22) Lactation

Question 1

Describe the structure of the mammary gland:

Answer 1

15-24 lobulated masses of tissue with fibrous and adipose tissue between lobes

Question 2

Describe the structure of each lobe in the mammary gland:

Answer 2

Made up of lobules of alveoli with myoepithelial cells surrounding

Question 3

Describe development of mammary glands in the fetus:

Answer 3

Invagination of epithelium forming lactiferous duct

Question 4

Why does development cease until puberty?

Answer 4

Requires oestrogen and progesterone

Question 5

Describe development of mammary glands during puberty:

Answer 5

Ducts sprout and branch, and alveoli begin development

Question 6

What stops male mammary gland development?

Answer 6

Prevented by androgens (testosterone)

Question 7

What are the stages of lactation?

Answer 7

Mammogenesis (prep of breast)
Lactogenesis (synthesis and secretion of milk from alveoli)
Galactokinesis (ejection)
Galactopoiesis (maintenance of lactation)

Question 8

What changes occur to the mammary gland during pregnancy?

Answer 8

Hypertrophy of ductular-lobular-alveolar system
Prominent lobules form
Lumina of alveoli dilate
Alveolar cells differentiate (mid pregnancy)

Question 9

What changes occur to the breast tissue near the end of pregnancy?

Answer 9

Nipple becomes erect
Areola enlarges
Montgomery tubercles form
Increased sensitivity

Question 10

What do Montgomery tubercles produce?

Answer 10

Oil (lubricate and protect)

Pheromones (specific to mum)

Question 11

Why isn’t much milk secreted in pregnancy?

Answer 11

High progesterone:oestrogen ratio, with progesterone blocking prolactin receptors

Question 12

What is produced in alveolar cells for lactogenesis?

Answer 12

Fat (SER), protein (golgi) and sugars secreted

Question 13

Why are nurse cells important?

Answer 13

Allow neutrophils and macrophages into alveolar lumen to protect against bacterial infections

Question 14

What substance is secreted from the breast for the first few days?

Answer 14

Colostrum

Question 15

How does colostrum compare to mature milk?

Answer 15

Less water, fat and sugar

More protein and immunoglobulins

Question 16

Why is IgA contained in colostrum?

Answer 16

Coat intestinal mucosa preventing bacteria entering intestinal cells

Question 17

What is the composition of mature human milk?

Answer 17

~90% water
7% lactose
3% fat
Proteins
Minerals and vitamins
Endocannabinoids

Question 18

What are the functions of endocannabinoids in human milk?

Answer 18

Stop baby suckling

Make baby sleepy

Question 19

What causes pituitary prolactin secretion?

Answer 19

Suckling stimulates mechanoreceptors that send impulses to hypothalamus to reduce dopamine secretion, promoting prolactin release

Question 20

What is the effect of prolactin?

Answer 20

Production of milk for next feed

Question 21

How is milk production maintained?

Answer 21

Sufficient suckling stimulus at each feed and regular feed , every 1-3 hours

Question 22

Why does milk production cease if no suckling?

Answer 22

Turgor induced damage to secretory cells

Question 23

Describe the let down reflex:

Answer 23

Suckling activates hypothalamus to release oxytocin via posterior pituitary. Causes myoepithelial contraction to squeeze milk out

Question 24

Give examples of events that maintain lactation:

Answer 24

Suckling
Crying of baby
Fondling baby

Question 25

What are some mechanisms that cause lactation to cease?

Answer 25

Lost feedback (not enough suckling)
Pain - increased turgor or infection
Menstruation
Suppression of prolactin 
Age

Question 26

Why is breast feeding good?

Answer 26

Fewer infections in baby
Bonding (oxytocin release)
Less risk of breast and ovarian cancer
Further contraction of uterus
Weight loss