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Anatomy and Physiology of the Breast
Alison TaylorBournemouth University
2006
Learning Outcomes
• Correctly identify the anatomical parts of the breast. • Distinguish between traditional diagrams of the breast
and new theories regarding breast anatomy from recent research.
• Describe briefly how the breast develops in females from fetus to lactating woman
• Explain the physiology of human lactation• Apply every day events to the physiology in order to
demonstrate how different factors can affect breastfeeding
Anatomy of BreastThe breast is composed of the following parts• Glandular tissue which makes and transports the milk• Connective tissue which supports the breast• Blood supply which nourishes the breast tissue and provides
the nutrients necessary for milk synthesis• Lymph which removes waste products• Nerves which makes nipple sensitive and allows baby’s
suckling to stimulate the release of hormones necessary for milk ejection reflex and the production of milk
• Adipose (fatty) tissue for protection from injury
Anatomy of the Breast
Blood supply to breast Lymphatic system of the breast
The Anatomy of the Breast
External structure• Vary in shape, size, colour and placement on chest wall• Lie generally each side of the midline of the anterior
chest wall between 2nd and 6th rib• Lie over the pectoralis muscle, and attached by
connective tissue• Usually hemispherical in shape,with an axillary tail, but
breast asymmetry is common
The Anatomy of the Breast
©Medela AG, Switzerland, 2006
The Anatomy of the Breast• The areola, a circular area of pigmentation lies midpoint.• Since the baby’s eyesight is not fully developed at birth it is
thought that the pigmented area may serve as a target to help the baby locate the centre of the breast
• Montgomery tubercles which are small sebaceous glands, secreting oil lie over the areola
• They provide lubrication and alter the pH of the skin discouraging the growth of bacteria on the nipple.
• They enlarge during pregnancy and have a pimply appearance http://www.007b.com/nipple_gallery.php http://www.007b.com/nipple_gallery.php
Anatomy of the Breast: New Research
• Hartmann and colleagues reported major new findings in 2002 concerning how the internal structure of the breast is organised (Mohrbacher and Stock 2003)
• Ultrasound examinations of the breast during breastfeeding by Hartman's research team in Australia have questioned traditional diagrams of the interior of the breast which date from the 1840's.
• However most textbooks and literature do not display the new structure yet, so the ‘new’ and the ‘old’ will be explored
Anatomy of the Breast
• Each mammary gland forms a lobe of the breast, divided by bands of fibrous tissue
• Until recently it was believed that each breast contained 16-20 lobes but the new research indicates that most women have 7-10 lobes per breast
©Medela AG, Switzerland, 2006
Anatomy of the Breast
• Alveoli are grape like clusters of glandular tissue• Alveoli are composed of milk secreting cells,
called acini cells that extract the nutrients necessary for milk production from the network of capillaries which surround each alveolus
• Enclosing each alveolus are myoepithelial cells which cause the alveoli to contract under the influence of oxytocin
©Medela AG, Switzerland, 2006
Anatomy of the Breast
For diagram of Myoepithelial cells surrounding the alveoli see:
Breastfeeding and human Lactation p154-155 (Riordan and Auerbach 1999)
or
Myles Textbook for Midwives p751 (Inch 2003)
Anatomy of the Breast
• Milk ducts are branch like tubules extending from clusters of alveoli
• It was thought that that smaller ducts then lead into larger duct called the lactiferous duct
• Current research suggests that glandular tissue is closer to the nipple
• And is described as being disorderly, more like the roots of a tree, with small duct intertwined with one another
©Medela AG, Switzerland, 2006
Anatomy of the BreastFor preliminary diagram of milk ducts based on research by Hartmann and colleagues see
La Leche League International The breast Feeding Answer Book (Mohrbacher and Stock 2003)
or click on hyperlink below:www.laleche.org.uk/ pages/books/newbab_anatomy.htm
Or visit the website:www.laleche.org.uk/pages/books/newbab_anatomy.htm
©Medela AG, Switzerland, 2006
Anatomy of the Breast• Until recently it was thought that just under the nipple and areola
the lactiferous duct widened to form the lactiferous sinus.• It was thought to be responsible for rewarding the baby with more
milk when he/she latched further onto breast • Hartmann’s research suggests that the lactiferous sinus does not
exist • It is proposed that the diameter of the ducts are the same all the
way from the nipple opening to further back in the breast • However it still appears that a bigger mouthful of breast enhances
milk flow received by the baby (Mohrbacher and Stock 2003)
©Medela AG, Switzerland, 2006
Development of the Breast• Development of the breast occurs in the fetus as early as four
weeks gestation • Inside the bud a rudimentary mammary ductal system is
formed• After birth growth of the gland during childhood is limited to
general growth • At puberty the effects of oestrogen and progesterone facilitate
further development of the ducts and the glandular system to form the adult breast
• Complete development of the mammary function occurs only in pregnancy
Development of the Breast
• From the 6th week in pregnancy the breasts undergo considerable enlargement and development
• Oestrogen is responsible for the growth of the lactiferous ducts, and myoepithelial cells, and increased blood flow to the breast
Development of Breast
• By 16 weeks colostrum is formed under the influence of HPL and prolactin
• Progesterone, prolactin and human placental lactogen (HPL) allows proliferation and enlargement of the alveoli.
