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Endo Exam 2 > Lactation > Flashcards

Lactation Flashcards

1
Q

Mammary glands

A 
Highly modified tubuloalveolar apocrine sweat glands

Structure:
Breast lobe
15-25 compound tubule-acinar glands of variable size
Within each lobe:
Lobules
Multiple acini
Terminal ducts
Drain each lobule
Lactiferous duct
Drains terminal ducts
Lactiferous sinus
A dilation in the duct immediately before the opening
Intralobular stroma
Hormonally responsive CT, little adipose
Interlobular tissue
Dense regular CT and adipose tissue
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2
Q

Terminal duct lobular unit (TDLU)

A

Grapelike cluster of alveoli with terminal ducts and intralobular stroma

Connective tissue
- Loose, collagen rich with dispersed adipose cells

Cells
- Luminal epithelial cells (Columnar to cuboidal)

Myoepithelial cells
-Flattened, basal

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3
Q

Inactive versus active mammary glands

A

Inactive
Stroma constitute the major portion of lobules
Luminal epithelium columnar, dispersed chromatin

Active
Proliferation of the duct system
Alveoli constitute the major portion of lobules
Luminal epithelium cuboidal, pale cytoplasm, prominent nucleoli

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4
Q

Nipple Parts

A

Areola, Areolar sebaceous glands, lactiferous ducts, bundles of smooth muscles

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5
Q

Areola

A

Pigmented skin (melanocytes)
Stratified squamous keratinized epithelium
Dermal papillae

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6
Q

Lactiferous ducts

A 
Transitioning epithelium
From the lactiferous duct
- Single layer of columnar or cuboidal
Within the lactiferous duct
- Stratified cuboidal
Near duct opening
- Stratified squamous keratinized epithelium
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7
Q

Breast cancer

A

80% are invasive ductal carcinoma
Carcinomas (Arise from epithelium:
Ductal- Within the duct, Lobular- Within the terminal acini)

Sarcomas
- Arise from stroma

In situ
- Has not yet invaded breast tissue, resides inside pre-existing lobules or ducts

Invasive
- Cells infiltrate breast connective tissue

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8
Q

Hormone receptor status

A

Determines responsiveness to therapeutic interventions

  • Estrogen-receptor positive (ER+)
  • Human epidermal growth factor expression (HER-2/neu+)
  • Progesterone-receptor positive (PR+)

Triple negative

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9
Q

Invasive Breast Cancer: Breast Epithelium

A 
(primarily ductal)
		Highly mitogenic
		Hormonally responsive
		Primarily Estrogen  
		(~75% E+, 65% of E+ are also PR+)

CYP19 aromatase inhibitor
Inhibits peripheral conversion: androgen –> estrogen
(postmenopausal)

Selective Estrogen Receptor Modulator (SERM)
(E.g.: Tamoxifen, agonist at bone and uterus; antagonist at breast)
(premenopausal)

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10
Q

Estrogens/Progesterone

A

Fetoplacental production
Mammogenic
Continue to rise throughout pregnancy

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11
Q

Prolactin (PRL)

A

Secreted by anterior pituitary gland during pregnancy
Mammogenic, lactogenic
↑ 10-20x from ~ 5th week until parturition
Estrogen stimulates production & inhibits action

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12
Q

Human chorionic somatomammotropin (hCS)/ Human placental lactogen (hPL)

A
  • Structurally similar to PRL and GH
  • Produced by the placenta
  • Lactogenic
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13
Q

State of lactation hormones near end of pregnancy

A

Near end of pregnancy:
breasts are fully developed but milk production is suppressed except for small amount of colostrum
- Inhibited by high estrogen & progesterone during pregnancy

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14
Q

Oxytocin

A

Neurohypophyseal hormone
Produced during parturition
Stimulates uterine contractions

Promotes contraction of myoepithelial cells resulting in milk ejection (“let-down”)

↑ oxytocin synthesis and release via positive feedback caused by suckling, anticipation of nursing, and audiovisual stimuli

