Larynx & Pharynx

Development of Larynx

• Supraglottis: From 4th Arch.

• Subglottis and glottis: From 6th Arch.
• Supraglottis: Above vocal cords.
• Glottis: At vocal cord level and 1 cm below.
• Subglottis: From 1 cm below vocal cords to lower cricoid border.

Development of Epiglottis

• Derived from hypobranchial eminence of floor of 4th arch.

Functions of Larynx

• Protection of Lower Airways

• Phonation

• Respiration

• Fixation of the chest

Differences between Adult and Infant Larynx

• In Infants, Submucosal tissue is more abundant.

• Allows edema/inflammation/infection to spread quickly.

Examination of Larynx

• Direct: Using Direct Laryngoscopy.
• 70 degree Endoscope
• 90 degree Endoscope

• Indirect: Using an Indirect Laryngoscopic Mirror (IDL).
• (Reflection of Larynx in Mirror)

One Liners

Pharynx N supply

• Pharyngeal plexus formed by:
• Glossopharyngeal nerve
• Vagus nerve
• Superior cervical sympathetic ganglion

• Note : Cranial part of XI nerve doesn't contribute to pharyngeal plexus(Recent update).

Motor Supply

• Motor fibers are SVE (Special Visceral Efferent)

• Mnemonic: Save to Eat

Nucleus Ambigus (medulla)

• Nucleus for CN 9, 10, 11

Sensory Supply

• Glossopharyngeal nerve (CN IX) – major role
• Sensation from:
• Soft palate
• Pharynx
• Posterior oral cavity

• Vagus nerve (CN X) – contributes partially
• Carries afferent from pharynx
• GSA (General Somatic Afferent)
• GVA (General Visceral Afferent)

Larynx N supply

A - Hyoid

B - Thyroid cartilage

C - Epiglottis

D - Cricoid cartilage

Development

• Cartilages from 4th and 6th arch mesoderm

Applied Anatomy

• Posterior cricoarytenoid = Safety muscle of larynx

Innervation

• All muscles of larynx derived from 6th arch.
• Supplied by RLN
• Except: Cricothyroid (4th arch → ELN of SLN)

SLN:

• External branch:
• Cricothyroid
• Controls vocal cord tensor.
• Function: Tensor, adductor (intrinsic muscle)
• Injury → Hoarseness (due to inability to tense cords) → Low pitch
• Mnemonic: Ele (ELN) monu CT (cricothyrodi) edukkan poyapo tension (Tensor) ayi

• Internal branch:
• SLN → ILN → Cough reflex
• Sensation above vocal cord
• Pierces thyrohyoid membrane
• Supplies epiglottis and posterior tongue (general & special sensation)

RLN:

• Supplies all intrinsic laryngeal muscles (except cricothyroid)

• Sensation below vocal cord
• (glottis, subglottis)

• Course
• Right RLN:
• winds around right subclavian artery
• Does not enter thoracic inlet
• Left RLN:
• winds around arch of aorta & ligamentum arteriosum (6th arch)
• Longer course
• Lies in tracheo-oesophageal groove

Nucleus:

• Nucleus Ambiguus (for SVE of vagus)

Applied Aspect

Nerve Injury

• Commonest RLN injured:
• Left RLN (longer course)

• Commonest cause bilateral RLN palsy:
• Surgical trauma (esp. Total thyroidectomy)

• B/L RLN Palsy
• ⛔ Posterior Cricoarytenoid → Safety muscle of VC → Abductor
• Stridor, aphonia, breathlessness (Life threatening)
• Inability to extubate

ㅤ	U/L RLN injury	SLN Injury
Presentation	• Unilateral vocal cord paralysis • Hoarseness • Post-op dysphonia • Dyspnea • Difficulty in deglutition	• ILN → Aspiration → Absent cough reflex • ELN → Low pitch
Vocal cord appearance	• RLN injury = Paramedian	• RLN + SLN injury = Cadaveric/intermediate

Types of Vocal Cord Palsy

• Complete/adductor palsy
• SLN + RLN palsy
• VC in cadaveric/intermediate position (3.5 mm from midline)

• Incomplete/abductor palsy
• RLN palsy
• Cricothyroid intact
• VC in median/paramedian position (1.5 mm from midline)

Clinical Features

• Lateralisation of VC
• Kashima → Type 2 thyroplasty
• Woodmans → cordectomy + Arytenoidectomy

Surgical Trauma

Site of injury	Nerve injured
Base of skull	Complete vagus / SLN
Carotid triangle	ILN / ELN / SLN
Upper pole of thyroid	ELN ↳ most common injured in thyroid surgery
Lower pole of thyroid	RLN ↳ 2nd most common injured in thyroid surgery ↳ Rt > Lt
Mediastinal	Left RLN ↳ also in Ortner’s / cardiovocal syndrome

