1. Histology of the
Breast and Placenta

2. Histology of the breast
Nipple
- The breast is an organ containing separate glands (mammary glands) each surrounded by connective tissue (stroma)
- Functional gland (lactation) is a compound tubulo-acinar gland
- Each mammary gland has its own duct (lactiferous duct) and sinus
- Each duct empties independently at the nipple

3. Mammary glands Ducts Alveoli Form majority of inactive gland
Mostly, non-secretory
Development regulated by estrogen
Alveoli
Derived from outgrowths of the ducts
Present during pregnancy and lactation
Cells synthesize and secrete milk
Development regulated by progesterone

4. Functional stages of the breast
Pre-puberty
Puberty
Adult
Pregnancy
Lactation
Regression

5. Functional stages of the breast
Pre-puberty
Composed entirely of ducts, no alveoli
Male and female structure similar
Puberty
Enlargement due to accumulation of adipose tissue
Increase in duct system and degree of branching
No alveoli present

6. Inactive (adult)
Glands composed entire of ducts with minor alveolar development during mid to late menstrual cycle

7. Mid-Pregnancy Late Pregnancy Increased branching of ducts (estrogen)
Alveoli develop from ducts (progesterone)
Late Pregnancy
Breast enlargement due to increased
alveolar development
Lumens of alveoli widen with accumulating
milk
Alveoli

8. Lactation Alveolar cells actively synthesize and secrete milk
Alveoli become widely distended with milk
Alveoli

9. Functional stages of the breast
Inactive Pregnancy Lactating

10. Lactation Apocrine - lipid secretion Merocrine - protein secretion
Lipid droplet coalesce in cytoplasm,
released as membrane bound vesicles containing some cytoplasm
Merocrine - protein secretion
Protein packaged in membrane-bound secretory vesicles, released by exocytosis
Protein
Lipid
Lipid
Lipid

11. Lactation Secretory products from alveolar cells Colostrum
Secreted immediately after birth
Protein rich
High antibody titer (plasma cells in CT)
Milk
Increased lipid content over colostrum
Contains protein, salts, carbohydrates,
vitamins and antibodies
Secretion starts several days after birth

12. Regulation of milk production and ejection
High levels of estrogen and progesterone during pregnancy prevent milk production by blocking the action of prolactin
Estrogen,
Progesterone
(before birth) X
Neurohormonal suckling reflex arc
Suckling initiates nerve impulses which
regulate secretions from the pituitary
Prolactin: Milk synthesis and secretion Oxytocin: Milk ejection

13. Functional stages of the breast
Pre-puberty
Puberty
Adult
Pregnancy
Lactation
Regression

14. Breast cancer
Most common female cancer in the US; 1/3 of all cancer diagnoses
Second most common cause of cancer death in women after
lung cancer
12.5% (1 in 8) of all women born the United States will develop breast cancer at some time in their life
250,000 new cases each year, 40,000 deaths

15. Breast cancer Cancers arise from the ductal cells:
Terminal ducts: Lobular carcinomas (20%)
Larger ducts: Ductal carcinomas (80%)
Types:
Ductal carcinoma in situ (DCIS) (15-30%)
Cannot penetrate the basal lamina and remains confined to the breast
Generally not life threatening, though can become invasive if not treated
Invasive ductal carcinoma (IDC) (70-85%)
Readily metastasize outside the breast
Contraindications for estrogen hormone replacement therapy

16. Placenta

17. Placenta
Transient organ formed by the fusion of fetal tissue, the chorion with the maternal uterine endometrium, the decidua
At term centimeters in diameter, 2-3 cm in thickness, g
9-10 weeks
25-30% coverage

18. Placenta
Functions:
- Provides exchange of respiratory gases and nutrients and wastes between maternal and fetal circulations. Provides 90 sq. meters of surface area!!!!
- Secretes hormones: Progesterone (progestins), estrogens, placental lactogens, and chorionic gonadotropins (hCG)
- Transports macromolecules, e.g., IgG
9-10 weeks
25-30% coverage

