37 Questions
Which part of the tracheobronchial tree contains plates of cartilage instead of rings?
Segmental bronchi
What is the main structural difference between the right and left main bronchi?
Number of cartilage bands in the left main bronchus
Which part of the tracheobronchial tree is located after the trachea bifurcates?
Main bronchi
Where are the bronchopulmonary segments located?
In the lung lobes
Which arteries branch with the bronchi to supply blood to the tracheobronchial tree?
Bronchial arteries
Where do bronchial veins drain the proximal part of the root of the lung?
Into azygos vein and SVC
What is the most distal branch that anastomoses with branches of pulmonary arteries in bronchioles?
Tertiary branch of the pulmonary artery
Which part of the tracheobronchial tree occurs after tertiary bronchi and lacks cartilage and glands?
Bronchioles
What is the arterial supply of the lung stroma?
Bronchial arteries
What is a common variation in the origin of bronchial arteries?
Varying sizes in different individuals
What is the function of lamellar bodies in type II alveolar epithelial cells?
Formation of surfactant
Which cell type secretes surfactant into the fluid lining the alveoli?
Type II alveolar epithelial cell
What is the primary source of the phospholipid surface film in the alveoli?
Tubular myelin from lamellar bodies
What is the average distance from the teeth to the vocal cords?
10 cm
Which of the following is the largest subdivision of a lung lobe?
Bronchopulmonary segment
Which neurotransmitter is most likely to produce bronchodilation?
Humoral release of epinephrine/norepinephrine
What is a possible response to attempting laryngoscopy in a fully awake patient?
Laryngospasm
Which type of cells specialize in gas exchange in the alveoli?
Type I epithelial cells
What is the main function of Type II alveolar cells?
Produce surfactant
Where are smooth muscle and elastic connective tissue fibers significant in the respiratory system?
Bronchioles
What is the predominant balance to the excitatory cholinergic system in the pulmonary plexus?
Visceral afferents
Which cells destroy airborne toxins reaching the bronchioles?
Club cells
Which fibers are responsible for inhibiting secretion from bronchial glands and weakly bronchodilating?
Sympathetic fibers
Which part of the lung is involved in gas exchange and supplied by a single 1st order respiratory bronchiole?
Acinus
Which cells function as stem cells in the alveoli?
Type II alveolar cells
Which system is predominantly responsible for bronchodilation during 'flight or fight' circumstances?
Sympathetic nervous system
Which part of the respiratory zone gives rise to elongated airways completely lined with alveoli?
Alveolar ducts
Which part of the tracheobronchial tree contains smooth muscle and is responsible for bronchoconstriction?
Terminal bronchioles
What is the primary function of the respiratory epithelium in the conducting airways?
Mucus production
Which type of cells found in the alveoli are responsible for the production of surfactant?
Type II alveolar epithelial cells
What is the main difference between the left and right main bronchi?
Number of cartilage rings
Which structure provides the motor and sensory innervation of the lungs?
Pulmonary plexuses
Which part of the tracheobronchial tree contains plates of cartilage instead of rings?
Bronchioles
What is the function of lamellar bodies in type II alveolar epithelial cells?
Surfactant secretion
Where do bronchial veins drain the proximal part of the root of the lung?
Azygos vein
What is the main structural difference between conducting and respiratory bronchioles?
Cartilage plates
Which cells and mediators affect respiratory airways, including club and mast cells and chemical mediators?
Smooth muscle cells
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.
Test your knowledge on the innervation of the lungs and airways, including the role of pulmonary plexuses, parasympathetic and sympathetic fibers, and the non-adrenergic/non-cholinergic system. Explore how these systems influence airway diameter, vasoconstriction, and gland secretion.
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