<What they are seeing now on
ultrasound is that the ducts can dilate at different parts of the breast,
not
just behind the nipple>

My understanding of the MER from dairy research  is that sporadic
dilatation of ductal structures has never been thought to be confined to
just the parts behind the nipple. (great similarities in function and
microscopic anatomy of all mammalian glands and ducts despite eventual
differences between the distal portions of udders/teats and
breasts/nipples)

I cannot lay my hands on it this minute, but I have a reference with a
diagram nearly 50 years old, I believe by Linzell, illustrating his idea
of what happens to a duct in any mammal during MER.

There are myoepithelial cells not only in a basket pattern around each
alveolus, but around nearly all ducts except the ductule (the smallest
tubing right off the alveoli). Around the ducts their pattern of
arrangement shifts to a combined spiral, longitudinal distribution.

Apparently in response to oxytocin, the myoepithelial cells sequentially
cause the ducts they surround to simultaneously shorten in length as they
dilate in diameter, to propel the milk forward (in a manner that reminds
me somewhat of peristaltic action of the GI tract, or a snake digesting a
mouse!) That's what constitutes a MER.

The myoepithelial cells contract not only in response to oxytocin but
also, in response to direct pressure on the myoepithelial cells. (Ever
wonder why a calf butts the udder or a kitten or puppy  (and many human
babies) "knead" mom while eating?)

What I remember Dr. Hartmann's answer to my questions about this at
several other seminars was that wherever ducts converge in the breast on
their pathway toward the front of the breast, the area of convergence of
the two (or more) ducts is temporarily a little wider than either of the
ducts themselves.

His description reminded me of what we experience when on the highway
with merging of other routes as they enter onto the main highway - for a
short distance until the merging lane is completely funneled into the
highway, the roadway is somewhat wider at that point.

<and there are no "lactiferous sinuses" as we know
them.>

Repeat those last four words very slowly, over and over and over. Just
because the sinuses are not "as we know them" does not mean that "there
are no lactiferous sinuses-period!" It means that it is our "knowing"
that is incomplete at this point in time.

I assure you, the histologists and breast surgeons placed this term into
the nomenclature of the parts of the breast, and have printed actual
electron microscope pictures of them. They *do* exist as separate
entities of the ductal system in the area of the nipple-areolar complex.
Granted, I doubt they are arranged precisely like the spokes on a bicycle
wheel as diagrams have led us to believe, but they are there, and are
palpable at certain portions of pregnancy and lactation.

In the "resting" or non-lactating breast, they are contracted, and their
shape is described in very interesting terms, and they are clearly
identifiable under a microscope to the trained pathologist or surgeon's
eye. There are even certain disease processes that affect just the
lactiferous sinuses!

What is missing from our understanding, it seems to me, is the process
that happens to the sinuses from the time they are seen two-dimensionally
under a microscope, contracted, in the non-pregnant breast, until the
time they are well expanded in full lactation and "caught in the act of
functioning" during these shadowy, still two dimensional ultrasound
images.

I maintain that between these two extremes are several stages where the
"bulging" state naturally occurs. An experienced examiner can palpate
them in most mothers from the mid-third trimester onward, and clearly
feel their slight bulging throughout the first weeks and months of
lactation until they have developed their full elasticity and the contour
the researchers describe at that point in time when these ultrasounds
have been filmed.

< (Branches starting at the nipple similiar to a tree's roots just as
Jean described.)>

It is fascinating to read how this occurs both in the embryonic
development of the breast, and as a result of the menstrual cycles, and
especially during pregnancy. Branching is a biologic phenomenon in many
organs and is just recently being explained in biomedical literature in
terms of physics (fractal geometry - the major blood vessels of the liver
are one example.)

<Next, to tie this in with hand expressing and pumps; when compressing
behind
the nipple where the baby's mouth would be, is to stimulate the MER
because
of the hormones are being stimulated not because one can just squeezes
out
milk?  Mothers should not expect to see milk the first compression with
their
fingers and should be encouraged to work around the nipple until the milk
starts to eject.  Right?>

Well, my answer is both yes and no. Deep stimulation behind the nipple
does seem very successful in stimulating MER, within a minute by direct
compression and more strongly in a few minutes as a result of oxytocin.

But if the fingers are placed in just the right place, one can expect to
see droplets of colostrum/milk immediately in nearly all mothers, well
before any MER occurs.

That's where I see knowledge of the nature of lactiferous sinuses being
of value. Milk transfer has to do with hydraulic pressure, (Pascal's
law?) and if compression (of the fingers, or the tongue, or the sinuses
against the pump flange) can be focused on just the right area of the
lactiferous sinuses, one can boost hydraulic pressure.

So, as I said, my explanation to the mothers when I teach them to
fingertip express will remain exactly the same: "There is no milk stored
in the human nipple. Tiny amounts are stored in little "balloons" under
the circle. Imagine them like little toothpaste tubes that you are trying
to empty. Remember how you have to start pressing from the far end to get
the most to come out?"

<This is all so fasinating to me and I do hope I am making sense in my
post.>

Likewise.

Jean
***********
K. Jean Cotterman RNC, IBCLC
Dayton, Ohio USA

             ***********************************************

To temporarily stop your subscription: set lactnet nomail
To start it again: set lactnet mail (or digest)
To unsubscribe: unsubscribe lactnet
All commands go to [log in to unmask]

The LACTNET mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software together with L-Soft's LSMTP(TM)
mailer for lightning fast mail delivery. For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html