The human larynx physiological and pathophysiological aspects

Otolaryngology-Head and Neck Surgery, 1990

Surgical manipulation of the laryngeal framework (phonosurgery) is rapidly gaining interest and attention. To date, however, a comparative objective evaluation of the various phonosurglcal techniques has not been reported. A theoretic model of the larynx, a four-mass model based on the work of Ishizaka (J Acoust Soc Am 1976:60:1193-8) and Koizumi et al. (J Acoust Soc Am 1987;82:1179-92), was developed and adapted to simulate laryngeal biomechanlcal behavior, as understood by current research. The model was then applied to a comparative evaluation of phonosurgical techniques. Input parameters that correlate laryngeal function and model simulation were devel oped. Surgical procedures were categorized according to their effect on these pa rameters. A model simulation of these techniques allowed comparison and prediction of the results of phonosurgery and a better understanding of the issues involved with surgical alteration of the voice. (OTOLARYNGOL HEAD NECK SURG 1990;103:380.)

Anatomical record (Hoboken, N.J. : 2007), 2018

In spite that vascular inconvenients or immunological rejections have been solved in relation with larynx transplant, a successful functional reinnervation has not been achieved. Some studies have suggested that laryngeal nerve connection may contain motor fibers, which could explain unexpected evoked responses in electromyographic studies or the different positions adopted of the vocal folds after similar nerve lesions. Ten patients with unexpected evoked responses after laryngeal nerve stimulation were selected. All the patients underwent a total laryngectomy due to oncological causes. In every case, laryngeal nerve connections were observed. All of them were morphologic and histologic processed for choline-acetyltransferase immunohistochemistry. The presence of motor axons in the nerve connections has been demonstrated, which would explain that the motor innervation to the laryngeal muscles could be dual through these variable connections. This also would justify the difficulty o...

2015

Many questions about the physiology of vocal folds vibration, mechanical properties of the vocal folds, impacts of pathologies on the vocal mechanism are investigated in different ways: physical modeling, experiments in vivo on animals or in human volunteers or patients, and also on excised larynges (animals or human/autopsic). Many parameters are involved in phonation and quality of the voice such as the source (flow, pressure), the action of laryngeal muscles and glottal configuration, temperature and humidity. Objectives: In order to independently control these parameters with a biologic model as similar as possible to in vivo human conditions, and also to reach a level of reproducibility that permits measurements comparisons, we have developed a dedicated test bench for human excised larynges. Several classic measurements are systematically recorded such as airflow, subglottal pressure, glottograph signal, sound (F0 and intensity), but also contact pressure between vocal folds. ...

European Archives of Oto-Rhino-Laryngology, 2001

A study of the effect of exogenous hazardous agents or conditions on the mechanical characteristics of vocal fold mucosa should meet three methodological criteria. 1) The outer surface of the mucosa should be exposed to the agent or condition while the inner surface is exposed to a physiological environment. 2) Even slight changes in mechanical characteristics should be detected.

