Anatomy, Physiology, and Assessments Flashcards
√What are the embryological precursors of the larynx? What is their blood supply? How do these precursors predict the patterns of laryngeal lymphatic drainage?
Supraglottic Larynx:
- Buccopharyngeal primordium, developed from the 3rd and 4th branchial arches
Glottic and Subglottic larynx:
- Formed by a union of lateral furrows that develop on each side of the tracheobronchial primordium, developed from 6th branchial arch
Blood Supply (dual) & Lymphatic drainage:
Supraglottis:
- Blood supply: Superior laryngeal arteries (from the superior thyroid artery > external carotid)
- Lymphatics follows the arteries down to the carotid sheath to drain into deep cervical chain nodes in level II & III
- Lymphatics drain bilaterally (b/c supraglottis forms as a whole with no fusion in the midline, unlike glottis/subglottis)
Glottis & Subglottis:
- Blood supply: Inferior laryngeal arteries (originating from the inferior thyroid artery > thyrocervical trunk > subclavian artery)
- Lymphatics follows the arteries to drain into the prelaryngeal and pretracheal nodes (level VI) before reaching the deep cervical chain nodes in level IV
- Glottis is formed by paired structures (union on each side of primordium) that fuse in midline. Lymphatics thus drain unilaterally and vocal folds have sparse lymphatics
- Glottic cancers must invade deeply before accessing lymphatics. Hence - Low incidence of LN mets and propensity for unilateral mets
√Outline the Embryology of the Larynx
- 4 weeks: Formation of the laryngotracheal groove in the ventral wall of the primitive pharynx
- 5-7 weeks: Elongation of the laryngotracheal diverticulum, separated from the dorsal foregut by the tracheoesophageal septum
- 8-9 weeks: Epithelial proliferation obliterates the laryngeal lumen
- 10 weeks: Recanalization of the laryngeal lumen is complete
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√Name the boundaries and subsites of the supraglottis, glottis, and subglottis.
What are the 5 subsites of the supraglottis?
Supraglottis Boundaries:
- Superior: Superior surface of epiglottis, hyoepiglottic ligament, AE folds
- Inferior: two definitions: (1) Midpoint of laryngeal ventricle, or (2) Superior most limit of the true vocal fold
- Anterior: Thyrohyoid membrane, thyroid cartilage
Supraglottis Subsites:
- Aryepiglottic folds
- False vocal folds
- Suprahyoid epiglottis
- Infrahyoid epiglottis
- Arytenoids
Glottis Boundaries:
- Superior: same as inferior supraglottis
- Inferior: 1cm below superior limit
- Anterior: Thyroid cartilage
Subglottis:
- Superior: 1cm below imaginary line described above
- Inferior: Inferior border of cricoid
- Anterior: Cricothyroid membrane, cricoid cartilage
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√Describe the Epithelial linings of the larynx.
What are the areas that are rich in glands? 4
Supraglottis:
- Epiglotiss, lingual surface: Non-keratinizing, stratified squamous cell epithelium (SSCE)
- Epiglottis, laryngeal surface - upper half and lateral borders SSCE, lower half respiratory (ciliated pseudostratified columnar epithelium with globlet cells)
- False fold: Respiratory epithelium (Pseudostratified columnar epithelium)
- Edges of the AE folds = stratified squamous epithelium
Glottis:
- Floor to ventricle to subglottis: Non-keratinizing Stratified squamous epithelium
- Anterior and posterior commissure: respiraotry epithelium
Subglottis:
- Respiratory epithelium - Pseudostratified columnar epithelium
Areas that are rich in glands:
- Ventricle
- Saccule
- Anterior and posterior commissure
- Subglottis in kids
√Describe the lymphatic drainage patterns of the larynx
Supraglottis: Bilateral II, III, IV
Glottis: Sparse lymphatics, metastasis rare unless deep invasion. (VI first if reached)
Subglottis: Commonly unilateral, can involve VI (III, IV, VII possible)
What are two paired joints of the cricoid?
- Cricoarytenoid
- Cricothyroid
Describe the cricoarytenoid unit. What is its importance?
Cricoarytenoid unit
= the functional unit of the larynx
= at least 1 arytenoid + its attachment to the cricoid
Significance: At least one cricoarytenoid unit is needed to maintain speech and swallowing without a tracheostomy
What are the cricoarytenoid joint stabilizers?
