1027 - Histology of the Menstrual Cycle Flashcards
What are the two components of the menstrual cycle?
Ovarian cycle - follicular and luteal phases
Endometrial cycle - menstrual (1-5), proliferative (5-14), and secretory (14-28) phases.
What are the components of the uterine wall?
Endometrium - stratum functionalis (lost and grows) and stratum basalis (permanent). Endometrium consists of glands of simple columnar epithelium in ‘sesame seed’ hormonally responsive stroma.
Myometrium - smooth muscle.
What are the organs and hormones involved in the ovarian and menstrual cycle?
Ovary - releases oestrogen and progesterone - these provide negative feedback for most of the cycle, but positive just before ovulation (over a threshold) - resulting in LH surge.
Uterus
Anterior pituitary - releases LH and FSH in response to GnRH (hypothalamus).
“hypothalamic - pituitary - ovarian axis”
Outline the follicular phase ovarian cycle and what hormones are dominant at each stage
Follicular phase days 1-14
1 - Follicle growth (FSH) - 1-5
2 - 5-14 - Follicles produce oestrogen, increases sensitivity to LH, and hits peak oestrogen (above threshold)
3 - 14 - Oestrogen peak triggers LH surge, which stimulates ovulation. Follicular capsule ruptures, ovum is released, and remaining follicle becomes corpus luteum. Basal body temperature rises by 1 degree.
Outline the luteal phase ovarian cycle and what hormones are dominant at each stage
Luteal phase days 14-28
1 - Follicle becomes corpus luteum - produces progesterone (some oestrogen).
2 - In absence of fertilisation, corpus luteum degenerates.
3 - Drop in progesterone triggers menstruation. FSH production resumes.
What is the role of oestrogen - when does it have greatest effect?
Oestrogen - greatest effect first half of cycle - proliferation of endometrium
Causes proliferation of endometrial stroma, and glands which sustain fertilised ovum.
Also responsible for development of female sex organs, fallopian tubes, breasts, preserve skeleton and skin.
What is the role of progesterone? When does it have greatest effect?
Progesterone - greatest effect second half of cycle
Changes the endometrium to prepare for implantation, nourish the fertilised ovum, and inhibits FSH.
Also inhibits smooth muscle contraction/relaxes it, swells breasts.
What occurs in the proliferative phase of the menstrual cycle?
Proliferative phase - days 5-14 - oestrogen dominant, most variable stage among women. Endometrium was desquamated by menstruation, leaving thin basal layer. Increased oestrogen (from folllicles) leads to stromal and epithelial proliferation, with gland and blood vessels forming faster than stroma grows become large and tortuous. Lots of mitotic activity.
What occurs in the secretory phase of the menstrual cycle?
Secretory phase - days 14-28 - progesterone dominant. Near constant, and accurate dating possible.
Endometrium produces glycogen and lipids to prepare for fertilisation - leads to sub-nuclear vacuolisation - ‘piano keys’. Secretes some (pink lumen).
Continued cellular proliferative, endometrium measures up to 5-6mm thick
Blood vessels and glands become more tortuous. Increased cytoplasm in stroma. No mitotic activity.
What is pseudodecidua? How does it differ from decidua?
Pseudodecidua - endometrial stromal cells swell with nutrients over menstrual cycle, becoming pale and vacuous by the late secretory phase.
Decidua is the endometrium of pregnancy - even more swollen due to high levels of progesterone secreted by intact corpus luteum post-fertilisation.
How is the blastocyst nourished prior to the placenta forming?
Progesterone causes cytological changes - blastocyst absorbs glandular secretions or phagocytoses endometrial stromal cells full of glycogen or lipids.
How does the endometrium change in menstruation?
Drop in oestrogen leads to vasospasm and necrosis/apoptosis.
‘Blue calls’ of dead endometrium - karyorrexis. Endometrium sloughs off.
Uterine contractions expel endometrium with fibrinolysin.
What is the hallmark of endometrial infection?
Inflammatory infiltrate with plasma cells.
