Modifications of erectile tissue components in the penis during the fetal period.

BACKGROUND: The penile erectile tissue has a complex microscopic anatomy with important functions in the mechanism of penile erection. The knowledge of such structures is necessary for understanding the normal physiology of the adult penis. Therefore, it is important to know the changes of these penile structures during fetal development. This study aims to analyze the development of the main components of the erectile tissue, such as collagen, smooth muscle fibers and elastic system fibers, in human fetuses. METHODOLOGY/PRINCIPAL FINDINGS: We studied the penises of 56 human fetuses aged 13 to 36 weeks post-conception (WPC). We used histochemical and immunohistochemical staining, as well as morphometric techniques to analyze the collagen, smooth muscle fibers and elastic system fibers in the corpus cavernosum and in the corpus spongiosum. These elements were identified and quantified as percentage by using the Image J software (NIH, Bethesda, USA). From 13 to 36 WPC, in the corpus cavernosum, the amount of collagen, smooth muscle fibers and elastic system fibers varied from 19.88% to 36.60%, from 4.39% to 29.76% and from 1.91% to 8.92%, respectively. In the corpus spongiosum, the amount of collagen, smooth muscle fibers and elastic system fibers varied from 34.65% to 45.89%, from 0.60% to 11.90% and from 3.22% to 11.93%, respectively. CONCLUSIONS: We found strong correlation between the elements analyzed with fetal age, both in corpus cavernosum and corpus spongiosum. The growth rate of these elements was more intense during the second trimester (13 to 24 WPC) of gestation, both in corpus cavernosum and in corpus spongiosum. There is greater proportional amount of collagen in the corpus spongiosum than in corpus cavernosum during all fetal period. In the corpus spongiosum, there is about four times more collagen than smooth muscle fibers and elastic system fibers, during all fetal period studied.

Development of the penis during the human fetal period (13 to 36 weeks after conception).

PURPOSE: We analyzed the development of the area of the penis and erectile structures (corpora cavernosa and corpus spongiosum) and the thickness of the tunica albuginea during the fetal period (13 to 36 weeks after conception) in humans to establish normative patterns of growth. MATERIALS AND METHODS: We studied 56 male human fetuses at 13 to 36 weeks after conception. We used histochemical and morphometric techniques to analyze the parameters of total penile area, area of corpora cavernosa, area of corpus spongiosum, and thickness of tunica albuginea in the dorsal and ventral regions using ImageJ software (National Institutes of Health, Bethesda, Maryland). RESULTS: Between 13 and 36 weeks after conception the area of the penis varies from 0.95 to 24.25 mm2. The area of the corpora cavernosa varies from 0.28 to 9.12 mm2, and the area of the corpus spongiosum varies from 0.14 to 3.99 mm2. The thickness of the tunica albuginea varies from 0.029 to 0.296 mm in the dorsal region and from 0.014 to 0.113 mm in the ventral region of the corpora cavernosa. CONCLUSIONS: We found a strong correlation between the total penile area, corpora cavernosa and corpus spongiosum with fetal age (weeks following conception). The growth rate was more intense during the second trimester (13 to 24 weeks of gestation) compared to the third trimester (25 to 36 weeks). Tunica albuginea thickness also was strongly correlated with fetal age and this structure was thicker in the dorsal vs ventral region.

Compositional changes of collagen and glycosaminoglycans in the tunica albuginea and corpus cavernosum from the human penis during the fetal and postnatal periods.

PURPOSE: We investigated the composition of collagen and glycosaminoglycans (GAGs) in the corpus cavernosum (CC) and tunica albuginea (TA) of normal human penises. MATERIALS AND METHODS: Penises were obtained from a 6-month-old child (group 1), a 2-year-old child (group 2), 18 to 34-year-old adults (group 3), 37 to 53-year-old adults (group 4) and 22 fetuses at 17.2 to 33.3 menstrual weeks (group 5). Total GAG and collagen concentrations were expressed per mg dry tissue and proportions of GAG species were determined by agarose electrophoresis and ion exchange chromatography. RESULTS: The GAG concentration in group 1 CC and TA was 1.32 and 0.52 microg/mg, respectively, and thereafter it increased noticeably. TA collagen concentration followed a similar pattern. TA had more collagen than CC in groups 3 (mean +/- SD 93.41 +/- 6.17 vs 53.77 +/- 11.18 microg/mg, p <0.001) and 4 (89.94 +/- 5.53 vs 55.39 +/- 5.89 microg/mg, p <0.01). In these groups TA and CC differed markedly in the proportion of hyaluronan, heparan sulfate and dermatan sulfate. In TA group 4 had slightly less hyaluronan and more chondroitin sulfate than group 3 but in CC the GAG proportions were similar. Collagen content in the whole fetal penis correlated with gestational age (r = 0.78, p <0.001). CONCLUSIONS: Collagen and the GAG concentration in the human penis undergo extensive modifications during development and shortly after birth but from ages 2 to approximately 46 years changes are limited to the proportion of GAG species in TA from older individuals. Reflecting diverse biomechanical roles, the extracellular matrix of CC and TA are markedly different.

The concentration of elastic fibres in the male urethra during human fetal development.

OBJECTIVE: To describe the distribution of elastic fibres in the developing male urethra and to provide stereological data of the concentration of elastic fibres in the human urethra. MATERIALS AND METHODS: Urethras were obtained from 10 fresh normal human fetuses at 15-36 weeks of gestation. A place-matched spongy urethra of a 27-year-old normal adult man was also analysed. Samples were fixed in Bouin's solution, embedded in paraffin and histologically processed. The elastic system fibres were evaluated by light microscopy using Weigert's resorcin-fuchsin technique after oxidation. Morphometric values were assessed by the point-counting method. The volumetric density (Vv) of elastic fibres was correlated with fetal age. RESULTS: At 15 weeks the elastic fibres were sparse and homogeneously distributed. The size and thickness of elastic fibres increased with age, mainly in the third trimester of gestation. Elastic fibres formed a randomly orientated network in the trabeculae of the corpus spongiosum. The mean (sem) Vv of elastic fibres in the spongy urethra was 5.2 (0.4)% in the fetus at 15 weeks and 14.8 (1.0)% at 36 weeks. In the urethra of the place- matched young man the Vv was 19.0 (1.3)%. The concentration of elastic fibres in the spongy urethra increased significantly with age. CONCLUSION: The high concentration of elastic fibres in the spongy urethra may partly explain its high extensibility. The progressive increase in elastic fibres during development implies functional adaptation of the fetal male urethra.