Ovulation and Menstruation

Physiology of the Female Reproductive System - Ovulation

Following ovulation, the fallopian tube receives the oocyte. Oocytes lack flagella, and therefore cannot move on their own.

High concentrations of estrogen that occur around the time of ovulation induce contractions of the smooth muscle along the length of the fallopian tube.
These contractions cause the oocyte to move towards the uterus, through the coordinated beating of the cilia that line the outside and lumen of the fallopian tube, which pulls the oocyte into the interior of the tube.
Once inside, the muscular contractions and beating cilia move the oocyte slowly toward the uterus.
When fertilization does occur, sperm typically meet the egg while it is still moving through the middle portion of the fallopian tube.

The Menstrual Cycle

The menstrual cycle lasts about 28 days and consists of several phases during which the endometrium undergoes changes due to secretion of sex hormones three phases of the menstrual cycle are:

Menstrual phase - reproductive hormone levels are low, and menstruation occurs, which is when the endometrial lining is shed. This phase typically lasts between 2 – 7 days with an average of 5 days.
Proliferative phase - menstrual flow ceases and the endometrium begins to proliferate/thicken. During this phase reproductive hormones are working in homeostasis to trigger ovulation on approximately day 14. Ovulation marks the end of the proliferative phase.
Secretory phase - the endometrial lining prepares for implantation of a fertilized egg. If no pregnancy occurs within approximately 10-12 days the endometrium will grow thinner and shed starting the first day of the next menstrual cycle.