In a larger perspective, the whole folliculogenesis, from primordial to preovulatory follicle, belongs to the stage of ootidogenesis of oogenesis.

Folliculogenesis describes the progression of a number of small primordial follicles into large preovulatory follicles that enter the menstrual cycle.

This remaining follicle, called the dominant follicle, will grow quickly and dramatically-up to 20 mm in diameter-to become the preovulatory follicle.

In all cases, the follicular phase of the menstrual cycle means the time between selection of a tertiary follicle and its subsequent growth into a preovulatory follicle.

Lee et al [ 33] showed that progesterone interacted with P-gp, inducing its expression in the granulose cell in preovulatory follicles to modulate steroid efflux.

There are several stages in folliculogenesis, starting with a primordial follicle, which then becomes a primary, secondary, early tertiary (antral), late tertiary and eventually a preovulatory follicle.

However, in porcine preovulatory ovaries (late follicular phase), which contain numerous preovulatory follicles but no luteal tissue, very strong LHR immunoreactivity was also detected (lane 3, Fig.

Yet, cell surface staining was observed only on classic LH/CG targets, granulosa and theca cells of preovulatory follicles and mature luteal cells, but also in the vaginal epithelium.

The process begins continuously, meaning that at any time the ovary contains follicles in all stages of development, and ends when a mature oocyte departs from the preovulatory follicle in a process called ovulation.

In porcine ovaries, LHR expression was detected in granulosa and theca cells of preovulatory follicles, but not in granulosa lutein cells of the mature CL [ 27 ] .

It is possible, therefore, that the strong expression of FS by the DF may serve to modulate BMP-15 action such that sufficient FSH receptors are expressed in the GC to permit the development of a preovulatory follicle.

This may represent synthesis of a receptor extracellular domain not yet associated with the cell surface, but remaining trapped intracellularly [ 18 ] Maturation of preovulatory follicles was associated with a transition of scarce granular cytoplasmic LHR immunoreactivity (ig, Fig.

By the end of the follicular, or proliferative, phase of the thirteenth day of the menstrual cycle, the cumulus oophorus layer of the preovulatory follicle will develop an opening, or stigma, and excrete the oocyte with a complement of cumulus cells in a process called ovulation.

Porcine tissues (Figure 3) Porcine preovulatory follicles showed distinct LHR staining of theca interna, lack of LHR expression in vascular layer under the follicular membrane, and transition of granular cytoplasmic to surface LHR immunoreactivity in granulosa cells (Fig.