- Posterior cricoarytenoid ligament
- Fibrous articular capsule
- Vocal ligament
Describe the borders of the Quadrangular Membrane. What is its significance?
Quadrangular Membrane
= Ligament that forms the AE folds and the false vocal folds
= Forms the superior border of the paraglottic space
Borders:
- Superior (free margin): AE fold
- Inferior: Vestibular ligament (of false vocal folds)
- Posterior: Arytenoid, corniculate, cuneiform
- Anterior-Superior: Lateral margin of epiglottis
- Anterior-inferior: Thyroid alae
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https://www.researchgate.net/profile/Jonathan-Wisco/publication/360266219/figure/fig1/AS:11431281094515081@1667483490719/Hemisected-view-of-the-larynx-The-thyroepiglottic-thyrohyoid-hyoepiglottic-and.png
Describe the Conus Elasticus. What is its significance?
Conus Elasticus
= Ligament that forms the vocal ligament
= Forms the inferior border of the paraglottic space
= Connects the cricoid cartilage with the thyroid and artyenoid cartilages, composed of dense fibroconnective tissue with abundant elastic fibers
Borders:
- Inferior: Attaches to cricoid cartilage
- Supero-Anterior: Attaches to anterior commissure at thyroid
- Supero-Posterior: Vocal process
- Superior free edge: Becomes the vocal ligament
- Anterior: continuous with cricothyroid membrane
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https://www.researchgate.net/profile/Camille-Finck/publication/6776751/figure/fig7/AS:601796301053963@1520490827232/Laryngeal-cartilages-and-conus-elasticus-From-SOBOTTA-Atlas-dAnatomie-humaine-Ferner.png
What is Broyle’s Ligament? What is its significance
Broyle’s Ligament
= Ligament connecting the anterior commissure to the thyroid cartilage
= Lacks perichondrium, so provides a point of invasion into the thyroid cartilage and pre-epiglottic space
https://image.slidesharecdn.com/anatomyoflarynx-180222171335/85/anatomy-of-larynx-45-320.jpg?cb=1665658829
What is the petiole?
Triangular point at the base of the epiglottis where the thyroepiglottic ligament attaches to the thyroid cartilage
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What is the angulation of the thyroid prominence?
Male - 120 degrees
Female - 90 degrees
√What are the attachments of the superior, middle, and inferior constrictor muscles?
SUPERIOR:
1. Skull base
2. Pterygomandibular raphe
3. Medial pterygoid plate
4. Mylohyoid line
5. Base of tongue
“Sue Me Punch My Base of tongue”
MIDDLE:
1. Stylohyoid ligament
2. Hyoid bone
INFERIOR:
1. Thyroid cartilage
2. Cricoid cartilage
Describe the boundaries, lymphatic drainage, and contents of the pre-epiglottic space. What is its significance? What is another term for the space?
Aka. Boyer’s space
Superior: Hyoid bone, Hyoepiglottic ligament, and valleculae mucosa
Anterior: Thyrohyroid membrane and thyroid cartilage
Posterior: (Infra-hyoid) Epiglottal cartilage and the thyroepiglottic ligament (posterior-inferior interface between pre-epiglottic space and paraglottic spaces)
Inferior: Lower portion of the hyoid bone until mid-portion of thyroid cartilage; thyroepiglottic ligament
Lateral: Open - continuous with the paraglottic spaces
Lymphatic Drainage: through thyrohyoid membrane and spread bilaterally to LN in Level II & III
Contents: Fat and areolar tissue
Significance:
- Involvement of the PES allows for spread into the paraglottic space (involvement of either entity upstages to T3)
- Easily invaded by an infrahyoid epiglottis mass due to fenestrations in the epiglottic cartilage
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Describe the boundaries of the para-glottic space. What is its significance? What is another term for the space?
Aka. Tucker’s space
Space that is lateral to the true&false cords and extends laterally to the thyroid cartilage (space between the thyroarytenoid muscle and cartilage)
Borders:
- Medial (from superior to inferior): Quadrangular membrane, Laryngeal ventricle, Conus Elasticus (lateral portion of the cricothyroid membrane, that comes up and forms the vocalis muscle)
- Lateral: Thyroid cartilage (anterior), Mucosa of medial wall of the piriform sinus (posterior)
- Inferolateral: Cricothyroid membrane
- Superior/anterior: Continuous with PES
- Posterior: Pyriform sinus
Significance: Extension into the PGS allows for spread into any of the 3 subsites of the larynx
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What are the borders of the pyriform sinus?
