L25 - Puberty and pregnancy Flashcards
Define when the 1st and 2nd polar bodies are formed in female sex cycle?
1st = At tertiary follicle at Metaphase II
2nd = after fertilization
Define the stages in the first week after fertilization/ preimplantation development of zygote?
Day 1: pronucleus stage (2 pronuclei)
Days 2-3: cleavage stage
Day 4: morula
Day 5: blastocyst
Day 6: blastocyst hatches from zona pellucida
Describe the cell types and structure of blastocyst?
- Trophectoderm (single layer, future placenta):
Syncytiotrophoblast: multinucleated,outer layer
Cytotrophoblast: mononucleated, inner layer - Inner cell mass: gives rise to fetus
- Blastocoel = Fluid-filled cavity
Describe the changes to endometrial stroma at 8th day of development?
At implantation site:
- Edematous, vascularize
- Stromal cells transform into Dedidual cells: increase in size
- Increase glycogen and lipid stores for implanting blastocyst
Describe the formation of primary stem villi on the 9th day of development
- Syncytiotrophoblast (outer): vacuoles form and fuse to form trophoblastic lacunae**
- Cytotrophoblasts (inner) proliferate > penetrate into syncytiotrophoblast to form primary stem villi
- Villi = single columnar cytotrophoblast epithelium surrounded by syncytiotrophoblast
Describe the formation of tertiary stem villi in placenta?
Fetal blood vessels form inside cytotrophoblast columns of the primary stem villi
Syncytiotrophoblast invade into maternal blood vessels > maternal blood flow into trophoblastic lacunae
Define the barriers between maternal and fetal blood at 4th week and 4th month? exam
4th week = 4 barriers
- Syncytiotrophoblast
- Cytotrophoblast
- Connective tissue
- Endothelium of fetal blood vessels
4th month – 2 barriers:
- Syncytiotrophoblast
- Endothelium
Define the layers and cores in the primary stem villi?
syncytial layer + cytotrophoblastic core
Define the layers and cores in the secondary stem villi?
syncytial layer + a cytotrophoblastic layer + mesodermal core***
Define the layers and cores in the tertiary stem villi?
2 layers remain: syncytial and endothelium:
syncytotrophoblast layer + villous capillary system in mesodermal core
5 functions of the placenta?
–Oxygen, carbon dioxide exchange (fetal lung)
–Nutrients, electrolytes exchange (fetal gut)
–Fluid volume regulation & waste disposal (fetal kidney)
–Maternal antibodies
- Placenta produces hormoens: e.g. estrogen (estriol) and progesterone
Compare the O2 dissociation curve between maternal and fetal blood?
HbF = more to the left than maternal Hb
> > bind to more O2 at same pO2
Explain how exchange between fetal and maternal blood occurs? think Hb conc and dissociation think metabolism
- HbF O2 affinity is higher
- HbF conc is higher
- Bohr effect:
In placenta, CO2 (from metabolism) diffuses from fetal to maternal:
- Decrease O2 affinity of maternal blood
- Increase O2 affinity of fetal blood
» O2 exchange
Define the endocrine function of the placenta?
Cytotrophoblast: hypothalamus-like hormones:
- corticotrophin releasing hormone (CRH)
- thyrotropinreleasing hormone (TRH)
Syncytiotrophoblast: pituitary-like hormones:
- human chorionic gonadotropin (hCG, LH-like)
- human chorionic somatomammotropin (HCS)
- human placental lactogen (HPL, GH-like)
- Steroid e.g. Progesterone, estrogen
Which hormone is used to indicate pregnancy? WHich cell produce?
Human chorionic gonadotropin (hCG)
embryo (blastocyst) and syncytiotrophoblast (placenta): From 8-9 days after ovulation
3 endocrine functions of human chorionic gonadotropin?
1) Maintains corpus luteum: increase estrogen, progesterone, relaxin secretion
2) Stimulates Leydig cells for fetal testosterone
3) Increase fetal adrenal DHEA-S (substrate of placental estrogen)
Cell type that secretes progesterone in placenta?
syncytiotrophoblast
Functions of progesterone in pregnancy? (5)
PREPARATION, ALL LOCAL
- Increase oviductal and uterine secretion
- Increase decidual cell development/ endometrial cell hypertrophy
- Lower abortion risk:
i) Decrease uterus contractility, sensitivity to oxytocin
ii) decrease PGE production - Decrease maternal immune response to fetus
- Increase ventilation and prepare breasts for lactation
Cell type the secretes estrogne in placenta?
