Female Larynx Research Articles

The Physiology of Vocal Damping: Historical Overview and Descriptive Insights in Professional Singers

Summary/ObjectiveVocal damping has been historically described as a distinctive phonatory glottic behavior where the posterior part of the vocal folds is strongly adducted and vibration occurs in the anterior part. The aim of the present descriptive study is to analyze anterior glottis phonation patterns in professional singers through a multidimensional approach, in order to better understand the physiological underpinnings of vocal damping and their relation to glottic vibratory mechanisms. MethodsTen professional singers (five males and five females) with no vocal complaints were recruited. Each subject was asked to produce ascending and descending glissandos in a spontaneous way; sustained vowels and little sung fragments in vocal fry, chest voice, falsetto, and whistle register. Each singer was asked to produce – where possible – damping sounds.A multidimensional investigation including acoustic analysis, electroglottography and videolaryngostroboscopy was carried out. ResultsAmong the enrolled singers, nine out of ten successfully produced vocalizations with a typical anterior-vibrating glottic pattern indicative of damping. All nine singers achieved a damping glottic configuration when vocalizing in the falsetto register and five were consciously able to switch between a full-glottic falsetto and a damping falsetto upon request. Three male and two female singers were able to produce a damping glottic configuration while emitting whistle notes. Three male singers demonstrated damping glottic configurations when producing chest notes in a belting style. ConclusionsIn conclusion, it is possible to state that damping is an existing and documentable glottic behavior, with a wide range of manifestations across vocal registers. The present preliminary study describes damping in the domains of chest voice, falsetto and whistle register. A proper damping phenomenon, defined as the modification of the glottic vibratory boundaries according to pitch variations, is described for M2 emissions, both in male and female larynx. The analysis of passaggio patterns allows to describe damping-M2 as a possible vibratory sub-mechanism.

Localization of TRPV3/4 and PIEZO1/2 sensory receptors in murine and human larynges.

The primary aim of this study was to identify expression of TRPV3 and TRPV4 chemoreceptors across perinatal and adult stages using a murine model with direct comparisons to human laryngeal mucosa. Our secondary aim was to establish novel cell expression patterns of mechanoreceptors PIEZO1 and PIEZO2 in human tissue samples. In vivo. We harvested murine laryngeal tissue to localize and describe TRPV3/4 endogenous protein expression patterns via immunofluorescence analyses across two developmental (E16.5, P0) and adult (6 weeks) timepoints. Additionally, we obtained a 60-year-old female larynx including the proximal trachea and esophagus to investigate TRPV3/4 and PIEZO1/2 protein expression patterns via immunofluorescence analyses for comparison to murine adult tissue. Murine TRPV3/4 expression was noted at E16.5 with epithelial cell colocalization to supraglottic regions of the arytenoids, aryepiglottic folds and epiglottis through to birth (P0), extending to the adult timepoint. Human TRPV3/4 protein expression was most evident to epithelium of the arytenoid region, with additional expression of TRPV3 and TRPV4 to proximal esophageal and tracheal epithelium, respectively. Human PIEZO1 expression was selective to differentiated, stratified squamous epithelia of the true vocal fold and esophagus, while PIEZO2 expression exhibited selectivity for intermediate and respiratory epithelia of the false vocal fold, ventricles, subglottis, arytenoid, and trachea. Results exhibited expression of TRPV3/4 chemoreceptors in utero, suggesting their importance during fetal/neonatal stages. TRPV3/4 and PIEZO1/2 were noted to adult murine and human laryngeal epithelium. Data indicates conservation of chemosensory receptors across species given similar regional expression in both the murine and human larynx.

