Tracheal Muscle Anatomy
Yes, the trachea contains smooth muscle, specifically the trachealis muscle located in the posterior membranous wall, along with an extensive elastic tissue framework that works together to regulate airway diameter and maintain structural stability. 1, 2
Primary Muscular Components
The trachea contains two distinct muscular elements:
Trachealis muscle: A transverse layer of smooth muscle located deep to the fibroelastic membrane in the posterior membranous wall (pars membranacea) of the trachea, which is the primary controller of tracheal lumen variation 1
Longitudinal muscle fibers: Scattered longitudinal smooth muscle bundles exist outside the main constrictor musculature, though these are rudimentary and appear to have minimal functional importance in humans 1
Annular constrictor muscle (m. constrictor tracheae): An additional circular smooth muscle component that has been identified in both human and animal tracheas 1
Anatomical Distribution
The smooth muscle architecture extends throughout the conducting airways:
Smooth muscle is present in the trachea and continues along the entire bronchial tree down to the terminal bronchioles 3
The muscle encircles the airway below the level of the main bronchus in a roughly circular orientation 4
In peripheral airways, smooth muscle occupies relatively more of the airway wall, reaching maximum proportion in the membranous bronchioles 4
Functional Role
The tracheal musculature serves critical mechanical functions:
Airway stability: The outer tracheal musculature and elastic cartilaginous arches work together to maintain stability of the tracheal wall 1
Lumen regulation: The trachealis muscle in the membranous wall is the main controller of tracheal diameter changes 1
Bronchomotor tone: Airway smooth muscle regulates bronchomotor tone throughout the respiratory tree, with shortening of smooth muscle modulating airway luminal diameter and resistance 3
Supporting Elastic Framework
The muscular components work in conjunction with an extensive elastic tissue network:
An extensive meshwork of elastic tissue exists within the trachea, with fibers predominantly arranged longitudinally and aggregated into discrete bundles within the membranous wall 2
A discrete fibroelastic membrane bridges the membranous wall of the trachea, with the trachealis muscle embedded within or deep to this membrane 2
This elastic framework has major clinical relevance to respiratory disease pathophysiology and aging, though it has been relatively neglected in medical literature 2
Clinical Significance
The conducting airways have multilayered walls consisting of mucous membrane, smooth muscle, and cartilage, forming an integrated structural unit 5
Understanding tracheal muscle anatomy is essential during procedures like tracheal resection, where careful dissection must preserve the structural integrity of these components 6
The smooth muscle is present and functional in utero, increasing in absolute area during growth with little further change during adulthood 4