Maturation and Atresia of Human Oocytes in Vivo

Abstract

A small number of oocytes mature and ovulate during the entire reproductive life of women, while a large population of oocytes degenerate during follicular development in the adult human ovary (1). A broad light microscopic survey of the cytological feature of oocytes randomly collected from ovaries of patients without apparent ovarian pathology, revealed that the follicular oocytes could be classified into four different types (2). Briefly, these oocyte types were (i) oocytes with nuclei containing diffused or filamentous chromatin (Type 1), (ii) mature oocytes with metaphase chromosomes or first polar bodies (Type 2), (iii) oocytes with clumped chromatin within the nuclei (Type 3),and (iv) degenerated oocytes (Type 4). The percentages of oocytes of each type during different reproductive states is given in Table 1.