Histophysiology of the mammary gland Flashcards
Mammary glands are highly modified tubuloalveolar apocrine sweat glands. What are the two main structural components?
Breast lobe
Interlobar tissue
The breast lobe is compsed of 15-25 compound tubule-acinar glands of variable size. What do you find in each lobe?
- Lobules
- Terminal ducts
- lactiferous ducts
- lactiferous sinus
- intralobular stroma
What do terminal ducts do?
drain each lobule
What do lactiferous ducts do?
Drain terminal ducts
What is the lactiferous sinus?
•dilation in the duct immediately before the opening
What is interlobular tissue composed of?
–Dense regular CT and adipose tissue
What is the structure of the terminal duct unit like? What is it composed of?
–Grapelike cluster of alveoli with terminal ducts and intralobular stroma
–Connective tissue
•Loose, collagen rich with dispersed adipose cells
What are the main cells of the TDLU?
•Luminal epithelial cells
–Columnar to cuboidal
•Myoepithelial cells
–Flattened, basal
How can you identify inactive breast tissue?
IS largely connective tissue
Is this active or inactive breast tissue?
Active
Active or inactive?
Inactive
Describe inactive mammary gland tissue
- Stroma constitute the major portion of lobules
- Luminal epithelium columnar, dispersed chromatin
What do we see in active mammary glands? What constitutes the major portion of the lobules?
- Proliferation of the duct system
- Alveoli constitute the major portion of lobules
- Luminal epithelium cuboidal, pale cytoplasm, prominent nucleoli
What are the four structures of the nipple?
- –Areola
- –Areolar sebaceous glands
- –Lactiferous ducts
- –Bundles of smooth muscle
What are the components of the areola?
- Pigmented skin (melanocytes)
- Stratified squamous keratinized epithelium
- Dermal papillae
Describe the cell types of the following:
- From the lactiferous duct
- Within the lactiferous duct
- Near duct opening
•From the lactiferous duct
–Single layer of columnar or cuboidal
•Within the lactiferous duct
–Stratified cuboidal
•Near duct opening
–Stratified squamous keratinized epithelium
How are the smooth muscle bundles arranged in the nipple?
- Arranged radially and circumferentially in CT
- Arranged longitudinally around lactiferous ducts
What are the majority of breast cancers?
–80% are invasive ductal carcinoma
What do carcinomas arise from?
–Ductal
»Within the duct
–Lobular
»Within the terminal acini
What is this?
An in situe (not yet invaded surrounding tissues) ductal carcinoma
What do we have here?
Invasive ductal carcinoma
What do sarcomas arise from?
stroma
What are the receptors that determine responsiveness to therapeutic intervention in breast cancer?
- Estrogen-receptor positive (ER+)
- Human epidermal growth factor expression (HER-2/neu+)
- Progesterone-receptor positive (PR+)
Primary ductal carcinomas are highly mitogenic, and are hormonally responsive. What hormone do they primarily respond to?
Estrogen
What does CYP19 aromatase inhibitor do?
Inhibits peripheral conversion: androgen –> estrogen
(postmenopausal)
What are the 4 major mammogenic and lactogenic hormones?
Estrogen
progesterone
prolactin
hCS/hPL
Near end of pregnancy: breasts are fully developed but milk production is suppressed except for small amount of colostrum. What is this inhibited by?
- Inhibited by high estrogen & progesterone during pregnancy
What is the major galactokinetic hormone (milk ejector)? How does it do this?
Oxytocin
•Promotes contraction of myoepithelial cells resulting in milk ejection (“let-down”)
What is the release and synthesis of oxytocin stimulated by?
•positive feedback caused by suckling, anticipation of nursing, and audiovisual stimuli
What are the four (more like 3 really) stages of lactation?
- Milk synthesis
- lactogenesis
- galactopoiesis
- milk ejection
What initiates milk synthesis?
Initiated after birth by the loss of placental steroids
What controls galactopoiesis (maintenance of lactation)
Mainly controlled by PRL which is increased by infant suckling
Initiation of lactation requires the coordinated action of what stimuli?
- ↑ Prolactin
- ↓ Estrogen and Progesterone
- ↑ Oxytocin
- Suckling
What is colostrum?
- thin, yellowish milk-like substance secreted first few days after parturition. High concentration of immunoglobulins.
- high in nutrients, fats, and antibodies to protect the newborn from infection
What can inhibit oxytocin secretion and suppress milk ejection reflex?
Negative maternal emotions (frustration, anger, anxiety)
What are the four steps of the suckling reflex?
- Suckling stimulus
- Inhibition of Inhibition
- Stimulates hypothalamic oxytocin production & release from posterior pituitary
- Inhibits hypothalamic production of GnRH
What pathway is activated by suckling?
Activates afferent neural pathway. Breast –> spinal cord –> hypothalamus
Explain step two of the suckling reflex: inhibition of inhibition.
Inhibition of Dopamine (Prolactin Inhibitory Factor, PIF) from the hypothalamus
Removes inhibition of lactotrophs –> ↑prolactin –> milk production
What does step 3 of the suckling reflex: hypothalamic oxytocin production & release from posterior pituitary, lead to?
Activates receptors on breast myoepithelial cells –> milk “let-down”
Step four of the suckling reflex Inhibits hypothalamic production of GnRH results in?
Results in ↓ LH and FSH, inhibition of ovarian cycle
Describe the composition of human milk
emulsion of fats in an aqueous solution containing sugar (lactose), proteins (lactalbumin and casein), and K+, Ca2+ , Na+, Cl- and phosphate.
How is cow’s milk different from human milk?
nearly three times more protein than human milk due to high casein content and higher electrolyte concentration.
What agents does breast milk contain 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)
What are the benefits of breast feeding to the infant? (4)
–Reduction in infections
•Secretory IgA
–Initial increased growth
–Decreased obesity in adulthood
–Positive effects on mental development
What are four benefits of breast feeding to the mother?
–More rapid and sustained weight loss
–Lactational amenorrhea
–Psychological benefits
–Cost effective
