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The physiology of the larynx and phonation

Terms in this set (11)

Muscles

The muscles that position the vocal cords when producing sound:
1.) Lateral crico-arytenoid muscles (adductors of the vocal folds)
2.) Thyroarytenoid muscle (they relax and shorten the ligaments of the vocal cords)
3.) Inter-arytenoid muscle (adduct the vocal folds to close the inlet of the larynx)
Muscles

The muscles that separates the vocal cords
1) Posterior cricoarytenoid muscles (work by abducting the vocal folds)
Muscles

The muscles that adjust length and tension of the vocal folds
1.) Vocalis muscle (this is the inner fibre of the thyroarytenoid muscle)
2.) Cricothyroid muscle which increases tension of the vocal cords and also plays a part in high-pitch singing too.
The different cartilage in the larynx and its functions
• There are three types of cartilage in the larynx:
1.) Thyroid cartilage- makes up the front of the larynx and is where the vocal cords are.
2.) Cricoid cartilage- lies just below the thyroid cartilage and is a place where the arytenoid cartilage can place themselves.
3.) Arytenoid cartilages- are a pair of pyramidal-shaped cartilages that connect with the cricoid cartilage at the back of the vocal folds.
Nerves of the larynx
• For sensory function of the larynx, the sensory branches of the recurrent laryngeal nerve and also the superior laryngeal nerve too.
• For motor function of the larynx, the motor branches of the recurrent laryngeal nerve and the superior laryngeal nerve.
Vocal folds consist of...
• Situated within the larynx
• Consist of three layers that together help with vocal cord vibration

1.) A loose mucosa structure made of an epithelium basement and the superficial lamina propria
2.) Vocal ligaments made up of the intermediate and deep lamina propria
3.) The vocal fold body which consists of the thyroarytenoid muscle which works by closing the glottis and also maintains tension of the vocal folds during speech/singing.
During breathing, what does the larynx do?
• During respiration, the vocal cords are abducted when undergoing forced inspiration (this is done via the action of the posterior cricoarytenoid muscles) which widens and increases the diameter of the laryngeal airway.
During swallowing, what does the larynx do?
• When swallowing, to ensure that food doesn't enter the air passage (the trachea and bronchi), the sphincters of the larynx stay contracted.
• When the pharyngeal stage of swallowing occurs (this phase occurs straight after the bolus that has been formed by the tongue is pushed backwards by extrinsic lingual muscles), the larynx becomes elevated- thus opening up the cricopharyngeal sphincter which allows swallowing to occur (it's important to note that the pharyngeal phase of swallowing occurs for the duration of a second).
• When this occurs the hyoid bone begins to rotate horizontally, this tilts the epiglottis backwards towards the posterior pharyngeal wall which in turn covers the opening to the larynx.
Fixating the chest and increasing intra-abdominal pressure (For having a poo/wee)
• The larynx serves an important function in helping increasing intra-abdominal pressure. This is important for the undertaking of daily activities such as passing urine/stool, climbing and lifting weights. This is done by closing the vocal cords which in turn provides an increase in pressure in the abdomen to allow such tasks.
What does the larynx do in coughing?
• Coughing is important as it helps expel foreign matter and mucus and also helps keep airways clear of unwanted pathogens. How the larynx aids with coughing is illustrated in these three steps:
1.) Inspiratory phase- this is where (to allow deep inspiration) the larynx opens wide.
2.) Compressive phase- the glottis is tightly closed and the expiratory muscles are strongly activated.
3.) Expulsive phase- air is pushed out at about 6-10 litres/sec when the larynx opens.
Phonation
1) As subglottal pressure builds up, the vocal cords completely close
2) Due to the increase in sub-glottal (lower portion of the larynx) pressure, the lower lips of the vocal cords separate and only the upper lip is in contact with each other
3) When the vocal cords separate completely, this releases a puff of air.
4) The increase in airflow leads to the elastic recoil of the vocal folds.
5) This leads to the lower lips coming into contact with each other again.
6) As this is happening, the mucosal wave occurs superiorly and laterally.
7) This leads to a reduction in the airflow which leads to the lower lips being completely closed.
8) Like how a zip works, the folds begin to close inferiorly to superiorly until a new cycle is propagated.
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