Ovarian follicle

Under an ovarian follicle (or follicles ) refers to the unit from the egg and the surrounding auxiliary cells in the ovary ( ovary ). The auxiliary cells are the follicular epithelial cells ( granulosa cells ) and two layers of connective tissue that surrounded them: the inner theca interna and theca externa the outer.

Follicular

The primordial follicles are created before birth. They are the result of ( the 6th week ) from the yolk sac to the gonad immigrant primordial germ cells and their mitotic division until the 5th month. You are in prophase I of meiosis and consist of the oocyte and a single layer plates follicular epithelium. The primordial follicles are stopped in their development until puberty. This pause is called dictyotene. At puberty hormone ( FSH) is secreted by the pituitary follicle, which stimulates the maturation of primordial follicles 5-15. You will primary follicles, which are characterized in that they form a cubic follicular epithelium, which is polar. The oocyte begins to grow. It becomes the secondary follicles ( follicular epithelium is multilayered, forming the theca cells of connective tissue ), in which the egg forms a shell of glycoproteins (zona pellucida ) and the follicular epithelium is multilayered and aligns radiate (corona radiata).

The next step, the tertiary follicles are characterized by the occurrence of a follicle ( antral follicular ), with a fluid (CSF follicular ) is filled. The egg is now in a cell clusters of granulosa cells, the Eihügel (cumulus oophorus ). Only now differentiated and the ( the follicular lumen ) surrounded connective tissue theca interna and theca externa.

In the course of follicular development, the vascular and cell-rich theca interna androgens which spread via diffusion through the basement membrane into the granulosa and there are flavored to estrogen, particularly estradiol produced.

With further increase in size of the mature Graafian follicle jump now arise (named after Reinier De Graaf ).

The control of these processes is performed by the follicle stimulating hormone ( FSH) from the pituitary gland. For ovulation occurs when the theca cells about 24 hours before ovulation (ovulation ) ( ie, when the oocyte is mature) begin to produce much estrogen. This increase in estrogen causes the pituitary gland secretion of luteinizing hormone, which in turn triggers the ovulation. At ovulation the mature oocyte ( along with zona pellucida and corona radiata) expelled from the follicle and outside of the ovary from the fallopian tubes, more precisely, its fimbriae was added, and continued in the pars ampullaris.

Following ovulation is formed from the follicle ( granulosa and theca cells ) of the corpus luteum, which is progesterone. Prevents progesterone, the uterine lining that is mined previously established (menstruation). The corpus luteum is built without fertilization (after about 9 days ) and progesterone production falls outside. This initiates the menstrual period. However, if the egg fertilized, it pours a hormone ( HCG, human chorionic gonadotropin ) from which further stimulates the corpus luteum in place of luteinizing hormone. The corpus luteum then grows and becomes the corpus luteum graviditatis. In the first two months of pregnancy, it is solely responsible for progesterone production, then the production is more and more taken over by the placenta.

Demise of follicles

Follicles may be destroyed at any stage and at any age. This process is called follicular atresia.

Swell

• Thomas W. Sadler; Medical Embryology; Thieme Verlag; 2003; ISBN 3-13-446610-4

• Female genital organ
• Histology of the Reproductive System
• Reproductive Medicine
• Endocrine organ
• Ovary