Lecture 7: Lactation and Human Milk Flashcards
What are the functional units of mammary gland?
Alveoli
What does each alveolus have?
A cluster of cells (secretory cells) with a duct in the centre to secrete milk
How are ducts arranged?
Like branches of a tree with each smaller duct leading to 6-10 larger collecting ducts, leading to the nipple
What surrounds the secretory cells?
Myoepithelial cells
What is the role of myoepithelial cells?
Contract under the influence of oxytocin and cause milk to be ejected into ducts
The mammary gland is made up of how many lobes?
15-25 lobes
Where do lobes drain into?
Collection duct
How many lobules make up a lobe?
20-40 lobules
What is each lobule comprised of?
40-100 alveoli
What is the structure of an alveolus?
- Surrounded by myoepithelial cells (contractile)
- Contain milk-producing lactocytes
Where is milk squeezed out of?
Lactocytes in alveoli
Why are alveoli well vascularized?
So that oxytocin may reach them
What happens to ovaries during puberty?
Mature and increase in estrogen and progesterone
How are mammary lobular structures initiated?
By increased estrogen and progesterone
How do mammary lobular structures mature?
- Ductal sustem matures
- Nipple grows
- Fibrous and fatty tissue increase around the duct
When are mammary lobular structures complete?
approx. 12-18 months after menarche (first period)
What hormones allow further preparation of the mammary gland?
Human Chorionic Gonadotropin (HcG) and Placental Lactogen
What stimulates the development of glands that will produce milk?
Estrogen
What happens to tubules and epithelial cells during pregnancy?
Tubules elongate and epithelial cells that line the tubules duplicate
What hormone stimulates the elongation of tubules and duplication of epithelial cells?
Progesterone
What is the role of prolactin during pregnancy?
Stimulates milk production via suckling (baby)
What are the two stages of prolactin levels during pregnancy?
- Breast development
- Inhibition of lactation
How is prolactin involved in breast development?
Stimulates the growth and development of the mammary glands
How is prolactin involved in the inhibition of lactation?
Although prolactin levels are high, high levels of estrogen and progesterone prevents actual production of milk
Why is the production of milk suppressed during pregnancy?
During last 3 mo pregnancy to allow for the body to prepare for milk production
What is the role of oxytocin?
Stimulates ejection of milk from the milk gland into ducts via suckling (baby) - ‘letdown’
What does the contraction of the milk ducts feel like?
Tingling, tightening or shooting pain - lasts about 1 minute
Oxytocin acts on the ?? as well as milk ducts
Uterus
How does oxytocin act on the uterus?
During and after delivery, causing it to contract (back to pre-pregnancy size)
Where is oxytocin released from?
Posterior pituitary
Where is prolactin released from?
Anterior pituitary
Milk ejection is stimulated by…
Oxytocin
Milk secretion is stimulated by?
Prolactin
How many stages of milk production are there?
3
What are the 3 stages of milk production?
Lactogenesis 1, 2 & 3:
1. Colostrum
2. Transitional milk
3. Mature Milk
When is colostrum produced?
Produced directly after birth and in 1st few days
What are the milk production levels of colostrum?
Low