A&P chapter 4

Biological Functions of Larynx

Seals airway in response to intrusion by foreign objects, Rapidly expels foreign matter away from airway, Produces phonation, Vocal folds permit holding breath

Structure of the Larynx

Musculo-cartilaginous structure, Located above the 1st, tracheal ring, Adjacent to cervical vertebrae 4 – 6

Three unpaired cartilages

Cricoid, thyroid, epiglottis

Three paired cartilages

Arytenoid, Corniculate, Cuneiform

Cricoid cartilage

Unpaired, hyaline cartilage, is a complete ring, at the top of trachea, just below inferior thyroid notch, articulates with thyroid via cricothyroid joint

Thyroid cartilage

Unpaired, hyaline cartilage, Largest laryngeal cartilage, Articulates with cricoid

cartilage, Via paired processes, Allows it to rock forward, and backward & glide, points forward like a tent

Epiglottis cartilage

Unpaired, elastic cartilage, Leaflike cartilage, Folds to protective airway during swallowing

Arytenoid cartilages

Paired, hyaline cartilage, Shaped like a tetrahedron, Ride on high-backed posterior & superior (curved & angled) facet of cricoid, Articulation with cricoid cartilage allows movement, Posterior attachment of vocal folds, attachment for abductory and adductory muscles, and vocal fold muscles

Movement of the Arytenoids

Rock (think rocking chair) which Allows vocal folds to Adduct/abduct and Shorten/lengthen, Glide (anterolaterally) which Affects vocal fold length, Rotate (around vertical axis)

Cuneiform cartilages

Paired, elastic cartilage, Reside within the aryepiglottic folds, Provide support for aryepiglottic folds

Corniculate cartilages

Paired, elastic cartilage, Ride on superior surface of each arytenoid, Landmark in the aryepiglottic folds

Cricothyroid Joint attachments

Cricoid and thyroid cartilages are attached via the anterior, lateral, and posterior ceratocricoid ligaments

Rocking/rotating (primary motion) Gliding (secondary)

Cricothyroid Joint movement

anterior and posterior cricoarytenoid ligaments

Cricoid and arytenoid cartilages are attached via the…

Rocking (primary) Gliding

Cricoarytenoid Joint movement

Hyoid bone

Union between the tongue and laryngeal structures, Anchor point for extrinsic

laryngeal muscles, Loosely articulates with the superior cornu of the thyroid cartilage

Greater & lesser cornu/horns, Body

Hyoid bone parts

Inner Larynx

Cartilages, ligaments, muscles, and mucosa of larynx together form a tube-like space with multiple adjustable valve-like constrictions

Vocal folds

bands of tissue that can be moved into and out of airstream

Cavity of the larynx

constricted tube with a smooth surface

Medial laryngeal surface

covered in mucous membrane

Laryngeal Membranes Extrinsic Ligaments

Attachments between hyoid or trachea and cartilages of the larynx

Thyrohyoid membrane, Lateral thyrohyoid ligament, Triticeal cartilage, Median thyrohyoid ligament, Hyoepiglottic ligament, Thyroepiglottic ligament, Cricotracheal ligament

Laryngeal Membranes Extrinsic Ligament names

Hyoepiglottic ligament, Thyroepiglottic ligament, Glossoepiglottic ligaments

Extrinsic ligaments that attach to the epigottis

Hyoepiglottic ligament

above the epiglottis

Thyroepiglottic ligament

Small stem at base of epiglottis

Glossoepiglottic ligaments

These produce the valleculae (space between base of tongue and epiglottis)

Laryngeal Membranes Intrinsic Ligaments

Connect cartilages within larynx, Support structures of larynx, Fibroelastic membranes, Vocal ligament

Connects Arytenoids, Epiglottis, and Thyroid, the Superior boundary is

the aryepiglottic fold

Quadrangular membrane

Cavities/Spaces of the Larynx

Aditus, Vestibule, Laryngeal ventricle, Glottis, Conus elasticus

Aditus

Entry to the larynx from the pharynx above

Vestibule

Space between aditus and ventricular folds (false vocal folds), also includes the Aryepiglottic folds & quadrangular membrane form the lateral walls

