Parturition, Lactation, and Neonatal Physiology Flashcards
Reciprocal changes between what two hormones are necessary for the onset of labor?
Progesterone and estrogen
Progesterone blocks contractions normally. So to give birth, how does this change?
How does estrogen help the labor process?
Progesterone receptors on the uterus become desenstized to the hormone
this leads to an increase in estrogen receptor expression
More estrogen binds and allows for an increase in myometrial contraction and cervical dilation
How do prostaglandins help with labor?
- Synthesis of prostaglandins is stimulated by estrogen, fetus, and contractions
- PGF2a potentiates oxytocin induced contractions by increasing gap junction formation
- Result is increased uterine contractions and cervical dilation
How does oxytocin help with labor?
- UTerus is insensitive to oxytocin until 20wks
- estrogen receptors increase oxytocin receptors
- help the myometrium contract and stimulates decidual tissue to produce PGF2a
What is the Ferguson Reflex?
during active labor, Oxytocin stimulates uterine contractions
this stimulates PGF2a production
This stimulus for this is cervical distension and these produce further cervical distension/dilation which drives the Ferguson Reflex (positive feeback loop to enhnace labor)
How does Relaxin help with labor?
- cytokine similar to insulin
- may help keep the uterus quiet during prengnacy and help to soften/dilate cervix toward end of pregnancy
What are the mechanical changes of labor?
- uterine size
stretch of Sm. M increases Ferguson reflex and furthers contractions and stimulates prostaglandin production
- Cervical remodeling
structural changes resulting in change from fetal support to birth canal
How is labor initiated?
Stress.
Placental produces CRH which increases contractions and accumulates in fetus
Fetus makes ACTH which increases fetal cortisol and placental CRH release
Fetal placental estrogen increases to enhance myometrial contractility
so stress causes labor. don’t be stressed.
What are the changes of the uterus and cervix during contractions?`
fully dilated cervix is drawn up just below the pelvic inlet
subsequent uterine contractions push fetus downward through the pelvis
first stage is longest, second stage usually less than an hour followed by placental delivery
How is the placenta delivered?
uterus contractions reducing area of attachement
sepration of uterus and placenta causes bleeding and clotting
oxytocin helps constrict blood vessels (synthetic given, or nipple stimulation can cause release of oxytocin-nursing)
What is the fetal stimuli for breathing after birth?
asphyxiation during birth
sudden drop in temperature/cooling
What are the causes for delayed breathing upon birth?
use of general anesthesia during delivery
prolonged labor
head trauma
Describe the baby’s first breath after birth?
alveoli are collpased and filled with fluid
more than 25mmHg negative inspr. pressure needed to overcome surface tension and open alveoli
first breath infant capable of -60mmHg and brings in about 40ml of air
deflation of lungs requires strong positive pressure to ovecome viscous resistance of fluid in bronchioles
Blood flow to the placenta shunts blood away from where?
How so?
blood is shunted away from the lower trunk in order to reach placenta
Umbilical arteries with lots of branches, capillary network returns deoxygenated blood.
Legs blood flow is connected to IVC
What does the umbilical vein do>
returns oxygenated blood to fetus from placenta
blood enters via ductus venosus
What organ is bypassed in the ductus venosus?
liver
liver is largely nonfunctional
direct route from umbilical vein to IVC via ductus venosus
How does the foramen ovale play a role in fetal blood flow?
hole in septum dividing atria, posterior aspect of the right atrium
RtL atrial shunt
bypasses right ventricle
How does the ductus arteriosus play a role in fetal blood flow?
RtL shunt between pulmonary artery to aorta
What is the overall effect of all of the shunts in neonatal blood flow?
the total blood flow pumped by the heart passes through different vascular circuits
What are the results of the patent foramen ovale?
20% of people by age 2yrs, FO doesn’t close
increased right atrial pressure can push open flap
can cause pulmonary hypertension or transient increase in pressure during BM, coughing/sneezing etc.
What is the result of a patent ductus arteriosus?
heart problem occuring shortly after birth
can be heard as a heart murmur
oxygenated blood in aorta mixes with deoxygenated blood in pulmonary artery
puts strain on heart and increases pulmonary blood pressure
When does the kidney begin development?
When is urine produced?
How much of the amniotic fluid is fetal urine?
develope at 8wks, done by 36wks
urine production begins between 10-20wks
70-80% of amniotic fluid is urine
Renal function matures rapidly during what trimester?
Functional development of the kidney completes closer to what age?
Third Trimester
1 month
What is the role of the fetal liver?
- poor conjugation of bilirubi, deficient plasma proteins and coagulation factor, poor gluconeogenesis
- infants use liver’s stored fats and proteins for metabolism until mother’s milk can be provided
What is the main form of hemeglobin in the fetus
When are normal adult levels of hemeglobin achieved?
Fetal form is HbF (A2Y2) with a higher O2 binding capacity
HbA2 is the adult form and normal levels are reached by 12th week of life
What are the main nutrients required by the neonate?
Ca and Vit. D for bone development (mother’s milk)
Iron (enough in liver, low in milk but with high bioavailability)
Vit. C (via milk)
What are the changes of the neonatal immune system?
- neonate inheritsimmunity from mother but does not make Ab for a while after birth
- most Ab from mother protect infant for about 6 months
- baby will make own Ab and gamma globulin around 12-20months
What is the anatomy of the mammary gland at birth and at puberty ?
At birth, the mammary gland is mainly a lacteriferous duct with few alveoli and will stay in this stage until puberty with minimal branching
At puberty, estrogen will cause lactiferous ducts to sprout and branch and develop alveoli
What is the funciton of the alveolar epithelium
What is the function of the myoepithelial cells?
luminal epithelium responsible for milk synthesis and secretion
sit between epithelial and basement membrane and contract to move milk from alveoli into ducts
How does the mammary gland change during the menstural cycle?
- mammary tissue is exposed to estrogen and progesterone
- breasts increase in size with adipose and CT deposition
- can become enlarged, tender, or secrete fluid and then undergo involution at the end of the cycle
Define:
Mammogenic
Lactogenic
Galactokinetic
Galactopioetic
promote porloferation of alveolar/ductal cells
promote milk produciton by alveolar cells
promote contraction/milk ejection
maintain milk production after it’s been established
What are the five ways of milk secretion?
secretory pathways
transcellular endocytosis and exocytosis
lipid pathways
transcellular salt and water transport
paracellular pathway
How does suckling stimuli (sight or sound of child) effect hormone release?
What happens next?
activates afferent neural pathway from breast to spinal cord and then to hypothalamus
Dopamine release is inhibited which results in prolactin release and milk production
While suckling increase prolactin and milk production, what is the effect of oxytocin release from the posteiror pituitary?
HOw does inhibition of GnRH play a role in this?
interacts with myoepithelial cell resulting in let-down
Inhibition of GnRH production decreases the release of LH and FSH and inhibits the ovarian cycle to prevent another pregnancy
How is lactation stopped?
when suckling stimulus is discontinued, milk accumulates, causes tissue damage
cell debris is phagocytized
lobular/acinar structures hypotrophy
ductal system predominates
full involution process can take 3 months