- Medial: aryepiglottic cords
- Lateral: thyroid cartilage
- Posterior: low pharyngeal wall
Discuss the normal length of the vocal folds in infants, adult males and females
Infant = 7-8mm
Male = 17-23mm
Female = 12-17mm
What are the layers of the vocal fold from superficial to deep?
- Epithelium (stratified squamous)
- Superficial lamina propria
- Intermediate lamina propria
- Deep lamina propria
- Vocalis muscle
*ILP + DLP = Vocal ligament
What are the cell types of each of the layers of the vocal folds?
- Epithelium (stratified squamous)
- Mucosal layer
- Stratified non-keratinizing squamous epithelium - Superficial lamina propria
- Few fibroblasts
- Scant elastic and collagen fibers - Intermediate lamina propria
- Mainly elastic fibers, few fibroblasts - Deep lamina propria
- Collagenous fibers, fibroblasts - Vocalis muscle
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Describe Reinke’s space and list two points of significance for this space
Reinke’s space = Space between the vocal ligament and the epithelium of the vocal fold (ie. the SLP).
Clinical Significance:
1. Fluid can accumulate here causing Reinke’s edema
2. Gelatinous matrix within Reinke’s space allows for vocal folds to vibrate freely
Differentiate the laryngeal vestibule from the laryngeal ventricle
Vestibule = The laryngeal inlet to the superior or surface of the false vocal cords
Ventricle = The pouch between the true and false vocal cords
√List the 6 different extrinsic laryngeal elevators and their innervations
Suprahyoid musculature (5):
1. Anterior belly of digastric (V3)
2. Posterior belly of digastric (VII)
3. Mylohyoid (V3)
4. Geniohyoid (C1 carried by hypoglossal nerve)
5. Stylohyoid (VII)
Sylopharyngeal (IX)
√List the 4 different extrinsic laryngeal depressors and their innervations
Strap muscles (4)
1. Omohyoid (Ansa, C1-3)
2. Sternohyoid (Ansa, C1-3)
3. Sternothyroid (Ansa, C1-3)
4. Thyrohyoid (Ansa, C1 only)
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What are the 4 “airway dilator” muscles?
- Genioglossus/Geniohyoid
- Anterior digastric
- Dilator naris
- Posterior cricoarytenoid
“Dilate a GAP”
√List the intrinsic laryngeal muscles, their innervations, and their functions.
Which muscles are located within the conus elasticus? Which for quadrangular membrane?
p4 paired muscles, 1 unpaired muscle
Abductor (only 1):
1. Posterior Cricoarytenoid (x2 paired)
- Innervation: RLN
- Function: only vocal fold abductor
Adductor (4)
1. Cricothyroid (x2)
- Innervation: External branch of SLN
- Function: Adducts, Lengths and tautens vocal folds to increase pitch
- Lateral Cricoarytenoid (x2)
- Innervation: RLN
- Function: Adducts vocal folds - Interarytenoid (x1 unpaired)
- Sometimes referred to as transverse and oblique arytenoids
- Innervation: RLN (bilateral innervation as it’s an unpaired muscle)
- Function: Adducts vocal folds - Thyroarytenoid (x2)
- aka. vocalis
- Innervation: RLN
- Function: Adducts, Shortens and relaxes vocal folds to lower pitch
WITHIN THE CONUS ELASTICUS:
1. Thyroaytenoid (vocalis)
2. Interarytenoid
3. Lateral cricoarytenoid
4. Posterior cricoarytenoid
WITHIN THE QUADRANGULAR MEMBRANE:
1. Thyroepiglottic (widen laryngeal inlet)
2. Aryepiglottic (close laryngeal inlet)
3. Thyroarytenoid
4. Cricothyroid
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Laryngology anatomy
List 2 functions of the superior laryngeal nerve
- Innervation to the cricothyroid
- Sensory mucosal innervation superior to the true vocal folds
Where do the recurrent laryngeal nerve and internal branch of the superior laryngeal nerve enter the larynx?
