Follicles defined

Female sexual development and behaviour in mammals occurs by default and requires no ovarian secretion, and it is only in genetic males that the testis can secrete hormones which destroy this female pattern and superimpose that of the male. Sexual differentiation is not so well defined in fish, and larval exposure to both synthetic estrogens and androgens is widely used in aquaculture to produce monosex cultures. Endocrine disruption of sexual differentiation in fish may therefore reflect both the complexity and diversity of such processes between different species. Some care is required in use of the terms hermaphrodite and sex-reversal since a true hermaphrodite has both functional testes and ovaries and a sex-reversed fish is fully functional as its final sex—both produce the appropriate viable gametes. Such functional sex-reversal is not possible in mammals, but in some species of fish it is the normal developmental pattern. In most of the cases of hermaphroditism or sex-reversal reported in the non-scientific press, there is evidence only for a few ovarian follicles within a functional testis. This may be considered as feminisation or a form of intersex, and is very clearly endocrine disruption, but it is certainly neither sex-reversal nor hermaphroditism. In some cases the terms have even been used to infer induction of a single female characteristic such as production of yolk-protein by males. 

LH secretion which induces rupture of the follicle and release of the mature egg into the fallopian tube. In the ovary a corpus luteum forms, which secretes progesterone (maximal at about day 21) to prepare the endometrium for implantation of an early embryo. If pregnancy does not occur, the corpus luteum involutes, progesterone levels fall, and the thickened endometrium is shed giving rise to menstrual bleeding, which is defined as starting on day 1 of the next cycle. 

All primary oocytes are already present about a week before birth. Many of these remain in an arrested diplotene stage of meiosis for many months before ovulation or loss by atresia. Stages of primary oocyte development are defined by the cytologic appearance of the oocyte and its follicle. 

Clinically, menopause is defined as the last physiologic menstrual cycle in which pituitary gonadotropins (e.g., LH, FSH) have stimulated the maturation of a primordial follicle and caused ovulation. The transition from full reproductive potential to final ovarian failure is known as the climacteric, a period that begins about age 40. As estradiol levels in the blood gradually fall below normal, the early symptoms of the climacteric occur, s including anxiety, mood swings, irritability, and in some instances,... 

Chuong CM, Cotsarelis G, Stenn K (2007) Defining hair follicles in the age of stem cell bioengineering. J Invest Dermatol 127(9) 2098-2100... 

Lyle S et al (1998) The C8/144B monoclonal antibody recognizes cytokeratin 15 and defines the location of human hair follicle stem cells. J Cell Sci 111(21) 3179-3188... 

In order to define the mechanisms by which molecules traverse the skin, the iontophoretic molecular transport of neutral or charged penneants through hair follicles of or through skin... 

---