This animation shows the caudal aspect of a 6-week-old embryo in 3D. The tail is moved to the side in order to show the external appearance of the cloaca under low magnification. Then, the image is magnified to distinguish the genital tubercle, cloacal membrane, cloacal folds, genital swellings, Rathke's fold and the urorectal septum. The image corresponds to the beginning of the indifferent stage of external genitalia development.

During the 7th week, the urorectal septum fuses with Rathke's folds and the cloacal membrane divides into the urogenital and anal membranes. The genital tubercle, future urogenital groove, primitive perineal body and future anal orifice covered by the anal membrane are visible. In addition, genital swellings, urethral folds and the urogenital membrane are also shown. In a 7-week-old embryo, the urogenital membrane disappears, and the urogenital groove is flanked by urethral folds and genital swellings. The genital tubercle and the urethral plate are also shown. This sequence marks the end of the indifferent stage of external genitalia development.

The next sequence animates the development of the external genitalia in the female beginning with a 7-week-old embryo. The first diagram summarizes development. Next, the genital tubercle bends to form the clitoris, and the preputium and frenulum clitoridis, labia minora and majora, definitive external urethral orifice, vestibulum of the vagina, vaginal orifice, hymen, vestibular glands, raphe perinei and anal orifice form. The sequence ends with a newborn girl.

The development of the corpora cavernosa of the clitoris is shown in transparency from the 7th week to birth.

The next sequence shows the development of the female external genitalia as viewed in profile . The external genitalia of a 7-week-old embryo are cut on the mediosagittal plane and then rotated toward the spectator. The diagram details the primitive urethra, definitive urogenital sinus and the paramesonephric tubercle between them. The urogenital groove, primitive urogenital orifice, genital tubercle, urethral folds and genital swellings are also visible. The next sequence shows the derivatives of these structures from the embryonal period through birth, i.e. the formation the clitoris from the genital tubercle, the development of the preputium clitoridis, frenulum clitoridis and labia minora from the urethral folds, and the enlargement of the definitive urogenital sinus to form the vestibulum vaginae. The formation of the definitive urethra, vagina, hymen and caudal portion of the uterus are also shown.

The next sequences are dedicated to the development of the external genitalia in the male . The diagram, viewed caudally, begins with a 7-week-old embryo and ends with an approximately 14-week-old fetus to show the growth of the genital tubercle to form the phallus, the closure of the urethral groove, the fusion of the urethral folds and the development of the scrotum.

Special sequences are dedicated to the development of the penis beginning with an approximately 10-week-old fetus. The urethral folds still delimit the urethral groove, whose depth opens the primitive urogenital orifice. Future glans penis and scrotal swellings start to develop. The image is rotated at this stage, so that the future glans penis points toward the spectator. Then, the phallus shaft is sectioned twice. The transversal section reveals the evolution of the urethral folds, urethral groove, urethral plate, corpus spongiosum and corpora cavernosa in 3D and in section. In an approximately 14-week-old fetus, the external urethral orifice opens at the tip of the glans penis. The sectioned surfaces of the penis shaft show the penile urethra surrounded by the corpus spongiosum and the corpora cavernosa.

The next sequence animates the transformation of the phallus into the penis as viewed in a longitudinal section for an approximately 10-week-old fetus. To reach this projection, the image is rotated horizontally at 90 degrees and sectioned mediosagittaly to point the future glans penis toward the spectator. Among other details, the diagram shows the phallus, the still non-fused urethral folds with the open urethral groove and the primitive urogenital orifice.

The next sequence shows changes that take place from the 10th to 12th week, including the elongation of the phallus/penis, the still-incomplete fusion of the urethral folds, the epithelial invagination into the glans penis, the formation of the corpora cavernosa and the corpus spongiosum as well as the growth of the scrotum. The closure of the primitive urogenital orifice is also shown, among other details. The development of the penis is then shown for the 12th and 14th weeks, including the opening of the external urethral orifice, the growth of the corpus spongiosum, bulbus penis and bulbourethral glands, the growth of the corpora cavernosa, and the formation of the primordium of the fossa navicularis. More details appear on the diagram.

The last sequence of this animation depicts the 14th week through birth. The external male genital organs are fully developed, and the preputium is separated from the gland penis.

Beginning with a 7-week-old male fetus, a horizontal section illustrates the state of the external genital organs at the end of the indifferent stage of penis development. The urethral groove is open, and the primitive urogenital orifice is visible in depth. The genital tubercle and the genital swelling are also sectioned. The corpora cavernosa and the corpus spongiosum occur in an approximately 8-week-old fetus. Over the course of the next two weeks (i.e. in an approximately 10-week-old fetus), the phallus elongates, the corpus spongiosum appears in the future glans penis, the corpora cavernosa form the crura penis, and the urethral groove transforms into the penile urethra. Other details are also shown on the last diagram of this sequence. In an approximately 14-week-old fetus, an epithelial cord starts to grow toward the penile urethra. Simultaneously, the epithelial plate covers the glans penis. Bulbourethral glands develop in posterior to the diaphragmatic and prostatic urethra. The animation continues through birth. The separation of the preputium from the glans penis and the further growth of bulbourethral glands are also shown.

The next non-animated diagram is dedicated to the homologies between male and female external sexual organs.

Several malformations of the external female and male sexual organs are described in the form of static diagrams depicting aplasia vulvae, synechiae labiorum, hymen imperforatus, clitoris duplex, hypertrophia clitoridis congenita, female external pseudohermaphroditism/ aplasia penis, micropenis, bifid double penis, phimosis, hypospadias, epispadias and exstrophy of the bladder.

(This animation is essential for students of medicine, veterinary medicine and biology as well as for departments of anatomy, histology, embryology and cell biology; it is also recommended for students of stomatology, departments or clinics for gynecology, andrology and sexology.)