| Abstract: | A three-dimensional internal structure microscopy (3D-ISM) can clarify the anatomical
arrangement of internal structures of equine ovaries. In this study, morphological changes
of the equine ovary over the first 12 months of life were investigated by 3D-ISM in 59
fillies and by histological analysis in 2 fillies. The weight and volume of the paired
ovaries initially decreased from 0 to 1 months to 2 to 3 months of age and then
significantly increased at 8 to 12 months of age. The ovulation fossa was first observed
around the 3rd month and became evident after the 6th month. The number of follicles with
a diameter of ≥10 mm and the diameter of the largest follicle increased gradually after 6
months of age. On a volume basis, the medulla accounted for nearly 90% of the whole ovary
at 0 to 1 months of age, but significantly decreased from 2 to 3 months of age. The volume
of the cortex increased progressively after birth and reached approximately 60% of the
total volume at 8 to 12 months of age. This significant development of the cortex
coincided with the increased number and size of large follicles observed from 6 months of
age. These results suggest that the development of the cortex plays a role in the
maturation of the follicles and the equine ovary undergoes substantial morphological
changes postnatally until puberty. |
