ERS25 Puberty And Pregnancy Flashcards
Pregnancy
280 days (40 weeks) after last menstruation (2 weeks of ovulation) 266 days (38 weeks) after fertilisation (IVF treatment)
First week of life
Follicles develop within ovaries before ovulation
—> Primordial follicles
—> Primary follicles
—> Secondary follicles
—> Tertiary follicles
—> Ovulation (Oocytes + Cumulus cells) + Corpus luteum (Granulosa + Theca cells)
Sexual intercourse, Sperm travels: Vagina —> Cervical canal —> Uterine cavity —> Fallopian tubes —> Ampulla (fertilisation occurs)
Fertilised zygotes start to cleave
—> Embryo
—> leave Fallopian tube into Uterine cavity (by 1st week)
—> Blastocyst
—> if Endometrium is right / Receptive to implanting embryo
—> Embryo attach and penetrate into endometrium
Preimplantation embryo development
Day 0:
Sperm + Oocyte (arrest at Metaphase 2, sometimes immature oocyte at Metaphase 1, Prophase 1, collected 36 hours after induction of ovulation)
Day 1:
Fertilised zygote:
- 2 pronuclei (1 from sperm, 1 from oocyte)
- 2 polar bodies (1st polar body + 2nd polar body)
Day 2:
Zygote divide into 2 cells
—> 4 cell stage
Day 3:
6-8 cell stage
Day 4:
- **Morula
- can no longer count no. of cells in embryo (∵ tight junctions between cells of embryo —> compact together to form ball of cells)
Day 5:
- **Blastocyst (2 cell types + fluid filled cavity)
1. Trophectoderm (epithelium on outside of blastocyst —> develop into placenta) —> Trophoblast
2. Inner cell mass (develop into fetus) —> Embryoblast
3. Blastocoel (fluid filled cavity —> grow in size)
Day 6:
Blastocyst come out out Zona pellucida (degenerating) in order to implant (Hatching of Blastocyst)
8th day of development
Trophectoderm
—> Trophoblast (after implantation)
—> **Cytotrophoblast (inner mononuclear cell) + **Syncytiotrophoblast (outer multinucleated)
—> Cytotrophoblast migrate into and fuse with Syncytiotrophoblast
Inner cell mass
—> Embryoblast
Endometrial stroma
—> near implanting embryo becomes **oedematous + **vascularised
—> Endometrial stromal cell transformed into Decidual cells
—> **↑ size, abundant secretory granules, cytoplasmic accumulation of **glycogens + lipid droplets
—> provide nutrition for implanting Blastocyst
9th day of development
Blastocyst deeply embedded in Endometrium (成粒入左去, 唔係lung住)
—> surface of endometrium at implantation site closed by ***Fibrin coagulum
Syncytiotrophoblast
—> small vacuoles occur and fuse
—> ***Trophoblastic lacuna (for maternal blood)
Cytotrophoblast
—> proliferate + penetrate into Syncytiotrophoblast
—> ***primary stem villi (cellular columns of Cytotrophoblast covered by Syncytiotrophoblast) (for fetal blood)
End of 3rd week of development
Fetal blood vessel gradually formed inside **Cytotrophoblast villi
—> Tertiary stem villi (containing **fetal blood)
—> ***Placental villi
—> ↑ area of exchange (↑ efficiency of process)
Syncytiotrophoblast invade into maternal blood vessel
—> ***maternal blood flows into Trophoblastic lacuna
Maternal blood / Fetal blood close to each other for ***exchange of nutrients, metabolic wastes
Development of placental villi
- Primary villi
- Syncytiotrophoblast (outside)
- Cytotrophoblast (inside) - Secondary villi
- Syncytiotrophoblast
- Cytotrophoblast
- Centre of villi —> ***Mesodermal core - Tertiary villi
- Syncytiotrophoblast
- Mesodermal core: **Villous capillary system (with **fetal blood) formed within
Gradual removal of barriers between Materal (outside villi) / Fetal blood (within villi in mesodermal core): 4th week: 4 barriers - Syncytiotrophoblast - Cytotrophoblast - Connective tissue - Endothelium (Fetal blood)
4th month: 2 barriers
- Syncytiotrophoblast
- Endothelium (Fetal blood) (直接掂住 Syncytiotrophoblast)
- 無左Cytotrophoblast + CT
***Functions of Placenta
- Exchange of metabolic and gaseous products
—> function as fetal lung, gut, kidney
- O2, CO2
- Nutrients, Electrolytes
- Fluid volume regulation, waste disposal
- Maternal Ab - Production of hormones (relationship like Hypothalamus/Pituitary)
Cytotrophoblast (~ Hypothalamus)
