Nancy posted a set of very succint observations re: size of nipple and
size of pump flange on digest #2003-1650, 11/24. For anyone who missed
it, I encourage you to go back and read it. Her final question:
<And does anyone know
the technical term for this "underlying tissue"? >
It is technically called the stroma of the mammary gland, interspersed
with- - - yes- - - -you guessed it- - -the lactiferous sinuses. This is
the term the histologists and surgeons use for those portions of the
ductal system right under/behind the nipple-areolar complex, connecting
to the larger ducts that branch upward into the breast. (Numerous
electron microsope pictures of these structures in the resting breast
have been published.)
The stroma consists of fat tissue, blood vessels, nerves, and lymphatics
as well as the connective tissue itself. In embryonic development, the
tissue that is destined to become the glandular/ductal tissue "invades"
the layer that is to become the connective tissue, diverging to
eventually develop into the separate lobes. The two types of tissue grow
in a way so "intertwined" that it is impossible to dissect them from each
other surgically, but they each function within their separate
boundaries.
The stromal tissue of the areolar area is almost devoid of fatty tissue
All the intraglandular fibrous septa converge there (because they
diverged from there in the first place during embryonic development ).
Nerves coming from all areas of the breast also converge there on their
way to meet and twine around the individual ducts that lead outward
through the center of the nipple. (This bodes well for stimulation of the
MER by compression on that area.) Surgeons observe that the absence of
any subcutaneous fatty layer at that level results in the close adhesion
between skin and glandular tissue, (the subareolar ducts, i.e. the
lactiferous sinuses.)
Which brings me to my favorite point. Suction of the pump does not pull
on milk in the way we have come to associate the vacuum effect of a straw
or a hollow needle directly immersed in fluid.
The pump pulls on flesh. (Technically, vacuum doesn't "pull" at all. It
lowers the pressure beneath atmospheric pressure so that this outside
pressure pushes the flesh into the vacuum area that "nature abhors" to
try to balance the pressures.) But just for simplicity's sake, let's use
"pull". When the vacuum pulls on flesh, that means it is pulling on blood
vessels, nerves, and lymphatics as well as the connective tissue itself,
plus any interstitial fluid between the cells, plus the lactiferous
sinuses, within which there is a small amount of milk.
As this tissue moves further into the pump flange it depends on where the
inner circular opening meets the lactiferous sinuses as they are extruded
into that part of the flange, whether or not the milk will be extruded
outward through the nipple openings (at which point, the vacuum then acts
directly on the milk), or whether the sinuses will remain too far away
from compression, if they have developed at a slightly deeper level than
the "average" or more commonly seen depth of about 3/4 to 1 1/4 inches
or about 2-3 cm. (measured from the base of the nipple).
Sometimes the process causes the inner ring of the flange to meet more
deeply set sinuses at their anterior end and this strips the milk
temporarily upward in the contributing duct (a little like squeezing a
toothpast tube at the wrong end). If the mom has a strong MER, there may
be some minimal milk collection, perhaps between vacuum surges, but this
is often what seems to be "wrong" about the fit of the pump flange.
It doesn't necessarily bear any relation to the size of the nipple
itself. Moms with small nipples can have deeply embedded sinuses, and
vice versa. IME, the sinuses are actually distributed at random depths
(like a bouquet of flowers) within the connective tissue, and certainly
not like the simplistic cartoon diagrams to which the illustrators have
reduced the real anatomy.
Of course, you don't want the inner channel of the flange to be so narrow
it pinches the nipple. But I think assessing the relative depth of the
lactiferous sinuses by hand expression has some value on estimating a
pump flange size that will result in efficient milk removal.
And remember, that the nipple itself may enlarge temporarily due to the
movement of interstitial fluid toward the vacuum. Barbara and Kay have
illustrated nicely in The Breastfeeding Atlas the enlargement of the
nipple in the non-engorged breast that results from pumping. The
potential is even greater in the engorgement stage. Dairy studies on
goats have also shown that shape of teats are temporarily changed by
vacuum,- the more the vacuum, the greater the alteration in thickness and
length from collection of edema.
This is my take on what I have seen and read. How does this set of
insights correspond with the observations of others?
Jean
******************
K. Jean Cotterman RNC, IBCLC
Dayton, OH, USA
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