This review examines the current level of knowledge and techniques available for the study of laryngeal reflexes. Overall, the larynx is under constant control of several systems (including respiration, swallowing and cough) as well as sensory motor reflex responses involving glossopharyngeal, pharyngeal, laryngeal, and tracheobronchial sensory receptors. Techniques for the clinical assessment of these reflexes are emerging and need to be examined for sensitivity and specificity in identifying laryngeal sensory disorders. Quantitative assessment methods for the diagnosis of sensory reductions and sensory hypersensitivity may account for laryngeal disorders, such as chronic cough, paradoxical vocal fold disorder, and muscular tension dysphonia. The development of accurate assessment techniques could improve our understanding of the mechanisms involved in these disorders. The larynx serves as a valve in the upper airway with multiple life-supporting functions such as maintaining opening of the vocal folds (previously referred to as vocal cords) for air exchange for respiration and closing during swallowing to help prevent aspiration of food and liquid into the trachea and lungs. Activation of the laryngeal musculature is continuous throughout life as the vocal folds are constantly being held open to varying degrees for air exchange for respiration and closed for airway protection during swallowing (Ekberg, 1982) or for chest stabilization during lifting by breath holding during exertion. The upper airway is dilated for inspiration (Amis et al., 1995) and relaxes on expiration. The only muscle producing vocal fold opening in the larynx is the posterior cricoarytenoid (Tully et al., 1991). The muscle is attached to the muscular process of the arytenoid cartilage and inserts on the middle and lateral part of the posterior cricoid. When it contracts, it pulls the arytenoid backwards and rocking the vocal process upward and laterally (Fig. 1). It is constantly active with greater increases in tone during inspiration for vocal fold opening (Poletto et al., 2004). This muscle is essential to life support (Zealear et al., 2003); with bilateral paralysis of the posterior cricoarytenoid, the inspiratory flow of the air results in a negative pressure between the folds sucking them into the midline and obstructing inspiratory airflow. During expiration, muscles that close the vocal folds are partly active to modulate airflow (Kuna et al., 1988). The closing muscles include the thyroarytenoid, which is the body of the vocal fold extending from the arytenoid cartilage, enveloping the vocal process, and inserting into the anterior inner commissure of the thyroid cartilage. As the thyroarytenoid contracts, it pulls the vocal process downwards and to the midline acting to shorten the muscle and close the vocal folds as it contracts (Fig. 1). The muscle actively closing the vocal folds is the lateral cricoarytenoid, which connects from the muscular process of the arytenoid to the rim and lateral side of the cricoid cartilage. When this muscle contracts, it pulls the muscular process forward and thus rocks the vocal process inward and downwards to the midline, effectively closing the vocal folds. The lateral cricoarytenoid is most active for voice and swallowing (Hillel, 2001). The other adductor muscle is the interarytenoid muscle, which stabilizes the two arytenoids side-by-side in the back of the larynx, preventing them from collapsing into the glottis space between the folds when the other adductors contract. This is the only muscle bilaterally innervated by the recurrent laryngeal nerve from both sides and therefore less affected by unilateral recurrent laryngeal injury (Kawakita et al., 1998). For voice, the vocal folds must be held in the midline with adequate tension and closure for expiratory airflow to induce vibration. Vibration is induced biomechanically by airflow between the vocal folds. With rapid flow between the folds, the pressure between the folds is lowered allowing for closure at the lower edge of the folds. Consequently, after vocal fold closure, the subglottal pressure increases and assists opening the bottom part of the folds. Subsequently, a wave of mucosal opening moves from the inferior to superior and lateral direction increasing the flow between the folds. This is followed by closing in the inferior position as the pressure drops. Thus, for voice to be produced, the laryngeal muscles play a role in bringing the vocal folds to the midline with precise length-tension characteristics to enable vibration while adequate expiratory flow is provided from the lungs. Thus, the role of the laryngeal muscles during voicing for speech is to set the vocal folds into an appropriate posture for phonation onset and offset. This depends on adequate contraction of the thyroarytenoid muscle, shortening the vocal fold and lowering the fold into the midline adding to closure and opposing lengthening action of the cricothyroid. The ratio of contraction levels of these muscles is important in changing fundamental frequency of vibration and the voice pitch (Titze et al., 1989). The only muscle not innervated by the recurrent laryngeal nerve is the cricothyroid, innervated by the external branch of the superior laryngeal nerve. This muscle lengthens the vocal fold as it moves the thyroid cartilage forwards and downwards over the cricoid cartilage in the front (Fig. 1). By lengthening the vocal fold, the cricothyroid increases tension in the vocal fold. The cricothyroid also increases opening during forceful inspiration (Kianicka et al., 1998). Alternatively, when the vocal folds are brought to the midline for voice production and the cricothyroid increases in activation, the

Otolaryngology–Head and Neck Surgery, 2018

Objective To determine the effect of vocal fold anterior web formation on fundamental frequency with a cadaveric excised larynx model. Study Design Experimental study with excised human larynges. Setting Academic tertiary care hospital. Subjects and Methods Sixteen freshly excised human larynges were evaluated with high-speed videoendoscopy and digital kymography during artificially produced vibration. Each larynx was assessed in 4 conditions: preoperative controls and after 25%, 33%, and 50% decreases in the vibratory portion of the vocal folds. The following parameters were evaluated: fundamental frequency, periodicity, vocal fold vibration amplitude, phase symmetry, and glottic closure. Results The mean fundamental frequencies were 208.87, 250.20, 292.37, and 342.67 Hz for preoperative controls and 25%, 33%, and 50% reductions in vibratory length of the vocal folds, respectively. Fundamental frequency increased with each increase in anterior glottic web extent, and the difference...

The Journal of craniofacial surgery, 2016

This study was to present long-term oncological results, as well as the variables, that can increase nodal metastasis and reduce survival in patients diagnosed in the early and late stages of laryngeal cancer. A total of 85 patients were included in the study. These patients were grouped as supracricoid partial laryngectomy (PL), supraglottic horizontal PL, and vertical frontolateral PL. Furthermore, at least 3 years of the long-term outcomes of the patients in these 3 groups were compared. Twenty-two of the patients (26%) had nodal metastasis, 16 (72%) of these patients were in Group I (P = 0.017); 14 patients (51%) had preepiglottic space (P = 0.075); 12 patients (50%) had paraglottic space involvement (P = 0.002); 9 (45%) patients with nodal metastasis had a depth of invasion more than 20 mm (P < 0.001). Out of the 16 patients who had positive intraoperative surgery margins, 5 (18%) of them had nodal metastasis (P = 0.589) and 14 (16%) patients were positive for perineural inv...

Medical & Biological Engineering & Computing, 1994

Seminars in Roentgenology, 2000

The Journal of Pathology, 1976