Normal VC position	during
Lateral	Deep inspiration
Paramedian	Rest
Median	Phonation

During total thyroidectomy for papillary carcinoma thyroid in a thirty-six-year-old lady, the
recurrent laryngeal nerve of right side was sacrificed for oncological safety. The next day, the patient complained of breathy voice. A fiberoptic laryngoscopy on the second post-operative day showed vocal cord paralysis of the right side. What would be the positions of the right and left vocal cords in this patient, on phonation?
(A) Right cadaveric, left intermediate
(B) Right intermediate, left intermediate
(C) Right paramedian, left median
(D) Right paramedian, left paramedian

ANS

C

Treatment of Vocal Cord Palsy

Isshiki’s thyroplasty types

• Type I (Medialisation/Proximalisation)
• Thyroid cartilage pushed medially
• Indication: U/L complete (adductor palsy)

• Type II (Lateralisation)
• Thyroid cartilage pulled laterally
• Indication: B/L RLN palsy

• Type III (Shortening)
• Part of thyroid cartilage cut
• Vocal cord shortened → pitch ↓
• Indication: Puberphonia
• Shorten the long man (shortening) who has guts (Gutzmann manoevre) but female sound (Puberphonia)

• Type IV (Tightening/Tensing)
• Indication: Androphonia
• Lengthen () the short female with male voice (androphonia)

Note

• Laryngeal inlet = epiglottis + arytenoid

• ILN injury → loss of cough reflex

Galen’s anastomosis:

• Between:
• Internal laryngeal nerve (from SLN)
• Recurrent laryngeal nerve (from RLN)

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Clinical Testing

• Hypoglossus (CN 12)
• Test: ask patient to protrude tongue
• If lesion present: tongue deviates towards the affected side (ipsilateral deviation)

• Glossopharyngeal N (CN 9)
• Test: pressure on soft palate/uvula
• Also supply Glossopharyngeus

• Circumvallate papillae
• Present in the anterior 2/3rd part of the tongue
• But special sensation carried by glossopharyngeal

• Jugular canal
• Carries the glossopharyngeal nerve (IX)
• Fracture of the jugular canal
• Loss of taste sensation in the posterior 1/3rd of the tongue

Cartilages

• The larynx is the voice box.

Types of Cartilages

• Unpaired: (3)
• Cricoid: Hyaline, only complete cartilaginous ring.
• Thyroid: Hyaline, largest cartilage.
• Epiglottis: Elastic.

• Paired: (4)
• Cuneiform: Elastic.
• Corniculate: Elastic.
• Arytenoid: Hyaline.
• Apex = Elastic
• Base = Hyaline
• Triticial: Elastic

• Hyaline cartilages calcify with age; elastic do not.

• Mnemonic: End with “Oid” → Hyaline → Calcify (HAI Oiiii)

Important Information

• Laryngeal Crepitus:
• Movement of cricoid against vertebrae.
• Normally positive.

• Laryngeal crepitus is absent in:
• Known as Moure's Sign or Bocca's Sign.
• Post cricoid carcinoma.
• Retropharyngeal abscess.
• Prevertebral abscess.

1. Thyroid Cartilage

• Butterfly-shaped.

• Alae meet at
• 90 degrees in males,
• 120 degrees in females.

• Muscles Attached:
• Oblique line:
• Sternothyroid
• Thyrohyoid
• Thyropharyngeus
• Inner surface:
• Epiglottis
• vocal cords

2. Cricoid Cartilage

• Signet ring shaped.

• Narrow arch anteriorly, wide lamina posteriorly.

• A lesion here results in Subglottic stenosis.

• Has Superior facet and Inferior facet
• Superior facet → attachment to Arytenoid Cartilage
• Inferior facet → attachment to Inferior horn of thyroid cartilage

3. Epiglottic Cartilage

• Leaf-like structure.

• Primary function: Protection of the Airway.

• Divided into Suprahyoid and Infrahyoid parts.

• Surfaces:
• Lingual: Stratified squamous epithelium.
• Laryngeal: Respiratory Epithelium.

4. Arytenoid Cartilage

• Pyramid shape.

• Vocal process: Attachment for vocal cords.

• Vocal cords
• Extend from Thyroid to Arytenoid cartilage.
• Has a muscular process

5. Corniculate Cartilage

• Also Known as Cartilage of Santorini

6. Cuneiform Cartilage

• Also Known as Cartilage of Wrisberg

Epithelium

• Mainly Respiratory epithelium lines larynx

• Exceptions (Stratified squamous epithelium):
• Lingual surface of Epiglottis.
• Upper margin of vocal cords.
• Aryepiglottic folds.