—> **Hypothalamic releasing / inhibitory like hormones e.g. CRH, TRH
—> **Growth factors
Syncytiotrophoblast (~ Pituitary)
—> **Pituitary hormone like hormones e.g. **HCG (LH-like), **HCS (Human chorionic somatomammotropin), HPL (Human placental lactogen, GH-like)
—> **Steroid e.g. Estrogen, Progesterone
Transport of O2 to fetus
- Haemoglobin O2 affinity:
Fetal > Maternal
—> allow fetal Hb to carry more O2 at same oxygen tension - Hb concentration is also higher in fetus
O2 dissociation curve:
Fetal curve on ***left of Maternal curve (same PO2, higher % saturation)
Bohr effect:
↑ [CO2], ↑ Temp, ↓ pH
—> O2 dissociation curve shifts to right
—> ↓ O2 affinity
Example:
CO2 diffuse from fetal to maternal blood in placenta
1. ↓ O2 affinity of maternal Hb —> release O2 —> diffuse into fetal blood
2. ↑ O2 affinity of fetal Hb (∵ less CO2)
Human Chorionic Gonadotropin
- ***Specific for placenta —> detection of pregnancy
- Produced by **Embryo + **Syncytiotrophoblast (after implantation, production ↑ in first 12 weeks)
- from 8-9 days after ovulation, peaks in 12 weeks —> ↓ afterwards
Functions ~ LH:
1. **Maintain Corpus luteum
—> ↑ steroids (Estrogen + Progesterone)
—> ↑ relaxin
—> **allow Corpus luteum to continue produce Estrogen + Progesterone
—> until Placenta itself can produce Estrogen + Progesterone
- ***↑ Fetal Testosterone
- ***↑ Fetal adrenal DHEA-S (substrate of placental estrogen)
***Progesterone from Placenta
- Produced by ***Syncytiotrophoblast
- ***keep ↑ throughout pregnancy
Functions:
1. ↑ Oviductal, Uterine endometrial gland secretion
- ↑ Decidual cell development (from endometrial stromal cells) —> nutrient supply for embryo
- Uterine quiescence
- ↓ Uterus contractility
- ↓ Sensitivity to Oxytocin (↓ stimulation of uterine contraction)
- ↓ Prostaglandin production (avoiding expulsion of fetus in early pregnancy) - ↓ Immune response to fetus (local suppression of immune response of mother)
- ↑ Maternal ventilation
- Prepare breasts for lactation
***Estrogens from Placenta
- Produced from ***Syncytiotrophoblast
- mainly ***Estriol (3 OH group —> different from that by Corpus luteum: Estradiol: 2 OH group)
- Lower potency than Estradiol
- Much higher amount produced (vs small amount of Estradiol)
- ***keep ↑ throughout pregnancy
Functions (stimulate growth):
- Enlargement of uterus, female external genitalia
- Growth of breast ductal structure
- Pelvic ligaments + Pubis symphysis relaxation/softening (with Relaxin) during parturition
- ↑ Progesterone synthesis (by ↑ LDL cholesterol uptake)
Embryonic period + Fetal period
Development of baby in 2 periods:
- Embryonic period
- Fetal period
Embryonic period:
- **1-8 week
- **Differentiation period
- 3 germ layer establishment (Ectoderm, Mesoderm, Endoderm)
—> formation of tissues and organs
- Shape of embryo changes greatly as a result of formation of organ systems
- 4th week: Pharyngeal arches, Heart bulge, Somites
- 7th-8th week (human-like): Ear, Eye, Toe
Fetal period:
- 3rd month onwards
- ***Maturation period
- Maturation and growth of tissues, organs, body
- ***Fewer malformation arise during this period
- Head:Trunk ratio ↓
***Maternal metabolism
1st phase: Anabolic phase (early stage of pregnancy, insignificant nutrient requirement from fetus)
Overall: ***↑ Genesis —> ↑ Maternal reserve for future fetal development
- ↑ insulin sensitivity
- ↑ lipogenesis, ↓ lipolysis
- ↑ protein synthesis —> growth of breast, uterus, musculature for pregnancy and labour
- ↑ glycogen store in liver / muscle
- normal / low plasma levels of glucose, a.a., fatty acids
2nd phase: Catabolic phase (accelerated starvation of mother, to ↑ nutrient supply for accelerated weight gain of fetus during growth period)
Overall: ***↑ Lysis, ↓ Genesis —> ↑ Nutrient supply to fetus
- insulin resistant (placental HCS)
- ↓ lipogenesis, ↑ lipolysis
- ↓ protein synthesis
- ↓ glycogenesis
- ↑ plasma levels of glucose, a.a., fatty acids
Maternal physiology
- ↑ Food intake, weight gain
- ↑ CO, blood volume
- ↑ Ventilation
- ↑ Urine formation
—> ↑ nutrient, O2 supply, Remove metabolic wastes
