Lecture 19: Mammary gland and lactation (Galvao) Flashcards
how does the mammary gland first develop in prenatallife?
as ridges of epidermis called mammary ridges
the mammary gland is a modified version of what gland?
sweat gland
In what order do mammary glands first develop?
primary mammary buds develop from mammary ridges, with branching and lengthening of the secondary buds and finally canalization (duct formation) occurring prior to birth.
what portion of mammary gland development occurs at puberty?
further duct and alveolar development - allmoetric growth (increased rate)
what is the influence of progesterone on mammary gland development?
it stimulates alveoli growth
what influence does estrogen have on mammary gland growth?
duct system growth
what influence does prolactin and growth hormone have on mammary gland development?
promote duct development
when do final stages of mammary gland development occur?
pregnancy
what influence do prolactin, adrenal corticosteroids and placental lactogen have on mammary gland development during pregnancy?
they develop terminal alveoli
what stimulates lactogenesis (production of milk)
a decrease in progesterone and an increase in prolactin
during pregnancy, terminal alveoli begin to grow into branches called…
lobules
what type of cells produce milk? and where is it secreted?
specialized epithelial cells and secreted into the lumen of alveolus
what are the 5 different ways of milk synthesis/secretion?
just remember the cow L-E-A-P-T over the moon: L - lipid E - exocytosis A - apical transport P - paracellular T - transcytosis
describe exocytosis
most components of the aqueous phase (casein and lactose) are secreted by exocytosis.
casein - produced in the rER,transferred to golgi, packaged into SV
lactose - produced in the golgi from glucose and galactose, packaged into SV
describe milk synthesis: lipid
produced in the sER from FA and glycerol, coalesce into large droplets are enveloped by the plasma membrane and released as a fat globule.
describe milk synthesis: apical transport
water, Na, Cl, K, bicarb, and monosaccharides can cross the apical membrane
describe milk synthesis: transcytosis
allows transport of IgA from the interstitial space (produced by plasma cells or from blood) into milk.
describe milk synthesis: paracellular
allow for transport of IGs and leukocytes in late gestation and infection (mastitis).
number of teats in a cow and their location
4 - inguinal
number of teats in the mare, goat, sheep and location
2 - inguinal
number and location of teats in a dog
(thoraco)abdominoinuginal 10 ( 8 -12)
number and location of teats in the pig
thoracoabdominoinguinal 14 (10 - 18)
number and location of teats in primates and elephants
thoracic - 2
supernumerary nipple - what is it and in what animal can it be a problem?
a supernumerary nipple is an additional nipple. can be a problem in cows.
colostrum - define
first milk from mom. it provides passive transfer of immunoglobulins (IgG) and provides protection against pathogens in the first month of life.
in what animal does antibody transplacental transfer occur and thus not need colostrum?
primates
factors affecting colostrum quality include:
age of mom, number of lactations, vaccination status, health status, volume of colostrum (less is better)
what 3 ways can cause failure of passive transfer?
- inadequate supply from dam
- failure to suckle
- failure to absorb into bloodstream
why is it important for the neonate to begin drinking colostrum ASAP?
because efficiency of absorption is ~ 25% at birth but gut closure occurs in a linear fashion beginning at birth and is completely closed by 24 hours and the calf needs ~ 4L of good quality colostrum.
what are the 4 stages of lactation?
- mammogenesis
- lactogenesis
- galactopoiesis
- involution
define mammogenesis
development of mammary gland
define lactogenesis
production of milk
define galactopoiesis
secretion and continued production of milk
define involution
atrophy of secretory cells induced by cessation of suckling and decreased prolactin and GH
when does momogenesis occur?
during pregnancy
high estrogen promotes development of mammary ducts
high progesterone promotes lobulo-alveolar growth
when does lactogenesis occur and what does it do?
during late gestation
progesterone falls and prolactin rises
this initiates milk synthesis
what stimulates galactopoiesis and what does it do?
prolactinand growth hormone stimulate galactopoiesis.
suckling stimulates oxytocin release and contract myoepithelial cells to initiate “milk let-down”
what stimulates milk production?
- removal of milk from mammary gland
- the higher the frequency of milk removal the higher the production
what overrides letdown hormone action?
adrenaline from nerve endings in response to unusual stimuli or pain
what decreases the rate of milk syntehsis?
allowing mammary gland to reach storage capacity; pressure atrophy
when does lactation peak?
3 - 8 weeks following its onset, then declines steadily
when does lactation peak in the bitch?
3- 4 weeks
when does lactation peak in the sow?
21 days
when does lactation peak in the cow?
30 days - 60 days
when does lactation peak in the mare?
30 - 60 days
same as the cow
how high are energy demands for the lactating cow?
super high! they produce 100 lbs of milk/day!
total energy needed = 60Mcal/day - 4.6 times maintenance
super human athletes need 6 - 7 Mcal/day - 2.4-2.8 times maintenance
define involution
the gradual regression of the mammary gland following lactation
what stimulates involution?
- decrease in prolactin and growth hormone - causes apoptosis of epithelial cells
- cessation of suckling - decreases stimulus for production causes increase in pressure and eventually pressure atrophy
