9.1: Breastfeeding and Human Lactation

Question 1

How does the weight of the mammary gland change during lactation?

Answer 1

More than doubles

Question 2

Describe how milk is released from alveoli including the stimulant involved

Answer 2

Oxytocin -> contracts myoepithelial cells around alveoli -> squeezes lactocytes -> triggers milk production -> flows down lactiferous ducts and out via nipple

*presence of prolactin is required for milk production

Question 3

What draws milk into the baby’s mouth?

Answer 3

Oral negative pressure

Question 4

Describe the changes to the breast during pregnancy and during the first few days after birth (2)

Answer 4

1. Areola darkens and grows -> visually easier for newborn

2. Breast becomes very vascous

Question 5

What are Montgomery’s tubules and what do they do?

Answer 5

Little lumps surrounding the areola, ‘Brail for the newborn’.

Has

1. Mammary milk glands -> breast milk
2. Sebaceous glands -> fluid smells/tastes like amniotic fluid (familiar for infant)

Question 6

When does mammogenesis begin and what happens? (3)

Answer 6

4 weeks gestation..
1. Fetus develops 2 milk streaks from axilla -> groin -> becomes the ‘mammary ridge’; a thickening of epithelial cells

2. Epithelial develops into
   - Sm muscle of nipple or areola
   - Those developing wards become future alveoli
3. Born with few ducts but breast tissue grows at puberty and with each ovulation
   * duct branches develop buds under the influence of estrogen and progesterone

Question 7

What does Lactogenesis I begin and what happens?

*include the two phases and specifically what rises in the plasma

Answer 7

1st phase - proliferation/hypertrophy of ductal-lobular-alveolar system at pregnancy

2nd phase - secretion from 16wks-post natal day 2

• alveoli accumulate colostrum
• breast, areola and nipple size increase
• fat droplets accumulate in alveoli cells Plasma lactose and alpha lactalbumin rise during this phase

Question 8

When does Lactogenesis II begin and what happens?

Answer 8

Day 3-8 postpartum

1. Continued prolactin -> increases milk content
2. Progesterone -> closes spaces btwn alveolar cells

• milk content (80-90% water, the rest are sugars, fats and proteins)

Question 9

What happens to HPL and prolactin serum levels throughout pregnancy and for the duration of the breast feeding period?

Answer 9

1. Both slowly rise (due to progesterone) during pregnancy.
2. Birth (expulsion of placenta) induces an HPL drop, prolactin levels rise rapidly but spike when the baby suckles (autocrine response).

This increase in prolactin levels leads to the body producing more milk and entering lactogenesis II. (Prolactin levels decrease in the months following birth but rise again whenever the baby suckles (autocrine response))

Question 10

What can happen to prolactin and HPL levels if the placenta isn’t completely delivered?

Answer 10

HPL levels and progesterone continues to be present which inhibits prolactin - this can cause a delay in lactogenesis II.

Question 11

What happens if the baby’s mother’s nipples aren’t stimulated enough in the week following giving birth?

Answer 11

Prolactin receptor sites start to close off which impacts the mother’s milk producing capability for the breast feeding period

Question 12

When does Galactopoiesis occur and what happens?

Answer 12

Day 9 to breast involution (child no longer requires the breast/6-9 months). Here there is primarily maintenance of secretions, IgG and total protein decline while fat and sugar rise to produce mature milk.

Question 13

What is the final phase of breast development and what happens? When does it typically occur?

*hint; milk secretion decreases when what builds up?

Answer 13

Involution; decrease in milk secretion as demand ceases and causes apoptosis of epithelia cells which is replaced by adipocytes. Milk secretion decreases in the buildup of inhibiting polypeptides and raised sodium levels. Typically starts around 40 days post-partum but can take longer (i.e continued autocrine stimulation)

Question 14

How and where is milk synthesized (include the organelles involved)? What are the 5 stages of synthesis?

Answer 14

Synthesized in the alveolar cells

• Fat produced in smooth ER
• proteins secreted by golgi
• sugars synthesized and then secreted

Stages:

1. Early colostrum
2. Late colostrum
3. Early transitional
4. Late transitional
5. Mature milk

Question 15

What is involved in the early-late colostrum stages?

Answer 15

First few days where neonate needs richer protein levels and minerals but have lower carbs, citrates, lactose and glucose

Next 24-48 hours there’s a sudden increase in these components as breast prepares for lactogenesis II

Question 16

What happens in the early-late transitional stages?

