Repro 11: Breast Flashcards
How many lobules are in each breast?
15-20
Where specifically within the breast is the site of milk synthesis?
The alveoli
Which cells surround the alveoli?
Myoepithelial cells, responsible for milk let down
How does the mammary tissue change during puberty?
Oestrogen causes ducts to sprout and alveoli to develop
What is mammogenesis?
Preparation of breasts
What is lactogenesis?
Synthesis and secretion from breast alveoli
What is galactokinesis?
Ejection of milk
What is galactopoiesis?
Maintenance of lactation
How do the breasts change during pregnancy?
Hypertrophy of ductular lobular alveolar system
Alveolar cells differentiate to become capable of milk secretion from mid gestation (2nd trimester)
Nipples become erect
Breast becomes more sensitive
Alreola enlarges
Montgomery tubercles form
What is the name of the secretion from breast in the first 3 days post birth?
Colostrum
How much colostrum is produced per day?
40ml
How does colostrum differ to mature milk?
More proteins, especially immunoglobulins
More fat soluble vitamins
How does human milk compare to cows milk?
More lactose
Less protein
(“Sweet and semi skimmed”)
How does the high progesterone:oestrogen ratio during pregnancy affect milk secretion?
Favours development of alveoli, but not secretion
How is milk secretion controlled from birth?
At birth steroid hormone levels fall (esp progesterone) which allows the alveolar cells to become responsive to prolactin
How does dopamine affect prolactin secretion?
Inhibits it
Does prolactin have a positive or negative feedback effect on GnRH?
Negative
How is milk production stimulated from the breast?
Suckling stimulates receptors in the nipple -> impulses to brainstem and hypothalamus -> reduces secretion of dopamine and promotes prolactin secretion
Suckling at one feed promote prolactin for production of the next feed
How is milk let down?
Baby suckling causes oxytocin to be released from the PP, which stimulates the myoepithelial cells to contract and squeezes milk out of the breast
What different mechanisms causes lactation to cease?
- lost feedback (not enough suckling)
- pain (increased turgor/ mastitis)
- menstruation (lumpy changes in breast texture)
- prolactin suppression (ergot, diuretics, retained placenta)
- age (gradual shrinkage of mammary glands begins at ~35)