1. Anatomy and Physiology of the Breast
Alison Taylor
Bournemouth University
2006

2. 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

3. Anatomy of Breast The 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

4. Lymphatic system of the breast
Anatomy of the Breast
Blood supply to breast
Lymphatic system of the breast

5. 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

6. The Anatomy of the Breast
©Medela AG, Switzerland, 2006

7. 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

8. 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

9. 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 lobes but the new research indicates that most women have 7-10 lobes per breast

10. ©Medela AG, Switzerland, 2006

11. 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

12. ©Medela AG, Switzerland, 2006

13. Anatomy of the Breast
For diagram of Myoepithelial cells surrounding the alveoli see:
Breastfeeding and human Lactation p (Riordan and Auerbach 1999) or
Myles Textbook for Midwives p751 (Inch 2003)
Oxytocin binds to specific receptors in the myoepithelial cells making them contract

14. 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

15. ©Medela AG, Switzerland, 2006

16. Anatomy of the Breast
For 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:
pages/books/newbab_anatomy.htm
Or visit the website:

17. ©Medela AG, Switzerland, 2006

18. 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)
(average size is about 1.2 ml)
Further research seems necessary

19. ©Medela AG, Switzerland, 2006

20. 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
During puberty , oestrogen and growth hormone stimulate the growth of the mammary ducts. In the second half of each menstrual cycle, progesterone stimulates development of the lactiferous ducts and alveoli. Proliferation of the epithelial tissue is a gradual process at each menstrual cycle.

21. 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
FIRST TRIMESTER: Increased blood flow of 50 % so vessels become more prominent. Lactiferous ducts and myoepithelial cells hypertrophy
SECOND TRIMESTER secretion of colostrum
THIRD TRIMESTER alveoli mature

22. 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

23. 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
Problem is some women have loads of acini cells whilst other have less. Once the acini

24. 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 hours following the birth

25. 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
Prolactin levels seem to be higher between 2am and 6am after frequent breastfeeding in the evening, when the breast is most fully drained. This is therefore a prime time for feeding, not for giving that supplementary bottle to give the mum a rest!!!
Breastfeed given at night gives a greater prolactin surgethan one given during the day
Prolactin and oxytocin make a mother feel relaxed so easy to go back to Sleep after feed in the night
SO prolactin release works on a supply and demand principle. When the baby suckles at the breast Prolactin releasing factor is released by the hypothalamus and stimulates the anterior pituitary gland to release prolactin.
When the baby stops feeding a negative feedback system occurs, prolactin inhibiting factor is released, inhibiting prolactin supply.
PIF is secreted into the breast milk which increases in amount as breast milk accumulates in the breast. This can just occur in one breast too so if baby does not latch correctly and is unable to effectively remove milk from the breast, the build up of PIF will ultimately result in reduced milk supply. Similarly the milk supply can be stepped up again by ensuring the baby removes the milk effectively and regularly.

26. 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
Talk about FIL in a minute!!

27. 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
See separate sheet
Anatomy in Motion

28. 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)

29. Physiology of Lactation
hypothalamus
Anterior pituitary
Posterior pituitary
nerve stimulation
Hormonal control of lactation
oxytocin
prolactin

30. 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

31. 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

32. References
COAD, J., DUNSTALL, M., Anatomy and Physiology for Midwives. Mosby, Edinburgh.
INCH, S., Feeding. IN: HENDERSON, C., MACDONALD, S., eds. Mayes’ Midwifery A Textbook for Midwives, Bailliere Tindall, Edinburgh.
LAUWERS, J., SHINSKIE, D., Counseling the nursing mother. A Lactation Consultant’s Guide. Jones and Bartlett Publishers, Boston
MEDELA Medela breast anatomy images. [online] Switzerland: Medela. Available from:
MOHRBACHER, N., STOCK, J., The Breastfeeding Answer Book. La Leche League International Inc, Schaumburg.
RAMSAY, D.T., KENT,J.C., OWENS,R.A., HARTMANN,P.E., Ultrasound Imaging of Milk Ejection in the Breast of Lactating Women. Pediatrics, 113 (2),
RAMSAY D. T., KENT, J. C. HARTMANN R. A. AND HARTMANN P. E., Anatomy of the lactating human breast redefined with ultrasound imaging. J. Anat.206, 525–534
STABLES, D., Physiology in Childbearing with Anatomy and Related Biosciences, Bailliere Tindall, Edinburgh.