Female Larynx Research Articles

The sexually dimorphic larynx of Xenopus laevis: development and androgen regulation.

The aims of this study were to characterize sexual dimorphism in the larynx of adult Xenopus laevis and to determine how sex differences arise during postmetamorphic development. The larger male larynx is a result of greater cell numbers in both cartilage and muscle. The dilator laryngis muscle of the male larynx has 6-7 times more muscle fibers than that of the female. At metamorphosis, the larynx is sexually monomorphic and feminine in phenotype. The DNA content of the male larynx doubles during the first 6 months following metamorphosis; there is no net DNA increase in the female larynx during this time. Both sexes experience a marked increase in laryngeal DNA content and mass between 6 months and adulthood. The number of muscle fibers in the male larynx increases at an average rate of 150 fibers a day during the first 10 months of postmetamorphic development. There is no net change in fiber numbers in the female larynx from metamorphosis to adulthood. Administration of the antiandrogen Flutamide to metamorphic frogs prevents the net addition of laryngeal muscle fibers in males. Thus, we propose that addition of postmetamorphic laryngeal muscle fibers in males is dependent upon the presence of circulating androgens. Exogenous testosterone administration results in an increase in laryngeal mass, DNA content, and cellular proliferation in juvenile frogs. Using [3H]thymidine injections to probe ongoing, as well as testosterone-induced, cell proliferation, we conclude that cellular proliferation is regulated differently in males and females during development. Thus androgen-induced proliferation is one cellular mechanism responsible for the sexual dimorphism observed in adults.

A morphological study of the human prepubertal and pubertal larynx.

AbstractMeasurements were made from ten Caucasian male and ten Caucasian female cadaveric larynges ranging in age from 9 to 18 years. The sample was divided into prepubertal and pubertal groups of each sex, respectively. Each specimen was dissected and measured according to a specified protocol so that data on linear and angular dimensions of the laryngeal cartilages and the weight of each cartilage were obtained. Results from this study highlighted differences in the developmental morphology of the circumpubertal larynx. With few exceptions, pubertal laryngeal measurements were significantly larger than prepubertal counterparts in both sexes. No clear sexual dimorphism was found between male and female prepubertal larynges though measurements of the prepubertal female larynx were closer to adult counterparts in size and weight than were those in the male. Thus the female larynx requires less growth per unit time to reach maturity than the male. By puberty, clear sexual dimorphism was evident in the larynx. Linear and weight measurements of the pubertal male larynx were significantly larger than in the female. Though the angle of the thyroid laminae was not significantly different in pubertal male and female cartilages, the thyroid eminence was clearly more prominent in the male. The vocal folds in both sexes reached essentially their adult length by puberty; however, the absolute length of the male vocal folds had increased by over two times that of the female.

Bio-acoustic investigations in the green frog, rana esculenta (L.)

1. At a pond near Tübingen, West-Germany, the calling period of the green frog, Rana esculenta, lasts for a period ranging from the middle to the end of April, to the beginning to the end of July. The calling period is parted because of two changes in the behavior of calling and the changing number of the calling groups in: pre spawning period, spawning period and post spawning period. 2. Male frogs form calling groups. The males of each group cry in a rhythmic chorus. 3. The calling activity is influenced by 3 external factors, weather, water temperature and temperature of the air. The dependance of calling activity by these factors is not linear. During a period of good weather the calling activity increases daily. During a period of bad weather there is a daily decrease. The highest calling activity is on sunny days with a water temperature of between 17.5 and 22°C plus or minus 1 degree. From this level the activity falls with decreasing or increasing water temperature asymptotic to zero. The lower limit of calling activity ranges from 10 to 12°C, the upper one by 36.5 plus or minus 0.5°C. With the growing increase of air temperature the number of calls per time period falls asymptotic to zero. 4. The male green frog emits 6 calls; one mating call, two territorial calls, two release calls and one distress call. The calls consist of impulses, which, in the case of the mating call, are arranged to characteristic impulse-groups. The female green frog also emits calls, but no mating calls. 5. The parameters of mating and territorial calls are influenced by the water temperature. With increasing water temperature the duration of calls decreases linear, on the other hand the sequence of impulses and the repetition rate of impulse-groups show a positive linear regression. Also the size of the frog influences the calling parameters. With the increase of body length the duration of mating calls and territorial calls decreases and the sequence of impulses increases; and with mating calls also the repetition-rate of the impulse-groups decreases. 6. The larynx of the green frog consists of 3 elements of cartilage, only one of Cartilago crico-trachealis and the two Cartilagines arytaenoideae, and also 4 pairs of muscles. The muscles are innervated by two branches of the Nervus vagus, named Nervus laryngeus brevis and Nervus laryngeus longus. The larynx of male and female are built the same, but the male larynx is larger. The larynx of Rana ridibunda ridibunda Pallas is little different from that of the green frog. Also in the case of this species the male larynx is larger than the female larynx. 7. The differentiation of the larynx structure in the green frog ends after the completion of the metamorphose. The young frogs emit calls which sound similar to that of the territorial calls of adult frogs.

Male and female voices.

It is an interesting fact that the only difference between the male and female larynx is one of size, and, further, that within each voice category marked differences in size are to be observed. The cords of a soprano are shorter than those of a contralto, and the cords of a tenor are shorter than those of a bass. In this they follow the parallel of instruments such as the violin, viola, cello, and bass fiddle. The larger the instrument and the longer the string, the lower the tone which can be produced. Conversely, the shorter the string the higher the tone the instrument can yield. Taken at its face value this would appear to be a very simple proposition. All that is necessary would be to examine the larynx and the length of the cords would indicate in which category a singer belongs. Unfortunately, however, the laryngoscope is hardly

35. Size of Male and of Female Larynx

35. Size of Male and of Female Larynx