Caruncle development in a neonate
Keywords: caruncle, placentation, bovine, neonate
Image size: 2629 x 1832 px
An interesting illustration of caruncle development in a newborn calf, shown by submerging the tract in water. This demonstrates that the bovine female has a pre-determined number of caruncles; they do not form in response to fetal stimulation. The contrary is true; fetal cotyledons develop as a result of endocrine stimuli from the caruncles.
Together with the cotyledons, these caruncles form placentomes i.e. multiple complexes of placental attachment. Hence the name of this form of placentation: "Multiplex" (multiple complex).
There are a set number of caruncles (up to 150). Therefore, in the event of a twin pregnancy, the placentomes must be shared by each conceptus. However, as reviewed by Burton and Wooding in "Comparative placentation: Structures, Function and Evolution" (eISBN: 9783540787976 ) the placentomes are larger in twin pregnancies and their combined weight is greater than that of a single pregnancy.
Not all ruminants have large numbers of caruncles; deer may only have 3 to 8 placentomes and are consequently referred to as "oligocotyledonary"!
Selected reference:
Atkinson, A. et al. 1984. Development of the caruncular and intercaruncular regions in the bovine endometrium. Biology of Reproduction 30: 763-774
