General gestational Data
|Mature female bottlenose dolphins in San Diego.|
The cetacean placenta is an epitheliochorial, diffuse organ that implants all over both uterine horns. It fills the entire uterus, with the umbilical cord inserting near the endocervical os. The time of implantation following fertilization is unknown. The main body of the fetus occupies one horn, while the tail occasionally extends into the other horn. The intrauterine position of the cetacean fetus has been illustrated by Slijper (1956, 1966). The position of the fetus is generally such that the tail delivers first. Wislocki & Enders (1941) were the first to describe the placenta of bottlenose dolphins.
General Characterization of the Placenta
|Dolphin situs in utero.|
5) Details of fetal/maternal barrier
The entire villous apparatus is covered with trophoblast; there are no denuded areas. The endometrium is covered with epithelium that is not eroded. Thus, the barrier is a complete epitheliochorial one. The trophoblast is cuboidal and has frequent vacuoles.
|Umbilical artery with arrow pointing at the rare branching vessel.|
|Higher magnification of the branching vessel in the umbilical cord.|
|Cross-section of an umbilical cords with four large and numerous tiny (black) blood vessels.|
|Umbilical cord with three vessels and large allantoic duct (right)|
|Barium sulfate injected cord vessels with tiny branches communicating among large vessels.|
|Spontaneously delivered dolphin placenta, seen from the fetal side to show the insertion of the umbilical cord and amnionic/allantoic membranes.|
|Delivered dolphin placenta with cord insertion above, near the middle.|
|Allantoic duct (left bottom) lined by squamous epithelium and with adjacent bundles of smooth muscle.|
|Terminal villi of normal dolphin placenta.|
surface of dolphin placenta.
Note the vacuolation of the single-layered trophoblast
villi of bottlenose dolphin. Note the vacuolated
trophoblast and the extensive subtrophoblastic capillaries.
7) Uteroplacental circulation
There are no specific publications dealing with either the uterine circulation or its physiology, but the arrangement of the pelvic vasculature was discussed by Rommel and colleagues (1993). They described that the uterus is surrounded by a complex countercurrent system of blood vessels, which, they suggested, is being used for cooling purposes. There is also an extensive consideration of various other circulatory aspects in their description.
8) Extraplacental membranes
There are no free membranes, but amnion and allantoic sacs are contained within the chorionic sac. The allantoic duct within the umbilical cord is occasionally lined by squamous epithelium and accompanied by bundles of smooth muscle.
Trophoblast external to barrier
|Villi of immature Brucella-infected placenta. There is inflammation and degeneration of villi.|
16) Physiologic data
Various physiologic data, endoscopy, semen cryopreservation, environmental contaminants and their effects, and contraceptive methods were discussed in a variety of contributions of the workshop edited by Duffield and Robeck (2000). Reddy et al. (1998) described the content of chemical contaminants in dolphins.
Other remarks - What additional Information is needed?
|Delivered term placenta of Beluga (Delphinapterus leucas).|
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