One of the things I learned at one of the conferences I attended is that when babies nurse (or probably with single pumping), when there are distinct different productions between the two breasts, if the first breast that is nursed is the lower producing breast, 70% of the available milk is removed and when it is nursed second, only 50% of the milk is removed. Baby takes 50% of the higher breast production no matter which one is started with.  And babies come off the breast during milk ejection not in the resting phase. 
 We have always thought that it was because of the baby "nursing more vigorously" when hungry.  But the explanation was that when milk ejection occurs, the milk tries to leave the breast through the ducts rapidly, but begins to retreat within 60 seconds or so.  The more compression of the nipple, the faster the retreat AND that the fuller the breast the more milk is ejected in the first minute or so.  That means if there is no baby attached to the opposite breast (or pump), if that breast is the lower producing breast, the milk retreats into less full areas (fluid doesn't go back when there is hydrostatic pressure pushing forward).  This then results in less pressure in the next let-down.  This helps explain why double pumping is more effective over the long haul than single pumping.  But I've used this information to guide hand expression and single pumping and which breast to start with and it really works!

-----Original Message-----
From: Lactation Information and Discussion [mailto:[log in to unmask]] On Behalf Of K. Jean Cotterman
Sent: Thursday, March 03, 2011 1:38 AM
Subject: Re: Hindmilk and foremilk

Sorry Anna if my answer was too ???? (involved?) You can't say I didn't warn you;-) I have been known to have other controversial and independent thoughts about the anatomy of the breast too;-)


But if you didn't get my drift, I was disagreeing with at least one dimension of Cathy's explanation, in that I personally am not convinced that nature permits the cream (or any other part of milk either) to rise back up all the way into the alveoli or the vicinity of the lactocytes. This is because of the micro-anatomy of the little tube called the ductule, (plus the specific gravity of the fat and skim components.)



I learned of the ductule from reading about the microanatomy of the human breast in the histology book I cited. I am not aware of anyone in the lactation community as yet ever having recognized or addressed it's presence. (or possible function.) I do not know if it exists in the microanatomy of the mammary glands of other mammals. It seems as if researchers could actually study that possibility in vitro.



I laid out my hypothesis in detail deliberately to stimulate further thought and perhaps challenge even further study on the matter, if someone thinks it important enough. Until and unless they do present evidence, I reserve the right to reason that no portion of the residual milk can ever travel completely all the way back up into the alveoli or adjacent to the lactocytes. Up to the top of the ducts, yes, but back into the alveoli??? No. For that reason, I don't worry too much about apoptosis of the lactocytes from comfortable external pressure anywhere on the breast.



I believe it must actually be the FIL in the new milk being secreted that, when enough milk builds up to provide the back pressure, works with the FIL to cause slowdown in the rate of production till MER and further milk removal changes the local condition of the lactocytes in the alveoli.


I do continue to wonder if the ducts themselves perceive chemical stimuli from the FIL in them and perhaps somehow send neural messages to the lactocytes to slow down production. Or not. Seems pretty farfetched to me, come to think of it. And I admit that extreme fullness of the ducts could certainly raise the overall pressure within the skin envelope of the breast to eventually help slow production. Plus plugs, mastitis and other bad things, of course.


But thank you for being so delicate about it to the group!


K. Jean Cotterman RNC-E, IBCLC
WIC Volunteer LC, Dayton OH

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