Anatomy of Larynx with Concept of Cancer Spread Dr Deepa Shivnani

Overview

Development of larynx (embryology) Paediatric v/s adult larynx Descriptive anatomy Cartilages of larynx Muscles of larynx Membranes Nerve supply / blood supply

/lyphatics Potential spaces Barriers of cancer spread

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LaryngoTracheal GrooveForms in the ventral wall of Pharynx in 4th week

Development of larynx

Embryology

Embryology

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Pharyngeal Arches - Derivatives

Paediatric v/s Adult

Pediatric Vs Adult larynx

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Pediatric AdultSizeLuminal shape Conical / Funnel

ShapedCylindrical shaped

Position C1/C2 C3-C6Epiglottis Omega Leaf ShapedThyroid Flat Shield LikeArytenoid Large SmallMucosa and Submucosa

narrowest part

Lax

subglottis

Adherent

glottis

Descriptive anatomy

Located between 3rd to 6th vertebra in adults

Measures 44 x 43 x 36 mm in men

36 x 41 x 26mm in women

Important Dimensions of the Larynx

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MALE FEMALE-Av Length 44 mm 36mm-Transverse Diameter 43 mm 41mm-AP Diameter 36 mm 26mm

Vocal cord Length-Child 8 mm

6mm-Adult 17-23 mm

15-19mm

Larynx framework

3 unpaired cartilage Epiglottis Thyroid Cricoid 3 paired cartilage Arytenoid Corniculate(santorini) Cuneiform(wrisberg) Laryngeal muscles Laryngeal membrane

Larynx

3 regions : Supraglottic GlotticSubglottic

Laryngeal subdivisions

Sites Extent Subsites Supraglottis Tip of epiglottis to

laryngeal ventricleEpiglottis ,False cordsAryepiglottic folds Arytenoid cartilagesPreepiglottic spaceVestibule

Glottis From laryngeal ventricle to an imaginary plane 1cm below this level

True vocal cordsAnterior commissurePosterior commissure

Subglottis From undersurface of true cord to inferior surface of cricoid cartilage

ANATOMY OF LARYNX

Cartilage framework

Extrinsic membranes

Intrinsic membranes

Mucosal folds

Vocal foldsVestibular folds

Anterior 3/5th of vocal cord is called intermembranous part- phonatory part

Posterior 2/5th of VC is called inter cartilaginous part-resp. part

Height of the VF diminishes towards ant.commisure-as the inf. Edge of VF slopes upwards

No lymphatics in this plane of VF

Muscles Of Larynx

Extrinsic Muscles – connect larynx to neighboring structures Elevators Depressors

Intrinsic Muscles – Attach laryngeal cartilages to each other Acting on Vocal cords Acting on Laryngeal inlet

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Extrinsic musclesSUPRAHYOID (ELEVATORS) Primary

elevators:stylopharyngeous

Salpingopharyngeous Palatopharyngeous

Secondary elevators Digastric muscle Stylohyoid Mylohyoid Geniohyoid Hyoglossus

INFRAHYOID (DEPRESSOR) Sternohyoid Omohyoid Sternothyroid Thyrohyoid

Extrinsic Muscles

The intrinsic muscles of the larynx

Adjust tension in the vocal ligaments

Open and close the rima glottidis Open and Close the rima vestibuli Control the inner dimensions of the

vestibule Facilitate closing of the laryngeal

inlet.

Intrinsic muscles of larynx- acting on vocal cord

Abductors• Posterior

cricoarytenoid

Adductors• Lateral

cricoarytenoid

• Transverse arytenoid

• Thyroarytenoid(external part)

• Cricothyroid

Tensors• Cricothyroi

d• Vocalis

Intrinsic muscles of larynx – acing on laryngeal inlet

Openers of inlet Closers of inlet

Thyroepiglottic Interarytenoids

Intrinsic musclesMuscle Origin Insertion ActionLateral cricoarytenoid

Lat part of cricoid arch

Muscular process

Adductor

Posterior cricoarytenoid

Medial surface of cricoid lamina

Muscular process

Abductor

Vocalis Back of thyroid prominence

Muscular process

Tensor

Interarytenoid Muscular process

Muscular process(opp side)

Closure of inlet

Cricothyroid Ant arch of cricoid

Lower fibres – lesser cornu of thyroid cartilageAnt fibres – thyroid lamina

tensor

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Adductors of the Vocal Folds:

Abduction of Vocal Ligament

LAT.CRICOARYTENOID: It rotates the arytenoids medially and thus adducts the vocal cords. The vocal folds become thin and elongated. The edge becomes sharp and stiff. Transverse and oblique arytenoids also adduct the vocal folds.

