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
Tubal Motility
- ESTROGEN acting at a receptors Stimulate TUBAL MOTILITY, whereas Progesterone INHIBITS Tubal Motility.
- BEFORE Ovulation, Contractions are GENTLE, with some individual variations in rate and pattern.
- At Ovulation, Contractions become VIGOROUS and the MESOALPINX CONTRACTS to bring the tube in more contact with the ovary while the FIMBRIA CONTRACTS Rhythmically to sweep over the ovarian surface.
- As Progesterone level rises 4-6 days AFTER Ovulation, it INHIBITS Tubal Motility. This may lead to RELAXATION of the Tubal Musculature to ALLOW passage of the Ovum into the Uterus by the action of the Tubal CILIA.
The Ovarina Cycle- LUTEAL PHASE
1) After Ovulation, the Residual component son the RUPTURED FOLLICLE forms the CORPUS LUTEUM (Yellow Body
2) FUNCIOTN OF THE CORPUS LUTEUM:
- Synthesize and Secrete STEROID HORMONE —> IF necessary Pregnancy Occurs (STIMULUS hCG)
3) CORPUS LUTEUM CONSISTS of:
a) FOLLICULAR aka GLANULOSA (Lutein) Cells —> Makes ESTROGEN!!!!!
b) THECA (Lutein) Cells —-> Makes ANDROSTENEDIONE and PROGESTERONE
***Note: Both FOLLICULAR and THECA CHOLESTEROL is a Precursor for Steroid Hormones!!!!!
Corpus Albicans
- Dense CT Scar formed from DEGENERATION of Corpus Luteum
- Remains for a variable period
- Gradually absorbed my MACROPHAGES within the STROMA
Hormonal Control of the Ovarian Cycle
- Early in FOLLICULAR Phase, ESTROGEN and PROGESTERONE levels are Low —> Feedback to INCREASE FSH and LH (Via GnRH from HYPOTHALAMUS) and thus, see rising levels of ESTROGEN
a) INITIALLY RISING ESTROGEN levels INHIBIT further FSH and LH release (NEGATIVE FEEDBACK)!!!!!!!!
b) LATER as Follicle is developing, the RISING Estrogen levels STIMULATE FSH and LH release (POSITIVE FEEDBACK)!!!!!!!!!!
- In LUTEAL PHASE, CORPUS LUTEUM makes ESTROGEN and PROGESTERONE—–> Feedback to Inhibit FSH and LH release —-> FSH and LH levels fall —-> thus ESTROGEN and PROGESTERONE levels fall
Uterus- Three Layers
1) ENDOMETRIUM:
- Functional Layer (STRATUM FUNCTIONALIS)
- Basal Layer (STRATUM BASALIS)
2) MYOMETRIUM:
- 3 layers of Circularly arranged Smooth Muscle
3) PERMIETRIUM:
- SIMPLE SQUAMOUS EPITHELIUM
Uterus- Endometrium
1) COMPONENTS:
- Simple COLUMNAR EPTHELIUM; lines the Endometrial Glands
- LAMINA PROPRIA: Fibroblasts, ground Substane, Type III Collagen
2) STRATUM FUNCTIONALIS:
- Proliferates and Sloughs off during MENSTRUATION
- Hormone Sensitive
- Cyclical Changes
3) STRATUM BASALIS:
- Regenerates Functional Layer (STEM CELLS)
- Not Hormone Sensitive
Uterus- Myometrium
- 3 layers of Smooth Muscle
(Middle layer is thickest and contains the ARCUATE ARTERIES “STRATUM VASCULARE) - Does not change with Menstrual Cycle
- Does undergo HYPERTROPHY and HYPERPLASIA during Pregnancy
Endometrial Blood Supply
- UTERINE Arteries give off ARCUATE Arteries in MYOMETRIUM
- ARCUATE Arteries branch to form 2 sets of Arteries (Endometrium gets dual blood supply)
- STRAIGHT arteries to STRATUM BASALIS
- SPIRAL (Helical) Arteries to STRATUM FUNCTIONALIS
- Important in Cyclic Shedding of STRATUM FUNCTIONALIS
Leiomyoma (Uterine Fibroid)
- BENIGN TUMORS that arise from the Overgrowth of Smooth Muscle and Connective Tissue in the Uterus
- Classified based on Location
- A Genetic Predisposition to LEIOMYOMA GROWTH Exists