Ventricular folds (aka false vocal folds)

Not normally used for phonation - made up of mucous membrane and vestibular ligament and sparse muscle fibers, Gap/space between them is rima vestibuli, Used to lubricate true vocal folds, for limited protective function

Laryngeal ventricle

Space b/w true & false (ventricular) vocal folds, Anterior portion is laryngeal saccule containing mucus glands to lubricate the vocal folds

Glottis

space between the vocal folds, variable sphincter that produces voicing, Runs from anterior to posterior commissure, Anterior 3/5 membranous glottis, Posterior 2/5 cartilaginous glottis

Conus elasticus

From inferior surface of true vocal folds to the inferior border of the cricoid cartilage

False Vocal Folds

Two folds of tissue directly superior to true vocal folds, Ligament, muscle, and mucosal surface, Thicker/heavier than true vocal folds

Angle of thyroid cartilage and Anterior lateral surface of arytenoid

False Vocal Folds attach at

Epithelium, Lamina Propria (Superficial layer, Intermediate layer, Deep layer) Thyroarytenoid Muscle

Vocal Fold Histology

Non-keratinized stratified non-ciliated squamous cells, Protects against abrasion & strong contact forces, Contains channels & microvilli

VF epithelium

Basement Membrane Zone (BMZ)

Anchors epithelium to superior layer of the LP, Two-layers with different types of collagen fibers

Lamina Propria

Consists of three layers, Superior Layer, Intermediate Layer, Deep Layer

Superior Layer of the Lamina Propria (SLLP)

Also known as “Reinke’s space”, Fewer elastic and collagenous fibers than the other two other layers – gel like, Thus, looser and more pliable

Intermediate Layer of the Lamina Propria (ILLP)

Mostly composed of elastic fibers, some collagenous fibers

Deep Layer of the Lamina Propria (DLLP)

More collagenous fibers, some elastic fibers

ILLP & DLLP together

make the vocal ligament, Elastic & collagenous fibers, densely packed as bundles that run almost parallel to the edge of the vocal fold

Collagen

Provides strength and structural support, Withstands stress, resists deformation when subjected to a force, Increasing in density from SLLP to DLLP

Elastin

Bring elasticity to the tissue – stretch and recoil (allows tissue to return to original shape after deformation) Mostly in MLLP

Hyaluronic Acid

In the VF tissue, HA acts as a shear-thinner, Affects tissue viscosity/flow, Acts as a space-filler, Acts as a shock absorber/damping, Helps with wound healing and is a cell migration promoter, Found throughout, but highest density in ILLP

Vocal Folds Membranous part

Anterior, lies between thyroid cartilage and tips of vocal processes of arytenoid cartilages; occupies 60% of the length

Vocal Folds Cartilaginous part

Posterior, lies between the vocal processes and most rearward point on medial

surface of arytenoid cartilages; occupies 40% of length

Laryngeal Ventricles (space/gap)

Depression between the ventricular and true vocal folds, Contain mucous glands that secrete mucus to lubricate the vocal folds

The Larynx

Suspended from a broad set of muscles, Muscles work together to achieve complex motions required for speech and non-speech

Intrinsic laryngeal muscles

Fine adjustments for phonation control, Have both origin and insertion within larynx (on laryngeal cartilages), Primary movers of vocal folds, including fine adjustment

Extrinsic laryngeal muscles

supra- and infra- hyoid muscles, Respectively raise and lower larynx, Have subtler effect on length of vocal folds, have one point of attachment outside the larynx, act as a Primary mover of the larynx as a whole, Critical for swallowing

Adduct/abduct vocal folds, Lengthen/shorten vocal folds, Tense/relax vocal folds

what the Intrinsic laryngeal muscles do

Innervation by branches of CN X (vagus nerve), Recurrent laryngeal nerve, Superior laryngeal nerve

