2.4.1 Physiology of the Placenta Flashcards
What is the functional role of invasive cytotrophoblasts?
Tap into the maternal vasculature (spiral arteries) after week 12 of gestation
Decidua assists in controlling the depth of invasion
Prior to this the placenta and developing fetus is somewhat hypoxic
Nutrient and waste exchange can then occur across the syntial layer of the placenta.
Describe how these hormones (estrogen, progesterone, insulin, GCs, Prl GH PL, and oxytocin) affect mammary gland development
Identify the components of implantation
What allows the placenta to produce estradiol?
DHEA from the fetal adrenal
Describe the production of CG (CG levels) throughout pregnancy
What type of blood?
Maternal blood
What are the three steps of cytotrophblast remodeling?
- Cytotrophoblast invasion of spiral arteries
- Maternal blood bathes placental villi
- Nutrient exchange across villi
(Blastocyst) Invasion and remodeling of the hypoxic environment occur during what time period of the pregnancy?
The first 12 wks
What are the four roles of decidualization?
controls invasion, nutrition, prevents immune rejection, Prl secretion
What hormones are produced by the syncytial layer (Syncytiocytotrophoblasts)?
Chorionic Gonadotrophin (CG)
Placental Lactogen (PL)
Progesterone
Estrogens
What cellular connection aids in myometrial contractions?
Gap Junctions
Which hormone is responsible for preparing the uterus for implantation?
Progesterone
Describe how maternal circulating levels of pituitary GH (GH1), placental GH (GH2), and IGF during pregnancy change.
What are the roles of PL?
Regulates metabolism, stimulating the conversion of glucose into FA’s and ketones, stored as fuels, promotes maternal mammary gland development
What is a major stimulator of oxytocin in milk propulsion?
Suckling
What is this an image of? What are the two roles of syncytiotrophoblasts?
Placental villi (floating)
Roles: Transport, endocrine
What is the role of CG?
Binds to LH receptors and stimulates progesterone production by Corpus Luteum
How does the production of PL change during the course of a pregnancy? (red)
CG regulates the synthesis and secretion of __ from the corpus luteum
P4
What changes occur in the functional and structural phase of luteolysis? (4)
Changes in: sensitivity to LH, blood supply, P4 and E2, leads to apoptosis
What two hormones play a role in lactation?
Prolactin - milk secretion
Oxytocin - propels milk
Describe placental steriodogenesis as it relates to the fetus and producing products for maternal circulation
What are the roles of relaxin, estrogens, prostaglandins, and oxytocin in parturition?
What hormones can be produced by the fetus?
DHEA
Describe the phases of menses, follicular, ovulation, and luteal
How long does the gamete reside in the Fallopian tube? In the uterus prior to implantation?
- Resides within the oviduct/fallopian tube for approximately 3 days
- Resides within the uterus approximately 3 days prior to attachment of the blastocyst to the uterine wall and subsequent invasion.
- Therefore, implantation occurs 6-7 days following ovulation.
Identify the maturity of the placenta
Left: 1st trimester placenta
Right: Full term placenta
What is the predominating hormone in the follicular phase? luteal phase?
Follicular: Estrogen
Luteal: Progesterone
Describe the blood flow to the placenta
High volume and low resistance
What are the two goals of the cyclicity of the HPG axis?
- Prepare a fertilizable oocyte
- Establish a uterine environment that promotes:
- Gamete movement (primarily via Estrogen)
- Implantation (Progesterone)
- The oocyte is viable/fertile for approximately 18 hr (6-24 hr range) following ovulation
What hormones can be produced from cholesterol in the placenta?
P4
NO Androgen synthesis b/c the lack of CYP17 (no estradiol)
What is the importance of the early rise of CG?
Rescues the corpus luteum and progesterone production
Compare CG and LH (secreted from, acts upon, composition, MW, t1/2, receptor)
What inhibits myometrial contraction? Stimulates it?
Inhibitor: P4
Stimulators: Estrogens
What hormones can be produced in the ovary?
P4 and Estradiol
Parturition relies on the positive feedback of what?
Oxytocin (leading to greater and greater contractions
Increase in secretion of CRH from the placenta stimulates what? (2)
Fetal adrenal DHEA production
Prostaglandin production
What are the roles of the 4 functional components of the placenta?
Cytotrophoblasts (placental stem cell characterisitics)
Anchoring villous – Attachment
Invasive cytotrophoblasts – Invasion
Syncytiocytotrophoblasts – Barrier, Endocrine, Transport
What allows the placenta to produce estriol?
16OH-DHEA from fetal adrenal/liver
On what side of the villi are the different types of blood?
Top: Maternal
Bottom: Fetal
Describe the feedback with oxytocin
Describe how hormone production occurs b/t the mother, placenta, and fetus. IMPORTANT
What are the four functional components of the placenta?
- Cytotrophoblasts
- Anchoring villous, columns of cytotrophoblasts
- Invasive cytotrophoblasts
- Syncytiocytotrophoblasts
What inhibits cervical maturation (collagen breakdown)? Stimulates it?
Inhibitor: P4
Stimulators: E, Relaxin, PGE2
Describe how the various levels of estrogen and progesterone change over the course of a pregnancy
Which hormone aids in gamete movement?
Estrogen
What is circumscribed in blue?
Placenta
Describe how the gamete moves and develops as it passes down the Fallopian tube
What are the effects of estrogen/progesterone on the uterus? What other sites do these hormones work on?
