From MIDWIFERY MATTERS, Issue No.104, Spring 2005
THE FAMILIAR DIAGRAMS and text describing the anatomy and physiology of the
breast appear fixed and known but recently this understanding has been challenged
by research undertaken in Australia (Kent et al 2003). The purpose of the research,
which was undertaken by Peter Hartmann's team in Western Australia, was to explore
the physiology of lactation to enable the development of an improved breast
pump. The project was sponsored by a breast pump manufacturer and while the
data on the new breast pump has been published (Mitoulas et al 2002), the data
collected on the lactating breast has not, although there are plans to publish
in 2004 (personal communication, Kent 2003).
Meanwhile the findings from this project have been presented at conferences
in Australia and the United States of America (Kent et al 2003, Hartmann 2002)
and referred to briefly in one publication (Mohrbacher and Stock 2003). One
of the problems of minimal published data and relying on conference feedback
is that, like Chinese whispers, the facts risk changing in their telling. Recent
discussions on the topic in the UK has been around the statement that breastmilk
sinuses no longer exist, but as Mohrbacher and Stock (2003) explain this is
not the full story and the full understanding of the research. I listened to
a presentation based on the original research while attending the International
Lactation Consultants Association conference in Sydney 2003 and linking this
with my clinical observations gave me a better understanding, integrating practice
and theory more closely.
The Developing Breast
The anatomical descriptions of the breast shows it to be the only organ not
fully developed at birth (Lawrence 1999). The breast changes in size, shape
and function prior to birth, through puberty, pregnancy, and during and after
lactation (Hartmann 2002). Breast development involves two distinct processes:
organogenesis (ductile and lobular growth) and lactogenesis (milk production).
From the fifth to seventh week of the pregnancy the fetus develops a mammary
ridge, which rises from the axilla to the inguinal region (Black et al 1998).
By about the sixth gestational week, the ridge becomes depressed into the pectoral
region, forming the primary breast buds (Moore 1993). At birth the main lactiferous
ducts are present as well as the nipples and areola (Black et al 1998).
During puberty each menstrual cycle stimulates proliferation and active growth
of breast tissue. The breast development is concerned with growth of the ductile
system and the formation of ductile buds (Black et al 1998). The surrounding
fat pads also develop, giving the breast size and shape but this is not related
to the functional capacity of the breast (Riordan and Auerbach 1999). Humans
appear to be the only mammals that experience breast growth during puberty (Hartmann
2002).
Breast tissue is very sensitive to hormonal changes, especially the hormonal
changes of early pregnancy. For many women this is the first sign of pregnancy.
The breasts are capable of full lactation from 16 weeks of pregnancy onwards
(Lawrence 1999) but women experience differing rates of growth and breast development
during pregnancy (Hartmann 2002). In the first trimester the mammary epithelial
cells proliferate and further ductile sprouting and branching starts. The ducts
proliferate into the fatty pads of the breast where the ductile end buds develop
into alveoli (Riordan and Auerbach 1999). In the third trimester the alveoli
epithelium differentiates, developing a secretary function, and the alveoli
become distended with colostrum.
The changing hormonal environment following birth enables further development
and maturation of the breast, which means that the nutritional needs of the
growing infant are met until the child is weaned from the breast.
Breast Anatomy
Some textbooks on breastfeeding describe the anatomical aspects of the lactating
breast in more detail then others but the general descriptions show that the
basic functional unit of the breast is the alveolus. From each alveolus a small
ductile drains colostrum or breastmilk into lactiferous ducts. Each ductile
appears not to communicate with others but merges into the larger lactiferous
ducts which eventually widen into lactiferous sinuses usually located in the
areola area of the breast (Lawrence 1999). The 15 to 25 lactiferous sinuses
are usually described as radiating out around the areola area with each sinus
draining into the nipple (Lawrence 1999, Riordan and Auerbach 1999).
Interestingly these descriptive accounts do not appear to have any referenced
anatomical sources although Lawrence (1999) discusses a study by Tobon and Salazar
(1975 cited Lawrence 1999) which reviewed surgical specimens from seven lactating
women. The findings from this study noted an engorgement of the lumen of some
of the ductiles but it is not clear whether this engorgement was a result of
surgical injury or a possible distention of a ductile. In Woolridge's (1986)
study of the anatomy of breastfeeding the lactiferous sinuses are depicted in
the illustration but they were not visualised in the ultrasound scans in the
study.
Kent et al (2003) also had difficulty discovering the original authors of anatomical
and physiological descriptions found in current breastfeeding textbooks. She
postulates that the original source may be The Anatomy of the Breast by Sir
Astley Paston Cooper which was published in 1840. Cooper's study of the breasts
of seven previously lactating cadavers, injected coloured hot wax into the breast
ductile system to help identify and clarify the drainage network. The technique
was probably very advanced in its time and led to illustrations of the breast
which are very beautiful in their own way but the method is crude when compared
to modern imaging techniques; the wax may have distended and displaced some
of the delicate ductile structures of the breast. Moreover, studying a non-lactating
breast from a cadaver cannot reveal it as a dynamic, functioning unit.
