Anatomy of Alveoli
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Questions and Answers

What is the approximate percentage of alveolar surface composed of simple squamous epithelium?

  • 5%
  • 95% (correct)
  • 20%
  • 50%
  • What type of fibers circumscribe the orifices of alveoli?

  • Elastic and reticular fibers (correct)
  • Collagen fibers
  • Smooth muscle fibers
  • Nervous fibers
  • What is the function of type I pneumocytes in preventing the seepage of extracellular fluid into the alveolar lumen?

  • They produce surfactant
  • They form occluding junctions with each other (correct)
  • They migrate between type II pneumocytes
  • They phagocytose particulate matter
  • Which type of pneumocytes have membrane-bound lamellar bodies that contain pulmonary surfactant?

    <p>Type II pneumocytes</p> Signup and view all the answers

    What is the role of alveolar macrophages in the alveolus?

    <p>To phagocytose particulate matter in the lumen of the alveolus as well as in the interalveolar spaces</p> Signup and view all the answers

    In patients with emphysema, what is decreased in the lung tissue?

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

    What is the narrowest barrier region in the lung?

    <p>Fused basal laminae of type I pneumocytes and endothelial cells</p> Signup and view all the answers

    What is the primary mechanism of O2 and CO2 exchange in the lungs?

    <p>Passive diffusion</p> Signup and view all the answers

    What is the function of the visceral pleura?

    <p>Covers and adheres to the lung</p> Signup and view all the answers

    What is the main difference between the left and right thoracic cavities?

    <p>The number of lobes</p> Signup and view all the answers

    What type of blood does the pulmonary artery supply to the lungs?

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

    What is the primary function of the bronchial arteries?

    <p>To supply oxygenated blood to the lungs</p> Signup and view all the answers

    What happens to the smooth muscle coats in individuals with asthma?

    <p>They undergo prolonged contraction during expiration</p> Signup and view all the answers

    What is the effect of steroids and β2-agonists on bronchiolar smooth muscle?

    <p>They relax the smooth muscle</p> Signup and view all the answers

    What is the characteristic of the pulmonary circulation?

    <p>Low-pressure system</p> Signup and view all the answers

    Study Notes

    Alveoli Structure

    • Alveoli have a prominent basal lamina
    • Alveoli openings are associated with alveolar sacs
    • Devoid of smooth muscle cells, instead circumscribed by elastic and reticular fibers

    Type I Pneumocytes

    • Compose ~95% of the alveolar surface
    • Simple squamous epithelium
    • Form occluding junctions with each other to prevent fluid seepage
    • Adluminal aspect covered by a well-developed basal lamina
    • Luminal aspect lined by surfactant

    Type II Pneumocytes

    • Compose ~5% of the alveolar surface
    • Dome-shaped apical surface juts into the alveolar lumen
    • Contain membrane-bound lamellar bodies with pulmonary surfactant
    • Synthesized on the RER and modified in the Golgi apparatus

    Alveolar Macrophages

    • Derived from monocytes that gain access to the pulmonary interstitium
    • Migrate between type I pneumocytes and enter the alveolar lumen
    • Phagocytose particulate matter in the alveolar lumen and interalveolar spaces
    • Assist type II pneumocytes in the uptake of surfactant

    Gas Exchange

    • O2 is exchanged for CO2 carried by blood in the lungs
    • CO2 is exchanged for O2 carried by blood in the tissues
    • Passage of O2 and CO2 across the blood-gas barrier is due to passive diffusion
    • Narrowest barrier regions consist of surfactant, type I pneumocytes, fused basal laminae, and endothelial cells

    Thoracic Cage

    • Divided into three regions: left thoracic cavity, right thoracic cavity, and mediastinum
    • Each thoracic cavity is lined by a serous membrane (pleura) consisting of simple squamous epithelium and subserous CT

    Pulmonary and Bronchial Arteries and Veins

    • Pulmonary arteries arise from the right ventricle and drain into the left atrium
    • Supply deoxygenated blood to the lungs from the right side of the heart
    • Involved in gas exchange and are a low-pressure system
    • Bronchial arteries arise from the systemic circulation and carry oxygenated blood
    • Travel in the septa between lobules of the lung and are a high-pressure system

    Innervation of the Lungs

    • Parasympathetic, preganglionic fibers descend into the vagus and terminate in the ganglia
    • Ganglia contain excitatory, cholinergic neurons and inhibitory, nonadrenergic neurons
    • Postganglionic fibers to the smooth muscle are excitatory or inhibitory

    Asthma

    • Smooth muscle coats contract at the end of expiration and relax during inspiration
    • In asthma, the smooth muscle coat undergoes prolonged contraction during expiration
    • Steroids and β2-agonists relax bronchiolar smooth muscle and are frequently used to relieve asthmatic attacks

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    Description

    This quiz covers the structure and characteristics of alveoli in the respiratory system, including their composition and features.

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