Ovulation, i.e., the emergence of the secondary oocyte from the follicle, depends on the disintegration of the follicle wall and the rupture of the ovarian surface.
A few hours after the FSH/LH peak one observes increased vascularization and edematous changes in the dominant follicle's surroundings. With time it is displaced towards the ovarian surface where it finally bulges out.
The hyaluronic acid, secreted by the granulosa cells, has the property that it binds water molecules: The more hyaluronic acid is made, the more water can be absorbed. In this way, a rapid increase of the amount of follicle fluid occurs and this leads to a dramatic increase of the tension in the follicle wall. This together with the effects of a lytic enzyme finally leads to the rupture of the follicle at a narrowly circumscribed place.
On the ovarian surface above the follicle that is about to burst, a white point forms shortly before the rupture (due to compression of the blood vessels), the so-called stigma.
The acquisition of the oocyte by the fallopian tube
In the meantime, the fimbriae of the infundibulum have placed themselves around the ovarian stigma and have sealed this location off.
Via a rotation about the axis of the suspensory ligament of the ovary and the ovarian ligament the ovary can turn the follicle that is about to rupture towards the fallopian tube.
When the surface ruptures the mass of cumulus cells, which are saturated with hyaluronic acid and which shelter the oocyte, reach the fallopian tube together with serous yellow follicle contents.
The outflow of the follicle contents is a procedure accompanied by coagulation processes. The protracted expulsion of the oocyte from the follicle makes it understandable that the fimbria funnel of the fallopian tube has enough time to flare itself over the ovulation location and to take up the oocyte-cumulus-complex with the accompanying volume of follicle fluid in the ampulla of the tube.
The oocyte in the cloud of cumulus cells following ovulation
In the fallopian tube, the secondary oocyte is surrounded by the corona radiata and scattered parts of cumulus cells (so-called cumulus cell cloud). The fluid that lies in between is sticky and stringy (effect of the hyaluronic acid) with a high concentration of progesterone (to attract the spermatozoa).