Muscles of Larynx

• All muscles of larynx derived from 6th arch.
• Supplied by RLN
• Except: Cricothyroid (4th arch → ELN of SLN)

• Larynx open
• TEa (Thyroepiglottis) opens larynx

• Larynx close
• when saying IA (Interarytenoid)

• When calling IA → everyone goes away → (IA - Unpaired)

• CT taken from outside (CT lies outside)

• Vocalis
• Change the pitch → by changing the mass of the cord

• Only unpaired muscle :
• Interarytenoid.

• Only intrinsic muscle lying outside :
• Cricothyroid.

Cricothyroid:

• Only muscle on extrinsic surface.

• 2 bellies

• Major tensor

• Supplied by External Laryngeal Nerve.

Interarytenoid/ Transverse Arytenoid:

• Only Unpaired muscle.

• Only muscle with Dual Innervation.

Membranes of Larynx

Extrinsic:

• Thyrohyoid membrane: Has openings for Superior laryngeal nerve and vessels.

• Cricotracheal membrane.

Intrinsic:

• Cricovocal membrane:
• Upper fibers form Vocal Ligament → True cords

• Quadrangular membrane:
• Extends between Epiglottis, Thyroid cartilage and Arytenoid
• Upper fibers form Aryepiglottic fold
• Lower fibers form Vestibular ligament (False cords).

• Cricothyroid membrane:
• Cricothyrotomy

4 Layers of Vocal Cords are (Superficial to Deep)

1. Epithelial layer

2. Superficial Lamina Propria

3. Vocal Ligament (formed by upper fibers of cricovocal membrane)

4. Vocalis (formed by median fibers of Thyroarytenoid muscle)

Reinke's Space:

• Submucosal space of true VC.

• Space between Epithelium and Superficial Lamina Propria.

• Reinke's Edema is accumulation here.

Spaces of Larynx

Para-glottic Space of Tucker

• Medially:
• Quadrangular membrane lower border → False cord
• Ventricle
• Cricovocal membrane → True cord

• Laterally:
• Thyroid cartilage

• PAra - Turcky

Pre-glottic Space of Boyer’s

Applied Aspect:

• Ca. supraglottis
• Affect Pre epiglottic space.

Lymphatics of Larynx

• Supraglottis: Drains to
• Upper deep cervical lymph nodes
• Middle deep cervical lymph nodes

• Glottis: Has No Lymphatics.

• Subglottis: Drains to
• Prelaryngeal
• Pretracheal
• then Lower deep cervical or mediastinal nodes.

Cavity of Larynx

Laryngocele

• An air-filled diverticulum from the larynx that develops due to increased pressure.

• (Enlargement of saccule) → Pierces thyrohyoid membrane → Extrinsic laryngocele (External neck swelling)
• ↑ Size on valsalva manoeuvre
• Hissing sound on compression : Bryce sign.

• Seen in trumpet blowers.

Indirect Laryngoscope (Laryngeal mirror)

 

• Mirror: Straight, mirror at end

• Structures seen (order):
• Oropharynx:
• Base of tongue, lingual tonsils, valleculae, medial & lateral glossoepiglottic folds
• Laryngopharynx:
• Piriform fossae, post-cricoid region, posterior pharyngeal wall
• Larynx:
• Epiglottis, aryepiglottic folds, arytenoids, cuneiform & corniculate cartilages, glossoepiglottic folds, pharyngoepiglottic folds, true & false cords, anterior & posterior commissure, subglottis, tracheal rings

• Structures not visible on indirect laryngoscopy: VESPA
• Vestibule
• Epiglottis (laryngeal part)
• Subglottic area
• Posterior cricoid area
• Apex of piriform fossa

Posterior Rhinoscopy (St. Clair Thompson mirror)

• Mirror: Bayonet shaped, 2 bends

• Structures seen:
• Adenoids
• Posterior ends of nasal Turbinates
• Opening of Eustachian tube
• Posterior border of nasal septum
• Torus tubarius
• formed by Salpingopharyngeus muscle
• Pharyngeal opening of eustachian tube (ET).
• 1.25 cm behind inferior turbinate.
• Formed due to lymphatic aggregation.
• Newly discovered salivary glands present here
• Clinical Significance
• Radiotherapy over these glands
• Xerostomia
• Dysphagia
• Sparing these glands
• Improves quality of life in patients receiving radiotherapy
• Fossa of Rosenmüller
• Recess posterior to torus tubarius
• Most Common site for carcinoma of nasopharynx.
• Upper surface of soft palate