Section 1: anatomy Flashcards
acinus
- A group of secretory cells
- In the breast, an acinus secretes milk.
alveolus
- a small sac at the end of a lobule to which milk is secreted and stored
- Located in the mammary gland
areola
Pigmented skin that surrounds the nipple.
colostrum
- The fluid in the breast at the end of pregnancy and in the early postpartum period
estrogen
- hormone
- causes growth of mammary tissue during part of each menstrual cycle
- assists in the secretion of prolactin during pregnancy.
lactiferous duct
- Milk ducts
- 15 to 24 tubes that collect milk from the smaller ductules and carry it to the nipple.
Lactobacillus bifidus
- principal Gram-positive bacillus found in the intestinal flora of breastfed infants.
lactoferrin
- A protein
- important immunological component of human milk
- binds with iron in the intestinal tract, making it unavailable to bacteria that require iron to survive.
lactogenesis
The initiation of milk secretion.
- Lactogenesis I is the initial synthesis of milk components that begins late in pregnancy
- Lactogenesis II is the onset of copious milk production 2 or 3 days postpartum.
lactose
- The major carbohydrate in human milk
- forms about 4% of colostrum and 7% of mature milk
- disaccharide
- metabolizes readily to glucose
- enhances calcium absorption.
myoepithelial cells
- Contractile cells
- surround the milk-secreting alveoli
- oxytocin causes these cells to contract, forcing milk into the ducts.
- A “letdown response” occurs when many cells contract at the same time.
nipple
- The pigmented projection at the tip of each breast
- lactiferous ducts open into about 15 to 20 pores through which milk flows.
oxytocin
- A lactogenic hormone produced in the posterior pituitary gland
- released during suckling, causing milk to be ejected and the uterus to contract.
progesterone
- hormone
- produced by the corpus luteum and placenta
- maintains pregnancy
- assists with mammary alveoli development.
prolactin
- hormone
- produced in the anterior pituitary
- stimulates development of the breast
- controls milk synthesis.
What is important for efficient milk removal?
A rapid first milk ejection
Research shows that a rapid first milk ejection will then lead to
more subsequent milk ejections.
When milk is not removed from the breast,
a protein called feedback inhibitor of lactation (FIL) is produced.
When the amount of Feedback Inhibitor of Lactation (FIL) increases
- a signal is sent to the hypothalamus to reduce prolactin
- milk production is reduced.
The majority of the glandular tissue is found
within 30 mm of the nipple
When does breast development begin
In the 4th week of embryonic life
What causes rapid development of breasts in puberty?
increasing levels of progesterone
Rapid growth in adolescence is characterized by
- Branching and lengthening of the ductal system
- increased development of connective tissue surrounding the ducts and alveoli
When does the major growth change occur?
12 to 24 months after the onset of the first menstrual period.
What hormone influences proliferation of the ductal system?
estrogen
Proliferation of the ductal system begins with
- each menstrual cycle
- continues until the breast reaches its maximum development state
Complete development of mammary function occurs when?
in pregnancy when the breasts increase in size and the nipple pigment darkens.
New breast structures continue to bud until what age?
about age 35
The basic units of the mature glandular tissue of the breast
The alveoli
Each breast contains how many lobes?
15-20 subdivided lobes
Each lobe contains how many alveoli?
10-100 alveoli
contractile units responsible for ejecting milk into the ductules,
myoepithelial cells
Myoepithelial cells surround the
secretory cells of the alveolus
The ductules merge to form
a larger duct, which leads to a duct opening called nipple “pores.
Milk is continually secreted where?
into the alveolar lumina
where is milk stored?
The alveolar lumina
Milk is stored in the alveolar lumina until
the letdown reflex triggers the myoepithelial cells to contract and eject the milk
The breast is highly
vascularized
What arteries supply the breast?
