Breast / Mammary Gland Histology & VM Lab - Bolender

Question 1

The mammary glands are are modified version of what other gland?

Answer 1

Apocrine sweat glands

Question 2

True or false: The ducts of the mature mammary gland are branched.

Answer 2

True.

Question 3

1. What are some of the changes that occur in breast tissue during female puberty?
2. Again, what hormone is responsible for the maturation of the breasts?

Answer 3

1. Developments:
   
   • Adipose tissue accumulates
   • Duct system branches
   • Rudimentary lobules appear
2. Driven by estrogen

Question 4

About how many lobes are in a typical mammary gland?

Answer 4

12-20

Question 5

List the hierarchical divisions of the mammary gland and its duct system.

Answer 5

From largest to smallest:

• Lobes
  
  • Drained by lactiferous ducts which expand into lactiferous sinuses
  • The sinuses (one for each lobe, not a single one per breast) open at the nipple
• Lobules
  
  • Drained by extralobular terminal ducts
• Terminal Duct-Lobular Unit
  
  • Drained by intralobular terminal ducts, which arise from the terminal alveoli/ductules

Question 6

What two types of stroma are the mammary lobes seperated by?

Answer 6

• Suspensory / Cooper’s ligaments
  
  • Fibrous connective tissue
• Adipose tissue

Question 7

What type of connective tissue is interlobular CT of the breast?

What about the intralobular CT?

Answer 7

• Interlobular: Dense irregular
• Intralobular: Loose
  
  • Also contains immune cells.
  • More cellular than fibrous, esp. during pregnancy

Question 8

The ducts of the mammary gland (including the terminal ductules/alveoli) are lined by how many layers of cells?

What cells are each of the layers composed of?

Answer 8

Bilayer of cells

• Inner (luminal) layer:
  
  • cuboidal to low columnar epithelial cells
• Outer (basal) layer:
  
  • flattened myoepithelial cells
  • thought to be discontinuous

Question 9

What skin (not mammary) glands are present in the nipple?

What skin glands are present in the skin of the areola?

Answer 9

• Nipple
  
  • Only sebaceous glands
• Areola
  
  • Sweat Glands
  • Modified sebaceous glands called areolar glands or Montgomery Glands / Tubercles

Question 10

What type of epithelium lines the lactiferous sinuses?

Answer 10

Squamous epithelium from the nipple surface that has extended into the sinuses

Question 11

What types of muscle fibers does the nipple contain?

Answer 11

Radial and circular smooth muscle bundles

Question 12

1. During pregnancy, what components of the breast are developed more fully?
2. Which components of the breast are noted to decrease?
3. What factors drive this breast development of pregnancy?

Answer 12

1. Development of the terminal ductules
   
   • Enlargement
   • Epithelial cells acquire lipid droplets (fuel?)
   • Epithelial cells acquire secretory apparatus
2. Decrease in fibrous CT and adipose tissue
3. Estrogen, progesterone, and growth factors

Question 13

What visible change of the nipple and areola occur during pregnancy?

Answer 13

Increased pigmentation

Question 14

What four hormones outside of the gonadal axis also influence mammary lobule development during pregnancy?

Answer 14

• Prolactin
• Placental lactogen
• Thyroxine
• Corticosteroids

Question 15

Terminal ductule hypertrophy occurs due to ____ production & storage. This begins during the _____ trimester.

Answer 15

milk, third

Question 16

What is the initial milk produced by the breast called?

What is the timeline for the production of this specific fluid?

Answer 16

Colostrum

late pregnancy to ~5 days postpartum

Question 17

Compare the composition of colostrum with that of the later-produced **breast **milk.

Answer 17

• Colostrum has
  
  • high amounts of:
    
    • Protein
    • Vit A
    • Na⁺, Cl^-
    • Abs
  • but has Low:
    
    • Lipid
    • CHO^​​
    • K⁺
• Milk has:
  
  • Protein
  • Lipids
  • Lactose
  • Lymphocytes
  • Monocytes
  • electrolytes (Na⁺, Cl^-, K⁺)
  • minerals (Ca, Fe, Mg)
  • Fat soluble vitamins
  • Abs

Question 18

Breast milk secretion occurs by which secretory mechansim(s)?

Answer 18

Two secretory methods:

• Merocrine for the protein component
  
  • Packaged into secretory granules –> exocytosis
• Apocrine for the lipid component
  
  • Released into the lumen with a tiny amount of cytoplasm

Question 19

Breast milk synthesis and secretion is under the control of which hormone(s)?

What leads to an increase in this hormone following parturition?

Answer 19

Prolactin!

Decrease in estrogen and progesterone after giving birth allow for increased prolactin secretion.

Question 20

What hormonal changes does the act of suckling stimulate?

Answer 20

• Increases prolactin release (10-20x baseline)
• Inhibits prolactin inhibitory hormone (PIH)
• Stimulates prolactin release factor (PRF)
• Stimulates oxytocin relase
  
  • Acts on myoepithelial cells for the milk “let down” response

Question 21

What changes occur as the mammary glands involute (during menopause)?

Answer 21

• Fibrocollagenous CT replaces adipose tissue, encloses lobules
• Increased elastin, fibroblasts
• Few ducts remain

Question 22

What is fibroadenosis of the mammary gland?

Answer 22

• Most common benign breast disorder
• Related to repeated exposure to variable estrogen and progesterone levels associated with the menstrual cycle
• Cyst formation associated with proliferation of terminal ductules and stromal tissue
• Slow growing masses of epithelium & CT

Question 23

What percentrage of breast carcinomas involve the duct epithelia?

What receptor do the majority of breast cancer tumors express?

In what percentage of breast cancers are the BRCA1 & 2 genes involved?

Answer 23

80-90%

Estrogen receptor

<5%

Question 24

What structural features of the breast unfortunately facilitate the metastasis of tumors?

Answer 24

• Rich blood supply
• Exensive lymphatic drainage

Question 25

Why do male patients with cirrhosis frequently exhibit gynecomastia?

Answer 25

• Decreased liver function leads to…
• Diminished catabolism of androstenedione, leads to…
• More substrate for conversion of androgens to estrogens
• Higher circulating levels of estrogens
• Mammary gland development in males