Oogenesis Flashcards
How does oogenesis differ from spermatogenesis?
Oogenesis begins before birth, with a finite number of primary oocytes. In contrast, spermatogenesis is a continuous process throughout life.
What triggers ovulation?
An LH surge causes the dominant follicle to release a secondary oocyte.
What occurs during the pre-antral stage of follicle development?
Follicular cells grow and proliferate - forms the stratified cuboidal epithelium known as granulosa cells.
Granulosa cells secrete glycoproteins which form the zona pellucida
Surrounding connective tissue cells also differentiate to become theca folliculi, which is responsive to LH.
How is the Graafian follicle different from other follicles?
It is the final stage of follicle development, with a fully developed antrum, high estrogen production, and readiness for ovulation.
What is the zona pellucida, and how does it function during oogenesis?
It is a glycoprotein layer around the oocyte that provides protection, mediates sperm binding, and prevents polyspermy.
Why does meiosis in oogenesis produce polar bodies?
Polar bodies ensure the oocyte retains most of the cytoplasm, providing resources for early embryonic development.
What are the roles of the theca interna and theca externa in follicle development?
The theca interna produces androgens, while the theca externa provides structural support.
How does the hormonal environment during puberty restart oogenesis?
Increased FSH and LH levels stimulate the resumption of meiosis in a cohort of primary oocytes.
What is the role of granulosa cells in follicular development?
Granulosa cells provide nutrients to the oocyte, produce estrogen, and form the antrum.
What occurs during the antral stage of follicle development?
Fluid-filled spaces form between granulosa cells
Eventually combine to form central fluid-filled space (antrum)
What occurs during the pre-ovulatory stage of follicle development?
LH surge induces this stage
Meiosis I complete - 2 haploid cells form, 1 becomes first polar body the other is secondary oocyte.
Both undergo meiosis II.
Secondary oocyte arrests in metaphase II.
Describe the primordial follice
A primary oocyte surrounded by a single layer of flat, pre-granulosa cells.
Describe the primary follicle
A primary oocyte surrounded by a single layer of cuboidal granulosa cells.
Zona pellucida begins to form
Describe the secondary follicle
A primary oocyte surrounded by multiple layers of granulosa cells and an emerging outer layer of theca cells.
Starts producing androgens which are converted by granulosa cells into oestrogen
Blood vessels begin to grow around follicle
Describe the antral follicle
A primary oocyte with multiple layers of granulosa cells and an antrum (a fluid-filled cavity). Theca differentiates into theca interna (producing hormones) and theca externa (supportive structure)
