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REPRO > Lactation > Flashcards

Lactation Flashcards

1
Q

Define mammogenesis

A

Mammary growth at puberty or during pregnancy

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2
Q

Define lactogenesis

A

Initiation of milk secretion at parturition (production of colostrum)

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3
Q

Define galactopoeisis

A

Continued milk secretion during lactation

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4
Q

Describe the embryological development of the mammary glands

A
  • originate from epidermis
  • Arise along 2 lateral lines on ventral surface of developing foetus
  • Called mammary ridge, thickened epidermal tissue, give rise to primary mammary bud
  • Extend from axillary region to inguinal region
  • Primary bud pushes into dermis to grow
  • Branch into secondary mammary bud
  • Will then branch out and canalise to form lactiferous ducts
  • Myoepithelial cells from mesoderm
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5
Q

Outline the significane of lactation

A
  • Free neonate from dependency on other foods
  • Allows offspring to continue development outside uterus
  • Sovial development and bonding
  • Natural contraception
  • Foetus born with minimal fat for ease of birth
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6
Q

Outline the adaptation allowing neonates to suckle and breath at the same time

A

Long hard palate, not present in birds

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7
Q

Describe the anatomy of the mammary gland

A
  • Glandular tissue, secretory epithelial cells and excretory ducts
  • Excretory ducts empty into gland cistern
  • Epithelial cells surrouding spherical lumen = alveolus (aka alveolar cells)
  • Myoepithelial cells around each alveolus and ducts
  • Groups of alveoli form lobules
  • Groups of lobules form lobes
  • As each gland develops, get development of a teat sinus
  • Some have internal sphincter in teat/streak canal
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8
Q

Where is the majority of control in the mammary gland?

A

In the teat/streak canal

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9
Q

What is the function of the myoepithelial cells?

A

Contraction will propel milk out of alveoli and into ducts

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10
Q

What speecies have thoracic mammary glands?

A
  • Man and other primates

- Elephant

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11
Q

What species have abdominal mammary glands?

A
  • Dog
  • Cat
  • Sow
  • Rat
  • Rabbit
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12
Q

What species have inguinal mammary glands?

A
  • Goats, sheep
  • Cow
  • Guinea pig
  • Mare
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13
Q

Which species have 2 mammary glands?

A
  • Man and other primates
  • Elephant
  • Goats, sheep
  • Guinea pig
  • Mare
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14
Q

How many mammary glands do dogs have?

A

~10

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15
Q

How many mammary glands to cats have?

A

8

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16
Q

How many mammary glands to pigs have?

A

8-18

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17
Q

How many mammary glands do rats have?

A

~10

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18
Q

How many mammary glands do rabbits have?

A

10

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19
Q

How many mammary glands to cows have?

A

4

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20
Q

How many teat canals per teat do humans, elephants and rabbits have?

A

8-10

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21
Q

How many teat caals do dogs have per teat?

A

8-22

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22
Q

How many teat canals per teat do cats have?

A

4-8

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23
Q

How many teat canals per teat do sows and mares have?

A

2

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24
Q

Which species have 1 teat canal per teat?

A
  • Rats
  • Goats, sheep
  • Cows
  • Guinea pigs
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25
Q

Compare teat sinuses between species?

A
  • In horses and cattle branches anastomose to form one teat sinus
  • In bitch, no coming together of ducts
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26
Q

Describe the mammary glands of marsupials

A
  • Within pouch

- Young forms direct seal around teat

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27
Q

Describe the mammary glands of monotremes

A
  • Mammary tissue essentailly a band of sweat glands

- No teats - milk runs out along hair shafts

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28
Q

Describe the suspensory apparatus of the bovine mammary gland

A
  • Suspensory ligament divided into 2 parts
  • Medial suspensory ligaments
  • Lateral suspensory ligament
  • Like 2 palstic bags in one hand - where they touchh is medial ligament, outsides are lateral ligaments
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29
Q

Describe the medial suspensory ligament of the bovine mammary gland

A
  • Arises from symphyseal tendon (attaches prepubic tendon to pubic symphysis)
  • Mainly yellow elastic connective tissue
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30
Q

Describe the lateral suspensory ligaments of the bovine mammary gland

A
  • Run from symphyseal tendon and external crus of the inguinal ring
  • Assisted by femoral fascia
  • Then run ventrally over lateral aspects of udder
  • Inelastic connective tissue
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31
Q

Describe the connective tissue in the bovine mammary glands

A
  • Runs through glands

- Come together to form 4 bands

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32
Q

Expain the lateral deviation seen in the engorged udder or older ruminants

A
  • Medial ligament stretchier

- Laterals cannot stretch

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33
Q

Describe the innervation of the mammary glands of the bitch

A
  • Only sympathetic supply
  • No PSNS
  • Controls vascular elements only
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34
Q

How are the myoepithelial cells stimulated?