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15
Q

Four Stages of Lactation

A

Milk Synthesis
Initiated by PRL and hPL in later pregnancy

  1. Lactogenesis
    Milk synthesis by alveolar cells and secretion into alveolar lumen
    Initiated after birth by the loss of placental steroids
  2. Galactopoiesis
    Maintenance of established lactation
    Mainly controlled by PRL which is increased by infant suckling
  3. Milk Ejection
    Passage of milk to the duct system, collection in ampulla and larger ducts, and delivery to infant
    Controlled by oxytocin release stimulated by suckling, anticipation of nursing, and audiovisual stimuli
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16
Q

Initiation of Lactation

A

Requires coordinated action of several stimuli:

↑ Prolactin
- Mammogenic, lactogenic, galactopoietic

↓ Estrogen and Progesterone

  • High estrogen & progesterone inhibit onset of lactogenesis
  • Abruptly fall following parturition

↑ Oxytocin
- Galactokinetic

Suckling

  • Inhibits hypothalamic dopaminergic neurons
  • Primary neural stimulus post-parturition
17
Q

Lactation Following Parturition

A

After birth, estrogen and progesterone levels drop and milk is produced in 1-7 days
Colostrum: special fluid few hours of nursing
- high in nutrients, fats, and antibodies to protect the newborn from infection

After initiation of lactation, amount of milk produced is mainly controlled by prolactin (galactopoietic)
- Produced in response to the suckling of the infant
- Neurohumoral reflex leads to burst of PRL secretion
PRL levels return to normal after a few weeks if no breast-feeding occurs
With continued breast-feeding, PRL levels maintain at a higher baseline level than in non-pregnant females

18
Q

Milk Ejection

A

Alveolar milk accumulates in the lactiferous sinuses or ampullae (enlargements of ducts near opening of nipple)

Suckling:
↑ hypothalamic release of oxytocin from posterior pituitary

Oxytocin:
↑ contraction of myoepithelial cells around the ducts

Negative maternal emotions (frustration, anger, anxiety) can inhibit oxytocin secretion & suppress milk ejection reflex

19
Q

Effects of Suckling on Hormone Release Maintaining Lactation and Milk Ejection

A

Suckling stimulus
Activates afferent neural pathway. Breast –> spinal cord –> hypothalamus

  1. Inhibition of Inhibition
    Inhibition of Dopamine (Prolactin Inhibitory Factor, PIF) from the hypothalamus
    Removes inhibition of lactotrophs –> ↑prolactin –> milk production

Stimulates hypothalamic oxytocin production & release from posterior pituitary
Activates receptors on breast myoepithelial cells –> milk “let-down”

  1. Inhibits hypothalamic production of GnRH
    Results in ↓ LH and FSH, inhibition of ovarian cycle
20
Q

Compositional Differences in Milk

A

Colostrum: thin, yellowish milk-like substance secreted first few days after parturition. High concentration of immunoglobulins.

Human milk: emulsion of fats in an aqueous solution containing sugar (lactose), proteins (lactalbumin and casein), and K+, Ca2+ , Na+, Cl- and phosphate.

Cow’s milk: nearly three times more protein than human milk due to high casein content and higher electrolyte concentration.

21
Q

Immunology and breastfeeding

A

Infant immune system is immature at birth
In utero, transfer of antibodies across placenta
Protection tapers off quickly after birth

Breast milk contains a number of different agents to protect the infant:
Secretory IgA
WBCs: neutrophils and macrophages
Growth factors: EGF (epidermal growth factor), NFG (nerve growth factor), IGF (insulin-like growth factor)

22
Q

Benefits of Breast Feeding

A

Infant

Reduction in infections
Secretory IgA
Initial increased growth
Decreased obesity in adulthood
Positive effects on mental development

Mother

More rapid and sustained weight loss
Lactational amenorrhea
Psychological benefits
Cost effective

Endo Exam 2 (14 decks)

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