Breast Physiology And Lactation

Question 1

What are the suspensorio ligament in the breast called and how does age affect them?

Answer 1

Cooper’s ligaments

Coopers droopers —> loose fibrous connective tissue causes droopy breasts

Question 2

How does the breast change with age?

Answer 2

Loss of glandular tissue to where it becomes extinct.

There is more fat so it’s easier to see a lesion

Question 3

Describe mammogenesis

Answer 3

• initial rudimentary duct system that has no buds and are just tubes
• puberty —> ductal elongation and bifurcation and formation of buds (immature alveoli) at the ends

Question 4

What are the 2 main hormones involved in mammogenesis?

Answer 4

Oestrogen - causes elongation and bifurcation of ducts and increase fat tissue

Progesterone - cause formation of immature alveoli at the ends of ducts

Question 5

What is the hierarchy of mammary gland structure?

Answer 5

Alveoli - sites of milk synthesis

Lobules - containing 10-100 alveoli

Lobes - contain lobules

Loves drain into 10 major lactiferous ducts which open to the nipple

Question 6

How many major lactiferous ducts are there?

Answer 6

10

Question 7

Describe the structure of a lobule

Answer 7

A collection of alveoli with a terminal intra-lobular duct

Alveoli contain acini cells (columnar epithelium) which produce milk

Alveoli are surrounded by myoepithelial cells and capillaries

Question 8

How many nipple pores are there?

Answer 8

10 nipple pores

Question 9

What breast changes occur during pregnancy?

Answer 9

• increased size due to hypertrophy and proliferation of ducts (oestrogen) and alveoli (progesterone and oestrogen)
• terminal alveoli differentiate into secretory cells
• more vessels = bluish veins
• darker areolae - target for baby
• Montgomery’s tubercles - bumps that keep nipple moist and produce odour to attract baby

Question 10

How do hormones change through pregnancy?

Answer 10

hCG -> increases and peaks at 10-13 weeks and slowly declines

Progesterone, prolactin and oestrogen gradually increase (increase faster in last 10 weeks)

Question 11

What hormone does oestrogen stimulate release of?

Answer 11

Prolactin (from anterior pituitary)

Oestrogen stimulates hypothalamopituitary axis

Question 12

Stage 1 lactogenesis

Answer 12

Occurs in mid-pregnancy

• production of lactose, casein and a-lactalbumin (milk specific proteins) which are reabsorbed into the blood
• high progesterone in mid pregnancy inhibits milk secretion

Question 13

What effect does progesterone have on milk secretion in mid pregnancy?

Answer 13

Progesterone inhibits prolactin receptors in alveolar cells

Question 14

What is given in miscarriage to stop milk production?

Answer 14

Dopamine - inhibits prolactin production and action

Question 15

A what hormonal changes take place at birth?

Answer 15

• decreased oestrogen, progesterone and hCG

- increased prolactin (initiates lactogenesis II)

Question 16

Lactogenesis II

Answer 16

Increased milk volume

Increased lactose, IgA, lactoferrin and oligosaccharides

(Milk must be removed from breast within 3 days postpartum for lactation to continue)

Question 17

What effect does suckling have?

Answer 17

• increases prolactin and oxytocin

Prolactin —> milk production
Oxytocin —> Milk ejection (contraction of myoepithelial receptors)

Question 18

What is galactokinesis?

Answer 18

Discharged of milk caused by suckling

1. Neural afferent reflex arc
   - mechanosensory receptors in nipple send ap to hypothalamus
2. Endocrine response in hypothalamus
3. Hypothalamus causes:
   - anterior pituitary —> prolactin
   - posterior pituitary —> oxytocin

Question 19

How is lactation maintained (galactopoiesis)?

Answer 19

Milk production slows when milk accumulates as there is more feedback inhibitor of lactation (FIL)

Question 20

Why does an emptier breast have higher fat milk?

Answer 20

Milk fat globules absorb to alveolar membranes and are displaced only when gland is near empty

Question 21

What is lactational amenorrhoea?

Answer 21

The disruption of the menstrual cycle due to breastfeeding

Breastfeeding disrupts the pulse pattern of gonadotropin-releasing hormone (GnRH) from the hypothalamus = less LH = no ovulation

Question 22

Describe the composition of breast milk

Answer 22

Week 1 = colostrum

• sticky and yellow
• low in fat and lactose
• high proteins and minerals
• immunoglobulins

3 weeks = mature

• higher calories
• high fat, sugars and protein

Question 23

What are the immunological benefits of breast milk? (Hint: 3 agents)

Answer 23

Antimicrobial agents

Anti-inflammatory agents

Immunomodulating agents

Question 24

What are the 2 main milk proteins?

Answer 24

Casein, a-lactalbumin

- nutritional benefits

Question 25

What is the main antibody in breast milk?

Answer 25

IgA antibodies

- prevents colonisation of gi, resp. And genitourinary tracts with bacteria

Question 26

What is lactoferrin?

Answer 26

• Essential for growth of good microorganisms
• blocks absorption of viruses
• intestinal growth and repair
• decreases pro-inf cytokines

Question 27

Lysozyme

Answer 27

• cell wall lysis
• binds endotoxin
• increases IgA

Question 28

A-lactalbumin

Answer 28

Promotes bifidobacterium growth

Question 29

Casein

Answer 29

Promotes bifidobacetrium growth and inhibits bacterial adhesion