Syncytiotrophoblast
Compare the estrogen analogues secreted by placenta and corpus luteum. Which is more potent?
Placenta = Estriol
Corpus luteum = estradiol
Estradiol much more potent, but placenta makes much more estriol than estradiol»_space; overall estriol exerts more effect
Functions of estriol in pregnancy?
LARGE ORGAN PREPARATION
1) Enlargement of uterus, female external genitalia
2) Growth of the breast ductal structure
3) Relaxation of pelvic ligaments and pubis symphysis (with relaxin)
4) LDL cholesterol uptake for synthesis of progesterone
Define pregnancy into 2 growth and development periods? Typical length of pregnancy?
1st-8th week = embryonic period
3rd month-birth = fetal period
40 weeks after last menstruation/ 38 weeks after fertilization
Describe the changes in metabolism in mother and fetus during Anabolic phase of pregnancy?
Mother: Accumulate energy reserve:
- Increase lipogenesis, protein synthesis, glycogen store
- Low plasma glucose, a.a., fatty acid
Fetus: little nutrient drain
Describe the changes in metabolism and weight in mother and fetus during Catabolic phase of pregnancy?
Mother: Accelerated starvation to give nutrients:
- Increase lipolysis
- Increase plasma glucose, a.a., FA
Fetus: Weight gain
Changes in maternal physiology during pregnancy?
- Increase food intake, weight gain
- Increase blood volume and cardiac output
- Increase ventilation
- Increase urine formation
What maternal and fetal factors trigger the start of childbirth?
Increase Oxytocin effects:
1) Increase estrogen: progesterone ratio»_space; oxytocin release from post. pituitary
2) Stretch of uterus and cervix ripening»_space; oxytocin release
3) Increase oxytocin receptor in myometrium
Other hormones:
Increase maternal PGE release + fetal Oxytocin, cortisol, prostaglandin
> > > > > cervical dilation, myometrial contraction
3 stages of labor?
Dilation stage
Expulsion stage
Placental stage
Describe the sequence of events in the dilation and expulsion phase of labor?
Dilation: regular, rhythmic uterine contraction»_space; widening/ripening of cervix until fully dilate
Expulsion phase: Force fetus out by uterine muscle and voluntary muscles of abdomen and diaphragm
Describe the sequence of events in the placental phase of labor?
Separation of placenta from dedidual tissue of the uterus
Expulsion of placenta and membrane
Myometrial contractions > constriction of blood vessels > prevent excessive bleeding
Describe the overall hormonal changes in puberty in girls and boys?
Girls:
FSH increase first, then Estradiol, then LH
Boys:
Increase FSH and LH simultaneously, then Testosterone increase
Describe the development of secondary sexual characteristics in female and male?
Female = breast, pubic hair, growth spurt
Male = penile, pubic hair, growth spurt, testicle descend
Mechanism of puberty initiation?
- Increase in pulsatile LH release at night »_space; preovulatory surge
- Increase sex steroid production
- Increase excitatory neurons, decrease inhibitory neurons at hypothalamus»_space; increase GnRH pulsatile release
2 hypothesis of pituitary-gonadal activation for puberty initiation??
–Gonadostat hypothesis
–Hypothalamic maturation
Explain the gonadostat hypothesis to start puberty?
Increased threshold for negative feedback regulation of FSH/LH secretion by steroids
> > Less sensitive to steroids (not as easy to feedback inhibit FSH/LH)
> > increase concentration of gonadotrophins and sex steroids
Explain the hypothalamic maturation mechanism for puberty maturation? Explain the neurological changes to kickstart puberty?
Maturation of the CNS»_space; increases output of hypothalamic GnRH»_space; Increase secretion of sex hormones
Increase excitatory neurons, Decrease inhibitory neurons and increase glial cell number in Arcuate Nucleus and Anteroventral periventricular nucleus just before puberty
» activate puberty GnRH increase
