When does stage two: Gestation occur? list some physical changes to mother
- about 38 weeks from conception
- physical changes
- uterine enlargement
- breast enlargement, able to produce milk
- inc blood volume and CO
- kidneys excrete additional waste from fetus -> urine output increases
during the first two trimesters, the uterus remains quiet due to ? What happens during third trimester
- inhibitory effect of high levels of progesterone
- last trimester, uterus becomes progressively more excitable -> braxton hicks contractions
What secretes Relaxin? Function of Relaxin?
- produced by corpus luteum of pregnancy and by placenta
- relaxes pelvic ligaments and softens uterine cervix by loosening connective tissue between pelvic bones
What is stage 3: parturition
- labor, delivery, birth
- *exact factors triggering increase in uterine contractility and initiating parturition are not fully established
theory behind estrogen role in labor induction
- high levels of estrogen cause
- increased gap junctions between myometrial cells -> uterus able to contract as a coordinated unit
- increased oxytocin receptors in myometrium -> increases uterine responsiveness to oxytocin -> increases uterine contractions
- increase production of prostaglandins
- contribute to cervical ripening
- also increases oxytocin receptors on myometrium
oxytocin is produced where and stored where
- hypothalamus
- posterior pituitary
profound effect of oxytocin at term is due to ? when is labor initiated?
- increase in concentration of myometrial oxytocin receptors
- there are ordinary levels of circulating oxytocin
- labor is initiated when oxytocin receptor concentration reaches a critical threshold
corticotropin releasing hormone CRH levels in maternal plasma act as what for parturition? what is associated with high and low levels of CRH
placental clock
- High CRH : associated with premature deliveries
- Low CRH: associated with late deliveries
theories for labor induction: role of CRH
- fetal portion of placenta secretes CRH into fetal circulation -> increased fetal ACTH
- increased ACTH -> stimulates DHEA from fetal adrenal cortex -> increases availability for placental conversion into estrogen
- increased ACTH -> stimulates cortisol -> lung maturation
Activation of what factor in the nucleus promotes cervical softening? how does it cause cervical softening
- nuclear factor (NF-kB)
- stimulates production of IL-8 and prostaglandin -> cervical softening
what normally causes activation of NF-kB in uterus
- uterine stretching
- increased production of macrophages as a result of increased pulmonary surfactant
what could activate NF-kB and result in premature labor
- bacterial infections
- allergic reactions
- multiple-fetus pregnancies
once contractions begin at labor onset, what increases force
- positive feedback cycle
- pressure of fetus against cervix increases oxytocin secretion
- positive feedback cycle progressively increases until cervical dilation and delivery are complete
what is Pitocin
pharmacological synthetic form of oxytocin
What are the three stages of labor? which is longest and shortest phase
- cervical dilation: longest (up to 24 hours)
- delivery of baby
- delivery of placenta: shortest (15-30 min)
what is involution of the uterus
uterus shrinkage to pregestational size after delivery
what initates prolactin? function of prolactin?
- withdrawal of placental steroids at parturition
- stimulates synthesis of enzymes essential for milk production by alveolar epithelial cells
lactation is sustained by what?
- suckling -> triggers release of oxytocin and prolactin
- oxytocin: causes milk ejection
- prolactin: stimulates secretion of more more
what hormone is responsible for mammary ductal growth
estrogens
what hormones are responsible for stimulation of development of mammary lobues and alveoli
- progesterone
- prolactin
- hCS (human chorionic somatomammotropin)
what hormones are responsible for stimulation of milk enzymes
- prolactin
- hCS
why does lactation not occur during pregnancy
- estrogen and progesterone block action of prolactin on breast
release of prolactin from lactotrophs in pituitary is controlled by what two hormones
- thyrotropin-releasing hormone: stimulatory
- dopamine: inhibitory
ovulation is suppressed as long as lactation continues because prolactin has what effects
- inhibits GnRH secretion
- inhibits action of GnRH on pituitary (inhibits FSH and LH release)
- anatgonizes action of LH and FSH on ovaries
- **must breast fed regularly
