UNIT 5 SECOND ORDER

Larynx Muscles

1. Cricothyroid

2. Lateral cricoarytenoid

3. Posterior cricoarytenoid

4. Thyroarytenoid or vocalis

Cricothyroid - O

1. Anterolateral part of cricoid cartilage

Cricothyroid - I

1. Thyroid cartilage

Cricothyroid - A

1. Stretches and tenses vocal ligament

Cricothyroid - N

1. External branch of superior laryngeal N (CN X)

Cricothyroid - B

1. Superior thyroid A

Cricothyroid clinical significance

1. External branch of superior laryngeal N can impair pitch modulation (professional voice users)

Lateral cricoarytenoid - O

1. Cricoid cartilage

Lateral cricoarytenoid - I

1. Arytenoid cartilage

Lateral cricoarytenoid - A

1. Adducts vocal folds

Lateral cricoarytenoid - N

1. Inferior laryngeal N (branch of recurrent laryngeal N, CN X)

Lateral cricoarytenoid - B

1. Inferior thyroid A

Lateral cricoarytenoid clinical significance

1. Weakness = incomplete glottic closure → hoarseness or aspiration

Posterior cricoarytenoid - O

1. Cricoid cartilage

Posterior cricoarytenoid - I

1. Arytenoid cartilage

Posterior cricoarytenoid - A

1. Abduct vocal folds

Posterior cricoarytenoid - N

1, Inferior laryngeal N (branch of recurrent laryngeal N, CN X)

Posterior cricoarytenoid - B

1. Inferior thyroid A

Posterior cricoarytenoid clinical significance

1. Only muscle that opens rima glottidis

2. Bilateral paralysis = airway obstruction and require tracheostomy

Thyroarytenoid or vocalis - O & I

• O

  1. Thyroid cartilage

  2. Cricothyroid ligament

• I

  1. Arytenoid cartilage

  2. Vocal ligament

Thyroarytenoid or vocalis - A

1. Relaxes vocal ligament, allowing for lower pitch

Thyroarytenoid or vocalis - N

1. Inferior laryngeal N (branch of recurrent laryngeal N, CN X)

Thyroarytenoid or vocalis - B

1. Inferior thyroid A

Thyroarytenoid or vocalis clinical significance

1. Dysfunction = vocal fatigue and diminished ability to vary pitch during speech

Transverse and oblique arytenoid

• A: Adducts arytenoid cartilages, closing posterior rima glottidis

• N: Inferior laryngeal N (branch of recurrent laryngeal N, CN X)

• B: Inferior thyroid A

• Important for firm glottic closure during swallowing

  • Dysfunction = aspiration

Oral cavity muscles

1. Genioglossus

2. Geniohyoid

3. Hyoglossus

4. Styloglossus

Genioglossus - O

1. Mental spine of mandible

Genioglossus - I

1. Entire dorsum of tongue

2. Inferior fibers attach to body of hyoid

Genioglossus - A

1. Depresses tongue

2. Posterior = protrudes tongue

3. Anterior = retracts apex

Genioglossus - B

1. Sublingual (branch of lingual A)

Genioglossus clinical significance

• Weakness/paralysis = posterior tongue displacement and airway obstruction

  • Unconscious or anesthetized patients

What does hypoglossal N (CN XII) innervate?

Oral cavity muscles!

