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