Intraglottal Pressure: A Comparison Between Male and Female Larynxes

Acoustic differences in the phonated sounds made by men and women are related to laryngeal and vocal tract structural differences. This model-based study explored how typical vocal fold differences between males and females affect intraglottal pressure distributions under conditions of different glottal angles and transglottal pressures, and thus how they may affect phonation. The computational code ANSYS Fluent 6.3 was used to obtain the pressure distributions and other aerodynamic parameters for laminar, incompressible flow. Typical values of the vocal fold length, the vertical glottal duct length, and the lateral vocal fold tissue depth were selected both for males and females under conditions of nine typical convergent/divergent glottal angles and three transglottal pressures. There was no coupling of the upstream or downstream vocal tracts, and also no vocal fold contact in these two-dimensional static glottal geometries. Results suggest that males tend to have greater intraglottal pressures for the convergent glottal shape that occurs during glottal opening, and the male glottis offers less flow resistance than the female glottis. These results suggest that the male vocal folds may vibrate more easily (ie, with lower transglottal pressure) but the tissue differences may nullify such an hypothesis. Also, the peak velocities in the glottis were dependent on the transglottal pressure driving the flow and the minimal glottal diameter, which were the same for both the male and female larynxes, rather than on the inferior-superior length of the glottis or the anterior-posterior glottal length. In addition, the tangential forces for larger glottal convergent angles was significantly greater in the female larynx. The entrance loss coefficients, however, were similar between the male and female larynxes, except for the uniform glottis for which the values were larger for the male larynx. The results suggest that the structural differences between male and female vocal folds should be well specified when building computational and physical models of the larynx.

A Tutorial of the Effects of Sex Hormones on Laryngeal Senescence and Neuromuscular Response to Exercise.

Purpose The purpose of this tutorial is to summarize how sex hormones affect both laryngeal senescence and neuromuscular response to exercise, highlighting the importance of considering sex differences in developing treatment for the senescent voice. Conclusion Men and women's voices are sexually dimorphic throughout the life span, including during the laryngeal adaptations observed during senescence. Therefore, presbyphonia (age-related dysphonia) likely clinically manifests differently for men and women due to differences in how the male and the female larynx change in response to aging. Because sexual dimorphism is evident in both laryngeal aging and response to exercise, voice therapy programs aimed at treating the typical and disordered aged voice should consider sex differences in their design.

Does sexual dimorphism vary by population? Laryngeal and ear anatomy in cricket frogs.

Acoustic communication in many anuran species can show the effects of both natural and sexual selection. This is reflected in the sexually dimorphic anatomy of the larynx and ear structures, as well as the allometric relationship of these morphological traits to head or body size. In this study, we examined laryngeal and ear structures of cricket frogs Acris crepitans not only as sexually dimorphic characteristics, but also as they differ across populations in environmentally different habitats. We used 2-way ANOVA to determine whether the volumetric or linear measurements of these structures differed by sex and population. Females have significantly larger body, head, and ear sizes, but significantly smaller larynges than males. Furthermore, females as well as males show larger body and head sizes, ears, and larynges in a dryer open habitat. An ANCOVA analysis shows that males, but not females, differ in laryngeal size across populations beyond the allometric changes attributable to head size alone indicating that males have a greater degree of laryngeal population variation. In contrast, our covariate analysis found that in both sexes many of the ear differences are non-significant once head size is accounted for, suggesting that most of the population-level ear variation is due to allometric effects of body size. We conclude that although both sexes show size differences in the larynx related to selection for larger body size in dry, open habitats, selection on males for larger larynx size related to the production of lower frequency calls in those habitats does not result in correlated changes in the female larynx. The results suggest that in anurans, selection for changes in body and head size affects both sexes equally, male calls and the vocal structures responsible for them can further diversify without concordant changes in females.

The impact of the menopause on the voice

During lifetime the female larynx is very sensitive to sex hormone fluctuations. In the menopause the serum levels of estrogens and progesterone decrease dramatically so that the ratio of estrogens-progesterone to androgens changes in aid of the last hormone. This article gives an overview of the recent literature about the impact of the menopause on the larynx and the vocal quality. Secondly the effect of hormone replacement therapy in the menopause on the larynx and the vocal performance is discussed. Most research in postmenopausal women show that the larynx is an estrogen-target. In the larynx of postmenopausal women mucosal changes are observed. These laryngeal changes can result in altered acoustic characteristics of the voice. The most important acoustic characteristics of the voice are changes in the fundamental frequency and the frequency range of the voice. The first reports in the literature about the role of hormone replacement therapy in the larynx point out a tendency of a positive, organ-conserving effect of hormone treatment on the larynx and probably the voice. However, more research is necessary to confirm these findings. A better understanding of the relation between sex hormones and the female larynx will make it possible to develop strategies to improve the vocal quality of postmenopausal women.

