What is the normal site of implantation?
The ampulla of the fallopian tube
During the ___________ phase, there is a refurbishing of ciliated epithelial cells of the fallopian tubes.
At higher levels of __________, the isthmus of the fallopian tube starts to cotnract with sympathetic innervation.
NOTE: It allows spermatoza into the ampulla, but prevents the oocyte from moving to the uterus before fertilization occurs.
Overview of Ovum transport
2. Ovum expelled
3. Ovum drawn into fallopian tube, due to fimbriae and cilia
4. Oocyte is trapped in the ampulla of the fallopian tube, due to estrogen action causing the isthmus to constrict
- Dwells for maximum of 32 days
5. Fertilization occurs
6. Progesterone inhibits estrogen, which releases the ampuloisthmic block
7. Fertilized ovum transported to uterus, via action of ciliated epithelial cells
8. Fertilized ovum floats free for as much as 4-5 days before implantation
- Removal of inhibitory glycoproteins from spermatozoa
What are the results of capasitation?
- Sperm motility
- Sperm metabolic activity
- Ability to fertilize oocyte
Rupture of the outer acrosomal membrane and rease of acrosomal enzymes.
*Provides ability to penetrate the culumus oophorus and zona pellucida
Where does the acrosome reaction occur?
In the ampulla of the fallopian tube
Function of hyaluronidase
Provides ability to penetrate the culumus oophorus
Function of acrosin
Provides ability to penetrate the zona pellucida
During fertilization, the sperm heads stops in the ___________ and fuses with the __________.
Perivitelline; oocyte vitelline membrane
NOTE: Fertilization occurs in the amplulla of the fallopian tube
Mechanism of fertilization
- At ejaculation, sperm cells are deposited in the vagina.
- Once deposited, they travel through the cervical canal, through the uterus, and then up to the ovum in the upper third of the oviduct.
- Movement and hyaluronidase facilitate penetration of culumus oophorus
- Movement and acrosin facilitate penetration of zona pelucida
- Sperm head stops in perivitelline space and fuses with oocyte vitelline membrane
- Sperm head contents enter vitelline space, initiate cortical reaction (to block polyspermy) and completion of meiosis II
- Extrusion of 2nd polar body
- Fusion of male and female pronuclei
Where does implantation occur?
In the endometrium of the uterus
What are the events of implantation?
1. 1st mitotic cell division occurs within 24 hrs of fertilization
2.Growth-> Morula stage-> blastocyst stage
3. Arrival in uterus 4-5 days postovulation
4. Blastocyst settles near a blood vessel and attachement begins (between days 5-9)
5. Trophoblast invasion begins
- Requires low levels of estrogen
6. Synthesis and secretion of hCG begins
7. Rescue of corpus luteum
NOTE: If the blastocyst implants too far away from a blood vessel, it will not be able to recieve nutirents by diffusion in the first 10 days
When is pregnancy detectable?
Prior to implantation and 1st missed menstrual flow
______ allows for rescue of the corpus luteum.
What role does estradiol play in fertilization, transport, and implantation?
- Stimulates growth of fallopian tube ciliated epithelial cells
- Facilitates adrenergic induction of "ampulloisthmic block"
- Facilitates trophoblast invasion of the endometrium
- May induce contraction of fallopian tube musculature
What role does progesterone play in fertiliztion, transport, and implantation?
- Stimulates beating activity of fallopian tube epithelial cilia
- Blocks E2 effect on fallopian tube ampulla isthmus muscle
What is the function hPL?
Modifies the metabolic state of the mother during pregnancy to facilitate the energy supply of the fetus.
NOTE: hPL acts as a growth hormone
What hormonal changes are seen throughout pregnancy?
Prolacting rises throughout pregnancy
hCG rises early in pregnancy
Progesterone rises until about two weeks berfore parturition
Estrogen constantly rises
FSH and LH remain low throughout pregnancy
What changes occur with the pituatary gland and its secretions during pregnancy?
- Increase in gland size
- Increases in prolatin, ACTH, TSH
- Decrease in GH
NOTE: GH decreases or stays the same
What changes occur with the andrenal gland and its secretions during pregnancy?
- Increased glucocorticoids
What changes occur with the thyroid gland and its secretions during pregnancy?
- Increase in size
- Increase in hormone secretion
What changes occur with the parathyroid gland and its secretions during pregnancy?
- Increase in size
- Increase in hormone secretion
What changes occur with the placenta and its secretions during pregnancy?
- Increase in human chorionic thyrotropin, cGH
- Increase in cACTH, cTRH, cGnRH
Hypopituitarism (decreased functioning of the pituitary gland), caused by ischemic necrosis due to blood loss and hypovolemic shock during and after childbirth
NOTE: May result from pituatary enlargement during pregnancy. Pituatary can be squished by the sella turcica
As placental GH increase, there is an increase in _____.
IGF-1, which plays a role in feedback inhibition of pituatary GH production
NOTE: As the placental GH increases, materal GH decreases
Why is the placenta not able to convert C21 steroids (pregnenolone, progesterone) into C19 steroids (testosterone)?
It lacts the cytochrome P-450-17 hydroxylase enzyme
The ________ is required for the synthesis of estrogen during pregnancy.
Fetal adrenal gland
NOTE: The pregnenolone from the placenta to the fetal compartment to make DHEA-S (Dehydroepiandrosterone sulfate)
What happens to th DHEA-S after it has been produced in the fetal adrenal gland?
It is transported to the fetal liver, where it is converted to estroil (E3)
NOTE: Estriol can work in the fetal and maternal system to regulate blood flow