Larynx – what to know ! Dr. S. Parthasarathy MD., DA., DNB, MD (Acu), Dip. Diabetes, DCA, Dip. Software statistics- PhD ( physiology), IDRA, FICA

What is it ? It consists of a complex arrangement of muscles, cartilage, membranes and ligaments. It extends from C3 to C6 in the midline Hanging from the hyoid to trachea Some what higher in children( 2nd to fifth? cervical vertebrae) and females Organ designed to coordinate deglutition respiration and phonation

What does it do ?? Breathing Preventing aspiration during deglutition Voice

Elevated epiglottis abutting the nasopharynx – more useful for aspiration prevention than phonation !!

Three levels of aspiration prevention

False vocal cords – inferior orientation - 30 mmHg--Develop a pressure to cough True vocal cords superior orientation – stops ingress of fluids – 140 mmHg – How difficult to ventilate in spasm !!

Male and female ??

Anatomy Anterior – superficial structure, is covered by the fascia platysma and skin Posterior –prevertebral , cervical vertebrae Superior – pharynx Inferior – becomes continuous with the trachea

Structure Cartilages (nine) – three unpaired and six paired Ligaments Muscles

Total nine Epiglottis Thyroid Cricoid Corniculate Cuneiform Arytenoid

Epiglottis !!

Epiglottis (elastic) – ‘leaf’-shaped; the lower, narrower end is attached to the thyroid cartilage by the thyro-epiglottic ligament upper broader end is free to project superiorly median glossoepiglottic fold and pharynx as two lateral glossoepiglottic fold

In Deglutition Hyoid bone move upward and forward Epiglottis bent posteriorly on laryngeal inlet Food slips to the lateral surface Taste sensation Assist in phonation Gag reflex Prevent aspiration of food

Superior and inferior cornua Thyroid Two laminae FUSION MORE IN MALE Notch Superior and inferior cornua

Thyroid cartilage In females, the sides join at approximately 120 degrees In males at closer to 90 degrees. This smaller thyroid angle explains the greater laryngeal prominence in males (the “Adam's apple”), the longer vocal cords, and the lower pitched voice

Vocal cords at the lower border

Cricoid cartilage (hyaline) – ‘signet ring’-shaped and situated at the C6 level. It articulates on its lateral border with the thyroid cornua, and on its upper border with the arytenoid cartilages..

Cricoid cartilage . cricoid is derived from the Greek words krikos and eidos, meaning shaped like a ring Only laryngeal cartilage- complete ring Smaller but thicker & stronger than thyroid

The two light arytenoid cartilages are shaped like three-sided pyramids, and they lie in the posterior aspect of the larynx-posterior joint Crico arytenoid arthritis In rheumatoid and SLE The lateral extension of the arytenoid base is called the muscular process. Important intrinsic laryngeal muscles, lateral and posterior cricoarytenoids, originate here. The medial extension of the arytenoid base is called the vocal process.

Two sets of paired fibroelastic cartilages are embedded in each aryepiglottic fold.[ The cuneiform and corniculate cartilages reinforce and support the aryepiglottic folds and may help the arytenoids move

Safe muscle of the larynx Only this opens Safe muscle of the larynx

Mechanism to prevent aspiration It contracts in 14 seconds while posterior crico arytenoid in 44 seconds Mechanism to prevent aspiration

Elevation of larynx- thyrohyoid, mylohyoid Depression of larynx- sternothyroid, sternohyoid Abductors – Posterior cricoarytenoid Adductor - Lateral cricoarytenoid, interarytenoid Regulation of cord tension – Cricothyroid (Tensor) – Thyroarytenoid – (Relaxors) – Vocalis (fine adjustment)

Vascular supply Superior laryngeal artery - superior thyroid A Inferior laryngeal artery – inferior Thyroid A Crico thyrioid artery -superior thyroid A SLV – STV -- IJV ILV - Brachiocephaliv V

Nerve supply Epiglottis – glossopharyngeal nerve Above vocal cords – internal branch of superior laryngeal nerve Below vocal cords – recurrent laryngeal nerve Motor All muscles of the larynx are supplied by the recurrent laryngeal nerve except cricothyroid ( ext. branch – superior laryngeal nerve )

Right recurrent – Subclavian round Left – aortic arch rounding Lengthier

Voice Vibrations/ second of the vocal cord Pitch = L/TM Depends on: a. Length of VC. b. Mass of VC. c. Tension of VC. Men 90- 500 Hz Women – 150 – 1000

Vocal folds vibrate faster as they're pulled longer, thinner, and more taut and vibrate more slowly when they're shorter, thicker, and floppier. The cricothyroid muscle and thyroarytenoid muscle coordinate with each other to create different pitches.

Thyro arytenoid causes relaxation When it is gone, tension – pitch goes up Cricothyroid – EXT – laryngeal nerve – tenses Problem to the nerve – relaxation – low pitch

Laryngeal paralysis can be Unilateral or Bilateral & may involve – 1. Recurrent laryngeal nerve 2. Superior laryngeal nerve 3. Both (Combined / Complete)

The recurrent laryngeal nerve may be traumatized during surgery on the thyroid and parathyroid glands. Malignancy or benign processes of the neck, trauma, pressure from an ET or a laryngeal mask airway, and stretching the neck may also affect the nerve

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Bilateral recurrent N palsy All the intrinsic muscles of larynx are paralysed, vocal cords lie in median or paramedian position due to unopposed action of cricothyroid muscles. • Clinical features : - Dyspnoea stridor

This is normal !

Inspiration and expiration in BL RLN palsy

PARALYSIS OF SUPERIOR LARYNGEAL NERVE Unilateral Weak voice with decreased pitch - Anaesthesia of larynx on one side - Occassional aspiration. - Askew position of glottis - Ant. Comissure is rotated to healthy side. - Shortening of V.C. with loss of tension & V.C. appears wavy - Flapping of the paralysed vocal cord – V.C. sags down during inspiration & bulges up during expiration Bilateral Both V.C. paralysis - Anaesthesia of larynx - Cough - Chocking fits - Weak & husky voice

Bilateral incomplete RLN On inspiration Bilateral incomplete RLN Addutors are intact !!

Summary Larynx – borders Cartilage Three levels of aspiration Sensory supply Muscles and their action Safe muscle Various positions

What is the laryngeal activity which comes with class ? Yawning

Thank you