Still image at rest. Still image during phonation.
Video of vocal folds movements as seen by using 70 degree endoscopy.
Mucosal waves as seen during videostroboscopy assessment.
The true vocal folds appear whitish in appearance. Its structure consists of the covering epithelium (stratified squamous epithelium), extracellular matrix (lamina propria) and muscles. Fine capillaries run parallel to its length. Lymphatic channels are very sparse, thus commonly called "watershed" area.
The mucosa above and below the vocal cord are lined by respiratory epithelium delineated by histological transition at superior and inferior arcuate lines. All the instrinsic muscles are supplied by the recurrent laryngeal nerve with the exception of cricothyroid muscles which are supplied by the external branch of superior laryngeal nerve. Both, the recurrent and external branch of superior laryngeal nerve are branches of vagus nerve (cranial nerve IX). The mucous membrane above the vocal cord is supplied by the internal laryngeal branch of superior laryngeal nerve and below the vocal cord by the recurrent laryngeal nerve.
The average fundamental frequency of an adult male
is about 125Hz and in female approximately 200Hz.
Maximal phonation time (MPT) is a the maximal time (in seconds) for which a person can sustain a vowel when produced on one deep breath at a relatively comfortable pitch and loudness. The normal values for male are between
25-35 seconds and in female between 15-25 seconds. (Source:http://www.speech-therapy-information-and-resources.com/maximum-phonation-time.html.