- internal mammary artery
- lateral thoracic artery
Function of the lymphatic system
removes waste products from the breast
Lymphatic system is made up of
nodes
lymph system originates in the
lymph capillaries
lymph system drains extracellular fluid towards
- axillary lymph nodes
- parasternal lymph nodes
Where are the axillary and parasternal nodes found?
along the intercostal thoracic artery (inside the thoracic cavity)
Why could the lymph nodes cause difficulty latching?
if the mother becomes extremely engorged due to the lymph fluid behind the areola.
What nerves supply the breast?
Branches of the second to sixth intercostal nerves
The fourth intercostal nerve branches and penetrates
- the posterior aspect of the breast
- 4 o’clock on the left breast
- 8 o’clock on the right breast
Which nerver supplies the greatest amount of sensation to the nipple and areola?
The fourth intervostal nerve
Trauma to the 4th intercostal nerve will cause
some loss of sensation in the breast
Is there nervous innervation of the epithelial cells that line the alveoli?
None has been found
secretory functions of the acinar epithelium could depend on
hormonal stimulation of prolactin, rather than sensory stimulation.
Where are Mongomery’s tubercules?
within the areola
Montgomery’s tuberciles consist of
- mammary milk glands
- sebaceous glands
- together called areolar glands.
The fluid from the areolar glands
lubricates the nipple and areola
Lubrication of the nipple and areaola may assist the infant in
finding the nipple, latching on, sucking, and increasing weight
In pregnancy, increased levels of estrugen stimulate
proliferation of the glandular tissue of the breast
Proliferation of the glandular tissue of the breast involves
the branching out and lengthening of the ductal system.
During pregnancy, higher progesterone levels promote the growth of what part of the breast?
lobes, lobules, and alveoli
During pregnancy, superficial veins in the breast become more prominent due to
increased vascularity of the breast tissue
Near the end of the first trimester, what happens to the Montgomery’s glands and pigmentaiton of areola?
- Montgomery’s glands enlarge
- pigmentation of areola darkens
SECOND TRIMESTER
What hormone stimulates the alveolar cells to differentiate in the second trimester?
Placental prolactin
Prolactin is prevented from exerting its effects by
an inhibitory factor from the hypothalamus
Why are high levels of prolactin during pregnancy not associated with milk production?
- Partly due to progesterone antagonism of prolactin
What happens to progesterone and estrogen levels at delivery?
They fall
What happens to prolactin levels at delivery?
Remain high
When does colostrum start being produced?
By the end of the second trimester
Do women who deliver infants prematurely have trouble lactating?
no
At the end of pregnancy, the breasts are ready to
secrete milk for the human infant
What are the stages of lactation?
- Lactogenesis I
- Lactogenesis II
- galactopoiesis
- Involution
What is lactogenesis?
The transition from pregnancy to lactation
When does Lactogenesis Stage I occur?
Mid to late pregnancy, during which the mammary gland has the capacity to secrete milk
When does Lactogenesis Stage II occur?
- day 2-3 to day 8 postpartum
- During which there is copius milk secretion from the breasts
What is Galactopoiesis?
The maintenance of established milk production
Following the delivery of the placenta, what hormones decline?
- Placental lactogen
- Estrogen
- Progesterone
Following delivery of the placenta, what hormones increase?
Serum prolactin
When serum prolactin increases after placental delivery
alveolar cells are stimulated to create milk
The suckling of the baby at the breast stimulates what?
- the nerve pathway from the nipple to the brain
- sends a message to the hypothalamus to inhibit secretion of prolactin inhibitory factor (PIF)
After delivery, oxytocin is released by what?
The posterior pituitary
Oxytocin does what?
- Acts on the myoepithelial cells surrounding the alveoli and ducts
- causes them to contract, initiating the milk ejection reflex
What maintains a milk supply?
Frequent suckling and efficient removal of milk
What is involution?
The process that removes milk-producing epithelial cells and replaces them with fat cells when they are no longer necessary
Prolactin appears to have what effect on breastfeeding women?