Survival trends in European cancer patients diagnosed from 1988 to 1999

We analysed data from 49 cancer registries in 18 European countries over the period 1988–1999 to delineate time trends in cancer survival. Survival increased in Europe over the study period for all cancer sites that were considered. There were major survival increases in 5 year age-adjusted relative survival for prostate (from 58% to 79%), colon and rectum (from 48% to 54% men and women), and breast (from 74% to 83%). Improvements were also significant for stomach (from 22% to 24%), male larynx (from 62% to 64%), skin melanoma (from 78% to 83%), Hodgkin disease (from 77% to 83%), non-Hodgkin lymphoma (from 49% to 56%), leukaemias (from 37% to 42%), and for all cancers combined (from 34% to 39% in men, and from 52% to 59% in women). Survival did not change significantly for female larynx, lung, cervix or ovary. The largest increases in survival typically occurred in countries with the lowest survival, and contributed to the overall reduction of survival disparities across Europe over the study period. Differences in the extent of PSA testing and mammographic screening, and increasing use of colonscopy and faecal blood testing together with improving cancer care are probably the major underlying reasons for the improvements in survival for cancers of prostate, breast, colon and rectum. The marked survival improvements in countries with poor survival may indicate that these countries have made efforts to adopt the new diagnostic procedures and the standardised therapeutic protocols in use in more affluent countries.

Quantifying the impact of androgen therapy on the female larynx

Objective To describe the timing of changes in fundamental frequency of the female voice following androgen therapy during female to male gender reassignment. Methods A 33-year-old female semi-professional singer undergoing gender reassignment and intramuscular androgen injections was examined at monthly intervals to monitor the impact of therapy on the voice. Laryngostroboscopy and acoustic analysis were performed simultaneously to monitor for potential laryngeal pathology. Results Pretreatment mean fundamental frequency (MF 0) was 228.45 Hz and ranged from 140.26 Hz to 430.64 Hz. Between month 3 and month 4 of treatment, MF 0 declined to 116.52 Hz and ranged from 90.75 Hz to 201.07 Hz. Shimmer increased from 3.4% to 7.8%. Noise to harmonics ratio (NHR) also increased from 0.12 to 0.17. The patient has continued to sing semi-professionally despite these changes in laryngeal function. Conclusion Androgen therapy exerted a profound change on mean fundamental frequency between the third and fourth months of treatment. In addition, pitch range was reduced in a commensurate fashion. Patients undergoing androgen therapy may undergo a significant change in speaking voice between the third and fourth months of therapy. Moreover, though these changes may exert a profound impact on the singing voice, patients undergoing gender reassignment may still be able to achieve personal and professional success in their singing careers.

Intubation Granuloma: Report of a Case

Laryngeal granulomas are the most common late complication of endotracheal intubation in adults when intubation-related subglottic granulomas result from severe trauma.1 Airway manipulation during intubation and the smaller dimension of the female larynx could be contributing factors to intubation granuloma.1 Seventy to 90% of all intubation-related laryngeal granulomas reported have been in female patients.2 Lower glottic proportion, narrowness of the glottis, and thinner arytenoid mucochondrium in women were also believed to predispose to injury.

Influence of gender and injection site on vocal fold augmentation

To determine the influence of gender and injection site on the amount of injectate needed to medialize an immobile vocal fold, and to describe the distribution patterns of the injected bolus. Surgical intervention in human cadaveric larynges in experimental setting. Cadaveric larynges were injected with calcium hydroxylapatite into the lateral or medial aspect of the vocal fold. High-resolution CT scans were obtained before and after injection. Males required 50% to 60% more material than females (P = 0.03). For both genders, lateral injections required more than medial injections (P < 0.001). Laterally injected boluses tended to distribute toward the cricothyroid space, with frank extrusions more common in females. The amount of injectate required to medialize male and female vocal folds is significantly different. The smaller size of the female larynx likely accounts for a higher incidence of extrusion through the cricothyroid space. These gender differences should be taken into consideration when performing injection laryngoplasty.

Simulations of temporal patterns of oral airflow in men and women using a two-mass model of the vocal folds under dynamic control

In this study we use a low-dimensional laryngeal model to reproduce temporal variations in oral airflow produced by speakers in the vicinity of an abduction gesture. It attempts to characterize these temporal patterns in terms of biomechanical parameters such as glottal area, vocal fold stiffness, subglottal pressure, and gender differences in laryngeal dimensions. A two-mass model of the vocal folds coupled to a two-tube approximation of the vocal tract is fitted to oral airflow records measured in men and women during the production of /aha/ utterances, using the subglottal pressure, glottal width, and Q factor as control parameters. The results show that the model is capable of reproducing the airflow records with good approximation. A nonlinear damping characteristics is needed, to reproduce the flow variation at glottal abduction. Devoicing is achieved by the combined action of vocal fold abduction, the decrease of subglottal pressure, and the increase of vocal fold tension. In general, the female larynx has a more restricted region of vocal fold oscillation than the male one. This would explain the more frequent devoicing in glottal abduction-adduction gestures for /h/ in running speech by women, compared to men.

