Ovarian and Menstrual Cycles Lecture (Dr. Cole) Flashcards
Oogenesis
1) Starts with PRIMORDIAL OOCYTE:
a) MITOSIS—> Millions of Oocytes
- Max Number of Oocytes (~7 Million) by ~20 Weeks Gestation
b) MEIOSIS begins 8 to 9 weeks Gestatio
- PRIMORDIAL OOCYTE —> PRIMARY OOCYTE
- Primary Oocyte held in PROPHASE I of Meiosis I until OVULATION
2) PUBERTY/ MENARCHE:
- Only ~400,000 Oocytes LEFT!!!!!!
- Primary Oocyte ends Meiosis 1 —-> SECONDARY OOCYTE
- Secondary Oocyte help in METAPHASE II until FERTILIZATION
- If Secondary Oocyte not Fertilized —–> Degenerates
3) MENOPAUSE
- No more Oocytes —> Menstrual Cycle ENDS!!!!
Ovaries
- Paired, Pelvic Organs found within BROAD LIGAMENT
- Supplied by OVARIAN VESELS (SUSPENSORY LIGAMENT)
- Temporary Endocrine gland to prepare the UTERUS for IMPLANTATION and to MAINTAIN the Developing Embryo
Ovarian Functions
- To produce FEMALE Gametes
- Secrete ESTROGEN and PROGESTERONE
- Regulate Postnatal Growth of Reproductive Organs
- Control development of SECONDARY SEX Characteristics!!!!!!!!!!!
Ovarian Structure
- GERMINAL EPITHELIUM
- TUNICA ALBUGINEA
- CORTEX: Oocyte CONTAINING Follicles!!!!!!!!!!!!
(In the Cortex, will find Follicles in Various Stages of Development) - MEDULLA: Stroma and Blood Supply
The Ovarian Cycles
THREE PHASES:
1) FOLLICULAR (Days 1 - 14)
2) OVULATION
3) LUTEAL (Days 15 - 28)
Follicular Phase
- Growth of the DOMINANT FOLLICLE
- Primordial to Tertiary (GRAAFIAN) Follicles
- Typically lasts 10 to 14 Days
- The duration of this PHASE is Variable due to Variable Length of MENSTRUATION
Ovulation Phase
- Oocyte REPTURES out to the GRAAFIAN Follicle
- Occurs MID-CYCLE at Day 14
- In response to SURGE in LH!!!!!
Luteal Phase
- CORPUS LUTEUM forms, Secretes PROGESTERONE and ESTROGEN to accommodate Potential Gestation
- This phase is relatively constant lasting 14 days!!!!!!!!
Follicular Phase Details
1) PRIMORDIAL FOLLICLE:
- Primary Oocyte surrounded by SQUAMOUS EPITHELIUM
- BEFORE Puberty; INACTIVE Follicle
2) EARLY PRIMARY or UNILAYERED FOLLICLE
- SINGLE LAYER of Cuboidal Follicular Epithelium
- ZONA PELLUCID begins to FORM
3) LATE PRIMARY or MULTILAYERED FOLLICLE
- Several Layers of CUBOIDAL FOLLICULAR Epithelial Cells
- ZONA PELLUCID forms GLYCOPROTEIN COAT around the Oocyte
4) SECONDARY FOLLICLE:
A) Follcilar Cells continue to Proliferate —-> STRATUM (Zona) GRANULOSUM
B) OVARIAN Stroma around the Follicle differentiates into:
1) THECA INTERNA: Squamous Cells surrounding Follicular Cells
2) THECA EXTERNE: Capsule-like layer continuous with the Connective Tissue of the Ovary
C) Fluid-Filled Cavities (CALL-EXNER BODIES) appear between Follicular Cells (FLUID IS LIQUOR FOLLCULI)
- Rich in HYALURONIC ACID
- ANTRUM begins to form
- Call Exner bodies also seen in OVARIAN TUMORS of GRANULOSAL ORIGIN!!!!!!!
5) MATURE (GRAAFIN) FOLLICLE:
- Antrum occupies much of the Space
- Oocyte displaced to ONE SIDE
- Developed CORONA RADIATA (Layer of Follicular Cells surrounding Oocyte)
- Developed CUMULUS OOPHORUS (Pedestal of Follicular Cells Anchoring Oocyte to the Wall)
- PRIMARY OOCYTE nearing Completion of MEIOSIS I (Not until Ovulation)
Follicular Phase Review
1) Primordial Follicle
2) Early Primary Follicle
3) Late Primary Follicle
4) Secondary Follicle
5) Mature Graafian Follicle
Control fo Ovaria Follicle Development
- Two forms of PARACRINE Signaling take epalce during FOLLICULOGENESIS
- GLANULOSA Cell-Primary Oocyte BIDIRECTIONAL Signaling
- THECA Cell- Granulos Cell Synergistic Communication
- Member of the TGF-Beta Superfamily feature Prominently amongst the growing list of Extracellular Ligands implicated in the BI-DIRECTIONAL COMMUNICATION
- GDF-9, BMP-15,
- AMH, Activin, Inhibin
(AMH from the MAIN FOLLICLE will shut down the other follicles so that the Main Follicle can grow the MOST)
Polycystic Ovarian Syndrome (PCOS)
- ENLARGED OVARIES with Multiple CYSTS
- Results from DISRUPTED FOLLICULOGENESIS caused by a DEFECT in the Paracrine OOCYTE-GRANULOSUM cell SINGALING mechanism
- INFREQUENT or PROLONGED menstrual periods, excess hair growth, acne, and obesity
- In adolescents, infrequent or absent menstruation may raise SUSPICION for the condition.
Ovulation
- Stimulated by SURGE of LUTEINIZING HORMONE (pars distills)
- FOLLICULAR Cells have now developed RECEPTORS for LH as well
- Induces Primary Oocyte to COMPLETE Meiosis I
- Secondary Oocyte enters MEIOSIS II but STOPS in
METAPHASE - Conversion of FOLLICULAR & THECAL cells
Ovary with Corpus Hemorrhagicum
- Blood Vessels of the THECA INTERNA invade the ANTRUM to become the CORPUS HEMORRHAGICUM
Mittelschmerz
- Mid-cycle PAIN due to OVULATION
- DISCOMFORT in Lower Abdomen due to PERITONEAL Irritation
a) Follicle RUPTURES releases fluid and blood that irritates the surrounding tissues
b) RIGHT or LEFT side – depends which ovary produced the oocyte
c) Can MIMIC Appendicitis
- Pain VARIES by person; Most do not experience any discomfort