INTRODUCTION
Female Reproduction is a complex phenomenon involving the ovary tubes and uterus. The ovary is different in the 7th week and starts forming primordial germ cells which in sdult life from oocytes. After minarche the development of the follicle containing the oocyte mature under the control of hormonecente in th released from pituitary gland hypothalamus. Hence reproduction is control from higher centers in the brain. The ovulation occurs with release of oocyte which passes through the fallopian tube and is fertilized there.The subsequent embryo implants in the uterus by day 6. The overy release hormone to support pregnancy.
THE FETAL OVARY
The Beginning of Ovarian Development
Sexual differentiation of the undifferentiated starts at around 7 th week of intrauterine life. The migration of the germ cells into the ovary formation of the follicles and the distinction into cortex and medulla are the key events in formation of the fetal ovary. Formation of the ovary first starts appearing as a thickening of the coelomic epithelium like cells ( GRELs) cells extendas deeply into the mesoderm thus forming distinct projection known as gonadal ridge.
Migration of the primordial Germ cells in the ovary
The primordial germ cells are endodermal in origin. They arise from the yolk sac and migrate from yolk sac to the genital ridge along the hindgut. Kit ligand and its receptor kit play a critical role in the survival of migrating germ cells. On reaching the gonadal ridge these stem cells which are diploid are termed as oogenia. oogenia along with stromal cells and vasculature enter into the devloping ovary by break down of the basal lamina underlying the mesonephric surface epithelium
;b b naDevelopment of the Fetal Ovary a
The GREL cells enclose the oogenia and form the ovigerous cords. The ovigerious cords lie at the periphery of the developing ovarian cortex. The medulla contain the stroma with the capillaries and remnants of mesonpherious known as rate ovarii. The ovigerous cords break up into smaller cords by basal lamina forms the primordial follicle. aaThe first primordial cells lie at the corticomedullary junction of the ovary. The ovary is first identified histologically by 10 th week of gestation
The Timeline of Human Ovarian Development
In 28 th days mesonpherious develops. Medial of the mesonepheric duct gonadal ridge appears in 35 days. The undifferentiated gonads are visible by 42 days and further development of the ovary and differentiation into cortex and medulla is completed by 10 th week of gestation. Between 10 and 12 weeks the diploid primordial germ cells cease mitosis and enter stage 2 meiosis
Factors Affecting the ovarian Development in the Fetus
Development of the fetal ovary requires a complex interplay between genetic and epigenetic factors. It is no more a default process as was thought earlier. The initiation of ovarian development in xx karyotype requires activation of genes Wnt -4 and DAX-1
Development of the ovarian Follicles
After the migration of the primordial germ cells (PGCs) to the ovary at 5 week of gestation, these cells undergo mitosis and form germ cells cysts in the fatal ovary. At 10-12 week of gestation thse seeds breakdown and form a primordial follicle pool. Each ovarian follicle then undergoes development in three stage
* Gonadotropin independent
* Gonadotropin responsive
* Gonadotropin dependent
Stages of folliculogenesis
primordial follicles
primary follicles
secondary follicles
Tertiary Follicle or the Preantral Follicle (400 micro meter)
This stage of the follicle is characterized by the appearance of cavity due to the accumulation of fluid in between the granulosa cells.The antral fluid is formed from transudation of plasma from thecal cappilaries and is rich in proteins,steroids and anticoagulants, This process is controlled by autocrine and paracrine factors and is not dependent on gonadotropins.
Grafian follicles or the Antral follicle
The largest and most mature of the tertiary follicles are called Graffian follicle. These will be selected for maturation each menstrual cycle. characteristic structural unit of graffian follicle is an antrum containing fluid called follicular fluid .
ANATOMY AND PHYSIOLOGY OF FEMALE REPRODUCTIVE SYSTEM
The hypothalamus, anterior pituitary gland and ovaries are responsible for regulating the female reproduction. The hypothalamus secretes a gonadotropin releasing hormone (GnRH)
To understand the function of the female reproductive system it can be divided into three compartments
* Hypothalamic pituitary level
* ovarian level
* uterus, Fallopian tube cervix and vagina
