1. Mammary glands

2. In general Milk producing organs
The number and location of the glands varys widely between mammals

3. Development overview

4. Development Evolved over 300 million years ago
Most likely from sweat glands
Embryonic, pubertal and reproductive stages

5. Embryonic MG development
The embryonic mammary mesenchyme provides inductive signals -> mammary epithelial cell differentiation
Wnt signaling (Outside -> receptor -> inside cell)
-> signals to regulate dorsal/ventral patterning of the placodes
-> Pairs of symmetrically localized placodes (1)

6. Embryonic MG development
TBX3 identified as an important factor, found in both human and mice (Wnt signaling)
BMP4 antagonizes Tbx3 (vice versa)
Add fibroblast growth factors (FGF)
-> placement and pattern of placodes

7. Embronic MG development

8. Embronic MG development

9. Embronic MG development
Formation of ductal lumen (Branching)
Generation of nipple structure (modifications of the skin, suppression of hair...)
PTHLH budding -> branching (g-protein), nipple formation

10. Pubertal development Even at birth, the gland is able to produce milk
Puberty -> Fast growth -> filling of the fat pad
Terminal end buds penetrate the fat pad
-> cap cells of TEB differentiate into myoepithelial cells = outer layer of tubular ductal bilayer around the inner luminal cells

12. Cell differentation

13. Function of the parts Myoepithelial cells contract to push milk out
Milk comes through lactiferous duct and out through nipple pores
Areolae
Areolae glands
Lipoid fluid (moisture)
Traget for the baby
Fat supports all the structures
Suspensory ligamens hold brests on place

14. Lactation Mammary gland undergoes many changes
Gland maturation & alveologenesis
Regulated by progesterone and prolactin (PRL)
Transformations
Ductal branching
Proliferating epithelial cells
 alveloar buds
 alveoli, milk secreting lobules

15. Lactation Baby suckles Mechano receptor neurons stimulated
Message to hypothalamus
Stimulates oxytocin production
Oxytosin stimulates myoepithelial cells
Inhibits dopamine
Dopamine inhibits prolactin

16. Prolactin Oxytocin Secreted by anterior pituitary
Three intramolecular disulphide bonds
Oxytocin
Stored in posterior pituitary gland
It has many functions in sexual reproduction

17. Other hormonal effects
Progesterone
Steroid hormone
Many function
For ex. In menstrual cycle & pregnancy
Induces alveoloar maturation together with prolactin
Growth hormone
Estrogen
ACTH

18. References