CRICOTHYROID : It rotates the cricoid cartilage lengthens the vocal cords by increasing the distance between the thyroid angle

and the arytenoids. The vocal fold thus becomes long and thin and the edges become sharp and

stiffened

Nerve supply of the larynx-SUPERIOR LARYNGEAL NERVE

Nerve supply of the larynx

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Nerve supply of the larynx

The upper branch supplies the mucous membrane of the lower part of the pharynx, epiglottis, vallecula, vestibule of the larynx and the lower branch descends in the medial wall of the piriform fossa beneath the mucous membrane and supplies the aryepiglottic fold and the mucous membrane of the larynx .

Recurrent laryngeal nerve

Enters larynx behind cricothyroid joint, divides into motor and sensory branches

Motor branch – all intrinsic muscles except cricothyroid

Sensory – mucosa below level of vocal cords, afferents from stretch receptors

Right LeftArises from vagus where it crosses subclavian loops under it, ascends in the TE groove

Arises at aortic arch, passes under it, ascends in the TE groove

Galen’s anastomosis

– internal branch of SLN ends by piercing inferior constrictor where it unites with a branch of RLN. It’s a purely sensory loop

Blood supply

Superior laryngeal artery – branch of sup.thyroid artery.

Inferior laryngeal artery – branch of inf.thyroid artery.

VENOUS DRAINAGE Follow A Sup laryngeal V enter IJV via sup thyroid & facial V. Inf laryngeal V drain into inf thyroid V-brachiocephalic V. Some drain into middle thyroid - IJV

Lymphatic drainageSpread to lymph nodes

Supraglottis – level II, III(upper deep cervical LN)

Subglottis – Level IV, VI

Histology

Supraglottis /sub glottis -respiratory pseudostratified columnar epithelium.

Glottic -stratified non keratinized squamous epithelium.

Vocal foldsExtend from

thyroid cartilage to arytenoids

Superficial layer – Reinke’s layer, loose fibrous

tissue

Intermediate layer, elastic

fibresDeep layer, collagenous

fibres, fibroblasts

Mucosa

Stratified squamous

Lamina propria

Muscle

Histology of the vocal cord

Laryngeal barriers to tumor spread

Laryngeal barriers to tumor spread

Laryngeal development, Anatomic barriers, Enzymatic activity. focal areas of vulnerability -

ossified cartilage and natural interruptions in the perichondrium.

Embryology barriers

supraglottis -midline buccopharyngeal anlage with rich bilateral lymphatics.

subglottis -propensity for extralaryngeal extension

Glottis - midline fusion of lateral tracheobronchial primordium

Anatomic barriers tumour spread is bounded by the ligaments ,connective tissue membranes and laryngeal cartilages and facilitated by the soft tissue spaces and musclesFibrous barriers ---”Tucker and smith “found the elastic and dense connective tissue to be relatively resistant to the tumour invasion

Effective barriers includes sub mucosal elastic layers---Conus elasticus---Quadrangular membrane---Ventricular connective tissue.---Hyoepiglottic ligament---Glossoepiglottic ligament---Vocal ligament tendon---Perichondrium

Other vulnerable area

Soft tissue space Venous structure-lacks elastic fibers. Muscle Anterior commissure- Broyles -devoid of a true inner perichondrium.

Chemical activatorsTumor growth -requires the formation of new capillaries tumour releases the tumour angiogenesis factor. enzymatic activity of the collagenase -activated by inflammation.Proteolytic enzymes -cleave type 4 collagen -tumor invasion.

Potential tissue spaces Reinke’s space Sub mucosal space between mucosa and vocalis muscle . Very early glottic cancer remain superficial ,rarely

penetrating the deeper tissue.

Paraglottic space: Between mucosa of larynx and thyroid cartilage . It contains thyro-arytenoid muscle .

Pre epiglottic space: Fat filled space lying between the hyoid bone and

thyrohyoid membrane anteriorly and infrahyoid epiglottis posteriorly.

PRE EPIGLOTTIC SPACE

Reinke’s space Submucosal space between

the mucosa of glottis and underlying vocalis muscle

This act as bursa allowing the mucosa to slide over the underlying tissues producing fluency in normal speech

Very early glottic ca remain superficial rarely penetrating deeper tissue

Mucosa of VC can therefore be stripped off without causing damage to underlying soft tissues with no alteration in voice

Paraglottic spaceBounded laterally - thyroid

cartilage and thyrohyoid membrane

superomedially - quadrangular membrane

inferomedially - conus elasticus

posteriorly - medial wall of piriform fossa.

This space contains thyroarytenoid muscle- infiltration of this space causes fixity of VC

Ossification of Laryngeal Cartilages hyaline cartilage-thyroid, cricoid, and

arytenoid Thyroid cartilage- (male) age 20 ( female) a

few years later Neoplastic invasion of the laryngeal

cartilages generally takes place in the ossifi ed portion of the cartilage.

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