A

Oxytocin, no neural signals

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35
Q

Describe the lymphatic drainage of the mammary glands in the bitch

A
  • Cranial glands: axillary and axxessory axillary lymph nodes
  • Caudal: superficial inguinal (mammary) nodes
  • Middle glands either drain cranially or caudally, no mixture
  • Can have more cranial glands draining caudally and more caudal glands draining cranially, no way to tell
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36
Q

Describe bovine lympatic drainage of the mammary glands

A
  • Lymphatic drainage arises in lobules, not alveoli

- Leaves gland via mammary lymph nodes (upper rear of udder in cattle)

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37
Q

Describe the innervaiton of the bovine mammary gland

A
  • Somatic sensory afferent from tactile receptors in skin
  • Sympathetic motor efferent along blood vessles (from lumbar and sacral sympathetic chains)
  • 4 spinal nerves in cattle (1st, 2nd lumbar, inguinal and perineal)
  • No PSNS
  • Myoepithelial cells controlled by oxytocin, not innervated
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38
Q

What is the blood supply to thoracic mammary glands?

A

Mammary arteries are branches of thoracic and pectoral arteries

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39
Q

What is the blood supply to abdominal mammary glands?

A

Branches of cranial and caudal superficial epigastric arteries

40
Q

What is the blood supply to inguinal mammary glands?

A

Branches of external pudendal artery

41
Q

Describe the blood supply to the mammary glands of cats and dogs

A
  • Anterior glands: lateral and internal thoracic, cranial superficial epigastric arteries
  • Caudal glands: caudal superficial epigastric arteries (from external pudendal)
42
Q

Describe the venous drainage of the bovine mammary gland

A
  • External pudendal veins into external iliacs then caudal vena cava
  • Superficial epigastric veins (aka milk veins) into internal thoracic v then cranal vena vaca
  • Perineal veins into internal pudendal vein then caudal vena cava
43
Q

What controls mammary gland growth?

A

Endocrine mediated

44
Q

Describe the growth of mammary glands between birth and puberty

A
  • Isometric (like any other tissue)

- No ability to secrete milk

45
Q

Describe mammary gland growth after puberty

A
  • Allometric growth
  • During oestrus or menstrual cycles ducts begin to branch under effect of oestrogen
  • More alveoli formed under influence of P4
  • Complete and grapid growht of ducts in presence of prolactin and GH (increase at puberty)
46
Q

Describe mammary gland growth in pregnancy

A
  • Terminal alveoli grow into lobules
  • Prolactin, adrenal cortical hormones adn placental lactogen
  • Relaxin from CL in pigs
  • Allows synthesis of milk
47
Q

What changes occur in mammary gland following lactation?

A
  • Atrophy and regression back to close to original size
  • Never same as before
  • Each successive lactation will get bigger, so more lactations means more capacity for milk
48
Q

Describe the process of mammary gland involution

A
  • Less milk needed, pressure increases in gland
  • Cells less function - pressure atrophy
  • Cells atrophic and die by apoptosis
  • Immune cells (lymphocytes and macrophages) invade tissue
  • Cells remain non-functional until next pregnancy
49
Q

What is the role of immune cell invasion in mammary gland involution?

A

Participate in production of IgG for next lactation

50
Q

Describe mammary gland involution in polytocous species

A
  • Occurs soon after birth
  • e.g. 8 teats but 5 young
  • Match amount of milk to number of young
51
Q

What are the 2 types of milk?

A
  • Regular milk

- Colostrum

52
Q

Describe colostrum

A
  • Secretion accumulated at end of last pregnancy and secretion formed during first 24 hours after parturition
  • More protein, fat, minerals and vitamins
  • Supplies newborn with immunoprotection
53
Q

When does colostrum need to be taken in by the neonate?

A
  • Ideally within first 6 hours
  • At the lates 24-48 hours after birth
  • After this will no longer absorb antibodies
54
Q

Why is colostrum produced for 4 days after birth?

A
  • Will not absorb antibodies in this time

- However will bind out viruses etc in abomasum of neonate

55
Q

Which species has milk that is appropriate for most species?