How the Intrinsic laryngeal muscles move

Innervation of various cranial and spinal nerves

How the Extrinsic laryngeal muscles move

what the Extrinsic laryngeal muscles do

Move larynx up/down, Stabilize larynx when acting together

Adductors

Lateral cricoarytenoid, Transverse arytenoid, Oblique arytenoid

Abductors

Posterior cricoarytenoid

Lateral cricoarytenoid

Rock arytenoid in and down

Transverse arytenoid

Medial compression to adduct vocal folds

Oblique arytenoid

Medial compression to adduct vocal folds

Posterior cricoarytenoid

The only abductor of vocal folds

Tensors

Cricothyroid, Thyrovocalis

Relaxers

Thyromuscularis

Pars recta, Pars oblique

Tensors: Cricothyroid

Thyrovocalis

Medial muscle of vocal folds

Thyromuscularis

Muscle mass lateral to thyrovocalis, Most muscular portion of vocal folds

Lateral Cricoarytenoid (LCA): Origin

Superior lateral surface of cricoid

Lateral Cricoarytenoid (LCA): Insertion

Muscular process of arytenoid

Lateral Cricoarytenoid (LCA): Course

Up and back

Lateral Cricoarytenoid (LCA): function

Pulls muscular process forward, Rocks arytenoids inward and down, Brings vocal folds closer together (adducts)

Lateral Cricoarytenoid (LCA): Innervation

Recurrent Laryngeal Nerve

Transverse (Inter)arytenoid: origin

Posterior arytenoid surface

Transverse (Inter)arytenoid: insertion

Same place, opp. arytenoid

Transverse (Inter)arytenoid: course

Transverse / lateral

Transverse (Inter)arytenoid: function

Pulls arytenoids close together, Adducts vocal folds, But much weaker than LCA

Transverse (Inter)arytenoid: innervation

Recurrent Laryngeal Nerve

Oblique (Inter)arytenoid: origin

Posterior base of muscular process of arytenoid

Oblique (Inter)arytenoid: insertion

Apex of opposite arytenoid

Oblique (Inter)arytenoid: course

Up and diagonal (oblique)

Oblique (Inter)arytenoid: function

Rocks apex of arytenoid down & medial

Oblique (Inter)arytenoid: innervation

Recurrent Laryngeal Nerve

Posterior Cricoarytenoid (PCA): origin

Posterior cricoid lamina

Posterior Cricoarytenoid (PCA): insertion

Posterior aspect of muscular process of arytenoid

Posterior Cricoarytenoid (PCA): course

Superior and lateral

Posterior Cricoarytenoid (PCA): function

Sole abductory muscle, antagonist to LCA, Rocks arytenoids back and out, Abducts vocal folds

Posterior Cricoarytenoid (PCA): Innervation

Recurrent Laryngeal Nerve

Recurrent Laryngeal Nerve

branch of the vagus nerve (cranial nerve X)

Cricothyroid (CT): Origin

Anterior medial cricoid cartilage

Cricothyroid (CT): Insertions

Medial (pars recta) - Lower surface of thyroid lamina, Lateral (pars oblique) – Junction of lamina & inferior cornu

Cricothyroid (CT): course

Up (pars recta); up and out (pars oblique)

Cricothyroid (CT): function

Rocks thyroid downward, Lengthens and tenses vocal folds, raises the pitch!

Cricothyroid (CT): innervation

Superior Laryngeal Nerve

Superior Laryngeal Nerve (SLN)

branch of the vagus nerve (cranial nerve X)

Thyroarytenoid has two parts

Internal/medial thyroarytenoid (thyrovocalis) and External/lateral thyroarytenoid (thyromuscularis)

Thyrovocalis (part of TA): Origin

Inner thyroid cartilage surface, just lateral to notch

Thyrovocalis (part of TA): Insertion

Lateral surface of vocal process of arytenoid