Prior to that it is best that the oocyte is in the fallopian tube, which is mostly 5 days prior to fertilisation. Movement to the fallopian tube is facilitated by the cilia.
Sperm. Many sperm needed to penetrate the corona radiata, then the enzymes at the head of the sperm tries to dissolve the zona pellucida. then one payload from one sperm is injected then ht e cortical granules are released to harden the zona pellucida.
The fertilized ovum goes thru cellular division and moves to the the uterus, it forms from zygote to the morula where it has a chance to become twins. (Day 1-4)
From Day 4-5 the zona pellucida is lost and thropoblast is formed it eventually become placenta and the blastoceale (fluid filled cavity)
6-7 the ovum is implanted as teh trophoblast secretes enzymes to merge with endometrium of the uterus.
Develops under the effect of progesterone and estrogen. It allows exchanges of nutrients for the developing zygote.
The function for it is to allow blood from both mother and baby to come into close contact with each other. So to provide sufficient nutrients but not allowing the immune system to destroy each other.
2.1 Hormones placenta produced
Human Chorionic gonadotropin (hCG)
Human placental lactogen (hPL)
Thyroid Stimulating Hormone
Corticotropin releasing hormone (CRH)
1st Key hormone of pregnancy.
Glycoprotein that is made up of 2 subunits alpha and beta.
Produced by the trophoblast cells
Then it is produced by the chorionic portion( Meaty) of the placenta.
Reaches a peak at 10 weeks.
Maintains corpus luteum, similar actions to LH, it enables it to secrete larger amounts of estrogen and progesterone.
It promotes the steroid hormone synthesis in the feta-placenta unit.
While in the mother it may be detected from approx 7 days after fertlization, elevated hCG may be associated with morning sickness.
It depresses maternal immunoreactivity.
2.1.2 Placental Estrogens
Increased in secretions of E1 to E3.
After the steroid hormones is produced and it stays stagnant until weeks 9 to 12.
At peak, E2 gives 0.3ng/ml that was the threshold. The E2 production is 10-25mg per day
and E3 is 40 -50 mg/day.
Growth of uterine smooth muscle and increased contractile activity.
Growth of duct tissue and deposition of fatty tissues
Promotes prolactin secretion
Prep for child birth, enlargement of external genitalia, relaxation.
Increased levels of renin-angiotensin system. to increase fluid retention.
Widespread effect on metabolism.
Development and maturation of lungs, kidneys and adrenal glands.
Steroid hormone produced by the corpus luteum and it then increased.
In the hypothalamus and the anterior pituitary, the placental progesterone leads to a negative feedback to suppress GnRH, LH and FSH. It also maintains pregnancy.
Uterus: Increased secretory phase to generate nutrients for baby, counter effects of oxytoxin and to prevent premature birth.
Growth of glandular tissue in preparation of lactation
Relaxation of smooth muscles, in vasculature and hence leads to a decrease in blood pressure. GI tract there's a slowing of transit line of food.
Human placental lactogen.
This is to decrease insulin sensitivity to promote glucose absorbtion to the placenta.
It is similar to the growth hormone and it promotes breast development.
produced by the anterior pituitary.
Initiated and maintain milk secretion after birth.
Involves in calcium secretion. Inhibits ovulation during lactation. It also develops lungs and osmotic regulation byt he fetal kidney.