>The milk that accumulates between feedings draws fluid from the
>circulation to maintain a balance of concentrations across the cell
>membranes resulting in the first milk being higher in volume but
>lower in fat.

My understanding (mostly from Peter Hartmann's presentations, etc) of
all this is that fat globules, along with all the other components,
are added to the milk in the alveoli, but that they are 'sticky' and
tend to adhere to the walls of the alveoli. Fats are not
water-soluble and exist in the milk in little membrane-surrounded
packages - globules.

Between feeds, the milk trickling down the ducts to the sinuses does
not take much of this fat as the globules are 'stuck'. When the MER
happens, the myoepithelial cells surrounding the alveoli squeeze the
alveoli and dislodge many of the fat globules and they are carried
off down the ducts. This is a little like fluid being squirted out of
a rubber bulb when squeezed. As the alveoli 'empty' and the
myoepithelial cells squeeze repeatedly, more and more fat globules
are dislodged and this results in increasing fat levels in the
'hindmilk'.
******************************************************************
Joy Anderson B.Sc. Dip.Ed. Grad.Dip.Med.Tech. IBCLC
Nursing Mothers' Association of Australia Breastfeeding Counsellor
Perth, Western Australia.   mailto:[log in to unmask]
******************************************************************

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