The Menstrual Cycle
Introduction • Refers to the monthly cyclic changes in the ovaries and the endometrium, starting with the preparation of an egg for fertilization and ending with menstruation. It’s a manifestation of the H-P-O-E axis. • It is regulated by the hypothalamo-pituitary- ovarian axis.
Phases of Menstrual Cycle • Menses: Days 1-5;- the thick endometrial wall is sloughing off, detaching from the uterine wall; rid by bleeding for 3 to 5 days. The detached tissue and blood flow through the vagina as the menstrual flow. 50 –150 ml is lost. • Proliferative Phase: Days 6-14; - stimulated by estrogen level increase the endometrium is repaired, blood supply to the endometrium is increased, becoming thick again; ovulation occurs at the ovary end (latter part) of this stage. (The length is variable) • Ovulation : Estrogen peak > LH surge > ovum release • Secretory Phase: Days 15-28; - rising levels of progesterone increasing the blood supply and build up of the endometrium, getting it ready for implantation if needed; no fertilization = hormones released to reduce blood flow to the endometrial wall, causing the cells to die off, ready for menses to begin on day 28.
- Winter '16
- Bill Oyieke