10 Questions
Which of the following is NOT a change that occurs during follicular maturation?
Decrease in the secretion of FSH by the anterior pituitary
The innermost layer of the ovarian follicle is called the:
Stratum granulosum
The ovarian follicle that contains the most mature oocyte is the:
Graafian follicle
Which of the following is not a function of the theca folliculi?
Producing the zona pellucida
The germinal epithelium of the ovary is composed of:
Stratified squamous cells
Which of the following is the correct order of follicular development?
Primordial -> Primary -> Secondary -> Graafian
The tunica albuginea of the ovary is composed of:
Connective tissue
Which of the following steroid hormones is NOT produced by the ovarian follicle?
Aldosterone
What is the primary function of the zona pellucida?
Facilitate sperm-egg binding and fertilization
Which cell type in the ovarian follicle is responsible for secreting the steroid hormones?
Thecal cells
Study Notes
Follicular Development
- Follicular development is the process by which female gametes are produced, with each follicle containing one oocyte.
- Primordial germ cells migrate into the gonadal ridge (ovarian cortex) and multiply by mitosis, producing oogonia.
- By the fourth and fifth months of fetal development, some oogonia enlarge and become primary oocytes.
Primordial Follicles
- Primordial follicles contain immature oocytes surrounded by squamous granulosa cells (aka follicular cells).
- These follicles are quiescent, showing little to no biological activity, and are arrested in meiosis I.
- The oocyte is about 30 μm in diameter in primordial follicles.
Activation of Primordial Follicles
- During ovarian follicle activation, the follicular (granulosa) cells of the primordial follicles change from squamous to cuboidal.
- They secrete proteins that are assembled to a glycoprotein polymer capsule called the zona pellucida.
- They become stratified (stratum granulosum) and form a sheath of connective tissue, the theca folliculi (theca internal and theca external).
Primary Follicle
- The oocyte and the follicle grow dramatically, increasing to almost 100 μm in diameter.
- The stratum granulosum keeps proliferating, reaching 6 – 12 cell layers thick.
Secondary Follicle
- Fluid-filled cavities appear among the granulosa cells and coalesce to form the antrum.
- Oocyte growth is completed, reaching a maximum size of about 200 μm in diameter.
Tertiary Follicle (Antral Follicle)
- The tertiary follicle is formed if the secondary follicle survives, and it increases considerably in volume due to rapid proliferation of follicular cells (50 million).
- The cumulus oophorus forms by the granulosa cells surrounding the oocyte (corona radiata).
- The tertiary follicle grows to about 2 cm in diameter and becomes a pre-ovulatory or mature follicle (dominant follicle).
Follicle Dominance
- Follicle dominance is the selection of one maturing follicle to further develop, resulting from competition between follicles.
- The dominant follicle is the one that will release its ovum.
Ovulation and Corpus Luteum
- Ovulation is the process during which the ovarian follicle ruptures, releasing the egg that can be fertilized.
- The oocyte is released, leaving behind the corpus luteum.
- The corpus luteum is a transient endocrine structure that secretes progesterone to prepare the uterine wall for implantation.
- If fertilization and implantation occur, the synchiotrophoblast secretes human chorionic gonadotropin, signaling the corpus luteum to continue progesterone secretion.
- If there is no fertilization, the corpus luteum degenerates after ~10 days and becomes a corpus albicans.
Test your knowledge on the stages of ovarian follicle development, from antrum formation to the growth of the oocyte. Learn about the formation of secondary and tertiary follicles and the role of granulosa cells in nurturing the oocyte.
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