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Basim Abu-Rafea, MD, FRCSC, FACOG Assistant Professor & Consultant Obstetrics & Gynecology Reproductive Endocrinology & Infertility Advanced Minimally Invasive Gynecologic Surgery Department of Obstetrics & Gynecology King Khalid University Hospital King Saud University
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Divide the cycle into three phases: 1.Follicular phase 2.Ovulation phase 3.Luteal phase.
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This process occurs over 10–14 days of time. Features a series of sequential actions of hormones and autocrine - paracrine peptides on the follicle. Follicle destined to ovulate.
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By 16–20 weeks gestation 6–7 million. 1–2 million at birth. 300,000 to 500,000 at puberty. 400 to 500 follicles will ovulate during a woman's reproductive years.
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Initial follicular development occurs independently of hormone influence. FSH stimulation rescues a cohort of follicles from apoptosis, propelling them to the preantral stage. FSH-induced aromatization of androgen in the granulosa results in the production of estrogen. FSH and estrogen increase the FSH receptor content of the follicle and stimulate the proliferation of granulosa cells.
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Selection process is a result of two estrogen actions: 1.A local interaction between estrogen and FSH within the follicle. 2.The effect of estrogen on pituitary secretion of FSH.
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Activin
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FSH ACTIONS Recruitment & Rescue Stimulates aromatization of androgens to estrogens Increases granulosa cell content of FSH and LH receptors stimulates proliferation of granulosa cells ESTROGEN Suppressive influence on FSH Positive feedback influence on LH secretion Induces LH & FSH receptors
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The primordial follicle is nongrowing. Consists of an oocyte, arrested in the diplotene stage of meiotic prophase. Surrounded by a single layer of spindle-shaped granulosa cells.
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The mechanism for determining which follicles and how many will start growing on any given day is unknown. Growth and atresia (apoptosis) are not interrupted by pregnancy, ovulation, or anovulation. This process continues at all ages, including infancy and around the menopause.
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Development of follicles occurs over the time span of several menstrual cycles. It takes approximately 85 days to achieve preovulatory status. (Rescued) by follicle-stimulating hormone (FSH)
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The LH surge initiates: The continuation of meiosis in the oocyte Luteinization of the granulosa Synthesis of progesterone and prostaglandins within the follicle Progesterone: Enhances the activity of proteolytic enzymes Essential to induce the midcycle FSH peak
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Mechanism of follicular rupture: Follicular pressure The dominant follicle protrudes from the ovarian cortex Enzymatic rupture of the follicular wall Gentle release of the oocyte surrounded by the cumulus granulosa cells
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Lasts 14 days FORMATION OF THE CORPUS LUTEUM After ovulation the point of rupture in the follicular wall seals Vascular capillaries cross the basement membrane & grow into the granulosa cells availability of LDL - cholestrole
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Marked in progesterone secretion Progesterone actions: Suppress follicular maturation on the ipsilateral ovary Thermogenic activity Endometrial maturation Progesterone peak 8 days after ovulation Corpus luteum is sustained by LH hCG rescues the corpus luteum
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The demise of the corpus luteum results in a nadir in the circulating levels of estradiol, progesterone, and inhibin. The decrease in inhibin-A removes a suppressing influence on FSH secretion in the pituitary. The increase in FSH is instrumental in rescuing an approximately 70-day-old group of ready follicles from atresia
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Mean length of the menstrual cycle is 28 days (21-35). Average duration of menses is 3 to 7 days. The normal estimated blood loss is 30 ml.
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Basal layer: Adjacent to the myometrium Unresponsive to hormonal stimulation Remains intact throughout the menstrual cycle Functional layer: Zona compacta superficial Spongiosum layer
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Follicular /proliferative phase Estrogen mitotic activity in the glands & stroma endometrial thickness from 2 to 8 mm Luteal /secretory phase Progestrone Mitotic activity is severely restricted Endometrial glands produce then secrete glycogen rich vacules Stromal edema Stromal cells enlargement Spiral arterioles develop, lengthen & coil
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Hormone withdrawal leads to a modest shrinking of the tissue height of the endometrium. Flow in the spiral vessels diminishes, venous drainage is decreased. These reactions lead to endometrial ischemia and stasis. The prostaglandin content (PGFα and PGE 2 ) reaches its highest levels at menstruation. The endometrium is infiltrated with leucocytes.
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The menstrual fluid is composed of: The autolysed functionalis Inflammatory exudate Red blood cells Proteolytic enzymes
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