Muscles of Larynx

🧠 Muscles of the Larynx

The muscles of the larynx are divided into two groups:

• Extrinsic muscles
• Intrinsic muscles

🔹 Extrinsic Muscles of Larynx

These connect the larynx to surrounding structures and maintain its position in the neck.

🧭 Classification of Extrinsic Muscles:

• Suprahyoid muscles – above the hyoid bone
• Infrahyoid muscles – below the hyoid bone

🛠️ Functionally:

• Suprahyoid muscles → Elevate the larynx
• Infrahyoid muscles → Depress the larynx

During swallowing, these groups work in coordination:

• When suprahyoids contract and infrahyoids relax → larynx elevates
• Laryngeal descent: Suprahyoids simply relax → elastic recoil brings it down

🔸 Infrahyoid Muscles (Depressors of Larynx):

• Thyrohyoid
• Sternothyroid
• Sternohyoid

🔸 Suprahyoid Muscles (Elevators of Larynx):

⬆️ Primary Elevators (direct attachment to thyroid cartilage):

• Stylopharyngeus
• Palatopharyngeus
• Salpingopharyngeus

⬆️ Secondary Elevators (indirect elevation via hyoid bone):

• Mylohyoid
• Geniohyoid
• Stylohyoid
• Digastric

🔹 Intrinsic Muscles of Larynx

These attach one laryngeal cartilage to another.

🎯 Functions:

• Coordinate movement of laryngeal cartilages
• Control shape, position, elasticity, and viscosity of vocal folds
• Move arytenoids at cricoarytenoid joint – opening and closing the glottis

🔸 Classification of Intrinsic Muscles

1️⃣ Muscles Acting on the Vocal Cords

🟢 Abductor – Opens vocal cords

• Posterior cricoarytenoid

  • Only abductor in the larynx

  • Origin: Posterior cricoid lamina

  • Insertion: Muscular process of arytenoid

  • Effect: Abducts and elongates vocal folds; edges become rounded and passively stiff

🔴 Adductors – Close vocal cords

• Lateral cricoarytenoid

  • Origin: Upper border of cricoid arch

  • Insertion: Muscular process of arytenoid

  • Action: Adducts and lowers vocal folds; sharpens edges

• Transverse arytenoid

  • Unpaired muscle

  • Spans between both arytenoid cartilages

  • Action: Adducts vocal folds with little change to stiffness

• Oblique arytenoid

  • Crosses from one arytenoid apex to the other

  • Action: Assists adduction; no major effect on fold stiffness

2️⃣ Muscles Controlling Tension of Vocal Folds

• Thyroarytenoid (including Vocalis)

  • Lies lateral and above vocal ligament

  • Vocalis: thickened lower part

  • Origin: Posterior thyroid prominence

  • Insertion: Vocal process and anterolateral arytenoid

  • Action: Lowers, shortens, and thickens the folds; stiffens them actively

• Cricothyroid

  • Only intrinsic muscle outside the laryngeal cartilaginous framework

  • Origin: Lateral cricoid arch

  • Insertion: Lower border and inferior horn of thyroid cartilage

  • Action: Tenses vocal folds by increasing distance between thyroid angle and arytenoids

3️⃣ Muscles Acting on the Laryngeal Inlet

🔓 Opener:

• Thyroepiglottic (part of thyroarytenoid) – widens inlet

🔒 Closers:

• Oblique arytenoid

• Aryepiglottic muscle (continuation of oblique arytenoid)

  • Together, they narrow the laryngeal inlet during swallowing