Anatomy and Histology of the Breast

Question 1

How are breasts different in non-lactating mothers?

Answer 1

They lack the glandular components and instead have fibrous components.

Question 2

What do suspensory ligaments do?

Answer 2

They keep the breasts close to the body and prevent sagging.

Question 3

What are the external components of the breast?

Answer 3

The body

The axillary extension/process that extends to the armpit.

Question 4

What is the function of areolar glands?

Answer 4

They have sebaceous glands that produce sebum to prevent chaffing of the breasts.

Question 5

What structures make up the breast internally?

Answer 5

The lobes (consist of lobules containing ductoalveolar components)

4 - 18 lactifrous ducts which meet at the lactiferous sinus.

Question 6

What are the structures contained in the nipple that can be seen on a cross-section?

Answer 6

Stratified squamous epithelium (keratinized)

Sebaceous glands (Not associated with hair follicles because sebum is secreted directly onto epidermal surface)

Dense CT with smooth muscle bundles. Smooth Muscles contract in response to cold, touch, and sexual arousal.

Question 7

What does cross section of inactive human breast show on histology?

Answer 7

Mainly duct elements and connective tissue

Cyclical changes in non-pregnant women (Some duct growth, limited lobular alveolar development, fluid accumulation in CT)

Question 8

What determines breast size?

Answer 8

The amount of fat in the breast.

Question 9

What changes cyclically in breast?

Answer 9

The lumen of the ducts in the breast fill with fluid if under the stimulation of oestrogen.

Question 10

What does cross section of active human breast show on histology?

Answer 10

Less CT

Lobulo-alveolar development

Lobules separated by septa of dense CT

Myoepithelial cells are located around alveolar cells to produce milk

Question 11

What do myoepithelial cells do? What hormone do they respond to?

Answer 11

They are located around alveolar cells and are important for milk production and secretion. (myoepithelial cells contract around the alveolar cells to release milk)

They respond to prolactin

Question 12

What arteries supply the breasts?

Answer 12

Laterally: Branches from the axillary artery

Medially: Branches from the internal thoracic artery

Question 13

What veins drain the breasts?

Answer 13

Veins parallel the arteries

Question 14

What lymph nodes drain the breasts?

Answer 14

Superior and lateral: Axillary nodes receive 75% of drainage.

Medial: Parasternal nodes

Inferior may be some drainage into the abdomen.

Question 15

What nerves innervate the breast?

Answer 15

2nd to 6th intercostal nerves give anterior and lateral cutaneous branches.

Nipple is innervated by the 4th intercostal nerve.

Question 16

What embryological tissue are breasts derived from?

Answer 16

Embryologically derived from ectoderm; visible ~4 weeks.

Paired epidermal thickenings extending from mid-axilla to inguinal region -> milk line.

Question 17

What is witches milk?

Answer 17

Secretory activity of newborn breasts due to exposure to mother’s hormones. This is normal

Question 18

How does breast size change during puberty?

Answer 18

Due to increase in amount of fat and the proliferation of the ducts.

Rudimentary lobules of alveoli develop in response to progesterone.

Question 19

What are the stages of growth of breasts during puberty?

Answer 19

1) Preadolscent
2) Breast bud stage - breast and papilla elevated; increase in areolar area
3) Increase in amount of breast tissue; increased pigmentation of areola
4) Areola and papilla form secondary mound above the level of the breast
5) Mature stage; erect papilla projecting above areolar, classification is independent of breast size.

Question 20

What stimulates fat increase in the breasts?

Answer 20

Oestrogen

Question 21

What stimulates lactiferous duct growth in the breasts?

Answer 21

Oestrogen

GH

Adrenal steroids

Question 22

What stimulates rudimentary lobules of alveoli?

Answer 22

Progesterone

Question 23

What are the stages of breast development during pregnancy to make it ready for lactation?

Answer 23

Proliferation (continues during gestation, breast milk is produced early during gestation to account for premature babies)

Lactogenesis (Secretory activation which occurs 40 - 48 hours after birth)

Lactation (Maintained by milk removal i,e infant demand) [prolactin controls milk production and oxytocin milk ejection]

Involution (Induced by accumulation of milk, loss of epithelial cells, gradual replacement of ducts and alveoli with stromal and fat tissue, involution process takes ~3 months due to lack of milk being consumed by the baby)

Question 24

How is lactogenesis initiated?

Answer 24

Drop in progesterone and oestrogen at parturition releases the inhibition on secretory alveolar cells. (in other animals prolactin is produced way earlier)

*Increase in milk volume by 50ml/day on day 2 to 500 ml/ on day 4 post-partum

Question 25

What is the normal maximal yield of milk per day?

Answer 25

~850ml/day or more

Question 26

What happens to the breast after menopause?

Answer 26

Structural atrophy (reduction of oestrogen)

Question 27

How is milk secretion hormonally controlled?

Answer 27

Nipple stimulation due to suckling sends signal through spinal nerve to hypothalamus to inhibit dopamine which makes it secrete prolactin from anterior pituitary.

Prolactin is released into the blood and acts on breasts to secrete milk.

Question 28

How is milk ejection controlled?

Answer 28

Nipple stimulation due to suckling

Spinal nerves relay message to the brain

Hypothalamus releases oxytocin into posterior pituitary where it is released.

Oxytocin is released into bloodstream and results in contraction of myoeptihelial cells around the alveoli.

This reflex can be conditioned and suppressed by stress.

Question 29

What is lactational amenorrhoea?

Answer 29

Temporary suppression of ovarian activity (+menstrual cycling) during breast feeding.

Question 30

Why does lactational amenorrhoea take place?

Answer 30

Normally: Women have pulsatile secretion of GnRH and LH within ~2 - 3 weeks and so ovulation takes place within 6 weeks.

During lactation: Lactation disrupts pattern of GnRH which results in LH levels being higher constantly.

Ovarian activity depends on changes in GnRH and LH.

Question 31

Why do pregnant women have a stop in their cycle?

Answer 31

High oestrogen and progesterone inhibit production of GnRH and LH which inhibits follicular development and ovulation.