Lecture 19: Mammary gland and lactation (Galvao)

Question 0

how does the mammary gland first develop in prenatallife?

Answer 0

as ridges of epidermis called mammary ridges

Question 1

the mammary gland is a modified version of what gland?

Answer 1

sweat gland

Question 2

In what order do mammary glands first develop?

Answer 2

primary mammary buds develop from mammary ridges, with branching and lengthening of the secondary buds and finally canalization (duct formation) occurring prior to birth.

Question 3

what portion of mammary gland development occurs at puberty?

Answer 3

further duct and alveolar development - allmoetric growth (increased rate)

Question 4

what is the influence of progesterone on mammary gland development?

Answer 4

it stimulates alveoli growth

Question 5

what influence does estrogen have on mammary gland growth?

Answer 5

duct system growth

Question 6

what influence does prolactin and growth hormone have on mammary gland development?

Answer 6

promote duct development

Question 7

when do final stages of mammary gland development occur?

Answer 7

pregnancy

Question 8

what influence do prolactin, adrenal corticosteroids and placental lactogen have on mammary gland development during pregnancy?

Answer 8

they develop terminal alveoli

Question 9

what stimulates lactogenesis (production of milk)

Answer 9

a decrease in progesterone and an increase in prolactin

Question 10

during pregnancy, terminal alveoli begin to grow into branches called…

Answer 10

lobules

Question 11

what type of cells produce milk? and where is it secreted?

Answer 11

specialized epithelial cells and secreted into the lumen of alveolus

Question 12

what are the 5 different ways of milk synthesis/secretion?

Answer 12

just remember the cow L-E-A-P-T over the moon:
L - lipid
E - exocytosis
A - apical transport
P - paracellular
T - transcytosis

Question 13

describe exocytosis

Answer 13

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

Question 14

describe milk synthesis: lipid

Answer 14

produced in the sER from FA and glycerol, coalesce into large droplets are enveloped by the plasma membrane and released as a fat globule.

Question 15

describe milk synthesis: apical transport

Answer 15

water, Na, Cl, K, bicarb, and monosaccharides can cross the apical membrane

Question 16

describe milk synthesis: transcytosis

Answer 16

allows transport of IgA from the interstitial space (produced by plasma cells or from blood) into milk.

Question 17

describe milk synthesis: paracellular

Answer 17

allow for transport of IGs and leukocytes in late gestation and infection (mastitis).

Question 18

number of teats in a cow and their location

Answer 18

4 - inguinal

Question 19

number of teats in the mare, goat, sheep and location

Answer 19

2 - inguinal

Question 20

number and location of teats in a dog

Answer 20

(thoraco)abdominoinuginal 10 ( 8 -12)

Question 21

number and location of teats in the pig

Answer 21

thoracoabdominoinguinal 14 (10 - 18)

Question 22

number and location of teats in primates and elephants

Answer 22

thoracic - 2

Question 23

supernumerary nipple - what is it and in what animal can it be a problem?

Answer 23

a supernumerary nipple is an additional nipple. can be a problem in cows.

Question 24

colostrum - define

Answer 24

first milk from mom. it provides passive transfer of immunoglobulins (IgG) and provides protection against pathogens in the first month of life.

Question 25

in what animal does antibody transplacental transfer occur and thus not need colostrum?

Answer 25

primates

Question 26

factors affecting colostrum quality include:

Answer 26

age of mom, number of lactations, vaccination status, health status, volume of colostrum (less is better)

Question 27

what 3 ways can cause failure of passive transfer?

Answer 27

1. inadequate supply from dam 2. failure to suckle 3. failure to absorb into bloodstream

Question 28

why is it important for the neonate to begin drinking colostrum ASAP?

Answer 28

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.

Question 29

what are the 4 stages of lactation?

Answer 29

1. mammogenesis 2. lactogenesis 3. galactopoiesis 4. involution

Question 30

define mammogenesis

Answer 30

development of mammary gland

Question 31

define lactogenesis

Answer 31

production of milk

Question 32

define galactopoiesis

Answer 32

secretion and continued production of milk

Question 33

define involution

Answer 33

atrophy of secretory cells induced by cessation of suckling and decreased prolactin and GH

Question 34

when does momogenesis occur?

Answer 34

during pregnancy high estrogen promotes development of mammary ducts high progesterone promotes lobulo-alveolar growth

Question 35

when does lactogenesis occur and what does it do?

Answer 35

during late gestation progesterone falls and prolactin rises this initiates milk synthesis

Question 36

what stimulates galactopoiesis and what does it do?

Answer 36

prolactinand growth hormone stimulate galactopoiesis. suckling stimulates oxytocin release and contract myoepithelial cells to initiate "milk let-down"

Question 37

what stimulates milk production?

Answer 37

- removal of milk from mammary gland | - the higher the frequency of milk removal the higher the production

Question 38

what overrides letdown hormone action?

Answer 38

adrenaline from nerve endings in response to unusual stimuli or pain

Question 39

what decreases the rate of milk syntehsis?

Answer 39

allowing mammary gland to reach storage capacity; pressure atrophy

Question 40

when does lactation peak?

Answer 40

3 - 8 weeks following its onset, then declines steadily

Question 41

when does lactation peak in the bitch?

Answer 41

3- 4 weeks

Question 42

when does lactation peak in the sow?

Answer 42

21 days

Question 43

when does lactation peak in the cow?

Answer 43

30 days - 60 days

Question 44

when does lactation peak in the mare?

Answer 44

30 - 60 days | same as the cow

Question 45

how high are energy demands for the lactating cow?

Answer 45

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

Question 46

define involution

Answer 46

the gradual regression of the mammary gland following lactation

Question 47

what stimulates involution?

Answer 47

1. decrease in prolactin and growth hormone - causes apoptosis of epithelial cells 2. cessation of suckling - decreases stimulus for production causes increase in pressure and eventually pressure atrophy