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Menstrual Cycle - Part 1

📌 𝐅𝐨𝐥𝐥𝐨𝐰 𝐨𝐧 𝐈𝐧𝐬𝐭𝐚𝐠𝐫𝐚𝐦:-   / drgbhanuprakash   📌𝗝𝗼𝗶𝗻 𝗢𝘂𝗿 𝗧𝗲𝗹𝗲𝗴𝗿𝗮𝗺 𝗖𝗵𝗮𝗻𝗻𝗲𝗹 𝗛𝗲𝗿𝗲:- https://t.me/bhanuprakashdr 📌𝗦𝘂𝗯𝘀𝗰𝗿𝗶𝗯𝗲 𝗧𝗼 𝗠𝘆 𝗠𝗮𝗶𝗹𝗶𝗻𝗴 𝗟𝗶𝘀𝘁:- https://linktr.ee/DrGBhanuprakash Menstrual cycle The cycle lasts 21–35 days on average The cycle consists of two phases: • Follicular phase : accounts for most of the variability in the length of the menstrual cycle • Luteal phase : lasts 14–15 days The cycle changes with age: First few years following menarche → irregular menstrual cycles (caused by immaturity of the hypothalamic-pituitary-gonadal axis) Days 1–14 Ovaries: the follicular phase --------------------------------------------- 1. FSH stimulates the development of several follicles in the ovaries → granulosa cells of follicles produce estrogen → suppresses 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 → release of FSH → subsequent LH surge initiates ovulation Endometrium: desquamation and proliferative phase • Desquamation (menstruation at days 1–4)  Absence of a pregnancy → resolution of corpus luteum → progesterone concentration decreases → induces vasospasms in the uterine spiral arteries, ischemia, and sloughing off of the functional layer of the endometrium • Proliferation (days 4–14): growing follicles produce estrogen (granulosa cells express aromatase, which converts androgens to estrogens) → stimulates proliferation of the endometrium Histology • Proliferation of endometrial epithelial cells (cells show high mitotic activity) • Endometrial glands are straight, tubular, and lined by simple columnar epithelium. • Stromal cells start to divide, enlarge, and accumulate glycogen. • Uterine spiral arteries start to regenerate and extend two-thirds of the way into the endometrium. Days 14–28 Ovaries: luteal phase ---------------------------------- • Ovulation: rupture of Graafian follicle → oocyte is released • Following ovulation, the granulosa cells produce LH receptors → LH-induced transformation of the Graafian follicle into the corpus luteum → produces progesterone → inhibits LH release via a negative feedback loop Endometrium: secretory phase • Endometrial differentiation promoted by progesterone → preparation of the functional layer of the endometrium for oocyte implantation Histology  Increased endometrial gland tortuosity  Glycogen-rich secretions  Edematous stromal cells  Uterine spiral arteries extend the full length of the endometrium. In the absence of pregnancy → ↓ progesterone levels → induces apoptosis of the functional layer of the endometrium (seen as shrinkage and fragmentation of endometrial cell nuclei) → menstruation #menstrualcycle #gyenecology #obg #follicularphase #letualphase #menstrualcyclephysiology #menstrualcyclembbs #menstrualcyclevideo #menstrualcycleusmle #menstrualcycle