Breast Anatomy and Lactation

Question 1

Describe the three main types of cell in the breast

Answer 1

1. Adipocytes
2. Stroma (fibroblasts/immune cells; structural support)
3. Epithelial cells (form lobules and ducts)

Question 2

Describe breast development during puberty. What signals trigger/support this?

Answer 2

• Ductal tree proliferates through fat, as Terminal End Bud invade, and differentiate into myoepithelium and branches out
• When reaches end of fat pad, replaced with low-proliferation cells
• This is supported by oestrogen, progesterone, ECM components, and other growth factors

Question 3

How are breasts affected by the menstrual cycle?

Answer 3

• Progresterone stimulates alveolar development, just like the endometrium
• And, like elsewhere, in the absence of fertilisation, low progesterone

Question 4

How are breasts affected by/across pregnancy?

Answer 4

• Alveolar proliferation (prolactin & progesterone)
• Mid-pregnancy, a sphere-like layer of epithelial cells forms
• Late pregnancy, milk genes are expressed and cytoplasmic lipid droplets are formed
• At birth, tight junctions close between alveolar cells, allowing for the lobules/ducts to function as designed

Question 5

What hormonal conditions cause breast milk production? Why does this make sense?

Answer 5

• High prolactin, low progesterone
• Signals pregnancy + delivery of the placenta

Question 6

How is breast milk production regulated?

Answer 6

• Initially, huge amounts produced during lactation switch (WIT?)
• Later, milk removal triggers production, and a supply-demand balance is created

Question 7

What does breast milk contain?

Answer 7

• Lactose and milk fat
• Antimicrobial factors
• Growth factors
• Digestive enzymes
• Hormones
• Minerals (how can this effect bones?)

Question 8

Describe endocrine control of lactation/breast feeding. What non-obvious things can cause it?

Answer 8

• Suckling increases production of prolactin (milk production) and oxytocin (milk ejection)
• This increases suckling
• Positive feedback loop ensues
• Can also be caused by crying baby/think about baby

Question 9

What is breast involution? What triggers it?

Answer 9

• When milk builds up inside the gland, it’s triggered (baby must no longer be breastfeeding)
• First (reversible phase) involves apoptosis of alveolar/epithelial cells
• Second (irreversbile) phase surrounding stroma is remodelled also

Question 10

Describe neurovascular supply of breast

Answer 10

• Internal thoracic and axillary a/v
• Anteiror/lateral cutaneous branches of 2-6th intercostal nerves (specifically, fourth intercostal for nipple)

(A/L easy to remmber, cutaneous easy to remember, 26 hard to forget, and 4 is the middle)

Question 11

Describe lymphatic drainage of the breast (think: which nodes did halsted remove first in radical mastecotmy)

Answer 11

• 2 breasts, 2 major drainage pathways
• Both first drain into the subaerolar plexus
• Then, most goes pectoral -> axillary -> subclavian (75%)
• Otehr 25% goes parasternal -> bronchomediastinal trunk