Lactation

Question 1

Describe the mammary glands

Answer 1

Embedded in breasts
15-20 lobulated masses of tissue
- Fibrous and adipose tissue in between
Lobes
- Alveoli
- Surrounded by blood vessels
- Lactiferous ducts (carry the secretions away)

Question 2

Describe the development of the mammary glands.

Answer 2

At birth only a few ducts present
At puberty
- Ducts sprout and branch
- Alveoli begin development

With each menstrual cycle
- Changes in breast tissue with changes in oestrogen &
progesterone (a cyclic growth pattern)

Question 3

Describe the development of the mammary glands during pregnancy.

Answer 3

Substantial further development
- Hypertrophy of ductular-lobular-alveolar system
- Prominent lobules form
- Alveolar cells differentiate to be capable of milk
production from mid gestation

Question 4

Tell me about the mammary glands during pregnancy.

Answer 4

Little milk secreted
High progesterone/oestrogen ratio
Favours growth but not secretion.

Question 5

Tell me about the mammary gland soon after birth.

Answer 5

It produces about 40ml per day of colostrum

• Less water, fat & sugar than milk produced later
• More protein, particularly immunoglobulins

Question 6

What happens to the colostrum from mammary glands over the 2 weeks after birth?

Answer 6

Composition gradually changes to ‘mature milk’

• 90% water
• 7% sugar (lactose)
• 2% fat
• Proteins (lactalbumin, lactoglobulin)
• Minerals & vitamins
• Energy value 27Mj.l/-1
• ‘Sweet and semi-skimmed’ compared to cows milk

Question 7

Describe the synthesis of breast milk.

Answer 7

In alveolar cells

• Fat in smooth endoplasmic reticulum
• Protein secreted via Golgi apparatus
• Sugar synthesised and secreted

Question 8

How is milk secretion controlled in mammary glands?

Answer 8

High progesterone oestrogen in pregnancy stimulates growth
Secretion allowed by fall in steroids
Promoted by prolactin

Question 9

What is prolactin?

Answer 9

Polypeptide hormone
Secreted by anterior pituitary gland
Controlled by dopamine from hypothalamus (inhibits)
Factors promoting secretion of prolactin reduce dopamine secretion (suckling)

Question 10

How is prolactin secretion promoted?

Answer 10

Promoted by suckling
Neuro-endocrine reflex
Suckling at one feed promotes prolactin which causes production of next feed
Which accumulates in alveoli and ducts
- Leads to turgor of the breasts

Question 11

What is the key to maintaining milk production?

Answer 11

Sufficient suckling stimulus at each feed

Milk production ceases gradually if no suckling - turgor induced damage to secretory cells (compressed blood vessels

Question 12

What is meant by milk let down?

Answer 12

Babies do not suck milk out of the breast
It is ejected by a let-down reflex

Myoepithelial cells surround alveoli
Contracted by oxytocin
To squeeze milk out of the breast
Oxytocin released from posterior pituitary

Oxytocin release a neuro-endocrine reflex
From suckling
- Anticipation of feed

Question 13

Is breast feeding good?

Answer 13

Yes
Babies fewer infections
Bonding
Encouragement needed to persist