The Breast And Lactation Flashcards Preview

MIDW1002 Scientific Underpinnings of Midwifery Care > The Breast And Lactation > Flashcards

Flashcards in The Breast And Lactation Deck (15):

Describe the changes that happen to the breast during pregnancy?

- increased vascularisation (8 weeks) -> tends to result in a marbled appearance of the skin du to the marked dilation of the superficial veins
- thickening of nipple skin
- tenderness of breasts, especially nipple areas due to engorgement of blood (4 weeks)
- full development of lobules (hypertrophy)
- dilation of alveoli and ducts
- pigmentation of nipple and areola (12 weeks)
- secondary areola may appear in darker skinned women
- montgomery's tubules become prominent
- small quantity of clear colostrum may be expressed in latter half of pregnancy (16 weeks secretion)


Describe the process of mammogenesis

- begins in the embryonic stage by 4th week of gestation
- primitive milk streaks from axilla to groin, this continues to thicken with inward growth to chest wall
- 12 to 13 weeks specialised cells differentiate further into smooth muscle areola and nipple
- epithelial cells develop into mammary buds, develop into a treelike pattern and proliferate to become alveoli
- placental sex hormones enter fetal circulation which stimulates formation of canals which continues until the fetus is 32 weeks
- from then lobular alveolar structures containing colostrum develop
-> fetal mammary glands increase 4 times in mass
-> nipple and areola develop further and pigment
- after birth neonates mammary tissue may secrete colostral milk


Describe the structure of the breast

- extends from 2nd-6th rib tail of breast into axilla
- glandular cells
- ducts
- adipose tissue
- connective tissue
- divided into lobes (15-20) by fibrous septae run from behind nipple to pectoral muscle
-> connections between lobes present
- attaching deep layer of subcutaneous tissue to skin are the suspensor ligaments or coopers ligament


Describe the structure of the nipple

- the nipple is at the centre, ducts open into the nipple but approx 9 open onto surface
- areola surrounds nipple and both contain erectile tissue
- within areolar are montgomerys tubercles which consist of milk glands and sebaceous glands (together known as areolar glands)
- glandular tissue is arranged in a ductal alveolar system (4- 18 per breast)
- grouped in grapelike lobules around branching system of ducts which join to form main lactiferous duct leading to nipple
- lactiferous ducts dilate into the ampulla


Describe the breast fatty tissue

- the external shape or size of the breast is not predictive of its lactation potential
- the ratio of glandular tissue to fat tissue rises to 2:1 in the lactating breast compared to a 1:1 ratio in non lactating women
- 65% of the glandular tissue is located within 30mm from the base of the nipple
- between 4 and 18 milk ducts are exiting the nipple
- the network of milk ducts is complex not homogenous, it is not always arranged symmetrically nor in a radial pattern
- the milk ducts near the nipple do not act as reservoirs for milk


What are acini cells?

- alveoli contain acini cells which produce milk
- the acini cells are surrounded by myoepithelial cells which contract an propel milk along the ducts


What happens when an infant breastfeeds?

- when an infant breastfeeds, the infant draws the nipple and areola into their mouth
- the mothers nipple elongates to about twice its normal length
- the nipple height is compressed between the tongue and the palate
- milk is ejected about 0.03 seconds per maximum nipple elongation
- suckling infants compress the areola with their gums which stimulates oxytocin release
--> the oxytocin release causes an increase in the diameter of the milk ducts and movement of milk in the ducts toward the nipple
- mothers may feel a sensation of pins and needles or pressure in he breast with milk ejection


Describe the action of prolactin

- it is produced in the anterior pituitary gland and released into circulation
- regulation of prolactin levels in the plasma is controlled by the dopaminergic system
- prolactin acts on the human breast to produce milk
-> occurs by binding to mammary epithelial cell receptors
-> stimulates synthesis of mRNA of milk proteins
- takes several minutes of infant suckling to cause prolactin secretion
- prolactin is also important in inhibiting ovulation


Describe the action of oxytocin

- it is produced by the posterior pituitary gland (neurohypophysis)
- suckling at the breast stimulates the posterior pituitary to produce and release oxytocin in an intermittent manner
- oxytocin acts on the breast to produce milk ejection or 'milk let down'
- oxytocin also causes uterine contractions
- opiates and B endorphins released during stress can block the release of oxytocin


What is FIL?

- it is feedback inhibitor of lactation
- recently described active whey protein which inhibits milk production in a full breast
- FIL seems to play an important role in regulation of milk supply
- FIL acts locally on each breast -> it is secreted into breast milk
- when the breast is not emptied FIL remains in contact with the alveolar cells
- FIL appears to act on an apical receptor on the alveolar cell
-> this inhibits secretion of milk constituents


Describe the process of lactogenesis for breast milk production

1. Mammogenesis -> breast growth increased
-> proliferation of ducts and glands under influence of oestrogen and progesterone

2. Lactogenesis 1 -> initiation of milk synthesis mid pregnancy
-> differentiation of alveolar cells from secretory cells
-> prolactin stimulates secretory cells to produce milk

3. Lactogenesis 2 -> closure of tight junctions in alveolar cell - triggered by drop in progesterone levels
-> onset of copious milk secretion
-> switch from endocrine to autocrine control
-> fullness and warmth in breasts

4. Galactopoiesis (day 9 beginning of involution)
-> Maintenance of secretion
-> control by autocrine system (supply and demand)
-> breast size decreases between 6-9 months Postpartum

5. Involution (average 40 days after last breastfeed)
-> decreased milk secretion from build up of inhibiting peptides
-> high sodium levels


What are the essential hormone changes for successful lactation?

- drop in progesterone
- release of prolactin from anterior pituitary
-> stimulates Lactogenesis
-> initiates milk secretion
- removal of breast milk by infant
- release of oxytocin from posterior pituitary


Describe progesterones role in breastfeeding

- lactation in pregnancy is inhibited by high levels of progesterone
-> it interferes with prolactin action at alveolar cell receptor level
- progesterone falls by about 10 times during the first 4 days


Describe prolactins role during lactation

- it follows a circadian rhythm - levels are higher at night than during the day
- levels decline slowly over course of lactation but remains elevated as long as she breast feeds
- prolactin rises with suckling - the more feeding the higher the prolactin levels
- prolactin not related to milk yield especially after lactation is established
- delays return of ovulation by inhibiting ovarian response to FSH
- prolactin drops with cigarette smoking
- rises with anxiety and stress
- depressed mothers have lower serum prolactin


Describe oxytocin's role in breastfeeding

- in response to suckling the posterior pituitary releases oxytocin
--> it causes milk ejection reflex
--> it also causes contracting of myoepithelial cells surrounding the alveoli, which is necessary for the removal of milk from the breast
- it is released in pulsatile waves and carried through the bloodstream to the breast
--> here it interacts with receptors on myoepithelial cells causing contractions
--> this forces milk from alveoli into the ducts where it becomes available to the newborn
- oxytocin plays a role in continuance of breastfeeding
- levels rise within a minute of stimulation
- contracts uterus
- has peripheral effects increasing blood flow
- increased thirst
- breast massage increases levels