Measurement of the linear dynamics of the descent of the bovine fetal testis

Abstract

Measurements were made on 86 male bovine fetuses collected from abattoirs in the vicinity of Sydney, Australia.The fetal body length was used to calculate the approximate day of gestational age (DGA); most fetuses were between 60 and 150 DGA. The distances from the caudal pole of the kidney (metanephros) to, respectively, the tip of the scrotum, the distal end of the testis and the internal ring of the inguinal canal were measured, as well as the dimensions of the testis and gubernaculum testis. Distances of (1) testis to inguinal canal, (2) inguinal canal to scrotum, (3) testis to scrotum and (4) gubernaculum to scrotum were calculated from these measurements, which were made on both left and right sides. The total length of the gubernaculum testis increased during transabdominal passage and during transinguinal passage of the testis. Furthermore, the gubernaculum appeared to maintain the testis at a relatively fixed distance from the scrotum during transabdominal passage so that the inguinal canal appeared to move towards the testis. The greatest distance between the testis and the tip of the scrotum was found during the transinguinal passage of the testis and was 2.8 cm for the left testis and 2.3 cm for the right. When located within the scrotum, each testis was still 1.6-1.7 cm from the tip of the scrotum, so the distance to be traversed was only 0.6-1.2 cm. Following passage of the testis through the inguinal canal, the gubernaculum became shorter and its distal tip was displaced toward the distal end of the scrotum. Traction by the gubernaculum could account for the final transposition of the testis from the external inguinal ring to the scrotum. Other factors involved in displacement of the testis include differential growth patterns as well as increases in the dimensions of the testis itself.

Cryptorchidism in common eutherian mammals

“…Distance between the testis and kidney increases greatly. Based on and redrawn from Edwards et al (2003). Wensing (1968) provided similar data for bull and boar fetuses.…”

“…4). The extra-abdominal gubernaculum increases substantially in size, by both cell division and swelling, to provide an anchor , Edwards et al 2003. Presumably the above changes along with fetal growth exert continuous tension on the testis, via the gubernacular cord, while the cranial suspensory ligament weakens.…”

“…We have taken the liberty of reinterpreting some conclusions in older publications with the benefit of recent information, without discounting the underlying observations. Central in our review were publications describing numerous dissections of fetuses, including those of: cattle (Gier & Marion 1969, Edwards et al 2003; dog (Wensing 1968, Gier & Marion 1969; horse (Bergin et al 1970); human (Hutson et al 1990(Hutson et al , 1997; pigs (Backhouse & Butler 1960, Backhouse 1964, Wensing & Colenbrander 1986, Wensing 1988; rabbit (Rajfer 1980, Elder et al 1982, van der Schoot 1993, van der Schoot & Elger 1993; and mouse/rat (Wensing 1986, Wensing & Colenbrander 1986, van der Schoot & Elger 1993, Shono et al 1994a, 1994bHutson et al 1997, Lam et al 1998, Hrabovszky et al 2002.…”

“…internal inguinal ring) and typically the future cauda epididymidis (not shown) is within the internal inguinal ring. Based on and redrawn from ; also Wensing & Colenbrander (1986) and Edwards et al (2003).…”

Marshall J. Edwards: Discoverer of maternal hyperthermia as a human teratogen

“…2). It is significant that 2 of Marsh's most recent contributions have to do with the descent of the bovine fetal testis (Edwards et al, 2003b) and the effects of heat (Edwards et al, 2003a). Marsh Edwards continues to leave his mark on the field of teratology, and we are grateful for his many contributions to our field.…”