Breast

The breast is an apocrine gland seen in both males and females. However, in females it has a specific function which is the production of milk.

Composition

The breast has an inhomogeneous structure which is predominantly composed of adipose tissue and glandular tissue. In addition, there are also suspensory Cooper's ligaments and connective tissue such as collagen and elastin. The adult breast has nearly 14-18 lactiferous lobes which drain into lactiferous ducts which further converge to drain at the nipple-areola complex

The glandular parenchyma is oestrogen dependent, thus on attaining menopause the glandular parenchyma atrophies. 

Location

The breasts are seen to overlie on the pectoralis major muscles and extend from the level of the second-to-sixth ribs:

  • superior: clavicle
  • inferior: middle of sternum
  • lateral: midaxillary line
  • medial: sternum

There is often an extension of breast tissue into the axilla called the axillary tail

  • thoracic intercostal nerve T3-T5
  • supraclavicular nerve from the cervical plexus

See main article: lymphatic drainage of the breast

During embryological development, breast tissue first appears as ectoderm ridges during the 6th week of gestation. This ridge grows thicker and leads to mesodermal compression. With further proliferation of the ectodermal cells there is a growth of the same into the mesodermal layer leading to a formation of clusters which further form lobules. In the fifth month of gestation some cords of ectodermal cells sprout from each of these lobules with the central parts undergoing apoptosis leading to formation of ducts. Similarly on the surface apoptosis occurs leading to formation of pits which protrude through the nipples after connecting with the formed ducts. 

Mammography
  • a wide variation of homogeneously dense, milky structures (representing glandular tissue) interrupted by areas of curved or round radiolucent fat 
  • Cooper's ligaments appears as curved, linear radiopacities
  • duct system is not normally visualised except near the nipple 2

See articles: mammography views; breast density

Ultrasound
  • glandular tissue appears variably hyperechoic and fat appears hypoechoic
  • ducts appear as regular interspersed tubular, hypoechoic structures
  • Cooper's ligaments appear as hyperechoic, linear structures and may cause acoustic shadowing 2-3
  • nipple can also cause acoustic shadowing, sometimes creating a pseudomass 3

See article: breast ultrasound.

MRI
  • T1: fat has moderate high signal; glandular, ductal and connective tissue has low signal 
  • T1C+: normal breast tissue is typically non-enhancing 2

See article: breast MRI.

Thoracic anatomy
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Article Information

rID: 25714
System: Breast
Section: Anatomy
Tag: breast
Synonyms or Alternate Spellings:
  • Mammary gland
  • Breast anatomy

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Cases and Figures

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    Figure 1: normal annotated mammogram
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    Figure 2: normal annotated mammogram
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