BE 02 Flashcards
Breast development: First month of gestation
Breast development commences - two lines of glandular tissue (milk lines or mammary ridges) along ventral service from axilla to medial thigh develop in both male and female embryos
Three major phases of growth that impact latctation
Embryological and infancy
Puberty
Pregnancy and lactation
Breast development: 5th week gestation
Milk lines in thorax region develop into ridge which will become breasts
Breast development: 2nd and 3rd month of fetal development
Nipples and areolae formed that overlie a bud of breast tissue composed of both the primary mammary ducts and a loose fibrous stroma
Breast development: Mid-pregnancy
Secondary buds develop and bifurcate into tubules that form the basis of the duct system. Each duct system opens separately into the nipple.
Breast development: Birth to puberty
At birth newborn’s breasts have formed mammary ducts and areola and nipple is present. Nipple usually inverted, everting shortly after birth.
Mammary glands of both male and female children remain inactive until puberty.
What is “witch’s milk”??
Breasts of babies soon after birth may release a milk-like substance, called witch’s milk. This is a result of maternal hormones crossing placental barrier, for which treatment is not usually required. This milk should not be expressed!
Breast development: Puberty to pre-conception
Breast develop (thelarche) usually first sign of puberty in girls. Avg age is 9.5 to 10.3 years.
Initially estrogen, then progesterone, influence growth of breasts in female…. Estrogen - increased growth, branching in duct system. Progesterone - (during luteal phase of menstrual cycle) causes ducts and alveolar buds to continue to proliferate. Other hormones (incl. prolactin, FSH, LH, growth hormone, somatotropin, TSH, ACTH also have roles in breast develop.
Most growth completed by 16yo.
Define lactogenesis 1 (secretory differentiation)?
the period in pregnancy when mammary epithelial cells differentiate into lactocytes with the capacity to synthesize unique milk constituents such as lactose
What hormone correlates with breast growth?
Increasing levels during pregnancy of human placental lactogen
Breast function is correlated with which hormone?
During pregnancy increasing levels of prolactin.
What hormone holds the secretory process in check?
High circulating plasma [progesterone]
Relation between pre-conception breast size and degree of increase of breast size during pregnancy?
NONE
Note: There is a wide variation in timing and degree of glandular growth.
Some women have extensive 1st trimester growth, some have gradual growth through pregnancy, some have NO growth until just before and/or after birth
The two components of the mammary gland (corpus mammae)
Parenchyma: ducts, lobes, alveolar structures
Stroma: connective tissue, adipose tissue (fat), blood vessels, lymphatics and nerves
Parenchyma components
Ducts
Lobes
Alveolar Structures
Stroma components
Connective tissue Adipose tissue (fat) Blood vessels Lymphatics Nerves
See Anatomy of the Human Breast Illustration
Pg. 6 BE 02
Define breast capacity
The maximum volume of milk able to be stored in the breast at any one time
Where is milk stored in the breasts?
Alveoli
NOTE: there is huge variation in breast capacity, and it is not related to breast size.
May also be different for each breast
Breast descriptors (quadrants)
Upper outer quadrant (closest to armpit) Upper inner quadrant (close to sternum) Lower outer quadrant (below upper outer) Lower inner quadrant (below upper inner) *AKA outer: lateral, inner: medial
Blood supply to the breast comes from….
Two arteries:
- Internal mammary artery: supplying 62-70% of blood to breast. Comes down on medial side of each breast.
-Lateral thoracic artery: supplying 30-40% of breast’s needs
Rate of blood flow to the breast.
Is there any correlation between blood flow and milk production?
Rate of blood flow: appx. 150-160 ml per minute.
No correlation between blood flow and milk production
Discuss lymphatic drainage in the breasts
Each breast has extensive lymphatic drainage.
Subareolar plexus and other superficial and deep nodes drain lymph primarily to lymphatic nodes in axilla, though some goes to interpectoral and internal mammary nodes
What characterizes breast engorgement?`
Stasis of milk in the alveoli and increased interstitial fluid (lymph)
What nerves supply the breast?
