</p> Signup and view all the answers

    Study Notes

    Blood Supply to the Lungs

    • The lungs have two circulations: bronchial and pulmonary
    • Bronchial circulation meets the lungs' metabolic requirements, part of the systemic circulation
    • Pulmonary circulation supplies blood to alveoli for gas exchange

    Pulmonary Circulation Characteristics

    • Accepts the entire cardiac output
    • Works with low pressure and low resistance
    • Mean arterial pressure 12-15mmHg
    • Mean capillary pressure 9-12mmHg
    • Mean venous pressure 5mmHg

    Adaptations for Efficient Gas Exchange

    • High capillary density in alveolar wall for large surface area
    • Short diffusion distance, thin layer between gas and plasma
    • High oxygen and carbon dioxide transport capacity

    The Blood-Gas Barrier

    • Thin layer between alveolar air and capillary blood compromising of type I pneumocyte and endothelial cell

    Ventilation-Perfusion Ratio

    • Matching alveolar ventilation with perfusion for efficient oxygenation

    Hypoxic Pulmonary Vasoconstriction

    • Ensures optimal ventilation perfusion ratio
    • Hypoxia in alveoli causes vasoconstriction of pulmonary vessels
    • Optimizes gas exchange by redirecting blood flow away from poorly ventilated alveoli

    Chronic Hypoxic Vasoconstriction

    • Can lead to right ventricular failure
    • Occurs at altitude or with lung diseases like emphysema
    • Increases vascular resistance, leading to chronic pulmonary hypertension
    • High afterload on right ventricle can lead to right ventricular heart failure

    Pulmonary Vessels and Gravity

    • Low pressure pulmonary vessels are strongly influenced by gravity
    • In an upright position, hydrostatic pressure is higher in lower lung vessels:
      • Vessels in the apex collapse during diastole
      • Vessels at the base are continuously patent, distended by gravity

    Effects of Exercise on Pulmonary Blood Flow

    • Increased cardiac output
    • Opens apical capillaries
    • Increased oxygen uptake by lungs
    • Reduced capillary transit time as blood flow increases
      • At rest 1s
      • During exercise 0.3s

    Lung Lymph Formation

    • Low capillary pressure minimizes lung lymph formation

    Pulmonary Edema

    • Increased capillary pressure causes fluid leakage, leading to edema
    • Impairs gas exchange
    • Treated with diuretics and addressing the underlying cause

    Cerebral Circulation

    • Brain has a high oxygen demand, receiving 15% of cardiac output
    • Grey matter oxygen consumption accounts for 20% of total body consumption at rest
    • High capillary density and reduced diffusion distance support high oxygen demand

    Cerebral Circulation Adaptations

    • Increased flow due to metabolic hyperaemia
    • Vasodilators:
      • Increased potassium concentration
      • Increased osmolarity
      • Inorganic phosphates
      • Adenosine
      • Increased hydrogen ion concentration

    Cutaneous Circulation

    • Plays a role in temperature regulation
    • Skin is the main heat dissipating surface

    Acral Skin and Arteriovenous Anastomoses

    • Specialized structures called artereovenous anastomoses (AVAs)
    • Specialized structures play a role in heat loss

    AVAs and Temperature Regulation

    • Under neural control, sympathetic vasoconstrictor fibers
    • Reduced vasomotor drive allows AVAs to dilate, creating a low resistance shunt to venous plexus
    • Allows skin temperature to rise, dissipating heat

    Summary

    • Each circulation has a specialized function
    • Adaptations exist to meet the specific needs of each circulation
    • Clinical problems can arise in various circulations

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    Related Documents

    Special Circulations Lecture Notes PDF

    Description

    Explore the intricate details of blood supply to the lungs, focusing on both bronchial and pulmonary circulation. Understand the adaptations that promote efficient gas exchange and the importance of the ventilation-perfusion ratio. This quiz will deepen your knowledge of lung physiology.

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