• High levels of oestrogen and progesterone prevents milk production
Physiology of Lactation• Lactogenesis is the initiation of milk
production involving a complex interaction of hormones and other factors.
• Following delivery of the placenta, oestrogen progesterone and human placental lactogen levels fall abruptly allowing a rise in prolactin and oxytocin levels.
• High levels of prolactin secreted by the anterior pituitary gland stimulates the acini cells to produce milk
Physiology of Lactation
• If breastfeeding is not initiated within the first few day, acini cells are not ‘primed’ and begin to deteriorate and ‘shut down’, affecting long term milk supply
• Milk volume generally increases significantly within 48-96 hours following the birth
Physiology of Lactation
• Prolactin levels in the blood rise with sucking stimulation at the breast and rise approx 45 mins after a feed, returning to their pre-breastfeeding levels about 3 hours later
• Acini cells in the alveoli continue to synthesise milk in response to the rise in prolactin levels
Physiology of Lactation
• Research indicates that prolactin levels are higher at times of higher milk production because of demand from the baby
• Conversely prolactin levels are lowest when the breasts are full and the baby feeds less frequently
Physiology of Lactation• Oxytocin released from the
posterior pituitary gland stimulates contractions of the myoepithelial cells surrounding the alveoli.
• This causes a milk ejection reflex (let down reflex) and milk moves down from the alveoli through the lactiferous ducts to the nipple openings
Anatomy in Motion
Physiology of Lactation
• The milk ejection reflex allows the baby to receive the ‘fatty’ milk known as `the hind milk which the baby needs for good weight gain
• Removal from the nipple is effected by rhythmical pressure by the baby’s tongue natomy in Motion
• Recent evidence suggests that during the let down reflex dilatation of the ducts occurs as the milk fat swirls through the ducts, moving towards the nipple, but then moves in the opposite direction when milk is not removed by the baby (Mohrbacher and Stock 2003)
Physiology of Lactation
hypothalamus
Posterior pituitary
Anterior pituitary
nerve stimulation
oxytocin
prolactin
Hormonal control of lactation
The feedback inhibitor of lactation• However, breastmilk is not only controlled by hormones released
centrally from the pituitary, but also from within the breast itself• Breastmilk contains a protein which can reduce or inhibit milk
secretion (FIL)• It protects the breast from the harmful effects of being too full.• If breastmilk is removed effectively, the level of FIL falls and
more milk is made• Frequent feeding speeds up speeds up milk secretion, by
removing FIL whereas infrequent or restricted or scheduled feeding may allow FIL to accumulate, slowing down milk production
Learning Outcomes Achieved?
• Correctly identify the anatomical parts of the breast. • Distinguish between traditional diagrams of the breast
and new theories regarding breast anatomy from recent research.
• Describe briefly how the breast develops in females from fetus to lactating woman
• Explain the physiology of human lactation• Apply every day events to the physiology in order to
demonstrate how different factors can affect breastfeeding
References• COAD, J., DUNSTALL, M., 2001. Anatomy and Physiology for Midwives.
Mosby, Edinburgh.• INCH, S., 2003. Feeding. IN: HENDERSON, C., MACDONALD, S., eds.
Mayes’ Midwifery A Textbook for Midwives, Bailliere Tindall, Edinburgh. • LAUWERS, J., SHINSKIE, D., 2000. Counseling the nursing mother. A
Lactation Consultant’s Guide. Jones and Bartlett Publishers, Boston• MEDELA 2006. Medela breast anatomy images. [online] Switzerland:
Medela. Available from: http://www.medela.com/anatomy_images.html • MOHRBACHER, N., STOCK, J., 2003. The Breastfeeding Answer Book.
La Leche League International Inc, Schaumburg. • RAMSAY, D.T., KENT,J.C., OWENS,R.A., HARTMANN,P.E., 2004.
Ultrasound Imaging of Milk Ejection in the Breast of Lactating Women. Pediatrics, 113 (2), 361-367.
• RAMSAY D. T., KENT, J. C. HARTMANN R. A. AND HARTMANN P. E., 2005. Anatomy of the lactating human breast redefined with ultrasound imaging. J. Anat.206, 525–534
• STABLES, D., 1999. Physiology in Childbearing with Anatomy and Related Biosciences, Bailliere Tindall, Edinburgh.