A

Goats

56
Q

What component of milk is the principle contributor to osmolarity?

A

Lactose

- Milk has same osmolarity as blood

57
Q

What proteins are present in milk?

A
  • Caseins
  • Lactalbumin
  • Lactoglobulin
  • Immunoglobulins
58
Q

Where is milk synthesised?

A

Epithelial cells of alveolus

59
Q

Describe the organelles that are used in milk synthesis

A
  • Mitochondria: ATP for producction, synthesis of fatty acids and non-essential amino acids
  • RER: synthesis of secretory proteins
  • SER: synthesis of phospholipids and TAGs
60
Q

Describe the secretion of fat from the alveolar cells

A
  • Bunch out of cytoplasm with small layer of cytoplasm around the edge
  • Membrane-limited lipid droplets
  • Helps keep milk as an emulsion
61
Q

How are proteins and lactose secreted?

A
  • Granules by exocytosis

- Lactose secreted with protein

62
Q

How is the water component added to milk?

A

Follows lactose by osmotic pressure

63
Q

Describe the synthesis of lipid in the mammary gland

A
  • TAG made from fatty acids in chylomicrons and LDL in blood
  • And from glucose (non-ruminants) or acetate and beta-hydroxybutyrate (in ruminants i.e. ketone bodies)
  • Same pathway as in tissues
  • Body fat broken down by liver
64
Q

Describe the synthesis of lactose by the golgi

A
  • Series of conversions starting with glucose
  • Glucose + ATP -> glucose-6-P and ADP
  • Glucose-6-P -> glucose-1-P
  • Glucose-1-P + uridine triphosphate -> UDP-glucose +PPi
  • UDP-glucose -> UDPgalactose
  • UDP-galactose + glucose via lactose synthase to make lactose and UDP
65
Q

Describe the cellular components of milk

A
  • Leukocytesnad dislodged mammary epithelial cells
  • Normal: 30,000-300,000 cells/ml
  • Inflammation can iincreas 10-100 times due to neutrophil invasion
  • Cell density is parameter of milk quality
66
Q

List the hormones involved in control of galactopoeisis

A
  • Prolactin
  • Oestrogen
  • Progesterone
  • Cortisol
67
Q

Describe the role of prolactin in milk synthesis

A
  • Regulates production of alpha-lactalbumin

- Density of prolactin receptors regulated by thyroid, adrenal and ovarian hormones

68
Q

Describe the role of cortisol in galactopoeisis

A

Necessary for growth and differentiation of golgi apparatus

69
Q

Describe the role of progesterone in the control of galactopoeisis

A
  • Blocks prolactin receptors during pregnancy, blocking milk synthesis
  • Stimulates glandular development
  • Remove P4, produce a-lactalbumin, lose inhibition and gain stimulation
70
Q

List the factors regulating continuous milk secretion

A
  • Hormones
  • Local conditions in alveoli
  • Secretion depends on prolactin
  • Release depends on oxytocin
  • Insulin and growth hormone
  • Accumulation of milk in alveoli
  • Feedback inhibitor of lactation
  • Suckling action of neonate
71
Q

Describe the role of insulin and growth hormone in galactopoeisis

A
  • Growth hormone can substitute for prolactin in ruminants

- Insulin and GH regulate metabolism and ensure adequate energy supply to udder

72
Q

Describe the feedback inhibitor of lactation

A
  • Modulates synthesis of lactose and milk protein

- Inhibits formation of secretory vesicles in golgi apparatus

73
Q

Describe mammogenesis during pregnancy and preparation for lactation

A
  • Placenta produces hromones to induce mammary growth
  • Higher in twin than singleton
  • Placental lactogen in synergy with oestrogen
  • Progesterone and oestrogen still present
  • P4 induces storage of arachidonic acid during pregnancy
  • E2 induces phospholipase A to allow conversion of arachidonic acid to PGF2a to lyse CL, reduce P4 and expose oxytocin receptors
  • mammary growth continues during milk secretion
74
Q

Describe placental lactogen

A
  • Prolactin and some GH activities
  • Produced by binucleate cells of placenta
  • Mainly sheep
75
Q

What hormone do sows use instead of placental lactogen?

A

Relaxin

76
Q

Describe the role of progesterone in mammogenesis

A
  • Provides growth element to glands
  • Grows in preparation, inhibits milk synthesis
  • Gland growth but no synthesis
  • Induces storage of arachidonic acid during pregnancy
77
Q

Describe the role of E2 in mammogenesis

A
  • Induces phospholipase A, thus arachidonic acid converted to PGF2a
  • Leads to luteolysis in species with CL
  • Softens cervix
  • PGF2a induces myometrial contractions
  • E2 exposes myometrial oxytocin receptors
78
Q

What stimulates lactogenesis to begin?

