Phys 2 Lactation

isabellepjk's version from 2017-04-28 12:56


Question Answer
what is the alveolus? explain its structurethe milk secreting unit, it is lines w/a single layer of epi. cells and surrounded by a dense capillary network and myoepithelial cells
describe the mammary gland from birth->before puberypresent, rudimentary duct system, parynchema consists of adipocytes and fibroblasts, growth proportional to body growth.
describe the mammary gland during sexual maturity (What two things to what during pubery to cause this)bigger, more mature. exponential growth during first estrus cycles Estrogen--> lengthening and branching of ducts. Progesterone--> lobulo-alveolar development
describe the mammary gland during pregnancy, why is it this way?gland becomes functional DURING GESTATION, stroma is replaced with alveolar tissue b/o long-standing high ESTROGEN/PROGESTERONE levels.
when does the actual production of milk occur? (name for this)(lactogenesis) only a few days before parturition
what does estrogen do to the mammary gland during puberty? what does progesterone do?estrogen=lengthen/branch ducts. progesterone=lobulo-alveolar development
what are the two phases of lactogenesis?INDUCTION (before birth) and MAINTENANCE (post parturition)
what is the induction phase of lactogenesis coordinated with?coordinated with parturition, milk production actually starts a few days BEFORE this, and the secretions accumulate in the mammary gland (=colostrum).
how is the induction phase of lactogenesis induced? (3)(1) withdrawl of progesterone prior to birth (2) inc in cortisol to induce prolactin receptors (3) inc in PROLACTIN a few days before birth, sitm by prolactin RH and suppression of prolactin IH= DOPAMINE.
what is colostrum? what are the contents/ solute conc of these?milk produced during induction phase (w/o removal). solute conc are 2-3 times that of normal milk (except lactose), with an Ig conc of 30-40xs that of normal milk
what does colostrum provide? (5)(1) passive immunity to newborn (GI mucosa attachement and absorption of Ig's-- needs to be in first 6-24hrs before GI closes) (2) conc nutrients (3) growth factors (eg somatomedins) and immune system factors (4) laxative (5) casomorphins
what is "group 1" of colostrum animals refer to?placenta epitheliochorialis- no Ig xfer in utero= COLOSTRUM-DEPENDENT
what is "group 2" of colostrum animals refer to?placenta endotheliochorialis- Ig xfer in utero + via colostrum
what is "group 3" of colostrum animals refer to?placenta heochorialis- Ig xfer sufficient in utero
maintenance phase- what is continuous milk secretion dependent on?on regular milk removal, which leads to release of prolactin
when is prolactin released during lactogenesis (maintainance)during suckling. tactile stim--> SC--> hypothalamus--> VIP (vasoactive intestinal peptide) release a/o dopamine (=PIH) inhibition- ant. pituitary secrete prolactin into circulation--> mammary prolactin receptors--> LACTOGENESIS
what inhibits lactation in most species?dopamine
what animal DOESNT use prolactin? what do they use instead?RuMINANTS use GROWTH HORMONE (=somatotropin) instead
how does milk let-down (ejection) occur?neuro-endocrine reflex-- touch and heat receptors/teats--> sensory nerves--> hypothalamus--> post. pit.--> OXYTOCIN release--> circulation--> contraction of myoepi cells--> milk letdown within 1 min after stim
what happens if there is no milk removal?pressure inc, which ceases milk production (regular removal essential for continued milk production)
how do some diary farms increase yield?oxytocin injections prior to milking (makes myoepi cells contract more)
lactation increases for how long? then gradually declines until the end, around __days (cows)3-4 weeks there is an inc, ends at ~305 days
what happens to the mother during the first few weeks of lactation?in a neg energy balance, will lose body condition.
what is the danger of using bovine growth hormone/somatotropin (bST) to get more milk?it inc production at the expense of body reserves, mobilizes the body stores, worsens the neg energy balance situation, and can put the cow in danger of hepatic lipidosis/ketoacidosis
cessation of milking/suckling at time of weening induces what?involution of alveolar tissue
what three things happen during involution?(1) alv. cells lysed by lysosomal enzymes (2) alv cells replaced by adipocytes (3) myoepi cells remain
what happens if the dry period is too short?alv cells are carried over to the next lactation, but have REDUCED SECRETORY CAPACITY! so reduced milk yield.
what is the minimum dry period for diary cattle?6 weeks