A calming effect
What are factors known to increase prolactin levels?
- sleep,
- infant suckling at the breast,
- neuroleptic drugs (drugs that decrease catecholamines, which in turn inhibit PIF secretion),
- efficient removal of milk from the breast.
What are medications hat decrease prolactin levels?
- dopamine,
- L-dopa,
- ergot
What is Human Placental Lactogen?
- hormone produced by the placenta
- high levels during pregnancy
- abrupt decline within hours following delivery.
What are other hormones that play a role in milk production?
- Human Placental Lactogen
- Glucocorticoids
- TSH
What role do glucocorticoids have in lactation?
- secreted by the adrenal gland
- regulate water transport across cell membranes.
What role does TSH have in lactation?
- promotes mammary growth
- regulates the maternal metabolism
- A thyroxin deficiency can decrease milk supply.
What is oxytocin?
a lactogenic hormone
Where is oxytocin produced?
Posterior pituitary
What are the effects of oxytocin?
- contraction of smooth muscle of the uterus and myoepithelial cells surrounding the alveoli and ducts
- –>initiating the milk-ejection reflex
Breastfeeding following delivery can reduce the risk of what?
Postpartum bleeding (by contraction of the uterus caused by oxytocin)
Oxytocin inhibiting factors
- stress,
- pain,
- anxiety,
- alcohol
- adrenaline.
Where is prolactin produced
anterior pituitary
What colour is colostrum?
- Thick and straw coloured
What is the nutrient content of colostrum compared to mature milk?
- higher in proteins than mature milk.
- also higher in fat-soluble vitamins and some minerals.
Most of the proteins in colostrum are what?
immunoglobulins
What prevents prolactin from exerting its effect on milk secretion during pregnancy?
Elevated levels of progesterone
How does progesterone prevent milk secretion during pregnancy?
Elevated levels of progesterone have inhibitory effect on prolactin
What non-medication factors decrese prolactin levels?
- pacifiers, ineffective suckling, supplements,
- severe blood loss
- nipple shields (possibly).
Where is Human Placental Lactogen produced?
The PLacenta
During pregnancy, human placental lactogen levels are
HIGH
In the hours following delivery, human placental lactogen levels
Decline abrubptly
What type of bacteria is lacobacillus bifidus?
Gram positive
Where is lacobacillus bifidus mainly found?
In the intestine of breastfed infants
The presence of the bacillus leads to
- low intestinal pH of fully breastfed infants
- discourages the colonization of bacteria.
Where are myoepithelial cells located?
surround the milk-secreting alveoli
What causes myoepithelial cells to contract?
oxytocin causes these cells to contract, forcing milk into the ducts.
What occurs when many myoepithelial cells contract at the same time?
A “letdown response”
What can a thyroxine deficiency do to milk supply?
decrease it
Where is progesterone produced?
Corpus luteum and placenta
What is the major carbohydrate in human milk?
Lactose
Lactose makes up what percentage of colostrum?
about 4%
Lactose makes up what percentage of mature milk?
about 7%
What type of carbohydrate is lactose?
A disaccharide
LActose metabolizes readily to
glucose
Lactose enhances absorption of what mineral?
Calcium
What drugs are known to increase prolactin levels?
- neuroleptic drugs
- (drugs that decrease catecholamines, which in turn inhibit PIF secretion),
What hormone
- stimulates development of the breast
- controls milk synthesis.
Prolactin
Estrogen’s MAIN JOB
Makes GLANDULAR breast tissue GROW during menstration and pregnancy
Stimulates prolactin release
Progesterone’s MAIN JOB in puberty
Rapid breast development
Progesterone’s main job in pregnancy
Makes lobes, lobules and alveoli GROW
Inihibits PROLACTIN
Maintains pregnancy
Prolactin’s MAIN JOB
MILK SYNTHESIS
OXYTOCIN’S MAIN JOB
LETDOWN
