Menstrual cycle: Also called as Female reproductive cycle. After puberty (10 - 12) yrs , the female reproductive system undergoes a repeated Cyclic process Called as menstrual Cycle. It lasts for 28 days (±7days) [ 21 days up to 35 days]. First menstrual Cycle is called menarch (10-12 yrs age) while last menstrual cycle is Called menopause (45-50 Yrs age) .
Folliculogenesis:
The process of formation of graffian follicle from primordial follicles is called folliculargenesis. It takes place in ovary every month after puberty under the regulation of hypothalamus and pituitary gland.
In Female, the oogonia are formed in Yolksac and migrated to ovary while the female is inside uterus of her mother during development before birth.
In ovary , primary oocytes are surrounded by a layer of flat epithelial Cells and Called primordial follicles. Maximum up to 7 million primordial follicles are formed. At the time of birth about 2 million are present and only about 30,000 to 40,000 primordial follicles are present in each ovary at the time of puberty. As the follicles regularly undergo follicular atrasia , process of degeneration of follicles.
The first meiotic division of primary oocyte begins inside uterus before birth during developmental period but does not get completed and remains arrested at diplotene stage.
In each month (menstrual cycle), about ( 10- 20) primordial follicles automatically get changed into primary follicles by local mechanism.
In general, this process alternates in two ovaries in each succeeding mouth or cycle.
The menstrual cycle is regulated by hormones , the main controller is hypothalamus, after hypothalamus pituitary hormones (FsH and LH) and then ovarian hormones (Estrogen & progesterone).
The primary follicles remain Covered by a layer Or many layer of Cuboidal Cells and are called granulosa Cells. These primary follicles Changes into secondary follicles under the influence of FSH. In the Secondary follicle , the granulosa Cells are multilayered and primary oocyte produces glycoprotein which forms a layer around primary oocyte Called Zona pellucida. zona pellucida allows only human sperm to enter inside oocyte and when one sperm enter inside the oocyte , it become rigid and prevents further entry of sperm i.e. polyspermy.
The secondary follicle secretes some substances which forms a layer of Connective tissue around it Called theca cells. The theca Cells further get differentiated into theca externa ( fibrous) and theca interna( granular and highly vascular). These theca Cells nourishes granulosa Cells and produces androgen like substance which is Converted into estrogen by granulosa Cells.
This estrogen Causes thickening of functional layer of endometrium. It makes cervical mucus thin to make entry of Sperm easier. It also passes to Hypothalamus and FSH production stops.
The first maturation division of primary oocyte get completed and secondary oocyte is formed.
A Cavity appears within the granulosa Cells Called antrum
which remains filled with fluid called liquor folliculi which is produced by granulosa Cells and provide Nutrients to oocyte.
The antrum divides granulosa Cells into outer thin layer and inner layer Which surrounds the ovum is Called corona radiata . The granulosa cells that attach the oocyte with the wall of follicle is Called cumulus oophorus. The fully mature follicle is Called graffian follicle.
The estrogen produced by granulosa Cells give negative feedback to hypothalamus and Production of FSH and LH decreases. Thus, all developing follicles except graffian follicle dies.
In graffian follicle, the Secondary oocyte starts second maturation division but get arrested in metaphase - II.
The granulosa Cells of graffian follicle produce estrogen and some where between middle of the Cycle under the positive influence of estrogen production of FsH and LH increases drastically.The production of LH increases by 10 times and is called LH surge. under the influence of LH, blood vessels passing into granuIosa cells dilate and the theca Cells produces proteolytic enzyme to dissolve Collagen fibers. the graffian follicle produces nipple like projection Called stigma which is avascular as pressure inside antrum increases , the stigma breaks and the ovum with zona pellucida and some granulosa Cells surrounding the ovum Called Corona radiata is released. This Process is Called ovulation. The remaining granulosa cells and the theca Cells form a temporary endocrine structure Called corpus luteum (yellow body) under the influence of LH. It's usual life span is 10-12 days. It produces large amount of progesterone(pregnancy hormone) and some estrogen.Also produces relaxin and inhibin. Under the influence of progesterone endometrium become more vascular, further thicker , glandular and secretory.
The released ovum is Captured by vibrating fimbrae. the fluid of antrum stimulates vibration of fimbrae.
If ovum does not get sperm or no fertilization takes , the egg dies within 48 hrs , called appotosis. In oviduct some macrophages /Neutrophils will phagocyte it.
If Corpus luteum does not get any message from Uterus about the fertilization , the Corpus luteum (yellow body) degenerates by ( 10 -12) days and get Changed into Corpus albicans(white body) then the level of progesterone decreases drastically and the functional endometrium goes into necrotic Change and the cells and blood vessels of functional layer Shed off Causing menstruation.
Amount of blood passed = ( 20 - 80) ml. per cycle.
If egg meets sperm in oviduct , fertilization takes place and at about 4 day blastocyst comes in uterus and get attached with endometrium by finger like projections called tropoblast and lies within the endometrium. In about 8th day, implantation get completed. The tropoblast produces HCG
(Human Chorionic gonadotropin) which reaches to Corpus luteum & then Corpus luteum increases in size and Produces more progesterone & estrogen.
HCG also passes into urine and is used for urine pregnancy test. HCG also Causes nausea.
Now, the Corpus luteum grows more and Called Corpus luteum of pregnancy and survive for about 3-4 months within which the Placenta is fully formed and produces progesterone. Now, Corpus luteum dies happily.
Day of ovulation = length of menstrual cycle - 14
The menstrual cycle Consists of 3phases:
⇒ Menstrual Phase
⇒ proliferative phase/ Follicular phase / Estrogen phase
⇒ secretory phase / Luteal phase / progesterone phase
Menstrual phase: The Shed off Cells and blood vessels of functional endometrium along with blood passes out through vaginal orifice. It lasts for (3-5) days.
Follicular Phase: lasts for 10- 12 days. under the influence of FSH folliculogenesis takes place in which primordial follicle Changes into graffian follicle. The granulosa Cells of graffian follicle produces estrogen which Proliferate functional layer of endometrium and makes cervical mucus thin.
At the end of this phase, under the positive influence of estrogen more amount of FSH and very large amount of LH is produced Called LH surge occurs & the graffian follicle ruptures and ovum is released. This process is Called ovulation which takes place in 14th day of cycle if cycle is of 28 days.
Luteal phase: under the influence of LH , the remaining part of graffian follicle (theca cells and granulosa cells) form Corpus luteum which produces more progesterone and less estrogen. This progesterone Causes further thickening of endometrium and makes it more vascular, glandular and secretory.
The ovum is received by fimbrae. If fertilization does not occur then egg dies within 48 hrs while Corpus luteum degenerates within (10- 12) days and get Changed into Corpus albicans. Thus, level of progesterone falls down and blood supply to endometrial lining stops and Cells of functional layer of endometrium under go necrosis. Thus, Cells of functional layer, blood vessels and blood shed off and Passes out through vagina as menstrual flow.