Answer 16

Begins with lactogenesis II, early transitions gradually to late in the next 1-2 weeks until milk becomes mature. Starts rapidly and gradually slows, but the changes are also unique to individual mothers (i.e can be impacted by individual conditions, etc)

Question 17

What is meant by the term “biological specificity of human milk”

Answer 17

Breast milk is a complex bio fluid important for hydration and immune protection, rich in many nutrients, hormones, enzymes, GFs and protective agents

Question 18

What is colostrum and when is it produced? How much is produced in one day? Describe three of its effects

Answer 18

Colostrum is the initial meal produced in lactogenesis I in small quantities to enable the immature kidneys to cope; 37 ml/day

1. Contains maternal phagocytes
2. Less water, fat and sugar but has more protein (particularly immunoglobulins).
3. Has laxative effect; as when the baby suckles it triggers peristalsis which helps clear meconium and promotes gut activity.

Question 19

Describe the detrimental effect formulas can have on the process of lactation
*4 things

Answer 19

1. Induces blood sugars and damages the counter-regulatory effect (colostrum much more effective than formula milk)
2. A breastfed preterm infant has much lower energy and fluid needs than a formula-fed infant - forms the basis of the risk for obesity if the baby isn’t breastfed
3. Lower cholesterol levels when older and lower risk of heart disease; since there’s a lot of cholesterol in breast milk it enables the body to metabolize and become used to high cholesterol levels early on
4. Since bovine (cattle) milk lacks lactoferrin manufacturers will add high quantities of iron, but the infant is unable to absorb more than ~7% without lactoferrin. This leads to an abundance of free iron floating in the infant blood if they have formula and iron attracts bacteria

Question 20

Name 8 important nutritional and non-bio active components of breast milk? Briefly describe each

Which element accounts for the majority of the carbohydrates?

Answer 20

1. Acids (i.e DHA, AA) which are both important for vision and cognitive function)
2. Vitamins (water-soluble increases lactation and fat-soluble decreases)
3. Anti-infective properties: most constituents influenced genetically and epigenetically. Known as white blood and cannot be replicated
4. Lactose (accounts for the majority of carbohydrates), enhances calcium absorption, metabolizes galactose and glucose supplying energy to rapidly growing brain. Its present in infant’s gut but these levels reduce over time (a certain level of lactose intolerance as they grow older)
5. Proteins; some for digestion and immunological processes
6. Mineral content; All are generally static except Mg which is high in the first few days and then drops and remains static

Question 21

What is the difference between preterm milk and normal “37 week/ birth time” milk that the mother produces? How does the mother’s milk adapt to the baby’s time of birth?

Answer 21

A mother’s milk is specifically designed for the baby at its time of gestation (and can’t be replicated)

Has much higher anti-inflammatory and immunomodulating components (although these are always present in breast milk)
Higher in energy (fats, proteins, nitrogen, vitamins/minerals) to ensure the baby can grow.

Question 22

How is active and passive immunity attained for the fetus *3 things

Answer 22

Placenta, GALT and BALT (gut and bronchus-associated lymphoid tissue)

Question 23

What is lactoperoxidase, cytokines and chemokines in breast milk responsible for?

Answer 23

Lactoperoxidase: kills streptococci

Cytokines and chemokines: protein signals

• Cytokines: responsible for body’s response of fever, swelling and tenderness, thought to be the reason breastfeeding has a positive affect for maternal mental health
• Chemokines: activate the immune system

Question 24

Name 5 components of non-antibody antibacterial protection in human breast milk

Answer 24

1. HMOs (human milk oligosaccharides)
2. Bifidus factor
3. Lactoferrin
4. Lactoperoxidase
5. Cytokines and chemokines

Question 25

How does the mother’s breast milk change to continue providing immunological protection for the baby once they’ve been born?

Answer 25

Small amounts of saliva drawn into the ducts as the infant breastfeeds, in the saliva is mRNA which changes the composition of the breast milk by sending messages to the mother’s milk cells about what the baby has been exposed to

Question 26

How are the hormones prolactin and oxytocin triggered and what do they do?

Answer 26

Prolactin: Suckling triggers the prolactin receptors to send afferent messages to the hypothalamus which stimulates the anterior pituitary to release prolactin into the blood stimulating milk production from lactocytes. Therefore, prolactin is essential for the maintenance of milk production.

