Repro 11.1 Lactation

Question 0

What are the lobes of the mammary gland made up of?

Answer 0

Lobules of alveoli
Blood vessels
Lactiferous ducts

Question 1

What does the mammary gland consist of?

Answer 1

15-20 lobulated masses of tissue

Fibrous connective tissue and adipose tissue

Question 2

What type of ducts are the Lactiferous ducts?

Answer 2

Exocrine, blind ended

Question 3

What is the site of milk synthesis?

Answer 3

Alveoli

Question 4

What are myoepithelia?

Answer 4

Smooth muscle cells surrounding the alveoli responsible for milk let down

Question 5

How do mammary glands differ at birth and post-puberty?

Answer 5

Few ducts at birth
At puberty oestrogens cause the ducts to sprout and branch and the ends form masses of cells that later become alveoli. Cyclic changes of the breast under the influence of oestrogen and progesterone during the menstrual cycle - endocrine ducts grow in literal phase and size may grow up to 20%

Question 6

What happens to the breast during pregnancy?

Answer 6

Rising titres of oestrogen and progesterone stimulate considerable hypertrophy of the ductular-lobular-alveolar system. Prominent lobules form and the lumina of alveoli become dilated. The alveolar cells differentiate in mid-pregnancy. Cells are capable of secretion at this time and contain substantial amounts of secretory material but milk is not secreted in significant quantities.

Question 7

What is colostrum?

Answer 7

Milk secreted by mammary glands just after giving birth (first week or so). Contains antibodies and is lower in fat but higher in protein than normal milk

Question 8

Why is IgG from breast milk not digested in the babies GI tract?

Answer 8

Neonatal gut is open so it crosses without digestion

Question 9

What is the composition of mature human milk?

Answer 9

Water - 90%
Lactose - 7%
Fat - 2%
Proteins including lactalbumin and lactoglobulin
Minerals - Ca Fe Mg K Na P S (can deplete maternal stores)
Vitamins - A B B2 C D E K
pH 7

Question 10

What is the energy value of mature human milk?

Answer 10

27MJ/L

Question 11

Where is milk fat synthesised?

Answer 11

Smooth enroll aspic reticulum of alveolar cells and passes in membrane bound droplets towards the lumen

Question 12

Where is milk protein secreted from?

Answer 12

Passes through Golgi apparatus and is released by exocytosis

Question 13

What are the benefits of breast feeding?

Answer 13

Fewer infections

Bonding

Question 14

What favours development of the alveoli in pregnancy?

Answer 14

High progesterone/oestrogen

Question 15

What causes lactation after birth?

Answer 15

Progesterone levels fall precipitously and oestrogen levels fall less so. This leads to alveolar cells becoming responsive to prolactin.

Question 16

Where is prolactin secreted from?

Answer 16

Lactotrophs in the anterior pituitary gland

Question 17

What effect does suckling do?

Answer 17

Initiates and maintains secretion by a neuro-endocrine reflex. Mechanically stimulates receptors in the nipple
Impulses pass to the brainstem and to the hypothalamus to reduce secretion of dopamine and vasoactive intestinal peptide, so promoting prolactin secretion

Question 18

What determines the amount of milk produced?

Answer 18

Prolactin - determined by the amount of suckling

Question 19

When is milk produced?

Answer 19

Continuously between feeds and accumulates in the ducts, increasing the turgor of the breast

Question 20

How does milk let down occur?

Answer 20

Dramatic increase in the secretion of oxytocin from the posterior pituitary gland. This contracts myoepithelia which eject the milk. It is NOT suckled out of the breast

Question 21

What happens if suckling stops?

Answer 21

Milk production gradually ceases, in part due to lack of prolactin levels, in part due to turgor-induced damage to the breast.
Milk production can also be suppressed by steroids

Question 22

Why is pregnancy unlikely while breast feeding?

Answer 22

Prolactin reduces fertility

Question 23

What happens to the breasts after ovulation?

Answer 23

Cell proliferation and stromal oedema increase

With menstruation see decrease in size of lobule

Question 24

What happens to lobules after cessation of lactation?

Answer 24

Atrophy of lobules but not to former levels

Question 25

What happens to breast tissue with increasing age?

Answer 25

Terminal lobular units decrease in size and number, interlobular stroma is replaced by adipose (mammograms easier to interpret)