Figure 3.

Transmission electron microscopic images showing the ultrastructure of oocytes and their surrounding cells in porcine primary follicles. (A) An early primary follicle with one layer of cuboidal granulosa cells beneath the basement membrane (BM) possessing an eccentric nucleus and clusters of organelles. (B) Note the clustering of organelles consists of mitochondria, endoplasmic reticulum, and vesicles, which are all tightened by the cement-like structure. The primary follicle has an even distribution of organelles throughout the ooplasm. Granulosa cells (GCs) are cuboidal in shape and oocyte cytoplasm contains mitochondria (M). ER, endoplasmic reticulum; O, oocyte; N, nucleus; M, mitochondrion; Mb, membrane.