Biochem of lactation Flashcards
breast development/differentiation results due to what hormones?
prolactin, progesterone, estrogens, growth hormone, cortisol, human placental lactogen (hPL)
what type of gland is the mammary gland?
it is an exocrine gland -
what features of breast milk are nourishing to the neonate?
1) fats, proteins, sugar, vitamins, minerals, water
2) protection = immunoglobulins absorbed via intestinal tract
Describe the different structures of the mammary glands pictured below
what part of the gland actually produces milk?
the alveolar cells
how is milk excreted from the alveolar cells?
myoepithelial cells contract when exposed to oxytocin
how long does the WHO recommend sole breastfeeding?
6 months -
what is the principle hormone responsible for lactation?
Prolactin
what cells in the anterior pituitary produce prolactin in response to signals?
Lactotrophs
negative stimulis = under inhibiotry control by dopamine
positive stimulus = thyrotropin-releasing hormone, oestrogen, progesterone and suckling reflex
describe the positive and negative influences on prolactin formation
high prolactin levels supresses what hormones?
FSH and LH - generally speaking ovulation does not occur during lactation = unreliable contraceptive control
what is hyperprolactinemia?
excess prolactin development associated with infertility b/c of the natural contraceptive effects of the prolactin cycle
what are the causes of hyperprolactinemia?
overproduction of prolactin (i,e) pituitary adenomas - reduced dopamine levels (disinhibition)
physiological stimuli = like suckling
hormonal effects = pregnancy, oestrogen therapy or hypothyroidism
drugs = antipsychotic drugs or opiate
what are the three changes during and after pregnancy?
- mammogenesis = development of ducts and alveolar systems of the breast
- lactogenesis - milk synthesis
- galactogenesis - milk letdown
what hormones are essential for mammogenesis ?
- prolactin - required for mammogenesis and lactogenesis, completes cellular differentiation and development of lactogenic capacity
- oestrogens - stimulate ductal development development begins at puberty
- progesterone - needed to complete mammogenesis of alveolar system
- insulin - required for multiplication of epithelial cells and development of lobulalveolar architecture
what are the three stages of lactogenesis?
1- mid pregnancy to about 30 hours post birth - capacity for lactogenesis but high levels of progesterone inhibit milk secretion and supress volume
2- 30-40 hours after birth to 2/3 months post-partum - delivery of placenta- decreases progesterone, estrogen and HPL - this abrupt withdrawal of progesterone in presence of high prolactin causes increase in milk volume
3- 2/3 months post-partum onwards - established lactation, autocrne control of milk synthesis (local unlike the other), primary control mechanism is milk removal by the babies diet
*therefore as long as the breast is emptied of milk, there will be initiation of milk development - which is why lactogenesis can go on indefinitely*
what is lactose composed of? What is the enxyme necessary for it’s synthesis?
lactose= glucose + galactose
- 2 glucoses required for each lactose molecule synthesized- one glucose converted to UDP- glucose- then UDP-galactose
lactose synthase enzyme is responsible for its synthesis
what are the two components of lactose synthase?
catalytic component = galactosyltransferase
regulatory = alpha-lactobumin
why does milk not come in until after the placenta is delivered?
b/c progesterone is still being produced when the placenta is attached - and this is inhibitory of the milk-protein gene expression in the mother
what cells contract and allow for expulsion of milk?
the myoepithelial cells surrounding the alveoli
what components of breast milk are we still trying to simulate in formula?
enzymes, vitamins, trace elements and growth factors - not fully understood yet
why can’t you substitute one species mlik for another’s?
it could be very damaging to the kidneys of children b/c for example bovine mlik has far more electrolytes than what are contained in human breast milk
why do we replace dairy fats in infant formula with fats of vegetable or marine origin?
we replace them for shelf life
is infant formula - safe and effective?
it is safe - not as nutritionally packed as breast milk, but it’s used when breast milk is not available
what are the components of human milk that is not found in formula?
Lactoferrin protein (for intestinal health)
- Anti-infectious oligosaccharides & glycoconjugates
- Growth factors
- Long-chain polyunsatursated fatty acids (LCPUFA)
–Docosahexaenoic acid (DHA, omega-3) and arachidonic acid (AA, omega-6)
•Fat-digesting enzyme, lipase
Components particularly important for preterm infant & infant with feeding problems
Breast milk: automatically adjusts to infant’s needs; levels adjust as baby gets older
what are some of the beneficial effects of human milk?
Improved gastrointestinal function, digestion, and absorption of nutrients
- Improved cognitive and visual development
- Improved host defense with reduced rates of infection (e.g. sepsis, necrotizing enterocolitis, and urinary tract infection)
- Enhanced maternal psychological well-being and maternal-infant bonding
what is colostrum?
first liquid produced - yellow and thicker milk that is very high in concentrated nutrition - low in fat and high in proteins and carbohydrates so it’s easy to digest
It has a super high concentration of antibodies especially IgA - helps to protect the lungs, throat, and intestines -
laxative effect - which helps pass the first bowel movements and prevents newborn jaundice -
what is weaning?
reduction of breast milk and/or
formula to replace it with more solid food
- Introduce more solid food after first six months (WHO)
- formula-fed, between 4-6 months of age
