pregnancy and placentation Flashcards
week 7
Histotrophic vs hemotrophic nutrition
Pre-implantation, nutrients from uterine secretions (histotrophic nutrition)
Post-implantation, nutrients from maternal blood via hemochorial placenta (hemotrophic nutrition).
Development of placenta (time)
Starts: 2wks after feralization (4 LNMP)
Fully functional: end of 12th week after ferilisation (14 LNMP)
Functions of placenta
Nutrition
- hemotrophic nutrition
-gas exchange
-waste excretion
immune
-immunomodulatory
-passive immunity
hormonal
-produces hormones that regulate fetal and maternal organs
How does the placenta develop?
Extraembryonic mesoderm of cytotrophoblasts and syncytitrophblast form chorion and chorionic villi
Endometrium differentiates into decidua
Fetal chorion and villi combine with decidua basalias = true placenta
Stages of Chorion development.
Primary stem vili – 11-13 days after F, CB expands into SB
Secondary stem vili – 16 days after F, extraembryonic mesoderm proliferates into projection (after gastrulation)
Tertiary stem vili – 21 days after F, mesoderm differentiates into CT and blood vessels
Compare histological structure of placenta in the three trimesters
Vili:
1- large
2- smaller and more vascular
3- even smaller and highly vascular
cells
1- 2 cell layers (CB and SB)
2- thinning of CB
3- minimal CB
Why are the vili of the placenta in the 3rd trimester, small and highly vascularised?
to support blood gas and nutrient exchange required by growing fetus approaching gastrulation
What hormones are secreted by the placenta?
HCG
Estrogen
Progesterone
Relaxin
Human chorionic Somatomammmotropin (hCS)
Human chorionic thyrotropin (hCT)
Corticotropin-releasing hormone (CRH)
Function of hCG
maintains corpus lutem
Supresses maternal immune system
Function of estrogen from placenta
Uterine enlragment
Breast development and blocks prolactin
Relaxes pelvic ligamnets
Functions of progesterone from placenta
Maintains functional endometrium
Prevents myometrial contractions
Breast development and blocks PRL
Increased respiratory tidal volume
Functions of relaxin
Relaxes pelvic muscles
Cervical softening
Function of Hman Chorionic Somatommotropin (hCS)
Decrease glucose metabolism and increased FA metabolsim
Breast development
function of
Human chorionic thyrotropin (hCT)
Increase rate of maternal metabolism
function of
Corticotropin-releasing hormone (CRH)
Stimulates cortisol production via fetal HPA axis
cells that separate maternal and fetal blood
Syncytiotrophoblasts
Cytotrophoblasts
Vilus CT
Fetal capillary endothelium
What are the maternal anatomical changes that occur in pregnancy?
Increased vascularity of reproductive organs
Weight gain (13kg) mostly fluids
Breast enlargement
Uterine enlargement
Pelvis and ligaments relax
What hormones cause breast enlargement?
E, PE, PRL, hCS and hCG
features of uterine enlargement
- fist size –>fills abdominal cavity
increased pressure on internal organs,
alters centre of gravity (lumbar lordoisis and backaches)
What are the maternal metabolic change in pregnancy?
Increased appetite
Increase FA metabolism, decreased glucose
Increase rate of maternal metabolism
What causes increased appetite in pregnancy and why?
cortisol
elevated fat strohgae and BGL)
Cause and purpose of Increase FA metabolism, decreased glucose
hCS
frees up glucose in blood for fetus
cause and purpose of Increase rate of maternal metabolism
hCT
elevated calcium for fetal bone development
What organ systems change in pregnancy?
GI
Renal
Respirartory
CV
