What are the associated control systems?

Usually the events associated with human development are principally under endocrine and neural control systems. The genetic make-up of the gametes also plays an important role as regards the final reproductive outcome.

The hypothalamus serves as the higher center control station for the associated endocrine glands. It releases the gonadotropic releasing hormone (GnRH) which in turn, influences the pituitary gland to release these hormones –Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH).

FSH is the hormone mainly responsible for follicular cell proliferation with the LH playing a relatively minor role. However, LH at its peak range triggers the events that lead to the release of the ova (ovulation) from the ovary.

It is important to note also that follicular cell proliferation during oogenesis (development of the ova), is associated with the release of another hormone by the proliferating follicular cells now classified into two i.e. the theca externa and theca interna cells. It is the theca interna cells that release the hormone called oestrogen (estrogen), which triggers proliferative changes in the uterine endometrium.

On the other hand, the remains of the proliferated follicular cells after ovulation, becomes transformed into a hormone secreting gland called the Corpus Luteum. It secretes progesterone –a hormone that enhances the endometrial changes induced by estrogen secretion. Specifically, it controls the phase of the menstrual cycle termed the luteal or secretary phase. It secretes estrogen as well and reaches its peak by the 3^rd to 4^th week of gestation.

1. 
   The corpus luteum continues to secret progesterone if pregnancy occurs and as such, maintains pregnancy up to the 20^th week when the placenta becomes fully developed and fully functional. In this circumstance, the corpus luteum is termed the corpus luteum of pregnancy. Progesterone reaches its peak by the 6^th week of gestation
   

2. 
   But if pregnancy does not occur, the corpus luteum degenerates and progesterone secretion ceases. In this circumstance, the corpus luteum is termed the corpus luteum of menstruation.
   

3. 
   Degenerated corpus luteums are transformed into whitish scar-like structures called the corpus albicans.
   

Other hormones associated with pregnancy include:

1. 
   Inhibin -produced by the ovaries and inhibits FSH production.
   

2. 
   The Human chorionic gonadotropin (HCG) secreted by the syncytiotrophoblast –a part of the developing embryo called trophoblast. This presence of this hormone in the blood or urine of a pregnant woman forms the basis for pregnancy test. HCG reaches its peak by the 9^th week. Functionally, HCG prevents immune attack on the developing embryo from the mother. It also maintains the endocrine functions of the corpus luteum.
   

3. 
   The Human chorionic somatomammotropin also known as Placental Lactogen secreted by the placenta. Its actions are similar to growth hormone and it influences partial breast development; decreases glucose level in mother and promotes the release of fatty acids
   

4. 
   Parathyroid hormone from the parathyroid gland. It secretions increases to maintain higher Ca levels.
   

5. 
   Aldosterone from the adrenal cortex. It secretion increases to influence renal reabsorption of sodium and the subsequent increase in fluid retention.
   

6. 
   Prolactin, which is the hormone that influences changes in the mammary gland; preparatory to lactation after
   
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