Oxytocin: Produced in response to suckling and when the mother sees or smells her baby, the same nerve pathway is triggered only the posterior pituitary is stimulated to release oxytocin into the blood which acts on the smooth muscle cells/myoepithelial cells of the alveoli - stimulating MER (milk ejection reflex)

Question 27

Name 5 major bioactive components of breast milk and briefly describe each

Answer 27

1. Lipids: TAGs broken down into FFAs and glycerol by lipase, also long-chain polyunsaturated fatty acids
2. Enzymes; amylase, lipase
3. GF and Hormones; cortisol, insulin, CCK, thyroxine, prolactin, insulin-like GF
4. Whey: immunological factors
5. Casein: inhibits microbial adhering to mucosal membranes

Question 28

What hormones are involved in the increase in prolactin post-birth? How is it secreted and when are its levels highest?

Answer 28

After birth the placenta HPL drops and so does estrogen and progesterone, the anterior pituitary pumps out prolactin in pulsatile ways, highest at night

Question 29

Describe the two main inhibitory pathways for prolactin

Answer 29

1. Dopamine or dopamine-like substances come from the hypothalamus known as dopamine agonists. (Factors that are dopamine antagonists will reduce dopamine and thus promote prolactin)
2. PIF (prolactin inhibiting factor) is a dopamine agonist, its inhibited by nipple stimulation/touch

Question 30

Why might mothers experience severe contractions in the early post-partum stage?

Answer 30

Because oxytocin is also released in pulsatile ways (to stimulate breast milk) which affects the uterus.

Question 31

How does cortisol affect the mammary system and where is it secreted from? What happens if levels become very high?

Answer 31

From the adrenal gland and it helps regulate water transport across cell membranes in lactation. High levels have a negative impact on oxytocin and delay lactogenesis, and if oxytocin is inhibited the mother will have no MER

Question 32

How does TSH affect the mammary system?

Answer 32

Promotes mammary growth and lactation

Question 33

Describe the local feedback inhibitor of lactation

Answer 33

Thought to be a compound within the milk, so if the milk stays in the breast and isn’t largely drawn out lactation becomes inhibited

Question 34

List four factors to consider when prescribing drugs into breast milk

Answer 34

1. Clinical condition
2. Age of infant/stage of lactation
3. Resources on; oral bioavailability, half life, plasma protein binding, milk plasma ratio, RID (relative infant dose)
4. Benefit outweighing risk `

Question 35

List four health risks for infants that aren’t breastfed and three for a mother who does not breastfeed

Answer 35

Infant:

1. Infectious disease
2. Resp infections
3. Diarrhea
4. Malocclusions

Maternal
Type 2 diabetes, breast/ovarian cancer

Question 36

Identify three symptoms of postpartum depression (PPD)

Answer 36

1. Difficulty bonding with the baby (only looking out for them out of a sense of duty)
2. Frightening thoughts (i.e hurting the baby)
3. Worrying that something is wrong with the baby

Question 37

Identify one charity or support group that can provide advice and support for people with PPD

Answer 37

National Childbirth Trust

Question 38

Name four conditions that may significantly affect a mother’s milk supply, how many women have true difficulties producing enough milk to feed their baby?

Answer 38

Only 1.9% have true difficulty producing enough milk, conditions that can affect the milk supply include:
PCOS, diabetes, hypothyroidism or hypoplasia (where both or a single breast hasn’t developed fully during puberty)

Question 39

How does the weight of the mammary gland change normally to during lactation?

Answer 39

Normally 150-200g -> 4-500 g in lactation

Question 40

What do Bifidus factors do and how is it protective of the infant? Name one example

Answer 40

They support the growth of lactobacillus that creates an acidic environment where harmful bacteria cannot grow
Eg: HMOs! (human milk oligosaccharides)

Question 41

Describe the lobule and alveoli tissue of the breast

Answer 41

15-20 lobules with 10-100 alveoli per lobule, lobules separated by fibrous adipose tissue

(bunches of blood vessels and lactiferous ducts)

Question 42

What determines how much lactation the mother will be able to do?

Answer 42

Density of breast tissue

*not size of breast

Question 43

How does the control over milk production change in lactogenesis II?

Answer 43

Hormonally controlled -> autocrine controlled *influenced under stimulation of the infant