What Is the Larynx?
The larynx (from Gk. larynx = the upper windpipe) is an air passage carrying air from the pharynx to the trachea (Picture 1). It contains the vocal cords (folds), so it is also called the voice box.
Adjective form of the larynx is laryngeal, for example, laryngeal cancer.
- Control of the airflow during breathing
- Sound creation
- Prevents of air from escaping the lungs, for example, during weightlifting
- Protection of lungs against foreign objects
Larynx is a short (1.5 inch) tube lying in the front middle part of the neck, between the pharynx above and the trachea below. It extends from the upper edge of the thyroid cartilage (laryngeal prominence – Adam’s apple) to the bottom edge of the cricoid cartilage. In skinny persons, both cartilages can be felt by fingers. The thyroid cartilage is connected to the hyoid bone by muscles. Larynx lies on the C3-C6 level of the cervical spine.
Behind the larynx, there is a lower part of the pharynx and the neck part of the esophagus.
Picture 1: Larynx position in the throat
Larynx Anatomy, Parts of the Larynx
The skeleton of the larynx consists of five main cartilages, connected by connective tissue membranes and muscles:
- Epiglottis, which covers the entrance of the larynx during swallowing (the upper surface of the epiglottis can be seen through the mouth)
- Thyroid cartilage, seen as a prominence (Adam’s apple) in the upper part of the neck, especially in men
- Cricoid cartilage on the bottom of the larynx
- Two arytenoid cartilages, attached to the vocal cords.
Picture 2: The larynx with the vocal cords; vertical section, looking from behind
A thyrocricoid membrane connects the thyroid and cricoid cartilage. A cleft can be made into this membrane to enable breathing in emergency situations, when foreign objects or swelling of epiglottis from severe infection or allergic reaction obstructs the entrance of the larynx. A pocket knife can be used to make a cleft through the skin and membrane, and a thin tube, like the chase of a biro pencil, should be put into the cleft to maintain air flow.
Laryngeal Muscles, Vocal Cords and Their Innervation
All laryngeal muscles are voluntary striated muscles. They are innervated by a left and right Superior laryngeal nerve and Recurrent laryngeal nerve (branches of the Vagus nerve– 10th cranial nerve). These nerves also enable sensations in the larynx mucosa.
Intrinsic (internal) laryngeal muscles alter the position, tension and shape of the vocal cords. They keep vocal cords apart during breathing and together during speaking (Picture 3).
Picture 3: Vocal cords are held apart during breathing (left),
and together during speaking (right)
Extrinsic (external) laryngeal musclesattach the larynx to the hyoid bone and other neck and head structures, and enable larynx elevation during swallowing and speaking (1).
Larynx Examination and Investigations
Your primary doctor can examine your larynx with the help of a small mirror held on the back of your throat (Picture 4). Your doctor for ear, nose and throat (ENT) can use laryngoscope to make a detailed investigation of the larynx and take samples (biopsy) of laryngeal mucosa. Histological changes of a sample can be then checked under the microscope. CT or MRI can be use to detect disorders in the laryngeal wall or adjacent structures.
Picture 4: Normal larynx as seen during larynx examination or laryngoscopy:
1=vocal cords, 2=vestibular fold, 3=epiglottis, 4=plica aryepiglottica,
5=arytenoid cartilage, 6=sinus piriformis, 7=base of the tongue
Disorders of the Larynx
Main disorders of the larynx include:
- Acute laryngitis with a sore throat is usually caused by common viruses, like Influenza virus.
- Chronic laryngitis, usually caused by long-term smoking or air pollution, often present with chronic bronchitis, is characterized by a chronic cough and spitting up phlegm.
- Reflux laryngitis with itchy or burning throatmay result from gastroesophageal reflux disease (GERD) or frequent vomiting.
- Nodules and polyps in the vocal cords are caused by long-term smoking or voice misuse.
- Ulcers are usually caused by endotracheal tube used during artificial breathing.
- Vocal cord paresis is caused by injury or pressure upon the laryngeal nerves.
- Laryngeal spasm
- Laryngeal carcinoma is mainly caused by long-term smoking and/or alcohol abuse.
- Laryngomalacia, common in infants, is an immature larynx folding inward during inhaling, therefore obstructing breathing.
- Presbylarynx is age-related degeneration of larynx tissues resulting in weak voice.
Hoarseness can be caused by any of above disorders.
- Detailed anatomy of the larynx and vocal cords (comcast.net)