♦ The endometrium is formed of 2 layers :
– Basal layer:
– Supplied by straight arterioles.
– Doesn’t undergo shedding (represents the reserve for endometrial regeneration).
– Functional layer: composed of 2 layers (spongy & compact).
– Supplied by spiral arterioles (most superficial).
– Undergoes cyclic shedding.
1. Proliferative phase (pre-ovulatory phase).
2. Secretory phase (post- ovulatory phase).
3. Menstrual phase (menstruation).
A. Proliferative phase.
♦ Start: just after menstruation with resting phase in the 1st 2 days.
♦ End: with ovulation.
♦ The main hormone: estrogen.
♦ Duration: 9 – 11 days when the cycle is 28 days (variable).
♦ Endometrial thickness: 3 – 4 mm just before ovulation.
♦ Glands: simple tubular lined with columnar epithelium.
♦ Stroma cells: ↑ in number & little cytoplasm.
♦ Vascularity: ↑
B. Secretory phase.
♦ Start: with ovulation of the same cycle.
♦ End: with the onset of menstruation of the next cycle.
♦ Main hormone: progesterone, with minor effect of estrogen.
♦ Duration: 14 days whatever the cycle (fixed).
♦ Endometrial thickness: 6 -8 mm just before menses i.e. double the proliferative phase.
♦ Glands: tortuous, lined with cuboidal epithelium & lumen is distended with secretions.
♦ Stroma: edematous & more cytoplasm.
♦ Vascularity: ↑↑↑.
* The 1st sign of ovulation in endometrium is subnuclear vacuole.
* Leucocytic infiltration occurs 3 days before menses.
* If pregnancy occurs: endometrium undergoes marked secretory changes & becomes called decidua of pregnancy.
C. Menstrual phase, (menstruation).
♦ Definition: cyclic uterine bleeding caused by shedding of the secretory endometrium.
– Onset: 1st menses (menarche): 11 – 13 years.
– Duration: * 2- 7 days (average 3-5 days).
* < 2 days: hyopomenorrhea.
* > 7 days: menorrhagia.
– Frequency: * 21 – 35 days (15 % of women are 28 days).
* < 21 days: polymenorrhea.
* > 35 days: oligomenorrhea.
– Amount: * 30 – 180 cc (average 50 – 100 cc).
* 3 napkins / day.
* < 30 cc: hypomenorrhea.
* >180 cc: menorrhagia.
– Colour: dark red & doesn’t clot on standing unless excessive (WHY?!!).
– Odour: offensive due to:
– Decomposition of blood elements.
– Mixing with sebaceous secretions of the vulva.
– Blood + bacteria + enzymes.
– Fragments of endometrium + cervical mucus + desquamated vaginal epithelium.
– Menstrual molimina: tolerable symptoms as headache, nausea & backache that
are relieved once menses occurs.
– Exaggerated molimina: premenstrual tension syndrome.
– Degeneration of C.L. leads to estrogen & progesterone withdrawal leading to
shrinkage of the endometrium.
– Shortening of the spiral arterioles by ↑ their coils leads to stasis of blood &
anoxia which leads to ischemic necrosis of the functional endometrial layer
followed by shedding.
– Control of menses:
– PG f 2α in the degenerated endometrium leads to VC & myometrial contraction
so, controls blood loss.
– Regeneration of endometrium of the basal layer.
– Estrogen withdrawal bleeding may occur at monthly interval from proliferative
Uterine Cycle ( Endometrial cycle )- The Phases of Endometrial Change
The Uterine Cycle
The uterine cycle is the monthly series of changes that the females uterus, or uterine tissue, undergoes in preparation for the implantation of a fertilized egg. Just like all other biological cycles, there are different phases – 3 in this case. The uterine wall is made of three layers: The outer perimetrium, the middle myometrium, and the inner and thinner endometrium.Only the endometrium undergoes the changes during the uterine cycle. All together, the uterine cycle takes about 28 days. But this can vary from 21 – 35 days.
The first phase of the cycle is menses/menstral phase. It’s the beginning of the uterine cycle where the unneeded uterine tissue sheds. This is followed by the proliferative phase. During the proliferative phase, the endometrial tissue regenerates. Last but not least, during the secretory phase, the arteries and glands that supply the tissue regenerate.
PHYSIOLOGY; THE MENSTRUAL CYCLE by Professor Fink
Review of the Menstrual Cycle. The Lecture includes a review of the anatomy of the female reproductive system, ovarian follicles, follicle cells, corpus luteum and corpus albicans, the role of the Pituitary Gland, the 28-day cycle, Follicle Stimulating Hormone (FSH), Luteinizing Hormone (LH), the Preovulatory (Follicular) Phase, the Postovulatory (Luteal) Phase, LH surge and ovulation, estrogen, progesterone, endometrium, menstruation, pregnancy and Human Chorionic Gonadotropin (HCG).
Reference is made to the Ovulation Test Kit, Chorionic Sac, Pregnancy Test Kit, Basal Body Temperature, Rhythm Method, Menopause, amenorrhea and Fertility Drugs.