Anatomy of the Larynx

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Laryngeal Cartilages & Framework - Skeleton Story

  • Location & Key Functions:
    • Situated at C3-C6 vertebral levels.
    • Essential for: Airway protection (prevents aspiration), Respiration (maintains patent airway), Phonation (voice production).
  • Unpaired Cartilages (Single):
    • Thyroid: Largest. Formed by two laminae fusing anteriorly (laryngeal prominence/Adam's apple). Superior & inferior horns project posterolaterally.
    • Cricoid: Signet ring shape. Only complete cartilaginous ring. Narrow anterior arch, broad posterior lamina.

      ⭐ Cricoid cartilage is the only complete cartilaginous ring in the airway.

    • Epiglottis: Leaf-shaped elastic cartilage. Stalk (petiole) attached to inner thyroid. Guards airway during swallowing.
  • Paired Cartilages (Bilateral):
    • Arytenoid (2): Pyramidal. Base articulates with cricoid. Apex (superior), vocal process (anteriorly, for vocal fold attachment), muscular process (laterally, for muscle attachment).
    • Corniculate (of Santorini) (2): Small, conical. Sit atop arytenoid apices, within aryepiglottic folds.
    • Cuneiform (of Wrisberg) (2): Small, club-shaped. Located anterior to corniculates within aryepiglottic folds, providing support.

Anatomy of the Larynx: Anterior and Lateral Views

Laryngeal Membranes & Spaces - Inner Sanctum

  • Extrinsic Membranes & Ligaments: Connect larynx to adjacent structures.

    • Thyrohyoid membrane: Connects thyroid cartilage to hyoid bone.
      • Median & Lateral thyrohyoid ligaments (thickenings).
    • Hyoepiglottic ligament: Connects hyoid bone to anterior epiglottis.
    • Cricotracheal ligament: Connects cricoid cartilage to first tracheal ring.
  • Intrinsic Membranes & Ligaments: Form internal fibroelastic framework.

    • Quadrangular Membrane (Superiorly):
      • Free upper margin: Aryepiglottic fold (contains aryepiglottic muscle, cuneiform & corniculate cartilages).
      • Free lower margin: Vestibular ligament (forms core of false vocal cord).
    • Conus Elasticus / Cricovocal Membrane (Inferiorly):
      • Free upper margin: Vocal ligament (forms core of true vocal cord).
      • Attaches to cricoid cartilage inferiorly.
  • Laryngeal Cavity Divisions:

    • Vestibule: Laryngeal inlet to vestibular folds.
    • Ventricle: Between vestibular folds (false cords) and vocal folds (true cords).
      • Laryngeal Saccule: Anterior extension of ventricle, contains mucous glands for vocal cord lubrication.
    • Infraglottic Cavity: Below vocal folds to inferior border of cricoid cartilage.
  • Reinke's Space:

    • Subepithelial space (superficial layer of lamina propria) of the true vocal cord.
    • Loose, pliable connective tissue; crucial for vocal fold vibration and voice quality.

Laryngeal membranes and spaces sagittal view

⭐ Reinke's space is the superficial layer of the lamina propria of the vocal fold, prone to edema (Reinke's edema), especially in smokers, leading to hoarseness.

Laryngeal Muscles & Function - Voice Box Dynamos

Intrinsic Muscles: (Voice production & protection; All supplied by Recurrent Laryngeal N. (RLN) except Cricothyroid)

  • Abductor (Opens Cords):
    • Posterior Cricoarytenoid (PCA) - Only abductor, 'Safety muscle' for breathing.
  • Adductors (Closes Cords):
    • Lateral Cricoarytenoid (LCA)
    • Transverse Arytenoid
    • Oblique Arytenoid
  • Tensors (Tenses Cords):
    • Cricothyroid (CT) - External branch Superior Laryngeal N. (SLN). Main tensor. 📌 Cords Tense.
    • Vocalis (part of Thyroarytenoid) - Medial fibers, fine tunes tension.
  • Relaxer (Relaxes Cords):
    • Thyroarytenoid (main bulk) - Main relaxer, shortens/relaxes vocal cords.

Extrinsic Muscles: (Laryngeal movement/support)

  • Elevators: E.g., Stylohyoid, Mylohyoid, Digastric, Geniohyoid.
  • Depressors: E.g., Sternohyoid, Sternothyroid, Omohyoid, Thyrohyoid.

⭐ The Posterior Cricoarytenoid (PCA) is the sole abductor of the vocal cords.

Intrinsic Laryngeal Muscles

Laryngeal Nerves & Vessels - Vital Connections

  • Nerve Supply (Branches of Vagus Nerve - CN X):
    • Superior Laryngeal Nerve (SLN): 📌 'SLN-In is In, Ex is Out' for branches.
      • Internal branch: Sensory to supraglottis; pierces thyrohyoid membrane.
      • External branch: Motor to Cricothyroid muscle.
    • Recurrent Laryngeal Nerve (RLN):
      • Motor: All intrinsic laryngeal muscles except Cricothyroid.
      • Sensory: Glottis & subglottis.
      • Left RLN longer (around aorta); Right RLN (around subclavian artery).
  • Blood Supply:
    • Arteries: Superior Laryngeal Artery (from Superior Thyroid Artery), Inferior Laryngeal Artery (from Inferior Thyroid Artery).
    • Veins: Parallel arteries; drain to Superior & Inferior Thyroid Veins.
  • Lymphatic Drainage:
    • Supraglottic: Superior deep cervical nodes.
    • Glottic: Sparse drainage.
    • Subglottic: Pretracheal, paratracheal, & inferior deep cervical nodes.

Laryngeal Nerves and Arteries Diagram

⭐ The left Recurrent Laryngeal Nerve has a longer course and is more vulnerable to injury in thoracic procedures.

High‑Yield Points - ⚡ Biggest Takeaways

  • Larynx: 9 cartilages (3 unpaired: Thyroid, Cricoid, Epiglottis; 3 paired: Arytenoid, Corniculate, Cuneiform).
  • Cricoid cartilage: the only complete airway ring. Arytenoids: key for vocal cord movement.
  • Posterior Cricoarytenoid (PCA): the sole vocal cord abductor (safety muscle).
  • Recurrent Laryngeal Nerve (RLN) supplies all intrinsic muscles except Cricothyroid (by ESLN).
  • Cricothyroid tenses vocal cords (↑ pitch); RLN injury causes hoarseness.
  • Sensory: Internal SLN (supraglottis), RLN (infraglottis).

Practice Questions: Anatomy of the Larynx

Test your understanding with these related questions

A patient presents with hoarseness and laryngoscopy reveals a warty, cauliflower-like growth on the vocal cord. Identify the most likely lesion.

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Flashcards: Anatomy of the Larynx

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Fenestrations in the tracheostomy tube are important for _____

TAP TO REVEAL ANSWER

Fenestrations in the tracheostomy tube are important for _____

phonation

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