The anatomy of the cremaster muscle during inguinoscrotal testicular descent in the rat

The antiandrogen flutamide perturbs inguinoscrotal testicular descent in the rat and suggests a link with mammary development

“…This finding agrees with a study by Matsuno et al [9], which hypothesized that the thickened cremaster muscle in the cryptorchid testis is because of prolonged cell proliferation. In contrast, in an earlier study, we reported that the muscle layer was thinner in the flutamide-treated cryptorchid testis [10]. However, in that study, the gubernacula were dissected out from the rat pelvis and subsequent anatomical distortion may have occurred.…”

What is new in cryptorchidism and hypospadias—a critical review on the testicular dysgenesis hypothesis

“…During the second phase, the testis migrates through the inguinal canal and across the pubic region to the scrotum. The testis and epididymis remain within a diverticulum of the peritoneum that elongates within the elongating gubernaculum [61]. In humans, the distal end of the gubernaculum remains bulky until after descent is complete.…”

Growth of the rat gubernaculum in vitro and localisation of its growth centre

“…In addition, Lam et al [7] showed that the rat gubernaculum also undergoes an extensive elongation and migration to reach the scrotum and that simple eversion is insufficient to explain the distance it must travel. Harnaen et al [17] have also shown that the cremaster muscle grows from the distal end of the gubernaculum, presumably from the distal progress zone, and not from the proximal internal oblique muscle, as stated in most anatomy books [16,17]. All these studies support the view that the gubernaculum grows out of the inguinal abdominal wall by a process very similar to a developing limb bud rather than simply pulling or pushing the testis into the scrotum.…”

“…A number of recent studies from our laboratory have suggested that the active growth centre of the gubernaculum is in the tip, as shown by it being the site of maximal mitosis in vivo [15], as well as the site of active uptake of fluorescent cell wall markers in vitro [16,17]. Also, it is the site of the most active apoptosis in vitro in the absence of CGRP in the medium [18] (Chan et al, in press, 2009).…”

“…These results lead us to postulate that the rat gubernaculum may grow out of the abdominal wall in a manner analogous to an embryonic limb bud, which contains a distal region of undifferentiated fibroblasts that multiply to produce all the structures in the fully grown limb. This region is known as the "progress zone" [16,17].…”