1. Genioglossus

2. Geniohyoid

3. Hyoglossus

4. Styloglossus

Geniohyoid - O

1. Inferior mandible

Geniohyoid - I

1. Body of hyoid bone

Geniohyoid - A

1. Pulls hyoid superiorly

2. Shortens floor of mouth

3. Widens pharynx

Geniohyoid - N

1. C1 via hypoglossal N (CN XII)

Geniohyoid - B

1. Lingual A

Geniohyoid clinical significance

1. Weakness = impair tongue base elevation, impacting safe swallowing

Hyoglossus - O

1. Hyoid bone

Hyoglossus - I

1. Inferior sides of tongue

Hyoglossus - A

1. Depresses tongue

2. Draws sides of tongue inferiorly (flatten tongue)

Hyoglossus - B

1. Lingual A

Hyoglossus clinical significance

• Surgical approaches to tongue or submandibular region

  • CN XII at risk where it passes superficial

Styloglossus - O

1. Styloid process

Styloglossus - I

1. Sides of tongue posteriorly

Styloglossus - A

1. Retracts tongue

2. Curls tongue (elevates) sides

Styloglossus - B

1. Ascending pharyngeal A (branches of facial A)

Styloglossus clinical significance

• Important role in swallowing by forming a trough with the tongue

  • Helps guide the bolus posteriorly

Orbit muscles

1. Inferior oblique

2. Inferior rectus

3. Lateral rectus

4. Levator palpebrae superioris

5. Medial rectus

6. Orbicularis oculi

7. Superior oblique

8. Superior rectus

Inferior oblique - O

1. Anterior part of floor of orbit

Inferior oblique - I

1. Sclera

Inferior oblique - A

1. ABD eyeball

2. Elevates eyeball

3. Laterally rotates eyeball

   • Allows you to look up and out when eye is adducted

   • Extorsion = external rotation of eye

Inferior oblique - N

1. Oculomotor N (CN III)

Inferior oblique - B

1. Infraorbital A

Inferior oblique clinical significance

• Overactivation = strabismus

Inferior rectus - O

1. Common tendinous ring

Inferior rectus - I

1. Sclera

Inferior rectus - A

1. Depresses eyeball

2. ADD eyeball

3. Laterally rotates eyeball

Inferior rectus - N

1. Oculomotor N (CN III)

Inferior rectus - B

1. Ophthalmic A

Inferior rectus clinical significance

• Entrapment = orbital floor fractures

  • Limits upward gaze

Medial rectus - O

1. Common tendinous ring

Medial rectus - I

1. Sclera

Medial rectus - A

1. ADD eyeball

Medial rectus - N

1. Oculomotor N (CN III)

Medial rectus - B

1. Ophthalmic A

Medial rectus clinical significance

• Palsy = exotropia and convergence difficulties

Lateral rectus - O

1. Common tendinous ring

Lateral rectus - I

1. Sclera

Lateral rectus - A

1. ABD eyeball

Lateral rectus - N

1. Abducens N (CN VI)

Lateral rectus - B

1. Lacrimal A

Lateral rectus clinical significance

• CN VI palsy = horizontal dipoplia

  • Can signal elevated intracranial pressure

Levator palpebrae superioris - O

1. Lesser wing of sphenoid bone

Levator palpebrae superioris - I

1. Superior eyelid

Levator palpebrae superioris - A

1. Elevates upper eyelid

Levator palpebrae superioris - N

1. Oculomotor N (CN III)

2. Superior tarsal muscle by sympathetic fibers

Levator palpebrae superioris - B

1. Ophthalmic A

Levator palpebrae superioris clinical significance

• Ptosis = damage CN III or sympathetic fibers (Horner’s syndrome)

Orbicularis oculi (orbital/palpebral) - O

1. Medial orbital margin

2. Lacrimal bone

Orbicularis oculi (orbital/palpebral) - I

1. Skin around margin of orbit

2. Superior and inferior tarsi

Orbicularis oculi (orbital/palpebral) - A

1. Closes eyelids

   • Palpebral: gently

   • Orbital: tightly (winking, squinting)

Orbicularis oculi (orbital/palpebral) - N

1. Facial N (CN VII)

Orbicularis oculi (orbital/palpebral) - B

1. Facial A

2. Superficial temporal A

Orbicularis oculi (orbital/palpebral) clinical significance

1. Dysfunction = dry eye

2. Exposure keratitis due to incomplete eyelid closure

Superior oblique - O

1. Body of sphenoid bone

Superior oblique - I

1. Tendon passes through trochlea to insert into sclera deep to superior rectus muscle

Superior oblique - A

1. ABD eyeball

2. Depresses eyeball

3. Medially rotates eyeball

   • Allows you to look down and out (depressing eye when adducted)

   • Medial rotation = intorsion

Superior oblique - N

1. Trochlear N (CN IV)

Superior oblique - B

1. Ophthalmic A

Superior oblique clinical significance

• CN IV palsy = vertical dipoplia

  • Reading or descending stairs

Superior rectus - O

1. Common tendinous ring

Superior rectus - I

1. Sclera

Superior rectus - A

1. Elevates eyeball

2. ADD eyeball

3. Medially rotates eyeball

Superior rectus - N

1. Oculomotor N (CN III)

Superior rectus - B

1. Ophthalmic A

Superior rectus clinical significance

• Lesions = impair upward gaze and dipoplia

Palate muscles

1. Levator veli palatini

2. Tensor veli palatini

Levator veli palatini - A

1. Elevates soft palate during swallowing and yawning

Levator veli palatini - N

1. Vagus N (CN X)