RLN - Cricothyroid joint
Internal branch of SLN - Pierces the thyrohyoid membrane along within the superior laryngeal artery
√List the laryngeal cartilages
Three paired cartilages:
1. Arytenoid
2. Corniculate (sits like a “crown” on the arytenoids)
3. Cuneiform (floats in AE folds to add structural support)
Three unpaired cartilages:
1. Thyroid cartilage
2. Cricoid cartilage
3. Epiglottis
Variable presence:
1. Triticeal cartilage: small cartilage located within the lateral aspect of the thyrohyoid membrane, that may be bilateral, unilateral or absent. It is considered a lateral anatomical variant
Describe the motor and sensory innervation to the larynx
Superior Laryngeal Nerve:
1. External Branch: Motor to cricothyroid muscle
2. Internal Branch: Sensation to supraglottis and glottis. Pierces through thyrohyoid membrane
Recurrent Laryngeal nerve:
a. Motor to all other intrinsic muscles of the larynx except the cricothyroid muscle
b. Sensation to the subglottis and glottis
c. Goes through the cricothyroid joint.
Nerve of Galen:
- Anastomosis between SLN and RLN at glottis
Describe the pathway and innervation of the superior laryngeal nerve
Branches from CNX at lower aspect of the nodose ganglion (sensory) ~36mm from jugular foramen/nucleus ambiguous (motor), divides ICA and IJV with CNXII
Internal branch:
- Sensory, enters larynx with superior laryngeal artery off of superior thyroid artery through thyrohyoid membrane, supplies false fold, epiglottis, pyriform sinus, Glottis and partly subglottis
External branch:
- Motor, supplies cricothyroid
- Runs on the posterior surface of the sternohyoid
What is Artenia Lusoria? 3
Right non-recurrent laryngeal nerve
Aberrant right subclavian (retroesophageal)
Absent innominate
What is the incidence of right and left NON-recurrent RLNs? What are they associated with?
Right: 0.5% (1/200) associated with aberrant subclavian artery (artenia lusoria)
Left: 0.004% (1/250000) associated with situs inversus and dextrocardia
What are the layers of the vocal folds? Describe 3 different anatomical schemes to describe this.
5 layer scheme:
1. Squamous epithelium
2. Superficial lamina propria
3. Intermediate lamina propria
4. Deep lamina propria
5. Vocalis (thyroarytenoid)
Vocal ligament = ILP + DLP
3 layer scheme:
1. Mucosa = epithelium
– separated by Reinke’s space = SLP
2. Vocal ligament = ILP + DLP
3. Muscle = Vocalis
2 layer scheme (cover + body):
1. Cover = Epithelium + SLP + ILP
2. Body = DLP + Vocalis
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Describe the Hirano’s Cover-Body theory of the larynx
Cover = Epithelium + SLP
Transition zone = ILP + DLP
Body = Vocalis
The contrasting masses and physical properties of the cover and body causes them to move at different rates which create vibration and sound at the level of the vocal folds.
Vocal adjustments are regulated by changing the mechanical and vibratory properties of both.
Describe the Myoelastic Aerodynamic Theory of phonation. What was the old theory of phonation?
Previous theory “Neurochronaxic Hypothesis” where vocal fold movement was caused by thyrhmic impulses in the nerves of the larynx. However, this was not reasonable given the frequency of vibration that was needed.
Myoelastic Aerodynamic Theory:
1. Inhalation = air enters lungs
2. Glottic closure = Voluntary adduction of the cords by the intrinsic laryngeal musculature
3. Expiratory force = Diaphragm contracts for expiration
4. Increased subglottic pressure builds below the glottis with expiration
5. Pressure opens the glottis from inferior and moves superiorly
6. Vocal folds spring back to midline (which involves 2 components)
i/ Aerodynamic component: Due to negative pressure from Bernouilli’s principle, as air rushes through a narrowed glottis, the vocal folds pull together
ii/ Myoelastic component: Elastic recoil occurs from the vocal folds
7. Cycle repeats, and this forms the mucosal wave
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What is the travelling wave theory in voice production?
- Vocal fold vibration occurs in lateral & vertical planes
- Sequence: lower margin separates, elliptical volume of air formed in subglottal vault, glottal puff is released as upper margin separates, lower margin returns to midline, then upper margin does also
- This occurs anterior then posterior
- Phase delay (vertical phase difference) - the time delay between closure of upper and lower vocal fold margins - should normally be 1/3-1/2 of the vibratory cycle