Oogenesis Overview

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Questions and Answers

What is the name of the stage in which a primary oocyte remains arrested until puberty?

Diplotene (correct)

Prophase I

Prophase II

Metaphase I

The zona pellucida is a structure that surrounds the primary oocyte.

False (B)

What is the name of the protein complex that holds sister chromatids together?

cohesin

The ______ is a mature ovarian follicle that releases an egg during ovulation.

graafian follicle Signup and view all the answers

Match the following structures with their correct descriptions:

primordial follicle = A single layer of squamous cells surrounds the arrested primary oocyte. primary follicle = The oocyte secretes activin, stimulating granulosa cells to proliferate. secondary follicle = A mature follicle that releases an egg during ovulation. graafian follicle = One cell thick layer of cuboidal cells surrounds the primary oocyte. Signup and view all the answers

Which of the following hormones is primarily responsible for stimulating estrogen production in the ovaries?

FSH (C) Signup and view all the answers

The cumulus oophorus is a structure that is present only after ovulation.

False (B) Signup and view all the answers

What is the role of cortical granules in fertilization?

Cortical granules release enzymes upon fertilization to prevent polyspermy. Signup and view all the answers

Which hormone plays a significant role in the transition of a ruptured follicle into a corpus luteum?

LH (D) Signup and view all the answers

The theca externa is the inner layer of the theca folliculi, characterized by its highly vascularized and glandular nature.

False (B) Signup and view all the answers

What is the primary function of the corpus luteum?

The corpus luteum primarily produces progesterone. Signup and view all the answers

The hormone ______ stimulates granulosa cell proliferation.

Activin Signup and view all the answers

Match the following hormones with their primary functions in the female reproductive system:

FSH = Stimulates follicle development and estrogen production LH = Triggers ovulation and corpus luteum formation Estrogen = Prepares the uterus for pregnancy Progesterone = Stimulates the formation of LH receptors on granulosa cells Signup and view all the answers

Which of the following processes is NOT directly involved in the regulation of meiotic arrest and resumption in oocytes?

Secretion of testosterone (C) Signup and view all the answers

Inhibin is a hormone secreted by the granulosa cells of dominant secondary follicles, and it inhibits the secretion of both FSH and LH.

True (A) Signup and view all the answers

What is the primary role of MPF (Maturation Promoting Factor) during oocyte development?

MPF regulates the transition from meiosis to mitosis and the cell cycle in early blastomeres. Signup and view all the answers

The ______ phase of the menstrual cycle is characterized by the thickening of the uterine lining due to the influence of progesterone.

Secretory Signup and view all the answers

Which phase of oocytogenesis is marked by the completion of meiosis I, resulting in the formation of a secondary oocyte?

Ootidogenesis (B) Signup and view all the answers

Study Notes

Oogenesis

Female gamete production: PGC → oogonia → oocytes
Male gamete production: PGC → spermatogonia → spermatozoa
Oogonia → primary oocytes (46, 4N)
Primary oocytes remain dormant in prophase I (diplotene) until puberty
Primary oocyte develops into a secondary oocyte
Secondary oocyte (23, 2N) arrests in metaphase II until fertilization
Mature oocyte (23, N)
Oocyte diplotene: Primary oocyte arrested in meiosis I, at diplotene stage of prophase I
Prophase I: Increases genetic variation and reduces chromosome number in daughter cells via meiotic process
Cortical granule: Vesicle in oocyte cytoplasm releasing enzymes to prevent polyspermy during fertilization
Condensins: Protein complexes crucial for chromosome condensation in mitosis and meiosis
Cohesin: Protein complex holding sister chromatids together
Primordial follicle (one cell thick; squamous): Surrounds arrested primary oocyte; GnRH stimulates FSH release, triggering follicle development
Zona pellucida: Surrounds secondary oocyte and polar body; binds sperm, species-specific barrier
Primary follicle (one cell thick; cuboidal): Complete follicular cell layer surrounds primary oocytes at birth; zona pellucida formation begins
Secondary follicle (many cell layers; cuboidal): Oocytes secrete activin, stimulating granulosa cell proliferation and estrogen secretion
Graafian follicle (mature follicle): Mature ovarian follicle releasing an egg during ovulation
Corona radiata: Part of cumulus oophorus, closest layer to zona pellucida
Cumulus oophorus: Surrounds oocyte in follicle; protection and development during fertilization
MIF (meiotic inhibitory factor): Causes first meiotic arrest (diplotene, prophase I) until puberty
FSH (follicle-stimulating hormone): Pituitary gonadotropin; acts on granulosa cells, stimulating estrogen production
LH (luteinizing hormone): Triggers ovulation, stimulates testosterone production
Theca: Cellular coverings from ovarian stroma surround developing follicle; differentiates into two layers:
- Theca interna: Highly vascularized and glandular
- Theca externa: Connective tissue-like outer capsule
Corpus luteum: Ruptured, empty follicle (granulosa cells); lutein reaction converts cells to progesterone-producing cells.
Progesterone: Prepares uterus for pregnancy (thickening uterine lining)
MPF (Maturation-promoting factor): Key regulator of cell cycle during fertilization and early development; regulates transition from meiosis to mitosis and early blastomere cycle
Estrogen: Stimulates LH receptor formation on granulosa cells; mainly produced by theca cells (enzyme production).
Activin: Stimulates granulosa cell proliferation
Inhibin: Secreted by granulosa cells; inhibits FSH (and LH) release via negative feedback, causing atresia of other follicles
Meiotic arrest and resumption: Involves second messengers and hormones
ARREST: Increased cAMP inactivates MPF, meiosis arrested; cGMP inhibits PDE3A.
RESUMPTION: LH surge, closes gap junctions, decreases cAMP, activates MPF
Menstrual cycle: Ovarian, endometrial, and hormonal events
Proliferative phase (Days 5-14): GnRH stimulates FSH/LH; secondary follicles secrete estrogen; LH/FSH surge for ovulation
Ovulation: Result of LH surge; ruptured follicle transforms to corpus luteum (progesterone secretion)
Secretory phase (Days 14-28): Progesterone prepares reproductive tract for implantation; inhibin production; endometrium sheds
Stages of Oogenesis
- Oocytogenesis: Oogonia develop into primary oocytes via mitosis; complete before/shortly after birth
- Ootidogenesis: Primary oocyte develops into secondary oocyte; begins prenatally, stops in diplotene, resumes at puberty (meiosis I completed); first polar body extruded.
- Oogenesis: Haploid secondary oocyte initiates meiosis II, stops at metaphase II until fertilization

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Description

This quiz explores the complex process of oogenesis, detailing the stages involved in female gamete production from primordial germ cells to mature oocytes. It highlights the role of various proteins and hormonal regulation during oocyte development. Test your knowledge on the intricacies of meiosis and the factors influencing oocyte maturation.