Anatomy and Physiology of the Breast Alison Taylor Bournemouth 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 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

Lymphatic system of the breast 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

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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

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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) Oxytocin binds to specific receptors in the myoepithelial cells making them contract

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

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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: www.laleche.org.uk/ pages/books/newbab_anatomy.htm Or visit the website:www.laleche.org.uk/pages/books/newbab_anatomy.htm

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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

©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 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.

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

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

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 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.

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!!

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

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 Anterior pituitary Posterior pituitary nerve stimulation Hormonal control of lactation oxytocin prolactin

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.