The Robinson Institute, Research Centre for Reproductive Health, Discipline of Obstetrics and Gynaecology, University of Adelaide, Adelaide, South Australia 5005, Australia.
Reproduction. 2010 Feb;139(2):309-18. doi: 10.1530/REP-09-0177. Epub 2009 Sep 28.
Follicle classification is an important aid to the understanding of follicular development and atresia. Some bovine primordial follicles have the classical primordial shape, but ellipsoidal shaped follicles with some cuboidal granulosa cells at the poles are far more common. Preantral follicles have one of two basal lamina phenotypes, either a single aligned layer or one with additional layers. In antral follicles <5 mm diameter, half of the healthy follicles have columnar shaped basal granulosa cells and additional layers of basal lamina, which appear as loops in cross section ('loopy'). The remainder have aligned single-layered follicular basal laminas with rounded basal cells, and contain better quality oocytes than the loopy/columnar follicles. In sizes >5 mm, only aligned/rounded phenotypes are present. Dominant and subordinate follicles can be identified by ultrasound and/or histological examination of pairs of ovaries. Atretic follicles <5 mm are either basal atretic or antral atretic, named on the basis of the location in the membrana granulosa where cells die first. Basal atretic follicles have considerable biological differences to antral atretic follicles. In follicles >5 mm, only antral atresia is observed. The concentrations of follicular fluid steroid hormones can be used to classify atresia and distinguish some of the different types of atresia; however, this method is unlikely to identify follicles early in atresia, and hence misclassify them as healthy. Other biochemical and histological methods can be used, but since cell death is a part of normal homoeostatis, deciding when a follicle has entered atresia remains somewhat subjective.
卵泡分类是理解卵泡发育和闭锁的重要辅助手段。一些牛的原始卵泡具有典型的原始形状，但更常见的是椭圆形卵泡，两极有一些立方状颗粒细胞。初级卵泡有两种基膜表型之一，要么是单层排列，要么是有额外层的。在<5mm 直径的窦前卵泡中，一半的健康卵泡具有柱状基底颗粒细胞和额外的基膜层，在横切面上呈环（“环”）状。其余的卵泡具有排列整齐的单层卵泡基底基膜，基底细胞呈圆形，并且含有比“环”状/柱状卵泡更好质量的卵母细胞。在>5mm 的尺寸中，仅存在排列整齐/圆形表型。优势卵泡和从属卵泡可以通过超声和/或对一对卵巢的组织学检查来识别。<5mm 的闭锁卵泡要么是基底闭锁，要么是窦前闭锁，根据细胞首先死亡的颗粒膜中的位置来命名。基底闭锁卵泡与窦前闭锁卵泡具有相当大的生物学差异。在>5mm 的卵泡中，仅观察到窦前闭锁。卵泡液中甾体激素的浓度可用于分类闭锁，并区分一些不同类型的闭锁；然而，这种方法不太可能在闭锁早期识别卵泡，因此将其错误分类为健康卵泡。还可以使用其他生化和组织学方法，但由于细胞死亡是正常同源平衡的一部分，因此确定卵泡何时进入闭锁仍然有些主观。
