2. The Mammary Gland The milk secreting organ Modified sweat gland
Exocrine gland

3. MAMMARY GLANDS
thoracic
inguinal
abdominal

4. MAMMARY GLANDS
4 abdominal; 15 openings / teat

5. MAMMARY GLANDS
2 thoracic, 6 abdominal, ; 3-7 openings / teat

6. MAMMARY GLANDS
2 thor., 6 abdom. 2 ing., ; 8-10 openings/ teat

7. MAMMARY GLANDS
4 thor., 2 abdom. 4 ing., ; 1 opening/ teat

8. MAMMARY GLANDS
2 inguinal ; 1 opening/ teat

9. MAMMARY GLANDS
2 inguinal ; 2 openings/ teat

10. MAMMARY GLANDS
4 thor., 6 abdom. 2 ing., ; 2 openings/ teat

11. MAMMARY GLANDS
4 inguinal ; 1 opening/ teat

12. Anatomy of the Mammary Gland
Mammary gland - milk secreting structure including teats, duct system, lobes, lobules, and secretory tissue
Modified sweat gland
Exocrine gland
Cow
Large & in inguinal region
4 teats/quarters = 4 separate glands
No mixing of ducts across quarters

13. Anatomy of the Mammary Gland
Rear quartes produce approx. 60% of the milk and the fore quarters produce the remaining 40%
The size and shape of udders vary with the 1) producing ability, 2) age, and 3) genetic of the cow

14. Anatomy of the Mammary Gland
Cow
Front & rear quarters separated by fine membrane
Left and right separated by median suspensory ligament
Supernumerary teats (some with duct and secretory system)

15. How much support is enough?
High producing Holstein cow
Empty Udder = 25 kg.
Milk = 30 kg
= 55 kg !!!

16. Udder Support in Cow Skin Fine connective tissue below skin
Connective tissue attaches front quarters to abdominal wall
Lateral suspensory ligaments (LSL)
Median suspensory ligament (MSL)
The subpelvic tendon

18. Udder Support in Cow LSL Sling around udder 2 layers
Inelastic, more fibrous than MSL

19. Lateral Suspensory Ligaments
Like a “hammock” around the udder
From the pelvis to the median suspensory ligament
Mostly fibrous tissue
Collagen
Attaches to the alveolar tissue
Provides internal framework

20. Udder Support in Cow MSL Primary support Relatively elastic 2 layers
Broken MSL – pendulous udder

21. Median Suspensory Ligament
Primary support of the udder
Two adjacent heavy sheets of tissue
Mostly elastic, some fibrous tissue
Attaches to the abdominal wall
Divides the udder into halves
Glands on each half are divided by sheets of tissue
© Biology of Lactation, Schmidt

23. Udder Support in Cow Lamella septa Connective tissue
Runs between LSL & MSL
Divides parenchyma into lobes and lobules

25. Duct System
Teat meatus, the small canal located in the end of each teat is .5 to 1 cm long and is the only sphincter in each gland
Seven or eight loose folds of membrane known as furstenburg rosette are located above the teat meatus
The teat cistern, the cavity within the teat hold 30 to 90 ml of milk.

28. The Secretory Tissue A Lobe: group of lobules
A Lobule: group of alveoli
Alveoli: cluster of alveolus
Alveolus: a single layer of epithelial cells surrounding a central lumen

31. Blood Supply to Mammary Gland
400 kg blood to produce 1 kg of milk
2 major arteries
Front ½ of udder
Rear ½ of udder
4 major veins
2 follow same path as arteries
2 mammary veins

34. © Biology of Lactation, Schmidt
Nervous System
Sensory (afferent) nerves in skin and teats
Positive stimulation of teats and surrounding area initiates milk let-down reflex via oxytocin
© Biology of Lactation, Schmidt

35. Nervous System
Sympathetic (efferent) (involuntary) nerves associated with arteries in the gland
Control blood flow to the gland
Innervation of sphincters muscles in teats
Stress causes vasoconstriction decreasing milk secretion and let-down
No parasympathetic innervation
No nerves to myoepithelial cells or alveolar cells

37. Lymph System of Mammary Gland
What is lymph & what does it do?
Supramammary lymph nodes
Lymph vessels
Factors that influence edema
Age
Diet (especially NaCl)
Exercise
Genetics

40. Mammary Gland Development
Five phases of mammary development
Prenatal (teats & cisterns dev.)
Prepubertal (limited growth)
Postpubertal
Pregnancy (most growth)
Early lactation

41. Mammary Gland Development
Major development occurs at puberty and during gestation
Hormones
Estrogen (growth of duct system)
Progesterone (development of alveolar tissue in combination with other hormones)
GH (growth of duct system)
Prolactin (initiation and continuity of lactation)

50. Mammary Gland Development

54. Mammary Gland Development

58. Anatomy of the Mammary Gland
Goats and sheep
2 teats/ 2 halves (glands)
Pig
12-14 teats – 2 glands and duct systems per teat
Mare
4 quarters/duct systems but 2 teats

60. Mammary Duct System

63. Epithelial Cell Lumen of alveolus Fat Droplet Fat Droplet migrating
Golgi Body
Lysosome
Nucleus
Mitochondria
Mitochondria
E.R.
Blood Vessel