Histologic study of the tunica albuginea of the penis and mode of cavernosus muscles' insertion in it.

□ The tunica albuginea (TA) is the outer covering of the corpora caveralosa (CCs) and corpus spongiosum (CS) of the penile shaft. 7'he different histoanatomical patterns of the TA, as well as the mode of attachment of the ischio-/ bulbo-cavernosus muscles (ICM, BCM) to the TA, were studied, aiming at elucidating their role in the mechanism of erection. Twenty-eight cadaveric specimens (18 adults, 10 neonatal deaths) were studied morphologically and histologically after staining with hematoxylin and eosin and Verhoeff-van Gieson stains. 7'he TA consisted in 20 specimens of 2 layers: inner circular and outer longitudinal, in 6 specimens of 3 layers: inner circular, longitudinal and outer circular, and in 2 of only one longitudinal layer. 7'he CS TA was formed of one layer of longitudinal fibers. The mode of cavernosus muscles insertion into the TA revealed 3 patterns. The conjoint BCM and ICM formed a fibrous belt over the CCs in 18 specimens, a muscular belt in 6 and no bell in 4. 7'he functional role of the variations in the TA morphological structure is not exactly known. We hypothesize that the 3-layered TA gives more penile rigidity than the double and single layers. Considering the type of cavernosus muscles insertion into the TA, it appears that the fibrous bell exerts more CC compression than the other 2 types of insertion.