Parturition, Lactation, and Neonatal Physiology

Question 1

Reciprocal changes between what two hormones are necessary for the onset of labor?

Answer 1

Progesterone and estrogen

Question 2

Progesterone blocks contractions normally. So to give birth, how does this change?

How does estrogen help the labor process?

Answer 2

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

Question 3

How do prostaglandins help with labor?

Answer 3

• stimulate strong myometrial contractions, cervical effacement, and initiates labor
• PGF2a potentiates oxytocin induced contractions by increasing gap junction formation
• synthesis of prostaglanins is stimulated by estrogen in fetus, oxytocin in uterus, uterine stretch

Question 4

How does oxytocin help with labor?

Answer 4

• UTerus is insensitive to oxytocin until 20wks
• estrogen receptors increase oxytocin receptors
• help the myometrium contract and stimulates decidual tissue to produce PGF2a

Question 5

What is the Ferguson Reflex?

Answer 5

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)

Question 6

How does Relaxin help with labor?

Answer 6

• cytokine similar to insulin
• may help keep the uterus quiet during prengnacy and help to soften/dilate cervix toward end of pregnancy

Question 7

What are the mechanical changes of labor?

Answer 7

• 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

Question 8

How is labor initiated?

Answer 8

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.

Question 9

What are the changes of the uterus and cervix during contractions?`

Answer 9

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

Question 10

How is the placenta delivered?

Answer 10

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)

Question 11

What is the fetal stimuli for breathing after birth?

Answer 11

asphyxiation during birth

sudden drop in temperature/cooling

Question 12

What are the causes for delayed breathing upon birth?

Answer 12

use of general anesthesia during delivery

prolonged labor

head trauma

Question 13

Describe the baby’s first breath after birth?

Answer 13

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

Question 14

Blood flow to the placenta shunts blood away from where?

How so?

Answer 14

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

Question 15

What does the umbilical vein do>

Answer 15

returns oxygenated blood to fetus from placenta

blood enters via ductus venosus

Question 16

What organ is bypassed in the ductus venosus?

Answer 16

liver

liver is largely nonfunctional

direct route from umbilical vein to IVC via ductus venosus

Question 17

How does the foramen ovale play a role in fetal blood flow?

Answer 17

hole in septum dividing atria, posterior aspect of the right atrium

RtL atrial shunt

bypasses right ventricle

Question 18

How does the ductus arteriosus play a role in fetal blood flow?

Answer 18

RtL shunt between pulmonary artery to aorta

Question 19

What is the overall effect of all of the shunts in neonatal blood flow?

Answer 19

the total blood flow pumped by the heart passes through different vascular circuits

Question 20

What are the results of the patent foramen ovale?

Answer 20

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.

Question 21

What is the result of a patent ductus arteriosus?

Answer 21

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

Question 22

When does the kidney begin development?

When is urine produced?

How much of the amniotic fluid is fetal urine?

Answer 22

develope at 8wks, done by 36wks

urine production begins between 10-20wks

70-80% of amniotic fluid is urine

Question 23

Renal function matures rapidly during what trimester?

Functional development of the kidney completes closer to what age?

Answer 23

Third Trimester

1 month

Question 24

What is the role of the fetal liver?

Answer 24

• 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

Question 25

What is the main form of hemeglobin in the fetus

When are normal adult levels of hemeglobin achieved?

Answer 25

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

Question 26

What are the main nutrients required by the neonate?

Answer 26

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)

Question 27

What are the changes of the neonatal immune system?

Answer 27

• 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

Question 28

What is the anatomy of the mammary gland at birth and at puberty ?

Answer 28

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

Question 29

What is the funciton of the alveolar epithelium

What is the function of the myoepithelial cells?

Answer 29

luminal epithelium responsible for milk synthesis and secretion

sit between epithelial and basement membrane and contract to move milk from alveoli into ducts

Question 30

How does the mammary gland change during the menstural cycle?

Answer 30

• 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

Question 31

Define:

Mammogenic

Lactogenic

Galactokinetic

Galactopioetic

Answer 31

promote porloferation of alveolar/ductal cells

promote milk produciton by alveolar cells

promote contraction/milk ejection

maintain milk production after it’s been established

Question 32

What are the five ways of milk secretion?

Answer 32

secretory pathways

transcellular endocytosis and exocytosis

lipid pathways

transcellular salt and water transport

paracellular pathway

Question 33

How does suckling stimuli (sight or sound of child) effect hormone release?

What happens next?

Answer 33

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

Question 34

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?

Answer 34

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

Question 35

How is lactation stopped?

Answer 35

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