Tsm32: larynx 15/10/08 Learning Outcomes

Download 54.5 Kb.
Size54.5 Kb.

TSM32: larynx 15/10/08

Learning Outcomes

Describe the functional anatomy of the larynx

  • The larynx joins the upper and lower respiratory tracts – from the pharynx to the trachea

    • Comprises muscle, ligament and cartilage suspended from the hyoid bone

    • Lined internally by mucosa forming a tubular passage for air

    • Acts as a valve to protect the lower respiratory tract and produces sounds

    • Sensory and motor supply all through branches of the vagus nerve (CNX)

  • There are three regions of the larynx divided by two pairs of folds in the mucosal lining:

    • Vestibule – between the laryngeal inlet and the vestibular folds (of the vestibular ligament)

    • Middle – thin area between the vestibular and vocal folds (with bilateral ventricles)

    • Infraglottic space – between the vocal folds (of the vocal ligament) and trachea

laryngeal cartilages

  • There are three main unpaired cartilages forming the bulk of the laryngeal framework:

    • Cricoid – shaped like a ‘signet ring’ with a broad posterior lamina and thin anterior arch

      • Caps the trachea

      • Articulates with the arytenoid cartilages superiorly

      • Articulates with the thyroid cartilage postero-laterally

    • Thyroid – largest cartilage, U-shaped, closed anteriorly but open posteriorly

      • Covers the bulk of the larynx and forms the anterior laryngeal wall

      • Anterior laryngeal prominence in the midline (Adam’s apple)

      • Articulates with the cricoid via small infero-posterior projections – inferior horns

      • Articulates with the hyoid bone superiorly via lateral thyroid ligaments from the superior horns

    • Epiglottis – leaf-shaped flap that can occlude or expose the laryngeal inlet

      • Attached at its ‘stem’ to the lower internal surface of the anterior thyroid cartilage

      • Suspended from the hyoid bone in the midline by the hyoepiglottic ligament

      • Projects postero-superiorly towards the pharyngeal tongue

  • There are also three sets of smaller paired cartilages:

    • Arytenoids – pyramid-shaped with posterior, antero-lateral and medial surfaces

      • Concave bases articulate inferiorly with the posterior cricoid cartilage

      • Articulate superiorly (at the apices) with the corniculate cartilages

      • Antero-lateral surfaces attach to the vocalis muscle and vestibular ligament

      • Anterior vocal processes attach to the vocal ligaments

      • Lateral muscular processes attach to the crico-arytenoid muscles

    • Corniculates – small, conical

      • Articulate at the base inferiorly to the apex of the arytenoid cartilage

      • Apices project posterior-medially

    • Cuneiforms – small, club-shaped

      • Suspended in the laryngeal membrane between the corniculates and the epiglottis

laryngeal membrane

  • The larynx is supported structurally by an internal fibroelastic membrane comprising two parts:

    • Cricothyroid ligament – inferiorly

      • Extends round the arch of the cricoid cartilage

      • Attaches at a point anteriorly to the internal surface of the thyroid cartilage

      • Attaches bilaterally posteriorly to the vocal processes of the arytenoid cartilages

      • Thickened free superior margin between these points forms the vocal ligament

    • Quadrangular membrane – superiorly

      • Extends round the lateral borders of the epiglottis

      • Attaches at a point anteriorly above the attachment of the cricothyroid ligament

      • Attaches bilaterally posteriorly to the antero-lateral surfaces of the arytenoids

      • Thickened free inferior margin between these points forms the vestibular ligament

  • There are two distinct openings between the mucosal folds visible from above in laryngoscopy:

    • Rima vestibuli – between the two vestibular folds (‘false’ vocal cords)

    • Rima glottidis – between the two vocal folds (‘true’ vocal cords)

laryngeal muscles and innervation

  • The larynx houses several intrinsic muscles which control various intrinsic movements:

    • Cricothyroid – pulls the thyroid cartilage down onto the cricoid; lengthens vocal ligaments

    • Posterior crico-arytenoid externally rotates the arytenoid cartilages; opens vocal ligaments

    • Lateral crico-arytenoid – internally rotates the arytenoid cartilages; closes vocal ligaments

    • Vocalis – follows the vocal ligaments; adjusts tension in vocal ligaments

  • The recurrent laryngeal nerve (branch of vagus) provides:

    • Motor innervation to all the above muscles except cricothyroid

    • Sensory innervation below the vocal folds

  • The superior laryngeal nerve (branch of vagus) provides:

    • Motor innervation to cricothyroid only

    • Sensory innervation above the vocal folds

Share with your friends:

The database is protected by copyright ©dentisty.org 2019
send message

    Main page