This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
There are two perineal spaces, one superficial space between the triangular ligament (superficial layer) and the deep layer of the superficial fascia (Colles's fascia), and the other, the deep perineal space, between the superficial layer of the triangular ligament and its deep layer.
The superficial space has on each side the crura of the penis attached to the ischiopubic rami and Govered by the ischiocavernosus (erector penis) muscles. In the median line anteriorly lies the urethra with its erectile tissue covered by the bulbocavernosus (accelerator urinae) muscle. The posterior portion lying on the triangular ligament is called the bulb, and reaches back to the central point of the perineum. From the central point the superficial transverse perineal muscles pass outward and somewhat backward to the rami of the ischia, and the sphincter ani passes back to the coccyx. The internal pudic artery comes forward from the spine of the ischium through Alcock's canal on the outer wall of the ischiorectal fossa, 4 cm. (1 1/2 in.) above the lower edge of the tuberosity; when it reaches the posterior edge of the triangular ligament it gives off the superficial perineal artery, which pierces it and enters the superficial perineal space, where it gives off the small transverse perineal artery, and then continues anteriorly to the base of the scrotum. The pudic nerve sends two branches forward in this space, the posterior or internal superficial perineal toward the middle, and the anterior or external along the outer side of the space accompanying the superficial perineal artery forward to the scrotum.
Fig. 476. - Perineal spaces.
This lies between the anterior and posterior layers of the triangular ligament. It contains the compressor urethrae (external vesical sphincter) muscle surrounding the urethra. Embedded in this muscle is Cowper's gland. Its duct, 2 cm. (4/5 in.) long, pierces the anterior layer of the triangular ligament to empty into the bulbous urethra. Immediately behind the compressor urethras is the deep transverse perinei muscle passing across from one ischiopubic ramus through the central point of the perineum to the other. Running along the outer side of the space is the continuation of the internal pudic artery. It gives off the artery to the bulb about 3 cm. (1 1/4 in.) in front of the anus, and then about 1.25 cm. (1/2 in.) below the subpubic ligament pierces the anterior layer of the triangular ligament and divides into the artery to the corpus cavernosum and artery to the dorsum of the penis; it is accompanied by the pudic nerve, which divides in like manner. Posteriorly this space is open, not being closed by any fascia except that lining the under or superficial surface of the levator ani muscle in the ischiorectal fossa. In the mid-line the continuation of the longitudinal fibres of the rectum called the prerectal or recto-urethralis muscle blend with the fibres of the deep transverse perineal muscle.