Many folks actually do believe in lactiferous sinuses, but to avoid controversy and get on with their clinical practice, they simply refer to the area by the name of "subareoar ducts" and go ahead and practice exactly as if there were "sinuses" there! I still use an old Childbirth Graphics demo breast, telling mothers it is my "cartoon breast". I tell them that the "little balloons" are really much, much smaller than drawn. I tell them to imagine them as tiny, tiny toothpaste tubes, and think about their own experiences with toothpaste tubes, remembering there are usually better results if you start pressing from the back. And then I go on to show how fingertip expression and off-center latch focuses the pressure near the back of the "little toothpaste tubes".



In my mind, one of the main functions of lactiferous sinuses is to give the infant, with only slight tongue motion, some mechanical advantage to create hydraulic power. This adds positive force during and after the MER to cause milk to pass through the narrow galactophores. In order to give that milk a pathway to lead it toward the esophagus, nature in her wisdom provides a vacuum, (which we know that nature abhors). Nature has designed the process, a marvel of engineering, knowing that the milk now propelled free of the nipple, will move to equalize the pressure. And lo and behold, it's now back where the automatic part of the swallowing reflex propels it onward with positive pressure toward the esophagus! I'm trying to learn something about hydraulic power because its effect in milk transfer fascinates me so. 



The dairy industry discovered decades ago (building on the knowledge of ancienct herdsmen) that the milk ejection reflex is the main force in milk transfer. As for vacuum being the main force, or the only force, etc., I often repeat to my clients: Vacuum does not pull. Other forces push! Breast pump engineers know that fact very well. I think LC's and others caring for breastfeeding mothers should be more aware of it too. It factors not only into milk transfer but also migration of excess interstitial fluid into the flange area during overhydration as well. That phenomenon is one of the main reasons that fingertip expression (after RPS if necessary) is so often more productive in the early days when "nothing comes out during pumping." In fact, migration of edema to equalize the vacuum often makes that problem worse. 


This also factors into the choice of an effective sized flange, as the flange tunnel is not to be judged by the size of the nipple, but by the distance behind the nipple base where the lactiferous sinuses can be pushed by atmospheric and other pressures to compress themselves against the walls of the tunnel so that hydraulic pressure will force the milk outward into the waiting vacuum. It is unfortunate that some women need a larger flange than is routinely supplied in $300 pumps and as a result suffer pain and ineffective milk removal, and often give up breastfeeding prematurely. for want of the knowledge of the benefit of a larger flange. 


I was curious about the concept of lactiferous sinuses five decades ago after first learning about them on the OB unit through the Ross and Carnation literature. I learned to palpate the sinuses in caring for hundreds of mothers on the nights when I was the sole nurse on the "uncomplicated"  postpartum floor. I have done so, prenatally as a childbirth and breastfeeding educator and as  prenatal nurse, and postnatally, in literally thousands of breasts in those five decades. When I became a maternity inservice clinician with on-duty library privileges, preparing for staff development, I began looking lactiferous sinuses up in the literature of other disciplines years before the ultrasound work was done.  


Aside from having difficulty believing the conclusions because of the research funding, I had found references in histology and breast surgery literature that described lactiferous sinuses in the resting breast, and even showed microscopic photographs. As for Sir Astley Cooper's research and the use of paraffin, I believe this may still be a valid technique in use in histology today. He was specific about having a specimen from a woman who had been recently breastfeeding for months or more, and the tissues in the sinus area were already elastic from the suckling, and would have filled and not simply have stretched directly from the injection of paraffin. Otherwise, why would other ductwork not have stretched too?? And then, he had to depend on an artist to convey the concept he discoverd. This was, in my estimation, science at its finest in the age before microscopes, photography and radiology were invented.   


To me, it makes the LC profession look naive, if not embarrassingly shallow to have been suckered into changing all their literature simply on the basis of one (industry financed) discipline alone. The breast cancer field, and the breast surgery field are far advanced in microscopic examination of various parts of the breast, with an official nomenclature that is necessary for clear communication because different kinds of breast disease occur only in specific areas or types of tissue. Lactierous sinuses are part of that nomenclature.


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.


As a profession, since we are yet so young, I feel strongly that our leadership itself need to be fostering research that taps into these other disciplines for cross-fertilization of anatomical ideas, rather than to act like Henny Penny and Chicken Little: "The sky is falling in, the sky is falling in," in reaction to this (commercially sponsored) research in one discipline alone.

 
The question comes to my mind, "Why would lactiferous sinuses be visible in tissues of children, both boys and girls, evident in (the resting breasts of) men as well as women, the only difference being the presence of a large amount of elastic tissue in the walls of the sinuses in the resting breast of the female, with this same phenomenon still beiing visible in microscopic view in the resting breast of the menopausal female? 


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


Haagensen CD, Diseases of the Breast, Third Edition 1986 W.B. Saunders Co: West Washington Square, Philadelphia, PA 19105

 
In the only organ that is incomplete at birth, why would this visible microscopic segment be present in childhood and adulthood when the breast is resting, then disappear when the breast is in its active phase, then reappear during menopause????? What purpose could it possibly serve in the immature or mature resting breast of both sexes? It can even be seen by ultrasound during its resting phase in the adult female.


Rizzato G, Chersivani R, Macorig D, Perrone R, Dynamic Breast Anatomy http://www.liveto.com/semi/sonic/pdf/se01.pdf

 
A microcopic view of lactiferous sinuses can be seen in Blue Histology, on the website of the histology department of the University of Western Australia itself.


To me this says that someone in radiology needs to study this in the 3 trimesters of pregnancy plus right after delivery and for the first month, because the Australian research was conducted only AFTER 4 weeks of nursing, which gave the walls of the sinuses time to develop elasticity by repetitive stretching of the thick walls of elastic tissue (during suckling). But what profit could have been expected from research into a time period which provided no market for breast pumps??


In addition to that, some histologist needs to microscopically examine this ductal area in an unfortunate woman who died in a traffic accident close to or right after delivery, as well as someone who has been nursing during the same period of the Australian research (1-6 months) to demonstrate histologically the progression of the process that makes the walls thin out during repetitive stretching so that it looks like the rest of the ducts on ultrasound after one month. 


We have no trouble realizing that other reproductive organs change their shape, location and thickness during various stages of reproduction. Why do we have such a problem believing that the elastic walls of lactiferous sinuses could thin and stretch after one or more months of suckling??


I am incapable of formal research, but by expressing clearly what I have learned clinically and in literature searches, and formulating these challenging questions, I hope I can suggest the urgent need for such research and thereby influence those who are capable of it.


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

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