Lactation

Question 1

List the constituents of human milk

Answer 1

90% water
7% lactose
2% fat
Proteins - lactalbumin, lactoglobulin 
Minerals, vitamins

Question 2

Describe in outline, the mechanisms of production of milk in the lactating breast

Answer 2

In alveolar cells:
Fat - SER –> membrane bound droplets
Protein - Golgi –> exocytosis

Question 3

Describe the hormonal control of the growth and development of mammary tissues

Answer 3

Birth - only a few ducts present
Puberty - ducts sprout and branch
During menstrual cycle - changes in tissue due to changes in oestrogen/progesterone
Pregnancy - hypertrophy of ductular-lobular-alveolar system (prominent lobules form, alveolar cells capable of milk production, secretion of milk suppressed, increased progesterone:oestrogen ratio)

Question 4

Describe the hormonal control of milk production

Answer 4

High progesterone/oestrogen –> milk synthesis

Low steroid levels after birth –> milk secretion

Question 5

Describe the control of milk secretion

Answer 5

Low steroid levels due to delivery of placenta
Prolactin secretion promoted by suckling - mechanical stimulation of nipple, neuroendocrine reflex (lower dopamine)
Suckling at one feed promotes production at next feed (accumulates in alveoli and ducts –> turgor)

Question 6

Describe the control of milk let down

Answer 6

Myoepithelial cells surround alveoli
Contracted by oxytocin –> squeeze milk out of breast
Neuroendocrine reflex from suckling (anticipation of feed, becomes a conditioned reflex)

Question 7

Where is prolactin synthesised and how it is controlled

Answer 7

Secreted by anterior pituitary
Controlled by dopamine from hypothalamus (inhibits)
Lactotrophs make prolactin spontaneously (controlled by inhibition)

Question 8

What is colostrum?

Answer 8

The milk secreted soon after birth
49 ml/day
Lower in water, fat, sugar than mature milk
Increased proteins, particularly IgG (passive immunity)

Question 9

Describe the mechanisms which produce cessation of lactation

Answer 9

If suckling stops (naturally or due to decreased production of steroids)
Low prolactin
Turgor induced damage

Question 10

Describe the structure of the normal breast, including its topography

Answer 10

Mammary glands - embedded in breasts, 15-20 lobulated masses of tissue, fibrous tissue connects loves, adipose tissue in between
Loves are made up of alveoli, blood vessels, lactiferous ducts