Lactation Physiology Flashcards
what are the stages of mammary development
- fetal mammary chain and bud development
- peri-pubertal spurt
- peri and postpartum differentiation
- involution
does fetal mammary chain/bud development depend on hormones
NO - growth is isometric
males: testosterone induces regression of mammary chain
does the pubertal spurt of mammary development depend on hormones
YES - requires high estradiol, cortisol, and GH
what hormones drive peri and postpartum mammary development
estradiol, cortisol, GH, progesterone, and prolactin
BOTH progesterone and prolactin must be present to completely develop ducts and alveoli
involution
“drying off period” that allows the mammary tissue to regress when not lactating
does the mammary tissue completely regress during involution
NO - mammary tissue will accrue with each lactation
in the last trimester, does the concentration of progesterone and prolactin increase
NO - the increased response comes from an increase in RECEPTOR number
effect of progesterone on mammary tissue and milk production
- promotes mammary tissue growth
- inhibits milk production
need HIGH progesterone to develop mammary glands, but LOW progesterone to initiate milk production
effect of prolactin on mammary tissue and milk production
stimulates milk production in mammary tissue
steps of lactogenesis
- a-lactalbumin and galactosyl transferase combine to form lactose synthase enzyme
- lactose synthase converts glucose and galactose into lactose
- lactose creates an osmotic gradient within the mammary gland to draw water in and produce milk
what is the rate limiting factor of lactogenesis
a-lactalbumin
effect of prolactin + cortisol
promotes a-lactalbumin expression in mammary epithelial cells to increase lactose synthase activity and lactogenesis
does cortisol alone stimulate a-lactalbumin
NO - requires prolactin
cortisol + prolactin results in a synergistic effect to amplify a-lactalbumin expression
effect of progesterone on a-lactalbumin
inhibits a-lactalbumin
hormonal changes that occur at parturition
- prolactin: increases to program lactation curve then decreases after parturition; NOT needed throughout lactation
- progesterone: withdrawal at parturition initiates lactation
- bST: stimulates milk production to extend the lactation curve
bST
bovine somato-mammotropin; growth hormone in dairy cattle used to extend length and yield of lactation
colostrum
first milk after parturition that is abundant in immunoglobulins for antibody transfer to neonate
required in species with epitheliochorial placentas
what is the window of neonatal colostrum absorption
within 24-36 hours BUT ideally want to administer within 1 hour
earlier ingestion = more efficient absorption while the gut is open
what hormone promotes colostrum absorption in neonates
prepartum fetal cortisol increase
premature babies = no fetal cortisol = poor colostrum absorption
milk ejection reflex
neuroendocrine reflex
- suckling induces OT release from posterior pituitary
- OT stimulates contraction of myoepithelial cells in mammary glands
- results in milk let down
does oxytocin stimulate lactogenesis
NO
drying off
increase intra-mammary pressure induces mammary epithelial atrophy leading to involution of the mammary gland over weeks between lactations
essential for regaining maximum milk production in next lactation cycle
lactational anestrus
suckling inhibits the reactivation of the hypothalamic pituitary axis to prevent cycling while the dam is lactating
occurs in NON SEASONAL animals only
do horses, sheep, or dairy cattle exhibit lactational anestrus
NO
- horses: have “foal heats” and can gestate again 2-3 weeks postpartum
- sheep: enter seasonal anestrus after lambing
- dairy cattle: reovulate 1-2 weeks postpartum due to production setting of milking (NOT nursing young - only get milked a couple times a day)
