Breast anatomy Flashcards
General features of breasts
- Modified and highly specialised sweat glands
- No special capsule or sheath
- Both males and females have them but they are well developed in females
- Breast size and shape result from genetic, racial and dietary factors
Location and relations of the breasts
- Extent: Breasts start at the 2nd or 3rd rib and extend to the 6th rib
- Transverse: Sternal edge to the mid-axillary line
- Axillary tail (of spence) or process – a small part of breast may extend towards axillary fossa
- What fascia does 2/3rds of the breast rest on?
- And what separates the two?
- What fascia does the other 1/3rd of the breast rest on?
- Deep pectoral fascia that covers the pectoralis major muscle
- The Retromammary space = loose areolar tissue
- 1/3 rests on the fascia covering the serratus anterior
Which ligament is responsible for supporting the breast by attaching it to the dermis and supporting the lobules of the gland?
The suspensory ligament of cooper
What is the Areola?
- A sebaceous gland (not associated with the hair follicles though)
- The pigmented area around the nipple - contains numerous sweat and sebaceous glands
- Enlarges during pregnancy
- Oily material secreted by the sebaceous glands provides a protective lubricant for nipple and areola during breast feeding
How many lobes are there in each breast?
- Adult women have 15-20 lobes of glandular tissue (parenchyma) in each breast
- Each lobe has 20-40 lobules
What drains the lobules in the breast?
Lactiferous duct - open independently on the nipple
Each duct has a dilated portion called the lactiferous sinus
Describe the anatomy of the nipple
- No fat or hair on the nipple
- Contains collagenous dense connective tissue, elastic fibres and bands of smooth muscle (contracts when erected)
- The tips of the nipples are fissured with lactiferous ducts opening into them
- Position is variable but around 4th intercostal space
What are the 4 quadrants of the breast?
- Superolateral quadrant - the axillary tail is an extension of breast tissue in the superolateral quadrant
- Inferolateral quadrant
- Inferomedial quadrant
- Superomedial quadrant
Male breast
- Rudimentary throughout life
- Formed by small ducts without lobules or alveoli
- Little supporting fibroadipose tissue
- Temporary enlargement => development of rudimentary lactiferous ducts in newborn & during puberty = gynaecomastia
Breast terminology
- Polymastia –An extra breast
- Polythelia – An extra nipple
- Athelia or Amastia - Absence of nipple or breast
What is the blood supply to the breast?
Medial aspect of the breast is via the internal thoracic artery (also known as internal mammary artery) – a branch of the subclavian artery.
The lateral part of the breast receives blood from four vessels:
- Thoracoacromial branches
- Lateral thoracic artery
- Lateral mammary branches
- Mammary branch
Venous supply/drainage of the breast
The veins of the breast correspond with the arteries
They drain into the axillary and internal thoracic veins.
The function of breast tissue is mainly controlled by what?
Hormones i.e oestrogen, progesterone, prolactin (milk secretion), corticosteroids etc
What nerves supply the breast and what are there main functions?
Anterior and lateral cutaneous branches of 4-6th intercostal nerves
- Mainly sensory fibres in the skin of the breast
- Also sympathetic fibres to the blood vessels and to the smooth muscle around the nipple for erection
Where does the majority of lymph drain into?
The axillary lymph nodes in the lateral quadrants. More than 75% of lymph drains here
Where does lymph from the medial quadrants drain to?
Parasternal nodes or to opposite breast
How do surgeons locate the Sentinel lymph node?
Using a radiolabelled colloid and a blue dye is injected at the time of surgery.
The combination of the two provides the most accurate means of localising the Sentinel node.
Structure of the lobules within soft tissue of the breast
- The soft tissue in breasts are made up of lobes which contain a network of glandular tissue consisting of branching ducts and secretory lobules in a connective tissue stroma.
- The connective tissue stroma that surrounds the lobules is dense and fibrocollagenous, whereas intralobular tissue has a loose texture.
What is the functional milk secretory component of the breast?
The terminal duct lobular unit
- A collection of alveoli arising from one terminal duct along with the surrounding intralobular stroma = a terminal duct lobular unit (TDLU)
Normal breast histology
Which 2 types of cells line ducts and acini/alveoli?
Luminal epithelial cells
Myoepithelial cells
Age related changes seen in the breasts
Pre-puberty
- Neonatal breast contain lactiferous ducts but no alveoli
- Until puberty, little branching of the ducts occurs
- Slight breast enlargement reflects the growth of fibrous stroma and fat
Puberty
- Branching of the lactiferous ducts
- Solid, spheroidal masses of granular polyhedral cells (alveoli)
- Accumulation of lipids in the adipocytes
Post menopausal
- Progressive atrophy of lobules and ducts
- Fatty replacement of glandular tissue
What changes occur in the breast during pregnancy?
- Enlarged lobules
- Acini are dilated
- Epithelium vary from cuboidal to low columnar
A = acini
Lo = Lobules
E = epithelial cells
S = septa
Lactating breast histology
- Acini distended with milk
- Thin septa between the lobules
