Anatomy and Physiology of Speech and Hearing Mechanism RHS 247 Lecture 3: Phonation Dr. Aseel Alkhamees

Phonation Previously discussed that speech mechanism linked to mechanical system consisting of: power supply, vibrating elements, and system of valves and filters. To produce speech sound energy in the form of relatively steady state of air from the lung, passes into the trachea and then to the larynx. The larynx is responsible of producing a vibrating air stream (then the vocal cords/vocal folds) constitute the vibrating elements, rapid opening and closing of the vocal cords interrupt the air stream to produce vocal tone. The vocal tract transform these vocal tone into meaningful speech sound. The larynx is located between the trachea inferiorly and the hyoid bone superiorly.

Biological functions of the larynx 1- prevent air from escaping from the lung 2- prevent foreign substances form entering the larynx 3- forcefully expels foreign substances which threaten to enter to the larynx or trachea. Non-biological functions of the larynx Sound production: the vocal cords are long, smoothly rounded bands of muscles tissue which maybe lengthened and shortened, tensed and relaxed and abducted and adducted. One of the extraordinary features of the larynx is that versatile structure capable of many rapid and subtle adjustment and capable of sound production over a very wide range of pitch and loudness.

The mechanism of sound generator During normal speech the vocal cords are spaced rather than widely apart. In vowel production vibration men rate is about 125 complete vibration per second Women are 210 complete vibration per second, children are even higher! Supportive framework of larynx The hyoid bone. Cartilaginous framework of larynx It consist of 9 cartilages and their connecting membrane and ligaments. Three of them are unpaired (larger) and three paired (smaller). Composed of hyaline cartilages. Composed of elastic cartilages. Unpaired Paired Thyroid Arytenoid Cricoid Corniculate Epiglottis Cuneiform

Thyroid cartilage Cricoid cartilage Is the largest of the laryngeal cartilages. Its composed of quadrilateral plates called the thyroid laminae. The union of the thyroid laminae is about 80 degree in adult male and 90 degree in adult female. It has a V-shaped notched called the superior thyroid notch. Cricoid cartilage Its located immediately above the upper most tracheal ring. It consist of two part: an anterior arch and posterior quadrate.

Epiglottis Cavity of the larynx A flexible leaf-like structure composed of yellow elastic cartilages. It located behind the hyoid bone and the root of the tongue. It attached to the thyroid cartilages just beneath the thyroid notch. One of the main function of the epiglottis is that it prevent food from entering the larynx during deglutition. It has a very little contribution in production of speech, it may modify the laryngeal tone. Cavity of the larynx Its extended from aditus laryngis to the inferior border of the cricoid cartilages. From the medial projection of true vocal cords the cavity can be divided into supraglottal and subglottal.

Supraglottal region Sub glottal region Vocal folds/cords Its located between ventricle cords (false vocal cords) and aditus  its called vestibule. Small supraglottal region located between the ventricle and true vocal cords  ventricle. Sub glottal region It located above the vocal cords and below the inferior margin of the cricoid cartilage. Its lined with ciliated columnar epitgelium. Vocal folds/cords True vocal cords lie parallel to each other and just beneath the false vocal cords and are separated by the laryngeal ventricle. Their origin are from the thyroid cartilage near the angle and below the thyroid notch. Each vocal cords consist of bundle of muscle tissue (thyroarytenoid) and vocal ligament which is continues with the conus elasticus

Histology of the vocal cords Epithelium Suprafacial layer of the lamina propria Intermediate layer of the lamina propria Deep layer of the lamina propria Vocalis muscle Muscles of the larynx 1- Extrinsic muscle: it have one attachment structures outside the larynx. 2- Intrinsic muscles: it have both attachment confined with the larynx.

Extrinsic muscle of the larynx 1- Sternothyroid muscle: long slender muscle located in the anterior neck, it completely covered the sternohyoid muscle, omohyoid muscle and lower 3rd of sternocleidomastoid myuscle. 2- Thyrohyoid muscle: located in the anterior neck and covered the sternohyoid muscle, omohyoid muscle. 3- Inferior pharyngeal constrictor .

Summary Biological/non-biological functions of the larynx. Cartilaginous framework of larynx: Unpaired/Paired Cavity of the larynx supraglottal and subglottal region. Histology of the vocal cords: 5 layers. Muscles of the larynx: Extrinsic muscle and Intrinsic muscles.