The H+/K+-ATPase (proton) pump is expressed in human laryngeal submucosal glands.

Diagnosis and treatment of gastroesophageal and laryngopharyngeal reflux disease has significantly increased over recent years. The larynx is highly sensitive to the effects of LPRD and is similarly responsive to proton pump inhibitor pharmacotherapy. The hypothesis of the study was that proton pump activity exists in the human larynx and plays a functional role in normal and/or pathological laryngeal tissue. Pathological investigation. Two fresh human cadaveric larynges (one male and one female larynx) were obtained as part of an exempt protocol from the Human Subjects Committee and were formalin fixed and paraffin embedded. Banked human stomach tissue was also obtained for use as comparative positive and negative control specimens. Sections were immunostained with monoclonal antibodies reactive with both alpha and beta subunits of the H+/K+-ATPase (proton) pump. Specimens were reviewed for staining pattern and intensity. Stomach parietal cells (known to produce gastric acid) exhibited strongly positive staining for both the alpha and beta subunits of the proton pump. There was no staining in stomach cells that were not morphologically consistent with the parietal cell. In the human larynx there were strong focal and identical staining patterns in the serous cells and ducts of the minor seromucinous glands by both alpha and beta monoclonals to the proton pump. There was variable staining in the laryngeal epithelium that was thought to be consistent with artifact staining resulting from tissue processing. The H+/K+-ATPase (proton) pump is present in serous cells and ducts of submucosal glands in the human larynx. Proton pump inhibitor pharmacotherapy may have a site of action in seromucinous glands of the human larynx, with possible relevance for patients treated for chronic laryngitis with or without laryngopharyngeal reflux disease.

Reevaluation of the Confounding Effect of Cigarette Smoking on the Relationship between Alcohol Use and Lung Cancer Risk, with Larynx Cancer Used as a Positive Control

Background. The effect of smoking on lung cancer risk has been well documented, while the effect of alcohol remains controversial. We examined the hypothesis that the apparent association between alcohol intake and lung cancer risk is fully due to the confounding effect of cigarette smoke.Methods. Our sample of hospitalized patients included 2,953 male and 1,622 female lung cancer cases; 521 male and 159 female larynx cancers cases; and 8,169 male and 4,154 female controls, admitted to participating hospitals between 1981 and 1994. All controls had been diagnosed with non-smoking-related diseases. Larynx cancer was used as a positive control for lung cancer. Relative risks were estimated through odds ratios, adjusted through multiple logistic regression.Results. Although the odds ratios for alcohol had been significantly elevated prior to adjustment for smoking (OR = 2.4, 95% CI = 2.0–2.8), alcohol had no effect on lung cancer following this adjustment (OR = 1.2, 95% CI = 1.0–1.4). By contrast, the effect of alcohol on larynx cancer remained high even after adjustment for smoking (OR = 5.6, 95% CI = 3.7–8.6).Conclusion. The often-reported association between alcohol and lung cancer risk can be fully explained by the confounding effect of cigarette use.

90: Subglottic Spread of Glottic Carcinoma: The Significance of Laryngeal Size as Related to Gender

Objective: Although it is accepted that there are size differences between female and male larynges, criteria for conservation laryngeal surgery for glottic carcinoma have not specifically addressed this matter. A laryngeal cadaveric anatomic study was undertaken to determine if the current criteria for conservation laryngeal surgery for glottic carcinoma is uniformly applicable to the female larynx. The past several decades have seen an increase in tobacco use among women, accompanied by an increased incidence of laryngeal cancer, thus underlying the relevance of a study of this nature Methods: Anterior midline measurements between key landmarks of the larynges of 10 female and seven male cadavers were carried out and assessed. These measurements included the following: (1) anterior commissure to inferior border of thyroid ala distance; (2) anterior commissure to superior border of cricoid cartilage distance; and (3) anterior commissure to inferior border of cricoid cartilage distance Results: The mean anterior commissure to inferior border of thyroid ala distance was 8.3 mm (range, 6 to 10 mm) in females and 11.8 mm (range, 10 to 13 mm) in males. The mean anterior commissure to superior border of cricoid cartilage distance was 17.5 mm (range, 15 to 21 mm) in females and 21.4 mm (range, 18 to 25 mm) in males. The mean anterior commissure to inferior border of cricoid cartilage distance was 23.7 mm (range, 20 to 27 mm) in females and 30 mm (range 26 to 35 mm) in males Conclusions: The female cadaveric larynges were, on average, smaller than those of the male counterparts studied with regard to all investigated parameters. Of specific interest was the difference in the mean anterior commissure to inferior border of thyroid ala distance between female and male specimens. Classic teaching indicates that conservation laryngeal surgery for glottic carcinoma with less than 10 mm of anterior subglottic spread is oncologically sound, because tumor would theorectically be contained within the thyroid ala. Our data suggest that use of conservation laryngeal techniques in some female patients having glottic carcinoma with less than 10 mm anterior subglottic spread may be contraindicated, because spread to the level of the cricothyroid membrane (and thus extralaryngeal access) can occur well within this distance

