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
What is the micronutrient make up of colostrum?
High levels of white blood cells, immunoglobulin A, vitamin A - immunity support
What is the macronutrient makeup of colostrum?
High protein, low fat
When is transitional milk produced?
After 1st couple of days (2-3 days of birth) up to approx. 10 days
What are the milk production levels of transitional milk?
Increased milk production, stimulated by maternal hormones - approx. 300-400ml/day
What is the macronutrient makeup of transitional milk?
Higher protein and fat than colostrum - still lower fat than mature milk
When is mature milk produced?
Begins around 10 days postpartum
What are the milk production levels of mature milk?
approx. 780ml/day during exclusive breastfeeding (0-6 months)
As milk matures the amount…
Increases
As milk matures, fat content…
Increases
What is the colour of colostrum?
Thick and yellow
Why is colostrum yellow?
From high concentration of carotenoids
When should breastfeeding be initiated?
Within first hour of birth - just as soon as possible
What feeding reflexes are healthy term infants born with?
- Suck and swallow
- Oral search (open mouth)
- Rooting reflex (turn head side to side)
What happens when suction is created by a babies mouth?
Causes the mothers nipple and areola to elongate and form a ‘teat’
What are the mechanics of milk moving from the milk ducts to baby’s mouth?
Baby’s jaw moves tongue toward areola, compressing it and causing milk to travel out into the mouth
What channels milk to the back of the babies oral cavity?
Peristaltic motions - forming groove in tongue
What are peristaltic motions?
Raising anterior portion of tongue and depresses and retracts posterior portion of tongue
What initiates the swallow reflex?
Receptors in back of baby’s oral cavity
What is the key to successful breastfeeding?
Proper latch and positioning
What is the typical milk production in the first month?
600mL
What is the typical milk production by 4-5 months?
750-800mL
What is the range per day in one infant of breastfeeding?
450 to 1200mL per day
What happens to breastfeeding when a mother has twins/triplets?
Increases to meet demand
When does milk production decline?
After 6/7 months to around 600mL
What percent of breastmilk is water?
88%
Do babies need water?
NO - there is plenty in milk
What is the foremilk?
Start of the milk that comes out is low in fat
What is the hindmilk?
End of the feed which is high in fat
What are the second largest component of BM?
Lipids - provide half the energy; contain cholesterol
What is the lipid content of BM correlated with?
Mothers diet, including trans fatty acid intake
What is the protein content of mature milk?
Relatively low (higher protein in less mature milk)
What are the protein classes in BM?
Whey, casein and non-protein nitrogen (nucleotides)
What is most of CHO in BM made up of?
Lactose (which enhances calcium absorption)
Other than lactose, what are the different types of CHO in BM?
- Monosaccharides (glucose)
- Poly and oligo (gut bacteria)
What are HMOs?
Human Milk Oligosaccharides
What are human milk oligosaccharides?
Complex, indigestible, medium-length CHO with lactose on one end
How are HMOs found?
Free or bound to protein as glycoproteins or lipids as glycolipids
How many oligosaccharides are there?
Over 150
Are HMO’s prebiotic or probiotic?
Prebiotic
How do HMO’s provide immunity to infants?
Stimulate growth of Bifidus bacteria (beneficial) and inhibit Escherichia Coli
How do HMO’s prevent infection?
Prevent binding of pathogenic microorganisms to the surface receptors of their target cell
What are group 1 micronutrient categories in BM?
Affected by maternal status - therefore can be restored
What are group 2 micronutrient categories in BM?
Not affected by maternal status
What do infant stores of group 1 micronutrients look like?
Infant stores are low and readily depleted, depend on adequate supply from BM
What is the iron concentration of human milk?
Average 0.35mg/L - low but highly bioavailable
Absorption of iron in BM vs formula
50% vs 10%
What is lactoferrin?
A protein with an anti-tumour effect, and has been found to significantly inhibit the growth of some cancerous cells
What are the benefits of lactoferrin in human milk?
- Immunity/infection resistance
- Binds to iron stores to help absorption
What is a major determinant of anemia risk during infancy?
Infants reserves at birth
What is sustained IDA associated with?
Irreversible and detrimental effects on intellectual and motor performance - restricts linear growth
How much of maternal circulating vitamin D is transferred into breastmilk?
20-30%
What can low vitamin D status in infants result in?
Rickets = soft, weakened bones
Vitamin D in BM vs Formula
20-70 vs 200
Why is it hard to increase the vitamin D content of BM?
Group 2 nutrient - maternal intake needs to increase a lot for BM content to increase only a small amount
What would a dose of between 200-500 IU per day of vitamin D do for BM?
Basically nothing, needs to be higher to support the infant
What is the recommendation for Vitamin D supplementation?
Give a supplement to baby itself until infant is mobile, or up to 12 months of age
