Lactation

Question 1

How do the mammary glands develop before any pregnancy?

Answer 1

At birth - only a few rudimentary ducts present
At puberty - ducts sprout and branch, alveoli begin development
With each menstrual cycle, get changes in breast tissue with changes in oestrogen and progesterone

Question 2

How do the mammary glands develop further in pregnancy?

Answer 2

Hypertrophy of the ductular-lobar-alveolar system
Prominent lobules form
Alveolar cells differentiate to be capable of milk production from mid-gestation

Question 3

How is milk secretion suppressed during gestation?

Answer 3

High progesterone:oestrogen ratio favours growth but suppresses secretion

Question 4

What is secreted straight after birth and what is it made up of?

Answer 4

Colustrum - about 40ml/day
Low concentration of water, fat and sugar
High in protein, particularly Ig for passive immunity

Question 5

Composition of mature milk?

Answer 5

90% water
7% lactose
2% fat
Proteins (lactalbumin and lactoglobulin)
Minerals and vitamins - notably calcium
Energy value = 27Mj/L

Question 6

What happens to the lactalbumin?

Answer 6

Broken down into amino acids for the baby

Question 7

Where are the components of milk synthesised?

Answer 7

In alveolar cells

• fat made in the SER
• proteins secreted via the Golgi
• sugar synthesised and secreted

Question 8

How is secretion controlled?

Answer 8

High progesterone:oestrogen in pregnancy stimulates growth

Secretion is allowed by a fall in steroids and promoted by prolactin

Question 9

Where is prolactin produced and what type of hormone is it?

Answer 9

Polypeptide

Anterior pituitary

Question 10

What controls the secretion of prolactin?

Answer 10

Dopamine from the hypothalamus inhibits it
Stimulated by suckling which is a neuro-endocrine reflex
Suckling at one feed promotes prolactin which causes production of next feed

Question 11

Where does milk for the next feed accumulate?

Answer 11

Alveoli and ducts

Makes breasts turgid

Question 12

How is milk production maintained?

Answer 12

Sufficient suckling stimulus at each feed

Question 13

How is milk production stopped?

Answer 13

No suckling, get turgor-induced damage - compresses blood vessels supplying the alveoli so cannot produce more milk

Question 14

How is milk ejected?

Answer 14

Ejected by let-down reflex
Neuro-secretory reflex of suckling causes oxytocin release from posterior pituitary
Oxytocin causes contraction of myoepithelial cells surrounding the alveoli to contract and milk is squeezed out

Question 15

Benefits of breast feeding?

Answer 15

Babies who are breast-fed have fewer infections

Bonding