Breast Anatomy Flashcards
What kind of gland is the breast?
apocrine
What are the parenchymal elements of the breast?
lobules, lobes, ducts, acini
What are the stromal elements of the breast?
skin, connective tissue, fat
Describe the make-up of a lobe (lobe to lactiferous sinus)
Lobe to numerous lobules
Lobules drained by small branching ducts
Ducts converge & form main lactiferous duct
MLD widens below nipple at lactiferous sinus
What is the lactiferous sinus?
reservoir for milk secretions
What happens at week 4 of gestation?
Paired mammary ridges develop from ectoderm
Milk lines disappear throughout the body except for where?
fourth intercostal space where mammary glands develop
What occurs at week 5 gestation?
mammary buds are visible
What happens between weeks 7-12 gestation?
Mammary buds branch several times to form mammary lobules
What happens at week 20 of gestation?
Small lumina develop within buds which elongate and become lactiferous ducts
When do primary breasts develop? What hormones influence this?
third trimester, placenta hormones
How many lobes with lactiferous ducts are developed at full term?
15-20
What develops from mesoderm?
fibrous connective tissue and nipple
What develops from ectoderm?
areola
What can occur in newborns due to maternal hormones?
mild breast tissue prominence and possible milk secretion
Where is the majority of glandular tissue in the breast?
upper outer quadrant
What is the functional unit of the breast?
Terminal duct lobular unit: extralobular terminal duct & lobule
Lobules contain intralobular terminal ducts that do what?
Drain 30-50 blind-ended ductules
What is the smallest functional element of breast tissue?
acini, tiny saccular milk-producing glands
What is fibroglandular tissue?
all non-fatty breast tissue
What components make up ducts?
Inner: epithelial cells
Myoepithelial
Basement membrane
What ductal structure aids in milk transport?
contractile fiber cells
What is loose intralobular stroma?
Connective tissue surrounding small ductal structures in lobules, provides lobular shape/definition
What is dense extralobular stroma?
Between lobes & lobules, supports larger ductal structures
What are Cooper’s ligaments?
dense connective tissue that separates fat, lobules, and lobes
Where do Cooper’s ligaments run?
From deep part of superficial fascia to skin
What are the 6 layers of the breast & posterior?
- skin
- subcutaneous fat (premammary)
- mammary zone (fibrous & connective tissue)
- retromammary zone (mainly fat)
- muscle
- thoracic cage
Breast skin is slightly thicker in who?
younger females
How thick is the skin typically?
2-3 mm
What are Montgomery’s glands?
sebaceous glands that appear as small bumps on areola
The subcutaneous fat layer is located between what? It does not extend below what structure?
Skin & breast parenchyma, doesn’t extend below nipple
What does the subcutaneous fat layer look like on US?
homogenous, mid-level gray lobules separated by echogenic ligaments
What 3 layers are Cooper’s ligaments seen in and which one are they primarily seen in?
Primary: subcutaneous, mammary, retromammary
Where is the superficial fascia? Where is the deep fascia?
Superficial: within subcutaneous fat, anterior to mammary zone
Deep: within retromammary space, posterior to mammary zone
Where is the mammary zone located?
within the superficial fascia and two fatty layers
Where is the mammary zone thicker?
UOQ
What is the Tail of Spence?
normal extension of tissue toward axilla
The mammary zone is made up of epithelial and stromal tissue. What elements are in each category?
Epithelial: acini, lactiferous ducts, epithelial cells, TDLUs, 15-20 lobes
Stromal: connective tissues ex. Cooper’s ligs, loose & dense connective tissue) & adipose tissue
What is the composition of the mammary zone before puberty compared to during adolescence?
Pre-puberty: mainly fatty, limited glandular tissue
Adolescent: increasing glandular tissue, fat decreases
What happens to the mammary zone during adulthood and post menopause?
Adult: varying glandular tissue, proliferation & involution each period, mild ductal dilatation
Post-menopause: decreasing glandular tissue & replacement with fat
How can HRT in post-menopausal women affect the composition of the mammary zone?
It can prohibit involutional changes (replacement with fat)
Where is the retromammary space located? What does it contain?
B/w posterior mammary zone & pectoral muscles, contains deep fascia & a smaller amount of fat lobules than subcutaneous layer
How does the retromammary space appear on US?
thin, mid-level gray parallel to pectoral muscle
What surrounds the chest muscles?
pectoral fascia
Where is the pectoralis major located?
- Beneath pectoral fascia
- Arises from clavicle & sternal costal cartilage
- Thickens beneath UOQ & attaches to humerus
Where is the pectoralis minor located?
- Deep to pec major
- Arises medially from 3, 4, 5 ribs, attaches to scapula
The pectoralis minor serves as an important landmark for what?
the levels of axillary lymph nodes
Where is the serratus anterior located?
Posterior to UOQ
To make sure that you have captured all tissue layers, what landmark should be seen in the far field of your image?
top of rib
What minimum depth should you take images at for image quality?
2.5 cm
Where do lymphatic channels originate in the breast?
Within connective tissue and lactiferous ducts
The lymphatic channels in the breast flow toward?
the subareolar plexus
Flow through the subdermal lymphatic channels is towards?
centrifugal toward outer lymphatics
Where does 75% of lymphatic drainage occur?
along inf border of pectoralis major muscle from posterior intercostal nodes to axillary lymph nodes
Where does 20% of lymphatic drainage occur?
Along the inner aspect of the breast posterior to sternum by smaller nodes of internal mammary chain
Where does 5% of lymphatic drainage occur?
Along the inferomedial aspect of breast by subcutaneous nodules
Where are level I, II and III lymph nodes located?
I: lateral to pec minor
II: deep to pec minor
III: med to pec minor
What is axillary lymph node dissection?
removal of level I & II nodes, typically with total mastectomy
How are level III nodes removed?
Radical mastectomy which excises pec minor
What arteries supply the breast?
Lateral thoracic artery and internal mammary artery
Where is the lateral thoracic artery located?
Arises from axillary artery, runs inf along lat border of pec major & gives rise to lat mammary branches
Where is the internal mammary artery located?
arises from subclav artery, posterior to cartilage of upper ribs lat to sternum, gives rise to med mammary branches
What drains the breast?
Deep & superficial venous systems
What does the deep venous system in the breast drain into?
Drains into internal mammary, axillary, subclav, and intercostal veins
What is the superficial venous system?
beneath superficial fascia and communicates from rt to lt breast
What nerves supply the breast?
Lat & ant cutaneous branches of intercostal nerves 2-6 supply majority, supraclav nerve may innervate superior/superolat parts
