RESUMO
Although it is currently believed that the vocal ligament of humans undergoes considerable development postnatally, there is no consensus as to the age at which it first emerges. In the newborn infant, the lamina propria has been described as containing a sparse collection of relatively unorganized fibres. In this study we obtained larynges from autopsy of human fetuses aged 7-9 months and used light and electron microscopy to study the collagenous and elastic system fibres in the lamina propria of the vocal fold. Collagen fibres were viewed using the Picrosirius polarization method and elastic system fibres were stained using Weigert's resorcin-fuchsin after oxidation with oxone. The histochemical and electron microscopic observations were consistent, showing collagen populations with an asymmetric distribution across different compartments of the lamina propria. In the central region, the collagen appeared as thin, weakly birefringent, greenish fibres when viewed using the Picrosirius polarization method, whereas the superficial and deep regions contained thick collagen fibres that displayed a strong red or yellow birefringence. These findings suggest that the thin fibres in the central region consist mainly of type III collagen, whereas type I collagen predominates in the superficial and deep regions, as has been reported in studies of adult vocal folds. Similarly, elastic system fibres showed a differential distribution throughout the lamina propria. Their distribution pattern was complementary to that of collagen fibres, with a much greater density of elastic fibres apparent in the central region than in the superficial and deep regions. This distribution of collagen and elastic fibres in the fetal vocal fold mirrors that classically described for the adult vocal ligament, suggesting that a vocal ligament has already begun to develop by the time of birth. The apparently high level of organization of connective tissue components in the newborn is in contrast to current hypotheses that argue that the mechanical stimuli of phonation are essential to the determination of the layered structure of the lamina propria and suggests that genetic factors may play a more significant role in the development of the vocal ligament than previously believed.
Assuntos
Prega Vocal/embriologia , Colágeno/ultraestrutura , Tecido Elástico/embriologia , Tecido Elástico/ultraestrutura , Feminino , Idade Gestacional , Humanos , Masculino , Mucosa/química , Mucosa/embriologia , Mucosa/ultraestrutura , Prega Vocal/química , Prega Vocal/ultraestruturaRESUMO
A study about the genesis of the inner lining which covers the mucous membrane of the chicken gizzard was made and histochemical test were employed to detect the presence of carbohydrate in the epithelial components of the mucous membrane. The histochemical treatment of the apical border of gizzard epithelium from the 5th, 7th, 9th, 12th, and 15th d of incubation revealed the absence of glycoprotein (with 1.2-glycol containing hexoses), sialic acid, and glycogen but weakly acidic sulphated mucosubstances were present. The same was observed in the medium 1/3 of the gizzard epithelium on 12th and 15th d. The upper 1/3 of the buddings, precursor of gizzard glands, on the 15th d, besides exhibiting the same histochemical characteristics of apical border, revealed, clearly visible, strongly sulphated mucosubstances. The histochemical reactions of the epithelium which covers the free surface and lines the pits from the 18th d of incubation and from the young chicken (0.5 h, 1 d, 3 d, 7 d, 3 weeks and 8 weeks) revealed the absence of glycoprotein (with 1.2-glycol containing hexoses), sialic acid, and glycogen, however, weakly acidic sulphated mucosubstances and strongly sulphated epithelial acidic mucin were present. On the 18th d, the glands presented a lumen and the accumulation of intraepithelial secretion displaced the upper part of the superficial epithelium, splitting, it.