9.1 Lactation Flashcards
Describe the Interior anatomy of the breast
- 15-20 lobules each separated by fibrous adipose tissue
- each lobule contains 10-100 alveoli (bunches of cells that contain blood vessels that feed into lactiferous ducts)
- lactocytes (milk producing cells) are surrounded by alveoli cells and each alveolus cell is surrounded by myoepithelial cells (smooth muscle cells that respond to oxytocin)
What hormone is responsible for hypertrophy of the ductal-lobular-alveolar system?
Oestrogen and progesterone
How does milk flow out into babies mouth?
milk does NOT flow out through baby sucking
it is triggered by oral negative pressure: as the baby drops its tongue and the mouth opens, it draws in a bolus of milk due to the negative pressure
Label the following diagram
Note: this diagram is not an accurate representation of the breast as it shows a single milk duct terminating in a single outlet… In reality there is a large network of ducts that all terminate into a single duct
What determines mother milk producing capacity?
What determine how often she needs to feed her baby and why is there variation in this?
Milk producing capacity: determines by the NUMBER of alveoli and DENSITY of breast tissue
The SIZE of the breast does NOT correlate to the milk volume potential
How often she needs to feed her baby: each mother will have her own magic number that indicates how often she should be feeding her baby to maintain supply of milk
Eg. Women that have endocrine disorders (eg. PCI) = higher number of times they need to feed in order to maintain supply
Describe the exterior structure of the breast and relate it to function
(Hint 2 main components that relate to babies senses)
These are changes that occur during pregnancy and the first few days after birth
1) Areolar
Structure and Function:
- during pregnancy areolar begins to darken and breast becomes very vascularised
- areolar grows significantly in the first few days after birth especially during lactogenesis (day 3)
- after birth the aim of the areolar area is for the newborn to be stimulated to find the nipple using their sense of sight as it is slightly darker
2) Montomery’s Tubercles
Structure and function
- these are little lumps surrounding the areola on the outer edges stimulate baby to find nipple using sense of touch
- they are sebaceous glands that secrete a serum that smells and tastes like amniotic fluid (diet of the foetus), which stimulates baby to use of sense of smell and tatse in order to find and drink from the nipple (familiarity)
- they can also secrete breast milk when greater production occurs
What are the 5 stages of breast development during pregnancy, with timeline?
1) Mamogenesis (begins around week 4 of foetal gestation)
2) Lactigenesis I
3) Lactigenesis II
4) Galactipoiesis
5) Involution
What occurs during stage 1 of breat development: Mamogenesis?
Begins at 4 weeks of foetal gestation under influence of oestrogen and progesterone
Foetus develops 2 milk streaks that arise from their axilla down to their groin ➞ thickens to form mammory ridge
These cells will differentiate into either SM cells of the nipple and areolar OR develop inwards to become branches alveoli
What are the 2 phases of Lactogenesis I and what occurs in each?
* What significant point is marked by this stage?
Phase 1 Proliferatve phase (upon pregnancy): cells proliferate ➞ hypertrophy of the ductal-lobular-alveolar system
Phase 2 Secretory phase (16wks pregnancy-day 2 post-natal)
- Colostrum production!! *
- breast, areola and nipple size increase
- fat droplets accumulate in alveoli cells
- rise in plasma lactose and alpha-lactalbumin
What is Colostrum and what is its purpose
At what stage of lactation development does it begin?
Colostrum is a fluid that is produced before breast milk. It is produced in small quantities during stage 2 of lactation development during the secretory phase (week 16)
Its purpose is nourish the foetus while allowing the immature kidney to cope
It has a laxative effect because it aids clearing of meconium through the trigger of suckling causing peristaltic contractions through the gut
Compare colostrum and breast milk
It contains maternal phagocytes and macrophages
+ MORE:
- proteins
- immunoglobulins
- water solubule vitamins
It contains LESS:
- water
- glucose
- fat solubule vitamins
- lactates
- citrates
Is the volume of colostrum important?
What crucial state does the neonate need to reach and why?
Therfore what can be said about formula milk use during the initial days?
The volume of colostrum during early days is less important
What is important is that the neonates can reach a catabolic state which allows mobilisation of glucagon stores in order to stabilises blood sugars. This is provided by colostrum
What occurs during stage 3 of breat development: Lactogenesis II?
Occurs day 3-8 postpartum
Spaces between alveolar cells close, triggered by drop in progesterone
Continuing presence of prolactin tiggers change from clostrum to copious milk production
Milk production changes from endocrine to autocrine control
Describe the changes in HPL, progesterone and prolactin during pregnancy in the endocrine period and what tiggers the switch to autocrine
Endocrine
During pregnancy:
- HPL slowly rises throughout pregnancy
- Prolactin levels rise similarly BUT the production of prolactin is stunted to a particular level
- In the presence of progesterone, this is what maintains pregnancy and this level of prolactin
At birth expulsion of the placenta causes:
- levels of HPL to immediately drop (+ progesterone)
- this disinhibits prolactin, causing levels of prolactin to rise dramatically
Switch to autocrine is triggered by baby suckling at the nipple and is required in order to maintain milk production and high prolactin levels (maintence is involved in the 3rd stage: galactopoiesis)
Give a common example of why there may be a delay in the completion of lactogenesis II
Sometimes there are occurrences where the placenta hasn’t completely been delivered which leaves fragments behind in the uterus.
This inhibits the levels of prolactin released due to the continuing presence of progesterone and HPL levels from the placenta fragments.
This can often cause a delay in lactogenesis II
What occurs during stage 4 of breat development: Galactopoiesis?
Occurs from day 9 to involution: there is
- maintenance of secretion (autocrine– supply and demand)
- Breast size decrease 6-9 months
What triggers the switch to autocrine control?
How do we specifically maintain secretions during galactopoiesis?
In order to maintain milk production we must maintain high prolactin levels:
this requires the baby to suckle at the breast which triggers further prolactin increase (indicates to body that baby is still there and breast milk is required)
At this point there is the switch to autocrine stimulation and breast milk production and prolactin levels are maximised
** MUST occur within first few days
Over the next few months prolactin levels slowly reduce but peak as the baby suckles indicating the autocrine response
Give 2 reasons why a mothers milk producing capability for the enitre breast feeding period may be impacted and why?
At what stage would this impact
1) baby being seperated from its organ formula
2) baby not being able to initally feed
Due to the lack of stimulation this causes the prolactin receptor sites to close off.
This impacts on the mothers milk producing cabibility for that enitre breast feeding period (unti/if she becomes pregnant again)
This would impact stage 2-3: the switch to autocrine and the maintenece of milk secretions