The roles of sex, innervation, and androgen in laryngeal muscle of Xenopus laevis

The relative contributions of innervation and androgen to three muscle fiber properties--twitch type, size, and number--were examined in the sexually dimorphic, androgen-sensitive laryngeal muscle of Xenopus laevis. In adults, the muscle contains all fast-twitch fibers in males and fast- and slow-twitch fibers in females; laryngeal muscle fibers are larger and more numerous in males than in females. Juvenile larynges are female-like in both sexes; male laryngeal muscle is subsequently masculinized by androgen secretion during postmetamorphic development. Because both laryngeal motor neurons and muscle fibers are androgen sensitive during masculinization, we examined the role of the nerve in androgen-regulated muscle fiber development. Laryngeal muscle of male and female juvenile frogs was unilaterally denervated, and effects on muscle fiber type, size, and number were examined 4 weeks later. Half of the frogs received a dihydrotestosterone pellet at the time of denervation. Androgen treatment converts laryngeal muscle from mixed slow and fast to all fast twitch in both innervated and denervated muscle. Thus, the nerve is not required for androgen-regulated fiber type expression in either sex. Denervation produces muscle fiber atrophy and androgen treatment induces muscle fiber hypertrophy in male and female larynx. Nerve and hormone effects are independent and additive; fiber size in androgen-treated denervated muscle is greater than in untreated innervated muscle, and fiber size in androgen-treated denervated muscle is smaller than in androgen-treated innervated muscle. There is no sex difference in the effects of innervation or androgen on fiber size. Denervation causes laryngeal muscle fiber loss in males but not in females. Androgen treatment protects male laryngeal muscle from denervation-induced fiber loss and causes fiber addition in innervated female laryngeal muscle. We conclude that there is a sexually dimorphic interaction between innervation and androgen in control of laryngeal muscle fiber number.

Effects of voice training in normal-speaking women: Videostroboscopic, perceptual, and acoustic characteristics

Several aspects of normal voices were investigated in eight female speakers (20-31 years) before and after voice training. The subjects were recorded on audio-tape during running speech and sustained-vowels and examined with video-fiberstroboscopy. Glottal closure pattern was evaluated by voice clinicians who analysed video-sequences using a 6-point rating scale. Audio-perceptual analyses of running speech and vowels were performed by experienced listeners who rated each of seven deviant voice quality parameters on a continuous scale. Acoustic analyses of fundamental frequency and of the relative level of the fundamental vs. the first formant were performed. Among the results, the posterior glottal chinks decreased somewhat in size after voice training, but were still observed in most subjects. For running speech, the degree of perceived breathiness, hypofunction, and vocal fry decreased while sonority increased significantly. Mean sound pressure level was raised by about 2 dB. and the mean fundamental frequency decreased significantly after training. For sustained vowels, the level of the first formant increased as compared to that of the fundamental. The results support the hypothesis that posterior glottal chinks found in women with trained voices are primarily caused by anatomical structures of the female larynx and not by vocal behavior.

