FOLLICULOGENESIS, OVULATION & CORPUS LUTEUM.pptx

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1. General Embryology: Ovarian follicle, Ovulation and Corpus Luteum COURSE TITLE: Gross Anatomy LECTURER: Dr Sabiu Bala Soja UNIT: Epigenetics and Neurodevelopmental Anatomy DATE : 1ST September, 2024

2. Outline 2 Ovarian follicle Development Folliculogenesis Ovulation Corpus Luteum Clinical correlation

3. OVARIAN FOLLICLE 3 Folliculogenesis Is a selective maturation of primordial follicle into a mature Graafian follicle or m ature Ovarian follicle each month in a woman of reproductive age Under the influence (FSH)/LH

4. Folliculogenesis (cont’d) 4 At the beginning of each ovarian cycle, 5-15 primordial follicles are stimulated to grow under the influence of FSH However only one of these follicles reaches full maturation under normal condition. The others degenerate and become atretic

5. Folliculogenesis (cont’d) 5 Primordial follicle: consist of primary oocyte that is surrounded by single-layer follicular epithelium (a layer of squamous cell) At puberty: surviving primary oocytes are 40,000. Oocyte grows in size. Follicular cells become stratified cuboidal ---granulosa cells. Granulosa and oocyte secrete a cellular glycoprotein layer --zona pellucida which provides nutrition. Stromal cells of ovary form theca folliculi --splits into secretory theca interna and fibrous theca externa.

6. Folliculogenesis (cont’d) 6

7. Folliculogenesis (cont’d) 7 Fluid filled spaces appear in granulosa cells – spaces coalesce to form antrum (secondary follicle). Granulosa cells surrounding oocyte form cumulus oophorous .

8. Ovulation 8 Is the Expulsion of the secondary oocyte with its surrounding granulosa cells (cumulus oophorus) outside the ovary following the rupture of mature Graafian follicle under influence of high concentration of luteinizing hormone( LH surge) and FSH

9. Ovulation (cont’d) 9 At the end of the proliferative phase of the uterine endometrium(Day 13 or 14 of menstrual cycle) The levels of FSH and LH suddenly rise very sharply As a result of positive feed –back signal by estrogen ,that is produce by theca and granulosa cells. The estrogen stimulates anterior pituitary gland to secrete more LH

10. Ovulation (cont’d) 10 LH Causes the follicle to enter mature vesicular stage To complete meiosis I and to enter meiosis II , where it is arrested in Metaphase approximately 3hours to ovulation LH facilitate extrusion of oocyte by increasing the collagenase activity Also increase prostaglandin concentration that cause local muscular contraction in the ovarian wall

11. Ovulation (cont’d) 11

12. Ovulation (cont’d) 12 As ovulation approaches, the Mature Vesicular follicle bulge onto the ovarian surface, resulting in the formation of a small nipple-shaped protrusion called Stigma The ovulated oocyte clings to the surface of the ovary by gelatinous cumulus oophorus and is actively scraped off by fimbriated oviduct mouth .

13. Corpus luteam 13 Is is an endocrine structure that secretes steroid hormones to maintain the uterine endometrium in a condition ready to receive an embryo.

14. Corpus luteam (cont’d) 14 After ovulation, membrane granulosa cells of the ruptured follicular wall , together with cell from theca interna , are vascularized by the surrounding vessels influenced by LH surge These cells transform to a yellowish pigment and change into lutein cells of the corpus luteum under the influence of LH These cells secrete estrogens and progesterone which causes the uterine endometrial layer to enter the progestational or secretory stage in anticipation for implantation of the embryo

15. Corpus luteam (cont’d) 15

16. Corpus luteam (cont’d) 16 The corpus luteum becomes large in size due to hypertrophy and accumulation of lipid in the granulosa and theca interna cells If no implantation occurs, the corpus luteum degenerates after about 14 days , and is converted to a scarlike structure called the corpus albicans Simultaneously, progesterone secretion is diminishes, precipitating menstrual bleeding .

17. Corpus luteam (cont’d) 17 If fertilization occurs, the luteolysis of corpus luteum is prevented due influence of human chorionic gonadotrophin hormone The corpus luteum prosper and form corpus luteum of pregnancy or corpus luteum graviditatis It continues production of progesterone until the end of 16weeks gestation

18. Corpus luteam (cont’d) 18 Later, the secretion of progesterone is taken over by trophoblastic component of the placental tissue Which is adequate for maintenance of pregnancy Early removal of corpus luteum graviditatis before 16wks gestation usually lead to miscarriage.

19. Clinical correlation 19 Ovarian Dysfunctions Primary Ovarian Failure(POF) or primary ovarian insufficiency (POI) Chronic Anovulation High Body Mass Index (BMI) BMI> 30 Polycystic ovarian failure A dvanced maternal age women that are poor responders to conventional Infertility treatments low ovarian reserve P repubertal cancer patients undergoing chemotherapeutic treatments

20. SUMMARY-Folliculogenesis, Ovulation & Corpus luteum 20

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