Oogenesis Part 1 | Journey from Primordial Germ Cell to Secondary Oocyte | Embryology Explained

In this video, I explain Oogenesis – Part 1, where I take you through the entire journey of oogenesis from embryonic life till the formation of the secondary oocyte.

I begin by clearly defining what oogenesis is and then briefly revise the embryological origin of primordial germ cells, explaining how they migrate to the developing ovary. Before moving ahead, I also revise the process of meiosis so that you can easily follow the chromosomal changes occurring at every stage of oogenesis.

Using simple charts, timelines, and visual aids, I explain how primordial germ cells multiply by mitosis to form oogonia, and how these oogonia then differentiate into primary oocytes during embryonic life. I emphasize the very important concept of arrest of primary oocytes in the diplotene stage of prophase I, and explain how these oocytes remain arrested until they enter the ovarian cycle after puberty.

I then explain the formation of primordial follicles and help you visualize the process with clear images. The entire timeline—from embryonic life to puberty—is explained along with the number of germ cells and oocytes present at each stage, so that the concept becomes both logical and memorable.

Next, I take you step by step through follicular development, explaining the features of the primary follicle, secondary follicle, formation of zona pellucida, development of theca folliculi, and finally the detailed structure of the Graafian follicle. I also discuss the LH surge, completion of meiosis I, formation of the secondary oocyte and first polar body, and the arrest of the secondary oocyte in metaphase of meiosis II.

I conclude this video by encouraging you to watch Oogenesis Part 2, where I will cover ovulation, corpus luteum, and the completion of oogenesis.

This video is especially useful for first MBBS students, OBGYN students, dental and physiotherapy students, aspiring embryologists, OBGYN residents, and anyone involved in infertility and assisted reproductive techniques.

Commonly asked exam questions addressed by this video

Describe oogenesis with a neat, labeled diagram.

Explain the stages of oogenesis with special reference to arrest of meiosis.

Explain follicular development from primordial follicle to Graafian follicle.

Why are primary oocytes arrested in diplotene stage of prophase I?

Draw and label a Graafian follicle.