Menstrual Cycle - Part 2
1,407๐ ๐
๐จ๐ฅ๐ฅ๐จ๐ฐ ๐จ๐ง ๐๐ง๐ฌ๐ญ๐๐ ๐ซ๐๐ฆ:- https://www.instagram.com/drgbhanuprakash
๐๐๐ผ๐ถ๐ป ๐ข๐๐ฟ ๐ง๐ฒ๐น๐ฒ๐ด๐ฟ๐ฎ๐บ ๐๐ต๐ฎ๐ป๐ป๐ฒ๐น ๐๐ฒ๐ฟ๐ฒ:- https://t.me/bhanuprakashdr
๐๐ฆ๐๐ฏ๐๐ฐ๐ฟ๐ถ๐ฏ๐ฒ ๐ง๐ผ ๐ ๐ ๐ ๐ฎ๐ถ๐น๐ถ๐ป๐ด ๐๐ถ๐๐:- https://linktr.ee/DrGBhanuprakash
Menstrual cycle
The cycle lasts 21โ35 days on average
The cycle consists of two phases:
โข Follicular phase: accounts for most of the variability in the length of the menstrual cycle
โข Luteal phase: lasts 14โ15 days
The cycle changes with age:
First few years following menarche โ irregular menstrual cycles (caused by the immaturity of the hypothalamic-pituitary-gonadal axis)
Days 1โ14
Ovaries: the follicular phase
---------------------------------------------
1. FSH stimulates the development of several follicles in the ovaries โ granulosa cells of follicles produce estrogen โ suppresses the release of FSH via a negative feedback loop
2. Selection of a dominant follicle (Graafian follicle)
3. High levels of estrogen trigger a positive feedback loop โ release of FSH โ subsequent LH surge initiates ovulation
Endometrium: desquamation and proliferative phase
โข Desquamation (menstruation at days 1โ4)
๏ผ Absence of a pregnancy โ resolution of corpus luteum โ progesterone concentration decreases โ induces vasospasms in the uterine spiral arteries, ischemia, and sloughing off of the functional layer of the endometrium
โข Proliferation (days 4โ14): growing follicles produce estrogen (granulosa cells express aromatase, which converts androgens to estrogens) โ stimulates proliferation of the endometrium
Histology
โข Proliferation of endometrial epithelial cells (cells show high mitotic activity)
โข Endometrial glands are straight, tubular, and lined by simple columnar epithelium.
โข Stromal cells start to divide, enlarge, and accumulate glycogen.
โข Uterine spiral arteries start to regenerate and extend two-thirds of the way into the endometrium.
Days 14โ28
Ovaries: luteal phase
----------------------------------
โข Ovulation: rupture of Graafian follicle โ oocyte is released
โข Following ovulation, the granulosa cells produce LH receptors โ LH-induced transformation of the Graafian follicle into the corpus luteum โ produces progesterone โ inhibits LH release via a negative feedback loop
Endometrium: secretory phase
โข Endometrial differentiation promoted by progesterone โ preparation of the functional layer of the endometrium for oocyte implantation
Histology
๏ผ Increased endometrial gland tortuosity
๏ผ Glycogen-rich secretions
๏ผ Edematous stromal cells
๏ผ Uterine spiral arteries extend the full length of the endometrium.
In the absence of pregnancy โ โ progesterone levels โ induces apoptosis of the functional layer of the endometrium (seen as shrinkage and fragmentation of endometrial cell nuclei) โ menstruation
#menstrualcycle #gyenecology #obg #follicularphase #letualphase #menstrualcyclephysiology #menstrualcyclembbs #menstrualcyclevideo #menstrualcycleusmle #menstrualcycle