Human female reproductive system. Hormonal regulation in pregnant female, Placenta, birth events and laclation


Human female organs:

Females produce gametes (eggs or ova) after fertilization, they also nourish, carry and protect developing embryo. After the offspring is born, the mother may nurse it for a time.
Female reproductive system consists of number of structures with specialized functions:

(1) Two ovaries produce eggs and the female sex hormones estrogen and progesterone.
(2) Two uterine tubes, one from each ovary carry eggs from the ovary to the uterus. Fertilization occurs in upper third of a uterine tube.
(3) If fertilization occurs the uterus receives blatocyst and houses the developing embryo.
(4) Vagina receives semen from the penis during sexual intercourse. It is the exist point for menstrual flow and is the canal through which body passes from uterus during child birth.
(5) External genital organs have protective functions and a play role in sexual arousal.
(6) Mammary glands contained in paired breasts produce milk for new born baby.

Hormonal regulation in pregnant female:

Pregnancy sets into motion a new series of physiological events. As the embryo develops the cells of the embryo and placenta release the hormone human chorionic gonadotropin (hCG) which keeps the corpus luterum from disintegration Progesterone that it secrets is necessary to maintain the uterine lining. Afterwards placenta takes over progesterone production and corpus luteum degenerates, by the female’s blood and in her urine as well that hCG immunological test can check for pregnancy.

As the embryo develops, other hormones are secreted. Prolactin and oxytocin induce the mammary glands to secrete and eject milk after child birth. Oxytoci and prostaglandins also stimulate the uterine contractions that expel the baby from uterus during child birth.

Placenta:
The embryonic membranes chorion and allantois gave rise to embryonic parts of the placenta. The placenta is the organ that sustains the embryo and featus throughout the pregnancy and through which gases nutrients and wastes are exchanged between the maternal and faetal systems. The tiny finer like projection that were sent out from the blastocyst during implantation develop into numerous chorionic villi which contain embryonic blood vessels. These blood vessels do not merge with those of the mother; two blood streams remain separate throughout the pregnancy. The umbilical and connects the placenta to the abdomen of the foetus. Two fetal umbilical arteries and one fetal umbilical vein spiral about each other in the umbilical cord.
It produces hCG that maintains corpus luteum from degeneration. Relaxin that facilitates labour and delivery. Prostaglandin that also facilitate labour.

Events of birth:
After 266 days after fertilization 280 days from the beginning of the last menstrual period, the human infant is born. The birth process is called patrunition. During patrunition the uterine muscles contract and the cervix dilate. The hormone relaxin produced by ovaries and placenta causes the mother’s pelvic bones to slightly separate so that the baby can pass through the birth canal.

Changing hormone levels initiate parturition. Pituitary gland secretes Adrenocorticotropic hormone (ACTH) which stimulates the adrenal glands to secrete steroids.

These steroids stimulate the placenta to produce prostaglandin’s that along with the hormone oxytocin cause the uterus to begin powerful muscular contractions. The contractions increase in frequency from 2 to 18 hours. Usually within an hour of these events the body expelled from the uterus. After the baby emerges, uterine contractions continue to expel the after birth. The umbilical cord is severed and the new born embarks on its nurtured existence in the outside world.

Lactation:
Lactation includes both milk production by mammary glands and milk release form the breasts. During pregnancy the breasts enlarge in response to increasing levels of the hormone prolactin. Before birth, placenta secretions of estrogen and progesterone inhibit milk secretion from the breasts. After the placenta has been expelled the concentrations of estrogen and progesterone drop, and the breasts begin to produce copious amounts of milk.

Mother’s breasts do not actually release milk until one to three days after baby is born. During these first days, the sucking baby receives colostrums, a high protein fluid present in the breast at birth. Colostrum contains an abundance of maternal antibodies and thus helps strength the baby’s immune system. It also functions as a laxative, removing fetal wastes called meconium retained in the intestines. After three days prolactin secreted from pituitary stimulates milk production. Newborn’s sucking stimulates the pituitary to release oxytocin as well as prolactin. Oxytocin triggers milk release from mammary glands.

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