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Questions and Answers
Which of the following describes the organization of conducting and respiratory bronchioles?
What is the function of the pulmonary plexuses in the lungs?
Which cells and mediators affect respiratory airways, including club and mast cells?
What is the significance of the tracheobronchial tree's differences in diameter, glands, and cartilage?
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What is the main source of the phospholipid surface film (SF) in the alveoli?
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What is the average distance from the teeth to the vocal cords?
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Which of the following is the largest subdivision of a lung lobe?
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What is most likely to produce bronchodilation?
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What is a possible response to attempting laryngoscopy in a fully awake patient?
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What is the angle of the right main bronchus (away from the midline of the trachea) in an infant?
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What type of cells form and secrete lamellar bodies in the alveoli?
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Which part of the tracheobronchial tree lacks cartilage and glands?
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How many main bronchi are present in the tracheobronchial tree?
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Which part of the tracheobronchial tree contains scattered cartilage plates?
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What is the arterial supply of the lung stroma?
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Which structure is surgically resectable and named according to the bronchi supplying them?
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Where do the bronchial veins drain in the lung stroma?
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Which part of the tracheobronchial tree is located after the trachea bifurcates?
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Which part of the tracheobronchial tree supplies lung lobes?
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Which part of the tracheobronchial tree contains pyramidal-shaped subdivisions of a lobe?
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Which part of the tracheobronchial tree occurs after tertiary bronchi and lacks cartilage and glands?
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Which type of cells in the alveoli are specialized for gas exchange?
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What is the main function of Type II alveolar cells?
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What is the predominant balance to the excitatory cholinergic system for bronchodilation?
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Which fibers inhibit secretion from bronchial glands and vasoconstrict pulmonary vessels?
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Which cells in the airways contain secretory granules filled with inflammatory mediators and can induce bronchoconstriction?
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Which cells secrete proteins, surfactants, and act as progenitors for club cells and ciliated epithelial cells?
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Which segment of the airways is completely lined with alveoli, alveolar ducts, and sacs?
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What is the main function of capillaries in the alveoli?
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What do nonciliated bronchiolar exocrine cells (club cells) destroy when they reach bronchioles?
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What is the primary function of free-ranging phagocytic alveolar macrophages in the alveoli?
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What is the main function of visceral afferent fibers from CNX and thoracic nerves in the pulmonary plexus?
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During 'flight or fight' circumstances, what hormonal release results in relaxation of airway smooth muscle?
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Study Notes
- The innervation of the lungs includes right and left plexuses that follow the trachea and bronchial tree.
- The pulmonary plexuses provide sensory and motor innervation to the smooth muscle and glands.
- Parasympathetic (cholinergic) and sympathetic (adrenergic) fibers provide weak motor effect on airway diameter, causing vasoconstriction and inhibition of gland secretion.
- Visceral afferents travel with CNX fibers and the non-adrenergic/non-cholinergic (NANC) system provides inhibition, including bronchodilation, which is the predominant balance to the excitatory cholinergic system.
- The pulmonary plexus includes autonomic and visceral afferent fibers from CNX and thoracic nerves.
- Vagal parasympathetic fibers are secretomotor, glands, and bronchoconstrictive – smooth muscle with postganglionic parasympathetic innervation being a major source of unitary smooth muscle contraction.
- Sympathetic innervation from fibers of T1 to T4 inhibit secretion from bronchial glands, vasoconstrict of pulmonary vessels, and inhibit bronchoconstriction of smooth muscle, while weakly bronchodilating.
- Visceral afferent fibers transmit sensory information, which are sparse compared to somatic structures, and are nociceptive and reflexive.
- Hormonal release of epinephrine and norepinephrine during "flight or fight" circumstances results in relaxation of airway smooth muscle, with β2 adrenergic receptors widely distributed in smooth muscle and combining with GPCRs in the plasma membrane of myocytes to cause smooth muscle relaxation and bronchiole dilation.
- Mast cells, which are heavily granulated and reside in the connective tissues of airways, contain secretory granules filled with inflammatory mediators, including histamine, proteoglycans, lysosomal enzymes, and metabolites of arachidonic acid, which can induce bronchoconstriction, stimulate mucus secretion, and increase permeability of bronchial vessels when degranulation occurs.
- Smooth muscle in airways contains significant amounts of collagen and elastic connective tissue fibers, with walls of bronchi and bronchioles having a thicker layer of smooth muscle relative to the diameter of the bronchiole lumen.
- The respiratory epithelium descending the tracheobronchial tree has varying heights and complexities, with the trachea and bronchus having ciliated pseudostratified columnar epithelium, conducting bronchioles having ciliated simple columnar epithelium, and terminal bronchioles having ciliated simple cuboidal epithelium, which is replaced by club cells.
- Club cells, also known as nonciliated bronchiolar exocrine cells, secrete proteins, including surfactant apoproteins A,B, and D, lipids, glycoproteins, and modulators of inflammation, act as progenitors for club cells and ciliated epithelial cells, and destroy airborne toxins that reach bronchioles.
- An acinus is a part of the lung supplied by a single 1st order respiratory bronchiole, with all structures to and including the alveolar sac, and all parts of an acinus are involved in gas exchange.
- Alveoli are composed mainly of a thin layer of squamous Type I epithelial cells, which are specialized for gas exchange, and Type II alveolar cells, which are cuboidal epithelium and produce surfactant, with surfactant reducing surface tension and produced in lamellar bodies derived from the Golgi.
- The respiratory zone is the segment of airways completely lined with alveoli, alveolar ducts, and sacs, and each respiratory bronchiole gives rise to 2-11 alveolar ducts, with alveolar ducts being elongated airways with walls completely lined with alveoli and having very small amounts of smooth muscle and elastic tissue.
- An acinus is part of the lung supplied by a single 1st order respiratory bronchiole and all structures to and including the alveolar sac, and all parts of an acinus are involved in gas exchange.
- Alveoli are composed mainly of a thin layer of squamous Type I epithelial cells and large, thin, flattened Type II alveolar cells, with Type II cells producing surfactant.
- Alveoli have a coverage of 10% alveolar surface by Type II alveolar cells, which function as stem cells, and free-ranging phagocytic alveolar macrophages monitor and remove debris and microorganisms.
- The adult human alveolus contains prominent cells, including capillaries, the interstitium, and the alveolar epithelium, with intimately related capillaries, the interstitium, and the alveolar epithelium.
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Description
Test your knowledge on the innervation of the lungs, including the role of pulmonary plexuses, parasympathetic and sympathetic fibers, and non-adrenergic/non-cholinergic (NANC) system in airway regulation.