A

Fall in progesterone removing prolactin inhibition

79
Q

Describe the onset of lactogenesis

A
  • Increase in udder volume during pregnancy follows increase in oestrogen and placental lactogen (mimicing prolactin)
  • Onset of milk secretion coincides with drop of P4 at parturition
  • Peak in cortisol stimulates increased conversion from P4 to E2
80
Q

Describe the role in control of lactogenesis by alpha-lactalbumin

A
  • Binds to galactosyltransferase and UDP-galactose to form lactose synthase
  • Needed to produce lactose
  • P4 inhibits this
  • Prolactin induces this
81
Q

Describe the mechanisms for the maintenance of galactopoeisis

A
  • Suckling stimulus -> PVN in hypothalamus
  • Tactile stimulation of mammae maintains prolactin production
  • Removal of milk
  • 2-3x daly suckling needed
  • Only tactile stimulationworks, oxytocin admin does not
82
Q

Describe how the suckling stimulus to the PVN of the hypothalamus acts to maintain galactopoeisis

A
  • Reduces dopamine which releases inhibition on prolactin release from ant. pit
  • Increases vasoactive intestinal polypeptide (VIP) which stimulates prolactin release
83
Q

What is required for milk ejection?

A
  • Sensory activation (not just suckling)
  • Neural activation
  • Oxytocin release
  • Contraction of alveoli and ducts
  • Mechanical transfer of milk
84
Q

Describe the milk ejection reflex

A
  • Stimulation of sensory neurones (suckling, smell, vision, sound), to hypothalamus
  • PVN nerves stimulated, release of oxytocin from neurohypophysis
  • Increases pressure in alveoli
  • Reduce resistance in small excretory ducts
  • Reduce resistance in teat canal
  • Myoepithelial cells surrounding alveoli - squeeze milk out of alveoli into ducts
  • Contract in response to oxytocin
85
Q

Describe the effect of suckling on parturition

A
  • Cervix stretches due to oxytocin
  • Sucking stimulates release of oxytocin
  • Thus suckling drive parturition of rest of litter
86
Q

Describe suckling in pigs

A
  • Set meal times
  • Mother lies down, calles young over
  • Allowed to feed for 2 minutes then shake off young
87
Q

Describe the metabolism during lactation

A
  • Changes in metabolism in many tissues
  • Coordinate redircection of metabolic resources
  • Homeorhesis occurs - reduced fat syntehsis and increased lipolysis, decreased uptake of glucose in muscle and adipose tissue, increase mammary uptake
  • Increased uptake of amino acids in mammary gland (breakdown of muscle protein insufficient)
88
Q

What regulates changes in metabolism during lactation

A
  • Prolactin
  • Growth hormone
  • Insulin
89
Q

Describe the endocrine control of mammary involution

A
  • After weaning
  • Loss of suckling = drop in prolactin
  • Local factors in milk that block secretion
  • Build up of pressure due to loss of milk removal
90
Q

How does lactational anoestrus occur?

A
  • Lactation reduces gonadotrophin secretion
  • Suckling induces opioid production
  • Blocks GnRH secretion preventing ovulation
91
Q

What is embryonic diapause?

A

Delayed implantation

- Extension of the period between blastocyst development and implantation

92
Q

How does lactation lead to embryonic diapause?

A

Reduces metabolic stress on animal that is simultaneously lactating and supporting a pregnancy

93
Q

List species that that have delayed implantation but not due to lactational delay

A
  • Badger
  • Stoat
  • Roe deer
  • Rat, mouse
  • Grey seal
  • Camels
94
Q

Give the roles of oxytocin

A
  • Contraction of myometrium
  • Milk ejection
  • Part of feedback cycle for luteolysis
  • Maternal and social bonding
  • Stimuli for parturition and milk let down
95
Q

List conditions affecting lactation

A
  • Pseudopregnancy
  • Galactostasis
  • Agalactia
  • Mastitis
96
Q

What is galactostasis?

A

Congestion of gland combined with oedema and inflammation

97
Q

What is agalactia?

A
  • Lack or reduced milk production
  • Inadequate nutrition or liquid intake, mastitis, other bacterial infections, mineral deficiencies
  • MMA in sows

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