The Amnion encloses and protects the embryo in a fluid-filled buoyant cavity (Jones and Lopez, 2006). The Chorion lines the amnion and the yolk sac become part of the placenta (Jones and Lopez, 2006).The Allantois is a source of urinary bladder along with blood vessels for the placenta (Jones and Lopez, 2006).
?cycle and the menstrual cycle are regulated by blood hormonal levels.
Ovulatory changes start on the first day of the menstrual cycle (Marieb, 2007). As the cycle starts, low Oestrogen along with progesterone levels in the bloodstream stimulate the hypothalamus to secret gonadotrophin-stimulating hormone (Gn-RH) (Marieb, 2007). In turn, Gn-RH stimulates the anterior pituitary gland to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH) (Marieb, 2007). Follicle development inside the ovary is prompted by heightened levels of FSH and to a lesser degree LH (Marieb, 2007). At the point when the folic matures, a spike in the LH level happens, resulting in the follicle to rupture and discharge the ovum, in this way starting ovulation (Marieb, 2007). After ovulation in the luteal phase, the collapsed follicle forms the corpus luteum, this on the condition its fertilization doesn’t occur, degenerates (Marieb, 2007).
During the follicular phase of the ovarian cycle, the increasing FSH and LH levels which stimulate follicle growth also stimulate increased secretion of oestrogen (Marieb, 2007). Oestrogen secretion peak right before ovulation (Marieb, 2007). This peak starts the spike in LH levels, this results in ovulation (Marieb, 2007). After ovulation, Oestrogen levels decrease fast (Marieb, 2007). In the luteal phase of the ovarian cycle, the corpus luteum is made and starts to release progesterone and oestrogen (Marieb, 2007). As the corpus luteum degenerates, levels of both ovarian hormones decline (Marieb, 2007).