Pregnancy Flashcards
Lactogenesis vs Milk let-down response
Lactogenesis: milk production
Milk letdown response: release of stored milk
Milk let down / ejection reflex
- Baby suckling sends impulses from the nerves of the nipple to the hypothalamus
- Anterior pitutiary releases prolactin: secrete milk into alveoli
- Posterior pituitary releases oxytocin: causes the myoepithelial cells to squeeze alveoli
Lactational amenorrhea
prolactin inhibits GnRH –> amenorrhea
This is why your period stops during pregnancy - to stop ovarian follicle development
Regression of mammary gland after lactation
Resorption of glandular tissue & reestablishment of c.t. and adipose tissue
How does the mamary gland change after menopause?
Connective tissue decreases (less cellular, more fibrous)
Involution of ducts & secretory units
Things leading up to implantation
Fertilization in the ampulla > 2,4, 8, cell stage > blastocyst rolls along the endometrium> implantation into the endometrium
When does implantation occur?
What important things happen during implantation?
Occurs during the secretory phase (days 21-24 of cycle)
- Syncytiotrophoblasts secrete hCG to rescue and maintain the corpus luteum
- Decidual reaction: hypetrophy of endometrial stromal cells
Why do we need so much progesterone and estrogen during pregnancy?
To maintain the thickness of the endometrial lining
25 days
We’re at day 40. Conception is day 15. Thus, conception occured 40-15 = 25 days ago.
Decidual reaction
the continued produciton of progesterone & estrogen cause endometrial stromal cells to hypertrophy and fill with glycogen & lipid
–> fibroblasts look more round
Functions of decidua
- Source of nutrients for embryo until vascular connections between mother and embryo are developed
- Barrier to further invasion of the uterine wall by the mebryo
- Endocrine function: prolactin, relaxin, and prostaglandins act on uterine muscle, cervix, and embryo
Relaxin
What produces it?
What is it stimulated by?
What are its funcitons?
- Produced by decidua, corpus luteum of pregnancy, and placenta
- Stimulated by hCG
- Fxns:
- Early pregnancy: suppress myometrial contractions
- Late pregnancy: soften cervix in preparation for parturition
Prolactin
What makes it?
Function?
Major source: maternal pituitary and decidua
Function: depress immune response to fetus
Prostaglandins
what makes it
function
Decidua
In late pregnancy, it contracts uterine smooth muscle and softens the cervix.
What are the blue arrows pointing at?
Decidual cells / Stroma cells
What changes do we see in the endometrium and myometrium in the pregnant uterus?
Decidual reaction: endometrial stroma becomes decidua
Myometrium: hyperplasia & hypertrophy
Tissue layers of the blastocyst (inner to outer)
- Cytotrophoblast (inner)
- Synctiotrophoblast (outer)
Describe the trophoblast
Peripheral cells of the blastocyst that attach the fertilized ovum to the uterine wall and contribute to the placenta
Cytotrophoblast (inner): mitotically active trophoblast-producing cells that fuse with the syncytiotrophoblast
Syncytiotrophoblast (outer): not mitotically active; multinucleate cytoplasmic mass invades the epithelium and underlying stroma of the endometrium
Syncytium
a multinucleate cellular mass produced by the fusing of cells.
Functions of the placenta
-
Endocrine
- Synthesizes & secretes hormones for maternal & fetal metabolism
- Independent; not subject to regulation by maternal or fetal signals!
- Fetal gut supplying nutrients
- Fetal lung exchanging gases
- Fetal kidney eliminating waste products & regulating fluid volume
Describe the components of placenta
- Fetal portion - chorion
- Chorionic plate
- Chorionic villae
- Cytotrophoblastic shell
- Maternal portion - decidual basalis
- Basal plate
- Placenta septa
What is the blue bar?
The chorion: contains the secondary villus, the cytotrophoblast, and the syncytio trophoblast
What is the blue line pointing at?
Cytotrophoblastic shell
Establishing placental circulation
The chorion (fetal criculation) sends out villi into the placenta, wher eit will capture maternal blood in the decidual basalis
Where is the maternal blood vs the fetal blood?
This is chorionic villi
The fetal blood supply would be within the villi (BV)
The maternal blood supply would be in the interstitial space (IS)
Histologically how do cytotrophoblasts look diff from syncytiotrophoblast?
Syncytiotrophoblasts look like packs of nuclei
Cytotrophoblasts have one fat nucleus
Free vs anchoring villi
Free villi dont connect to the decidual basalis
Anchoring villi do
Describe the placental barrier that blood, gas, and nutrients have to cross to get to the fetus
Syncytiotrophoblast
Cytotrophoblast
Connective tissue (extraembryonic mesenchyme)
Fetal endothelial cell of blood vessel
What crosses the placental barrier?
- Exchange of gases & nutrients (glucose, aa, proteins)
- Transferrin (iron to fetus)
- Steroid hormones
- Fetus eliminates CO2 and waste
- Maternal antibodies (esp igG) provides passive immunity to the newborn
- Alcohol, drugs, some viruses (birth defects)
The placenta secretes numerous steroid & protein hormones that affect maternal AND fetal metabolism
How is it regulated?
Independent!
not subject to regulation by maternal or fetal signals
Urinary estriol & serum hCG
Fetus is responsible for estriol
hCG is only ever produced by the placenta by syncytiotrophoblast only (whereas, progesterone can come from corpus luteum of pregnancy AND placenta).
Cytotrophoblast hormones
IGF-I and IGF-II to stimulate proliferation/differentiation
GnRH, CRH, TRH, and somatostatin to act on the syncytiotrophoblast
Syncytiotrophoblast hormones
- hCG, human chorionic ACTH, human placental GH, and human chorionic thyrotropin
- Progesterone
- Estradiol
- Inhibin A: suppress mother’s FSH
- Human chorionic somatomammotropin (hCS)/hPL: shunts nutritional substrates to fetus
Funcitons of progesterone secretion from placenta
- Inhibits maternal immune responses
- provide precursors to fetal adrenal glands
- quiets uterine contractions
- stimulates mammary gland development
Function of estrogens released from sycytiotrophoblast
- Stimulates growth of uterine smooth muscle
- Stimulates mammary gladn development
Can’t synthesize androgen precursors for estradiol synthesis; must use fetal adrenal glands
Function of human chorionic somatommaotropin (hCS) aka hPL
Shunt nutritional substrates to fetus
Where do androgen precursors for estradiol synthesis come from in placenta?
androgen precursors come from the fetal androgen gland
describe the process of placental steroidogenesis
- Mother sends cholesterol to the placenta
- Make pregnenolone to be sent to the fetus
- Make progesterone
- Fetus makes DHEA from pregnenolone and then creates the androgen precursor to be sent back to the placenta for it to then make estriol
Progesterone & Estrogen synthesis
Which occurs independently of the fetus? Which can be used to assess fetal health?
Progesterone synthesis tells us about placental health
How long does hCG maintain estrogen & progesterone secretion until?
Until the end of the 1st trimester, then placenta takes over
High levels of sex steroids from the placenta suppress __ to prevent __.
the hypothesis/pituitary axis to prevent ovulation
Prolactin’s action on the mammary gland during prengancy is blocked by ____. What causes the lactogenic effect to start?
Blocked by E & P during pregnancy
Extrusion of placenta during birth –> drop in E & P –> lactogenic effect commences
Review of pregnancy hormone levels