Nerves arising from branches of the 4, 5 and 6 intercostal nerves
What is the most sensitive part of the breast?
Areola. Sensitivity increases at birth.
What is significant about the lowermost branch of the 4th intercostal nerve?
It becomes more superficial close to the areola in the lower outer quadrant - at about 5 o’clock on left breast and 7 o’clock
What controls milk release from the breast, which is essential to establishing and maintaining milk production?
A neuro-hormonal reflex that causes the Milk Ejection Reflex (MER) AKA the let-down reflex
How is the MER initiated (flow of activities)
Initiated PHYSICALLY by stimulation of nipple and areola –> Nerve impulses travel to the HYPOTHALAMUS –> Causes release of OXYTOCIN from the posterior pituitary gland –> and PROLACTIN from the anterior pituitary gland –> Oxytocin travels through blood stream to breasts –> Causes myoepithelial cells surrounding each alveolus to CONTRACT –> Forces milk into ductal system and toward nipple.
What happens after MER to the remaining milk?
Milk flow reverses, returning milk to alveoli when MER subsides.
Minimal residual breastmilk only remains in ductal system when there is no MER
What surgical injury could prevent functioning of MER?
Eg reduction mammoplasty, prei-areolar incisions that sever the 4th intercostal nerve.
How is oxytocin released?
Pulsastile fashion
Each release effective for 1.5-2 mins *Assoc w duration of MER
Avg # MERs per BF session
3-8
MER:
- are both breasts affected?
- What is infant milk intake assoc with?
- BOTH are affected at once
- Infant milk intake assoc w # and duration of milk ejections
Simulatory factors in oxytocin release (4)
hearing a baby cry
thinking about baby
preparing to BF
being usual time baby feeds
Inhibitory factors in oxytocin release (4)
fear
pain
embarrassment
anxiety
What all does oxytocin do? (7)
- causes myoepithelial cells surrounding alveoli to contract, initiating MER
- causes increased uterine activity, reducing risk of hemorrhage
- causes skin temp of breasts to rise, providing warmth to infant
- exhibits flight-fight antagonist fx, decreasing maternal anxiety
- increases calmness and social responsiveness
- during early hours after birth enhances parenting behaviors
- causes thirst
In what three areas of the body is fatty tissue found?
- Subcutaneous: directly beneath skin. Minimal near nipple, increasing in thickness farther from nipple.
- Intraglandular: intermingles with the glandular tissue and is difficult to separate.
- Retromammary
* Amt of fatty tissue present varies between women, but similar between breasts of same woman.
Define Coopers Ligaments
Loose structure of connective tissue which provides suppot for the glandular and fatty tissues.
How does accessory tissue in breast develop? What might the accessory tissue be composed of?
Incomplete regression of milk line, which stretches from the axilla to groin during embryological development. May develop anywhere along milk line.
May include glandular tissue, areola and/or nipple.
What is hyperadenia?
Where is it commonly found?
What happens to it during pregnancy?
How is it distinguished from the tail of Spence?
Def: presence of addiitonal mammary tissue w/ or w/o nipples.
Found commonly: axilla
Preg: Undergoes similar changes to normal breast during menstrual cycles, pregnancy and lactation.
Spence: distinguishable from axillary tail of Spence d/t lack of anatomical connection to breast.
How to treat engorged hyperadenic tissue, as may happen at lactation initiation.
Symptomatic tx: cold packs/cold cabbage leaves; oral analgesics/NSAIDs for relief until tissue involutes, usually in a few days. Sometimes this process can take more than a week.
Define Polythelia (AKA x2)
How common?
What do they look like?
Occasionally associated with…
Presence of nipple w/ no associated breast tissue, and is additional to normal breasts. AKA hyperthelia or accessory nipples.
Fairly common - 2-6% of adult women.
Found anywhere along embryonic milk line. Often mistaken for moles.
While rarely require tx, occ assoc w/ congenital urogenital abnormalities.
Define hyperplasia
When does this become an issue for most women?
Over-develop of breast. Often defined as greater than 400mm^3 = moderate hypertrophy.
80% of cases start in adolescence.