Reproduction -Mammary Gland Flashcards Preview

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Flashcards in Reproduction -Mammary Gland Deck (28)
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1
Q

What is the function of the teat canal aka streak canal in the mammary gland & where is it?

A

The streak canal/teat canal keeps milk in/bacteria out of udder. It is the canal immediately proximal to the teat sphincter.

2
Q

What is the teat cistern?

A

Teat duct with capacity of 30-45 mL; separted from teat canal by Furstenberg’s rosette

3
Q

What is the gland cistern?

A

Collecting duct for mammary ducts, capacity up to 400 mL; separated from teat cistern by cricoid fold aka cisternal ringfold; from here branch the mammary milk ducts.

4
Q

What is the stroma in the mammary gland?

A

Connective tissue of mammary gland that acts as support system.

5
Q

What is the parenchyma of the mammary gland?

A

Glandular, secretory tissue.

6
Q

What are the alveoli of the mammary gland?

A

Secreting epithelial cells called alveolar cells; each surrounded by capillary network and myoepithelial cell, which contracts to eject milk into lobule.

7
Q

What is the function of the duct system of the mammary gland?

A

Storage & transport of milk; lined by two layers of epithelium; myoepithelium arranged longitudinally; shorten to increase diameter to facilitate milk flow

8
Q

What are the lobules and lobes of the mammary gland?

A

Clusters of alveolar tissue supported by stroma;

alveoli → lobules → lobes

9
Q

What is a galactophore?

A

Receives milk from lobe, empties into gland cistern.

10
Q

What separates the mammary gland into four quarters?

A

Median, lateral and intermammary ligaments. The lateral side produces ~60% of milk, median ~40%.

Median suspensory ligament - separates R & L halves of udder; connects udder to abdominal wall; made of lamellae, elastic tissue that stretches

Lateral suspeonsory ligament - inflexible; surrounds outer wall of udder; attached to prepubic & subpubic tendons

Intermammary groove - formed where lateral suspensory ligament & median suspensory ligament meet

11
Q

How many gallons of blood need to pass through the udder to make one gallon of milk?

A

400 gallons.

12
Q

Which arteries supply blood to the udder?

A

External pudendal arteries

&

cranial mammary artery.

13
Q

How does blood exit the udder?

A

Via the:

External pudendal veins

&

Subcutaneous abdominal veins

14
Q

When does mammogenesis begin and where?

A

Week 7-8 of gestation -
primary & secondary ducts develop from paired mammary ridges on ventral surface of developing embryo

15
Q

What are the hormones involved in mammogenesis?

A
  • *Oestrogen (E2)**
  • major influence at puberty, when primary & secondary ducts grow & divide, + ↑ in lobuloalveolar units
  • aids devt of stromal tissue
  • deposition of fat
  • inhibits secretion of milk
  • *Progesterone (P4)**
  • promotes development of lobules & alveoli
  • ↑ alveolar-cell proliferation, enlargement → secretory
  • inhibits milk secretion (only w/ stim. from PRL)
  • IGF-1, cortisol, PRL & relaxin aid in lobuloalveolar growth
  • IGF-1, cortisol & relax in aid in ductal growth
16
Q

When does mammogenesis end?

A

Pregnancy only

  • receptors for E2 & P4
  • in cow, P4 elevated thru gestation, E2
    during 2nd half
  • E2 & P4 elevated → geometric cell multiplication → lobuloalveolar growth
  • *∴**
  • 1st half: ductal growth & alveolar formation
  • 2nd half: mostly lobuloalveolar growth w/ continuing ductal growth, due to influence of progesterone
17
Q

Lactogenesis is the onset of milk secretion. When does it begin and where?

A
  • *Lactogenesis 1**
  • late pregnancy*
  • secretory activity accelerates
  • colostrum produced
  • *Lactogenesis 2**
  • Days 2/3 - 8 postpartum*
  • copious milk production - milk vol. ↑ rapidly from 36-96 hours postpartum, then levels off
18
Q

What are the hormones involved in lactogenesis?

A

Triggered following expulsion of placenta by ↓ P4 & E2 & continued PRL (uninhibited release from ant. pituitary)

Prolactin - (PRL):

  • ↑ by oxytocin, ↓ by dopamine (PIH)
  • suckling response inhibits PIH; levels rise & fall in proportion to frequency, intensity & duration of nipple & suckling stim
  • falls ~50% in first week postpartum in breastfeeding women
  • if no breastfeeding, PRL returns non-pregnancy levels by Day 7 postpartum
  • JAK-stat signalling cascade important in milk
    production
19
Q

When does lactogenesis end?

A

If milk is not regularly suckled, pressure atrophy - pressure from increasing milk volume applied to alveolar cells inhibits lactation.

20
Q

What is galactopoeisis?

A

Maintenance of lactation.
Requires removal of milk from breast.

21
Q

How does galactopoesis begin?

A

Post-partum suckling.

22
Q

What hormones are involved in galactopoeisis?

A

Suckling → Thyroid Stimulating Hormone (TSH), Growth Hormone (IGF-1) & ACTH influence general metabolism
PRL - stimulates milk synthesis

23
Q

What does milk ejection refer to, and when does it begin?

A

Expulsion of milk from alveoli
“let down”.

24
Q

Which hormones are involved in milk ejection?

A

Milk Ejection Reflex (+ feedback):

Suckling → Oxytocin (post. pit)
- causes myoepithelia to contract → stored milk pushed down into ducts thru collecting sinuses → nipple pores/teats

25
Q

What is involution?

A

Termination of milk secretion & mammary gland regression

26
Q

When does involution begin?

A

Cow: Within 7 days of drying off
Mammary epithelial cells de-differentiate during dry period; aging cells lost by apoptosis & replaced by division of remaining cells

Rodents: Defoliation; mammary epithelial cells fall of basement membrane; requires more extensive regeneration at start of next lactation

27
Q

When does involution end?

A

When mammary epithelial cells return to normal size & shape.

28
Q

What is the composition of milk? What affects the composition, and how does it differ between species and breeds?

A

Milk composition & volume produced are very variable between & within species.

In general, milk is comprised of fat, protein, lactose & ash. It also contains immunoglobulins from the mother, and growth hormone.

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