Anatomy of the Larynx: Cartilages, Muscles, Nerves and Blood Supply
The larynx is a cartilaginous, muscular and ligamentous organ connecting the laryngopharynx to the trachea. It maintains a patent airway, protects the lower respiratory tract during swallowing and houses the vocal folds for phonation.
Airway protection, respiration and phonation. These depend on coordinated movement of the laryngeal cartilages and intrinsic muscles under vagal control.
Learning objectives
- Identify the laryngeal cartilages, membranes and cavities.
- Explain intrinsic muscle actions.
- Outline sensory, motor and vascular supply.
- Relate anatomy to airway emergencies and vocal-cord palsy.
Position and subdivisions
The adult larynx lies in the anterior neck, roughly from C3 to C6. It is suspended from the hyoid bone, opens superiorly into the laryngopharynx and continues inferiorly as the trachea. The cavity is divided into the supraglottis, glottis and subglottis.
| Region | Extent and contents |
|---|---|
| Supraglottis | From laryngeal inlet to vestibular folds; includes epiglottis, aryepiglottic folds and vestibule. |
| Glottis | True vocal folds and the rima glottidis between them. |
| Subglottis | Below the vocal folds to the inferior border of the cricoid cartilage. |
Laryngeal cartilages
Largest cartilage; two laminae meet anteriorly to form the laryngeal prominence. Superior and inferior horns articulate with adjacent structures.
Only complete cartilaginous ring of the airway; signet-shaped with a broad posterior lamina.
Elastic leaf-shaped cartilage that helps shield the laryngeal inlet during swallowing.
Pyramidal cartilages on the cricoid; vocal and muscular processes anchor folds and muscles.
Small elastic cartilages supporting the posterior aryepiglottic folds.
Joints, membranes and folds
- Cricothyroid joints permit tilting that changes vocal-fold tension.
- Cricoarytenoid joints permit rotation and gliding to abduct or adduct the vocal folds.
- The thyrohyoid membrane joins thyroid cartilage to hyoid and is pierced by the internal laryngeal nerve and superior laryngeal vessels.
- The cricothyroid membrane links thyroid and cricoid; its median portion is an emergency airway landmark.
- The quadrangular membrane contributes to vestibular folds; the conus elasticus contributes to vocal ligaments.
The false or vestibular folds lie superior to the true vocal folds. The laryngeal ventricle lies between them.
Intrinsic muscles
| Muscle | Main action |
|---|---|
| Posterior cricoarytenoid | Only abductor of the vocal folds; opens the rima glottidis. |
| Lateral cricoarytenoid | Adducts vocal folds. |
| Transverse and oblique arytenoids | Adduct arytenoids and close posterior glottis. |
| Cricothyroid | Tenses and lengthens vocal folds, raising pitch. |
| Thyroarytenoid and vocalis | Relax, shorten and finely adjust vocal-fold tension. |
| Aryepiglottic/thyroepiglottic fibres | Narrow or widen the laryngeal inlet. |
The posterior cricoarytenoid is the only muscle that abducts the vocal folds. Bilateral paralysis can cause critical airway obstruction.
Nerve supply
All laryngeal nerves are branches of the vagus nerve.
- Internal laryngeal nerve: sensation above the vocal folds and afferent limb of the cough reflex.
- External laryngeal nerve: motor to cricothyroid; injury causes difficulty producing high-pitched sounds.
- Recurrent laryngeal nerve: motor to all other intrinsic muscles and sensation below the vocal folds.
The left recurrent nerve loops under the aortic arch; the right loops under the subclavian artery. Their long course makes them vulnerable in thyroid, neck and thoracic disease or surgery.
Blood supply and lymphatics
Superior laryngeal vessels arise mainly from the superior thyroid vessels; inferior laryngeal vessels arise from inferior thyroid vessels. Venous drainage follows corresponding veins. Supraglottic lymph drains mainly to upper deep cervical nodes, whereas subglottic lymph drains toward pretracheal, paratracheal and lower deep cervical nodes. The true vocal folds have relatively sparse lymphatic drainage.
Clinical anatomy
- Cricothyrotomy: emergency access through the median cricothyroid membrane.
- Vocal-cord palsy: unilateral disease causes hoarseness; bilateral positioning determines airway risk.
- Laryngeal oedema: small increases in mucosal thickness can severely narrow a child’s airway.
- Foreign body: stimulation above the cords triggers cough; obstruction may cause stridor.
- Cancer spread: lymphatic patterns differ across supraglottic, glottic and subglottic regions.
Continue with the physiology of phonation and physiology of swallowing.
Key examination points
- Cricoid is the only complete airway cartilage.
- Posterior cricoarytenoid is the only vocal-fold abductor.
- Cricothyroid is supplied by the external laryngeal nerve.
- All other intrinsic muscles receive recurrent laryngeal motor supply.
- Sensation above the cords is internal laryngeal; below is recurrent laryngeal.
References and further reading
- NCBI Bookshelf: Anatomy, Head and Neck, Larynx.
- NCBI Bookshelf: Laryngeal Muscles.
- NCBI Bookshelf: Larynx Vocal Cords.
For education only. Apply current Uganda Clinical Guidelines, local protocols and specialist advice.
