breast Flashcards
what are the purposes of the breast?
- nutrition of the young
2. spacing of pregnancies e.g. contraceptive
derivation of the breast
- mammary glands are modified sweat glands
- they’re derived from tissue that is first identified in the mammary (or milk) crests that arise between the axilla and the groin
- breast development begins with the formation of mammary buds at about 6 weeks
first development of the breast
takes place as a down growth of the dermis to form the primary breast bud
secondary buds develop from the primary bud
-they become the lactiferous ducts
canalisation
under the influence of hormones e.g. P4 and E2, as gestation progresses the buds develop lumens (become canalised)
is induced by placental steriods (P4 and E2)
lactiferous ducts at birth
by birth 15-20 lactiferous ducts are present
when are breast fully developed and could potentially make milk
at birth
milk production would require hormonal stimulus
because the fetus has been exposed to the placental steroids and maternal hormones at birth some babies do make a colostrum-like secretion called witch’s milk
increase in male breast tissure
gynaecomastia
structure of the nipple
raised (usually) cyclindrical pigmented structure
can be inverted
the lacterferous ducts join the skin at the nipple
structure of the areola
pigmented circle of tissue surrounding the nipple
contains sebaceous glands which give a granular texture to the surface
internal structures of the breast
major component = adipose tissue of the pectoral fat pad
breasts are supported by ligaments = suspensory ligaments of cooper
lobes within the breast
human breast contains 15-20 lobes each made up of milk-secreting lobules
each lobules connect to a signle lactiferous duct
these structures look a little like a bunch of grapes
estrogens effect on the breast
causes cell growth of epithelial cells that make up the milk producing alveoli within the lobules
menstrual cycle and the breast
estrogen and progesterone promote the growth of the alveolar buds - successive cycles cause increased growth
estrogen essential for…
breast growth
progesterone induces
side branching of ducts
prolactin
necessary for alveolar development but also stimulates casein and causes milk production
produced in large amounts in pregnancy and falls at birth
hormones cause
the expansion of the alveoli and ductile system. The ducts grow, branch and bud
lactational amenorrhea
Is the temporary postnatal infertility that occurs when a woman is amenorrheic (not menstruating) and fully breastfeeding.
lactational amenorrhea can last for 9 months
- it is an effective form of contraception in some women
- is entirely unpredictable
progesterone prevents
major milk production
is a smooth muscle relaxant and prevents milk ejection
no ejection of milk during pregnancy
what induces the secretion of prolactin
suckling of the infant on the nipple induces secretion of prolactin by the anterior pituitary (outside of pregnancy)
secretion is stimulated by a neuroendocrine reflex
-cutting the nerves to the nipple prevents this reflex
endocrine control of lactation
suckling causes reduced secretion of dopamine (prolactin inhibiting factor) into the portal blood
concurrently vasoactive intestinal peptide (VIP) secretion by the paraventicular nuclei is increased
both factors act on the lactotrophs to secrete prolactin
prolactin induces production of milk proteins
amount of suckling is proportional to the amount of prolactin secreted
milk ejection response
MER
suckling also stimulates synthesis and secretion of oxytocin by the posterior pituitary
oxytocin induces the contraction of the myoepithelial cells of the alveoli causing ejection of the milk into the ducts
factors that induce the MER
- stimulation of the female reproductive tract can induce oxytocin release
during sex - crying of baby
- smell of baby
supernumeroury nipples/breasts
- usually found along the line of the embryonic milk ridge
- additional nipples can occur on the breast or along the milk ridge and lactiferous ducts can exit the breast at sites outside the nipple
