Gonneke writes:
<Following a question about Lilipadz on a Dutch Lactation Specialists
Discussion list I have found myself in a discussion of the function of
nipple muscles. I've always understood that the circular and radiant
muscles around the nipple are there to make the nipple protude and be
firm and to help milk getting out (re Lawrence and others). Now it seems
to be that in some publications it is stated that these muscles act as
sphincters, meaning they keep the nipple pores closed between feedings.
That would then mean that weakening of these muscles would make the woman
leak milk and, the other way around, that muscles could be trained to
keep the nipple pores closed and stop leaking. Nowhere in lactation
literature nor via medline nor in the lactnet archives can I find this
theory. Can someone enlighten me? >

This has interested me too, but I have not found any reputable reference
to it in any of the primary (those who actually look under the
microscopes) embryological and histological literature that I sometimes
read for recreation;-) Fascinates me!

Azzopardi JG, Ahmed A, Millis RR. Nomenclature of the Microanatomy of the
Breast: Parts Affected in Different Diseases: Normal Structure and
Involution, In: Problems in Breast Pathology In: Major Problems in
Pathology, Vol. 11 in series, Bennington JL, Ed., W. B. Saunders Co.
Ltd., London, 1979.

Hughes ESR. The Development of the Mammary Gland, Annals of the Royal
College of Surgeons, Oct. 25, 1949 pp. 99-119.

Haagensen CD, Diseases of the Breast, Third Edition 1986 W.B. Saunders
Co: West Washington Square, Philadelphia, PA 19105
   (He was an eminent breast surgeon, and does surmise that the circular
and radial muscles of the areola are for the purpose of helping empty the
lactiferous sinuses. But I discounted that as his personal assumption
probably borne of never having had much working contact with the
lactating breast and the physiology of latching and suckling. He does not
mention anything about 'sphincter muscles' per se.) 

Montagna W, Macpherson E, Some Neglected Aspects of the Anatomy of Human
Breasts, Journ Inv Derm, July 1974, Vol 63;1: p. 10-16.

Russo J, lRusso IH Development of the Human Mammary Gland in: The Mammary
Gland, Development, Regulation, and Function ed. by Neville MC, Daniels
CW 1987 Plenum Press, NY. pp 67-93.

I recently had a chance to briefly scan a book"The Mammary Gland" from
the 1950's by a pioneer researcher in the veterinary field, Charles
Wesley Turner. Although there was very little mention of the human
breast, I found it fascinating to learn how many things they have learned
about anatomy of dairy cattle such as the ways to predict good producers
(by the large amount of venous development to route the circulation back
toward the heart). There are apparently some breeds of cattle that do
seem to have a sphincter muscle within the teat. I think it may have been
referred to as the rosette of Furstenburg, Other breeds of cattle
apparently do not, and perhaps the same with goats. I hope to borrow the
book again some day soon, just for curiosity's sake.

This is my personal take. I do not believe there are sphincter muscles in
the human breast. But I do believe there is a mechanism that may have
some effect on stemming leakage, depending on the anatomy of the
particular woman's nipple-areolar complex, the degree of her possible
oversupply, often tied to the strength of her particular MER, which I
think can be partly associated with the number of lobes in her breast,
and/or the pattern of nursing ('first breast first' or one side for
several feeds).

Azzopardi states : "The sinus communicates with the surface of the nipple
via the collecting duct or galactophore. In its proximal portion this
duct is lined by epithelium similar to that of the rest of the ductal
system, but its superficial portion is sealed by keratinizing stratified
squamous epithelium continuous with the nipple surface. The junction
between the glandular and the squamous epithelium is abrupt." 

Other histologists refer to this as the squamo-columnar junction, which
occurs at the proximal end of the galactophores, close to where they meet
the subareolar ducts, (if you prefer not to be heard using the term
'lactiferous sinuses' ;-) Keratinizing stratified squamous epithelial
cells are like those that continue onto the skin of the outside of the
nipple, areola and breast. Squamous epithelial cells are platelike and
firm, to protect from invasion of infectious organisms. 

They do actually sluff off and even plug the galactophores in the resting
breast and the pregnant breast. It seems to me that these cells would be
much less flexible and elastic than the columnar cells lining the surface
of the inner ducts, and I imagine that they would therefore tend to slow
down the exit of the milk when no suckling was at work. If a woman has
shorter nipples with less connective tissue and/or muscle in the nipple
button itself, combined with shallow sinuses, I envision that she would
tend to leak more easily. In fact, I believe that is the explanation for
some mothers I have seen that find leakage a problem in the last
trimester of pregnancy. It doesn't take much stimulation of say, a sheet
rubbing across the nipples, or a mild Braxton Hicks contraction to elicit
a mild MER and start them leaking. I have counseled them that wearing a
soft sleep bra seems to reduce the tendency by muting the stimulation.

Other mothers have a comparatively longer/thicker nipple, and sometimes
some have deeper sinuses so the squamo-columnar junction is buried
somewhat further behind the base of the nipple, and tends to slow any
leakage when there is no suckling. When there is the compressive power of
efficient suckling, I doubt that this cellular difference slows the milk
down that much. 

If a mom has quite an overabundant milk supply, IME that is quite often
associated with an overactive MER, perhaps plenty powerful enough to 'get
by" the squamo-columnar junction, especially if she has short
galactophores and shallow sinuses. Then again, pressing on the nipples
and consistenly stemming leakage might conceivably lead to a better
balancing of supply resulting in a slightly less forceful MER, thereby
seeming to have "conditioned" the leaking.

The number of lobes has a relationship with the number of galactophores
exiting the nipple, and I think some women have more lobes than many
others (we call them 'milk goddesses' in our office), and therefore more
galactophores. It's my observation that many of these women have such a
good supply that they find less leakage (and less distress in the baby)
by eventually (after supply is well established) tamping down the supply
somewhat. One way that seems to work well is by gradually nursing more
and more feedings on the same breast, such as all those within an 8 or
even a 12 hour period, then using the other breast for the next 8-12
hours. In such cases it might be a better balanced supply and not
necessarily the anatomy of the nipple-areolar complex that would reduce
the tendency to leak.

At least, that's the way I imagine it from what I've read and seen and
palpated.

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(R)
mailer for lightning fast mail delivery. For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html