Physiology of Larynx
The larynx is essential for protecting the lower airways, phonation (voice production), respiration, and chest fixation.
1. Protection of Lower Airways
Protection is the larynx’s most ancient function, preceding voice production. It safeguards the respiratory tract by:
- Sphincteric closure: The laryngeal opening closes through three sphincters – the laryngeal inlet (aryepiglottic folds and epiglottis), false vocal cords, and true vocal cords, ensuring that food and foreign particles do not enter the airways.
- Respiratory cessation: When food touches the posterior pharyngeal wall or tongue base, respiration halts reflexively via the ninth cranial nerve.
- Cough reflex: Upon detecting foreign particles, the larynx triggers a cough to expel them, acting as the “watchdog of the lungs.”
2. Phonation
The larynx functions like a wind instrument, producing sound through the aerodynamic myoelastic theory. Voice is generated when:
- The vocal cords adduct or come together.
- Exhaled air from lung contraction builds infraglottic pressure.
- This pressure forces the vocal cords open, creating small puffs of air that vibrate the cords, producing sound. This sound is amplified through the mouth, pharynx, nose, and chest, while lips, tongue, palate, and teeth shape it into speech.
- Intensity depends on lung-generated air pressure.
- Pitch is determined by the frequency of vocal cord vibration.
3. Respiration
The larynx helps regulate airflow, with the vocal cords opening (abducting) during inspiration and closing (adducting) during expiration to control air entry into the lungs.
4. Fixation of the chest
When the larynx closes, the chest wall stabilizes, allowing thoracic and abdominal muscles to function optimally. This fixation is crucial for activities like pulling, lifting, climbing, coughing, vomiting, defecation, urination, and childbirth, where a closed glottis supports a stable thoracic cage.
——– End of the chapter ——–
Reference Textbooks.
- Scott-Brown, Textbook of Otorhinolaryngology-Head and Neck Surgery.
- Cummings, Otolaryngology-Head and Neck Surgery.
- Stell and Maran’s, Textbook of Head and Neck Surgery and Oncology.
- Ballenger’s, Otorhinolaryngology Head And Neck Surgery
- Susan Standring, Gray’s Anatomy.
- Frank H. Netter, Atlas of Human Anatomy.
- B.D. Chaurasiya, Human Anatomy.
- P L Dhingra, Textbook of Diseases of Ear, Nose and Throat.
- Hazarika P, Textbook of Ear Nose Throat And Head Neck Surgery Clinical Practical.
- Mohan Bansal, Textbook of Diseases of Ear, Nose and Throat Head and Neck Surgery.
- Hans Behrbohm, Textbook of Ear, Nose, and Throat Diseases With Head and Neck Surgery.
- Logan Turner, Textbook of Diseases of The Nose, Throat and Ear Head And Neck Surgery.
- Arnold, U. Ganzer, Textbook of Otorhinolaryngology, Head and Neck Surgery.
- Ganong’s Review of Medical Physiology.
Author:
Dr. Rahul Bagla
MBBS (MAMC, Delhi) MS ENT (UCMS, Delhi)
Fellow Rhinoplasty & Facial Plastic Surgery.
Renowned Teaching Faculty
Mail: msrahulbagla@gmail.com
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