ANDROGEN AFFINITY ON HUMAN LARYNGEAL TISSUES

Some phenomena implicate androgenic steroid as existing effects in laryngeal sexual differences and disease. For this reason, specific androgen binding proteins in tissue from the laryngeal region have been examined, and antiandrogens have been used to treat laryngeal carcinoma. However, there have been few experimental data documenting its presence, especially concerning with the location of receptors for androgenic steroids in male and female larynx. To investigate this problem whether androgen is taken up by the tissue of human laryngeal carcinoma or normal mucosa of the larynx, an autoradiographical study was performed. Tumors used in this study were moderately differentiated squamous cell carcinomas. Immediately after resection, the samples were put into Eagle's MEN, and incubated at 37°C for 1 hour with a specific radio ligand, 3H-Testosterone (3H-T). 3H-T and its metabolites were found to be concentrated in nuclei of epithelial cells of the male vocal cord and some parts of male laryngeal carcinoma tissues. This suggest some effect of testosterone on these cell nuclei. However, the silver grain distribution in the cell nuclei per 10000m2 of nuclear area (average specific concentration) was not uniformly distributed in the same specimen. Male laryngeal carcinoma cells can possibly be classified into several cell types, according to the extent of silver grain distribution of nuclei. Laryngeal carcinoma seems to be composed of various cell types with different sensitivity to androgenic steroid. Nevertheless, distribution of the silver grains per cell was similar in the same specimen of laryngeal carcinoma. Quantitative analysis of the intracellular distribution of radioactivity by silver grain counting showed about 60-75 % of 3H-T to be associated with the nuclear compartment of the small cell type of laryngeal carcinoma and the epithelium of vocal cord bordering on the basementmembrane. This value appeared to be similar to the results in other sex hormone target organ reported elsewhere. These findings provide some evidence that human laryngeal tissue, especially vocal cords, and laryngeal carcinomas might be one of the target organs for androgenic steroids.

Physiology of the female larynx

The Recording and Research Center, The Denver Center for the Performing Arts, 1245 Champa Street, Denver, CO 80204 Anatomically, the female larynx differs from the male in vocal fold length, thickness, angle of the thyroid laminae, resting angle of the glottis, vertical convergence angle in the glottis, and a number of other ways. The vocal fold tissue itself differs with respect to the thickness of the mucosa and fiber composition, e.g., the ratio of connective tissue to muscle tissue. Biomechanically, it has been found that the stress-strain curves are slightly more linear in females than males. Based on these and other known differences in morphology and viscoelastic properties, a scaling procedure is attempted for fundamental frequency, intensity, and other acoustic properties. Some rationale is give also for why females develop pathology at different sites in the larynx, given what is currently known about mechanical stress in the tissues.

Vocalizations by a sexually dimorphic isolated larynx: peripheral constraints on behavioral expression

The clawed frog Xenopus laevis uses sexually dimorphic vocalizations, mate calling and ticking, to advertise reproductive state. The basic unit of vocalization is a brief click, produced by the movement of cartilagenous disks located within the larynx. The rate of click production in the male-specific mate call (71 Hz) is an order of magnitude faster than the rate of click production in female typical ticking (6 Hz). To determine if vocalization rate is constrained by the periphery, male and female larynges were isolated and response of the muscles to nerve stimulation was studied. Laryngeal muscle response is markedly dimorphic in the 2 sexes, both in the amplitude potentiation of electromyograms and in the rate at which discrete tension transients can be produced. At 6 Hz (ticking), both sexes generate discrete tension transients in response to each stimulus pulse. In response to nerve stimulation at 71 Hz (mate calling), male laryngeal muscle generates discrete tension transients while female laryngeal muscle does not. Since expression of sex-specific vocalizations is regulated by androgenic hormones, responses of laryngeal muscle to nerve stimulation in androgen-treated adult females and castrated adult males were also examined. The responses of laryngeal muscle from castrated and intact males are similar. Androgen-treated female larynx is partially masculinized but does not produce tension transients at the mate call rate. These physiological results are in close agreement with behavioral observations. Sounds produced by the isolated larynx were nearly identical in spectral properties to those produced by an intact male. We determined that the production of a discrete tension transient is prerequisite to click production. Thus, one reason females do not mate call, even when treated with androgens, is that female laryngeal muscle cannot produce discrete tension transients at a rapid rate.

Histologic and histochemical study of effects of anabolic steroids on the female larynx.

The larynges of 30 unmated, mature female albino mice were examined histologically and histochemically after injecting them with 19-nandrolone phenylpropionate. Permanent irreversible changes, in the form of parakeratosis and squamous metaplasia of the epithelium, and hypertrophy of the muscle fibers, were observed together with persistence of increased alkaline phosphatase enzyme intensity in the endothelium of capillaries and increased activity of nonspecific esterase in the muscles. Similar changes may be responsible for the alteration in the human female's voice after prolonged treatment with anabolic steroids.