Woolridge (1986) had used ultrasound scanning to observe the anatomy of suckling,
demonstrating the dynamic processes involved. Kent et al (2003) also used ultrasound
to study the lactating breasts of twenty-eight women. They describe a ductile
system, which appears convoluted, closely intertwined, and with multiple branching
of the ducts especially close to the nipple and with no obvious sinuses. This
appears very different from the straightforward drainage system with milk sinuses
described elsewhere (Lawrence 1999, Riordan and Auerbach 1999). They consider
that the convolutions and multiple branching of the ductile system close to
the nipple may have been described as milk sinuses, especially when dilated
with milk before or during a feed.
Relating Breast Anatomy to Practice
Personal reflection on Kent's findings, helped me to clarify some of the difficulties
some women experience when learning how to hand express their breastmilk. Most
textbook and information sheets on hand expression have stressed the importance
of manually locating 'milk sinuses' or a 'magic spot' (Riordan and Auerbach
1999, Limbs and Things 2003). It has been assumed that if women position their
hands correctly on their breast they should be able to express breastmilk. In
practice, a few women find this very difficult. Kent's findings suggest that
mothers need to locate the glandular tissue where the multiple ductile branches
occur; for most women this will be in the areola but for some this tissue may
be elsewhere. Interestingly, I have found that women experiencing such difficulties
in hand expression often instinctively move their hands higher on the breast
until they can express breastmilk. When I ask them what prompts them to do this
they often describe their search for 'knobbly bits' to put pressure behind;
they cannot find these knobbly bits in the areola. This observation besides
illustrating the individuality of women's breasts also demonstrates the role
of oxytocin as oxytocin release is pushing the milk out of the contracted alveola
into the dilated ductile system (Mepham 1987).
In earlier studies Kent et al (2003) and Hartmann et al (2002) showed that there
is variation from woman to woman in the lumen size of the ductiles of each breast.
Our experiences of supporting breastfeeding women supports variation between
individuals; we see differing rates of milk transfer between feeding dyads and
overall differing lengths of feeds.
The research by Kent et al (2003) also identified seven to ten lobes per breast.
Each lobe consists of a single major branch of alveoli and milk ducts that end
at the nipple; this is half the number stated in textbooks (Riordan and Auerbach
1999, Black et al 1998). Perhaps our clinical observations and those by artists
such as Tintoretto are more accurate. Tintoretto shows seven to ten jets of
milk from Hera's breast which form the stars in the milky way.
Reflections
It was unnerving to discover that our knowledge of breastfeeding is not based
on reliable anatomical research. I found the presentation during the conference
very uncomfortable and in many ways challenging. Initially I was in a state
of denial following the presentation but this was soon followed by a moment
of 'gestalt' when I realised how theory and practice now slotted into place.
The next challenge was to consider this new data in the light of my present
practice and how I shared this new knowledge with others. Reflection following
the presentation of this research has also changed my approach to teaching health
professionals on the anatomy of the breast to a more questioning attitude related
to practice and related to observations in practice. Meanwhile, I eagerly await
publication of the full research.
REFERENCES
Black R, Jarman L and Simpson J (1998). The Science of Breastfeeding, Jones
and Bartlett, London.
Cooper A P (1840). The Anatomy of the Breast, Longman Orme, Greene Brown and
Longman, London.
Hartmann P (2002). 'Control of breast function throughout the lactation cycle
in women', paper presented at the International Lactation Consultants Conference,
Boca Raton, USA, July 2002.
Kent J, Ramsay D, Mitoulas L, Cregan M and Hartmann P (2003). 'New insights
into breast function and breast milk expression', International Lactation Consultants
Conference, Sydney, Australia, August 2003.
Lawence R (1999). Breastfeeding: A guide for the medical profession, 5th edition.
Mosby, St Louis.
Limbs and Things. (2003). Hand expression model leaflet. www.limsandthings.com
Mepham T (1987). Physiology of Lactation, Open University Press, Milton Keynes.
Moore K (1993). The Developing Human - Clinically Orientated Embryology, Saunders,
Philadelphia.
Mitoulas L, Lai C, Gurrin L, Larsson M and Hartmann P (2002). 'Effects of vacuum
profile on milk expression using an electric breastpump', Journal of Human Lactation,
18, 6, 353 -360.
Mohrbacher N and Stock J (2003). The Breastfeeding Answer Book, 3rd edition.
La Leche League: Illinois, USA.
Riordan J and Auerbach K (1999). Breastfeeding and Human Lactation, 2nd ed.
Jones and Bartlett, London.
Tobon H and Salazar H (1975). 'Ultrastructure of the human mammary gland. II.
Postpartum lactogenesis', In: R. Lawence, (1999). Breastfeeding: a guide for
the medical profession, 5th edition. Mosby, St Louis.
Woolridge M (1986). 'The anatomy of infant sucking', Midwifery, 2, 164 - 171.
Address for correspondence: St Mary's Maternity Hospital, Milton Road, Portsmouth PO3 6AD Tel: 02392 28600 2544 e-mail: Sarah.brown@porthorp.nhs.uk or Sarah@lcsouthuk.biz
Updated LW July 8, 2005