In the last anatomy session I talked about the anatomy of the breast (or mammary gland), changes through life, and the similarities between the male and female breast. I started off by talking about supernumerary nipples, using James Bond’s fake nipple as a bad example in the film, “The Man With The Golden Gun”. I might have talked a bit of rubbish about Scaramanga, so for better information check Wikipedia: Francisco Scaramanga.
The major components of the breast are adipose tissue (fat), glandular tissue (mostly ducts) and connective tissue. The amount of fat determines the size of the breast, and the connective tissue determines the shape. The connective tissue sheets separating the glandular tissue into lobules form suspensory ligaments (or Cooper’s ligaments) that attach to the anterior and inferior skin of the breast and to the posterior tissue. For most of the time the glandular tissue exists as a system of ducts that open individually at the nipple. The breasts are attached to the chest wall at the fascia overlying the pectoralis major muscles, and an axillary tail of the breast extends up towards the axilla, passing inferiorly to pectoralis major and piercing the deep fascia.
This link to the axilla explains some of the blood supply and lymphatic drainage of the breast. Most of the breast drains lymph laterally to axillary lymph nodes, which are often palpable and accessible to biopsy when concerned about the transfer of malignant cells from a breast mass. The medial parts of the breast drain fluid to parasternal lymph nodes, however, which are deep to the sternum and ribs. As we’re mentioning breast cancer (but you will learn much more about this in other lectures) be aware of the potential involvement of connective tissue. With an inflammatory carcinoma, blockage of lymphatic ducts and oedema, the pull on the suspensory ligaments can be seen on the skin as a dimpling of the breast where the ligaments attach (peau d’orange).
Arteries pass to the structures of the superficial anterior thoracic wall from the axillary artery, and include the lateral thoracic artery, the thoracoacromial artery and the internal thoracic artery. These will all supply blood to the breasts and the muscles beneath, and are matched by veins draining to the axillary vein.
Before puberty the breasts of boys and girls are similar, and the duct system exists in both. With the hormonal changes of puberty (in particular, increased levels of oestrogens) the breasts develop in girls as a secondary sexual characteristic, largely due to increased depositions of fat here. The adult breast will change again with the onset of pregnancy, as the breast becomes prepared for feeding the newborn. The duct system lengthens and becomes surrounded by proliferating epithelial glandular tissue that will make the milk. The breast becomes larger, and the nipple will usually darken and also become larger. After weaning of the baby from breast feeding the glandular tissue of the breast will largely return to the pre-pregnancy state, and the size of the breast will be reduced. Changes to the nipple during pregnancy will also commonly revert to the pre-pregnancy state.
These changes to the tissue within the breast are all caused by particular hormones. As the same tissues exist in the male breast it is possible for these same changes to occur if stimulated by female hormones (see gynecomastia). Men, therefore, are also susceptible to breast cancer.
With the hormonal changes of the menopause, changes to the breast occur again. The glandular tissue will normally atrophy, and the secretory alveoli will disappear. The connective tissue will become weaker and more likely to stretch and the amount of adipose tissue in the breast may increase or decrease, causing marked changes to the shape and size of the breast.
For more information about breast anatomy, development, feeding, and so on, try visiting these websites:
– www.007b.com (extensive, layman’s information about breasts)
– “Breastfeeding Does Not Create Sagging Breasts”, American Society of Plastic Surgeons
– Breast Cancer, Cancer Research UK
