After about a week of fertilization, the blastocyst is implanted within the endometrium of uterus it establishes the pregnancy which refers to the time from conception to birth. In human beings it is approximately 9 months ± 7 days. Fertilization occurs in the middle portion of the fallopian tubes are at the ampullary-isthmic junction of the fallopian tube. Ovulation occurs in the middle i.e. 14th day of menstrual cycle when usually a single secondary oocyte is released from either of the ovary alternately.
The first day of menstruation is the first day of cycle, so menstrual phase lasts from 1st to 4th day. Proliferative phase from 5th to 14th day. The secondary oocyte released on the 14th day, remains viable up to 15 to 18 hours in the ampulla following ovulation.Premenstrual phase lasts from 15th to 28th day. In the pre menstrual period progesterone stimulates the uterine glands to produce increased amounts of watery mucus.There is also a similar increase in the secretion of watery mucus by the vaginal glands and by the glands of the fallopian tubes. Thisphase is also called progestational, because progesterone prepares the uterus for pregnancy or luteal phase because this phase is controlled by the corpus luteum or secretory phase because the endometrium becomes highly secretory. In the absence of fertilization, thecorpus luteum degenerates and changes into a white body called corpus albicans.
The permanent disappearance of menstrual cycles in life of woman is called menopause.Normal cyclic menstruation extends between menarche and menopause. Menopause normally occurs at the age of 45 ± 50 years Menopause is the result of changes in the pituitary gland and hypothalamus.In this phase the secretion of oestrogen and progesterone is abruptly reduced.
After implantation the chorion develops finger like projections called chorionic villi, which are surrounded by uterine tissue and maternal blood. Now between the foetus and wall of uterus an intimate association is formed by chorionic villi and uterine tissue which is called placenta. Soplacenta is formed partly fromchorioallantoic membrane of the foetus and partly from the uterine wall of the mother. Foetus is connected to the placenta by a long cord, called umbilical cord.Use pregnancy week by week due date calculator to track your baby’s growth, from the day of conception till birth.
Functions Of Placenta
Placenta supplies nutrients from mother to the foetus. It supplies oxygen from mother blood to the foetus and carbon dioxide from foetus to the mother. The waste material produced by the embryo also passed to the mother blood through placenta. It allows certain antibodies from mother to the foetus. It secrets a number of hormones like human chorionic gonadotropin, oestrogen, human placental lactogen (hPL), progesterone etc.Due date calculator of pregnancyis an amazing way to figure out the step by step development of your child. Chorion, also known as serosa or false amnion, encloses the embryo along with other extraembryonic membranes.In humans placenta develops from chorion and that is why human Placenta is chorionic placenta.
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