19. Blastocyst Stage of the embryo that implants into the uterus
Composition:
Trophoblast cells form the peripheral rim of the blastocyst cavity; invade the decidua and form the fetal portion of the placenta
Inner cell mass, an eccentrically located cluster of cells inside the trophoblast which develops into the embryo
(decidua)

20. Trophoblast differentiates into: Cytotrophoblast (inner)
Syncytiotrophoblast (outer)
Vascular spaces form in the syncytiotrophoblast which connect with material circulation
Cytotrophoblast grows out radially forming villi and laterally to enclose the intervillous spaces
16 days
21 days
Intervillous space
Syncytio-
trophoblast
Cyto-
tropho-
blast
Decidua (maternal)
Chorion (fetal)

22. Fetal side (Chorion) Stem villi Maternal side (Decidua) 40x 100x
Inter-
villous
space

23. Chorionic villi
Core of fetal connective tissue with fetal blood vessels
Cytotrophoblast: Simple cuboidal epithelium; becomes discontinuous during late pregnancy
Syncytiotrophoblast: Single cell (syncytium), multinucleated Covers the surface of the villus, facing the intervillous spaces and contacts maternal blood
Possesses microvilli and abundant organelles associated with both protein and steroid hormone production
Secretes a variety of hormones
Chorionic plate
Cyto-
trophoblast
Syncytio-
Blood
Intervillous
space
Inter-
villous
space
Decidua

24. The Decidua, the maternal placenta
Decidua basalis – underlies the implanted conceptus forming the maternal portion of the placenta
Decidua capsularis – covers the luminal surface of the conceptus; fuses with decidua parietalis, obliterating the uterine lumen
Decidua parietalis - lines the remainder of the uterus

25. Decidua basalis

26. Placental Blood Flow Fetal Maternal V A
Umbilical arteries (2) travel from the fetus through the umbilical cord to the placenta. Carry blood that is high in carbon dioxide and low in nutrient content
Umbilical vein (1) returns oxygen-rich, nutrient-rich blood to the fetus V A
Umbilical
cord
Wharton’s jelly
(mucus CT)
Maternal
Spiral arteries penetrate trophoblastic shell and spurt blood into the intervillous spaces, bathing the villi

27. Placental interhemal barrier
Chorionic
villus
Intervillous space
(Maternal blood)
Separates maternal and fetal blood supplies, which normally do not mix.
Beginning in the fetal capillary, this barrier consists of:
- Capillary endothelial cell and its basement membrane
- Fetal connective tissue of villus
- Cytotrophoblast and its basement membrane
- Syncytiotrophoblast

28. Placental interhemal barrier
Separates maternal and fetal blood supplies, which normally do not mix.
Beginning in the fetal capillary, this barrier consists of:
- Capillary endothelial cell and its basement membrane
- Fetal connective tissue of villus
- Cytotrophoblast and its basement membrane
- Syncytiotrophoblast

29. Placental interhemal barrier
Separates maternal and fetal blood supplies, which normally do not mix.
Beginning in the fetal capillary, this barrier consists of:
- Capillary endothelial cell and its basement membrane
- Fetal connective tissue of villus
- Cytotrophoblast and its basement membrane
- Syncytiotrophoblast

30. Placental interhemal barrier
Separates maternal and fetal blood supplies, which normally do not mix.
Beginning in the fetal capillary, this barrier consists of:
- Capillary endothelial cell and its basement membrane
- Fetal connective tissue of villus
- Cytotrophoblast and its basement membrane
- Syncytiotrophoblast

31. Placental interhemal barrier
Separates maternal and fetal blood supplies, which normally do not mix.
Beginning in the fetal capillary, this barrier consists of:
- Capillary endothelial cell and its basement membrane
- Fetal connective tissue of villus
- Cytotrophoblast and its basement membrane
- Syncytiotrophoblast