Quiz 12

Question 1

Teats

Answer 1

• the only exit for the secretion from the gland and the only means for the calf to receive milk
• only one teat drains one gland

Question 2

Supernumerary Teats

Answer 2

• about 50% of all cows have extra teats called this
• they are non-functional and often removed in dairy cows
• generally they are removed before 1 year of age

Question 3

Pseudo-teat

Answer 3

• has no streak canal meaning it has no connection to the internal structures of the gland

Question 4

Streak Canal

Answer 4

• functions as the only orifice of the gland between internal milk secretory system and the external environment
• it is the main barrier against intramammary infection
• it is kept closed by sphincter muscles around the streak canal
• it is lined with a skin-like epidermis that forms the keratin material that has antibacterial properties

Question 5

What happens when a cow is milked?

Answer 5

• the sphincter muscles relax allowing the orifice to open
• since the streak canal remains open for an hour or more after milking there is ready access of bacteria to the inside of the gland
• during the dry period the epidermal tissue lining the streak canal forms a keratin plug that effectively seals off the canal

Question 6

How to prevent bacterial infection post milking?

Answer 6

1. Post-milking germicidal teat drips minimize the chance of bacteria gaining access to the gland after milking
2. Keeping cows standing for a time after milking, such as providing them with access to fresh feed, will also help minimize teat end contamination

Question 7

Furstenburg’s Rosette

Answer 7

• these are mucosal folds of the streak canal lining at the internal end of the canal
• it may fold over the canal opening due to pressure when the udder is full

Question 8

Alveoli in the cow’s udder

Answer 8

• responsible for the synthesis of milk

Question 9

Ducts in the cow’s udder

Answer 9

• the tubes by which milk drains from the alveoli down to the gland cistern
• the tubing by which milk moves from the alveoli to the teat for milk removal

Question 10

Udder Cisterns in the cow’s udder

Answer 10

• functions for milk storage (about 100-400 mL)
• also called the gland cistern
• it opens directly into the teat cistern
• a large cavity where milk can collect between milkings
• open areas between the teat and the large ducts

Question 11

Duct Types

Answer 11

1. Interlobar Ducts
2. Intralobar Ducts
3. Interlobular Ducts
4. Intralobular Ducts

Question 12

Interlobar Ducts

Answer 12

• Primary ducts that drain multiple lobes

- they are lined with two layers of non-secretory cells and have many myoepithelial cells

Question 13

Intralobar Ducts

Answer 13

• are within a lobe and drain several regions of the lobe

Question 14

Interlobular Ducts

Answer 14

• secondary ducts that drain multiple lobules
• they are lined with one layer of secretory cells and are surrounded by myoepithelial cells
• they participate in the oxytocin-induced milk ejection

Question 15

Intralobular Ducts

Answer 15

• drain multiple lobules within a single lobe

Question 16

Secretory Tissue in the udder

Answer 16

• is organized into lobes, with each lobe containing multiple lobules
• each lobule contains 150-220 microscopic alveoli

Question 17

Lobe

Answer 17

• a groups of lobules surrounded by a connective tissue sheath
• each mammary gland has numerous lobes

Question 18

Lobules

Answer 18

• clusters of 150-220 alveoli that are encapsulated by a connective tissue sheath

Question 19

Alveoli

Answer 19

• are sack-like structures where milk is synthesized and secreted
• cluster of alveolus

Question 20

Alveolus

Answer 20

• the discrete milk producing unit

- estimated to hold about 1/5 of a drop of milk

Question 21

The lumen of the alveolus is lined by

Answer 21

• a single layer of secretory epithelial cells

Question 22

The epithelial lining of the lumen of the alveolus is surrounded by

Answer 22

• contractile myoepithelial cells

Question 23

Myoepithelial cells

Answer 23

• THEY ARE NOT INNERVATED and contract in response to the hormone OXYTOCIN
• results in milk being squeezed out of the alveolar lumen and into the small ducts

Question 24

Outside of the myoepithelial cells the alveolus is surrounded by

Answer 24

• a connective tissue basement membrane

Question 25

The capillary bed on the outside of the alveolus is part of

Answer 25

• the stromal (connective tissue) between alveoli

Question 26

How to picture a group of alveoli

Answer 26

• as a clump of grapes with the stems acting as the small ducts leading from the alveoli

Question 27

Sensory nerves are found in the

Answer 27

• teats and skin

- these are critical for initiating the neural pathway of the milk ejection reflex

Question 28

Why is the blood supply to the mammary gland very important?

Answer 28

• because all of the milk precursors come from the blood
• on avg 400-500 units of blood passes through the udder for each unit of milk synthesized by a high producing dairy cow
• there is no crossover of blood supply (anastomosis) between udder halves

Question 29

Arterial Flow Order in the Udder

Answer 29

1. Heart
2. Abdominal Aorta
3. Internal and External Iliacs
4. Femoral
5. External Pudendal
   - passes through inguinal canal and allows for downward distention of udder when filled with milk
6. Mammary Artery
7. Anterior and Posterior Mammary Artery

Question 30

Venous Flow in the Udder

Answer 30

• three veins on each side carry blood from the udder
  1. External Pudendal Vein
  2. Subcutaneous Abdominal Vein (milk vein)
  3. Perineal Vein

Question 31

Venous Circle

Answer 31

• anastomoses between anterior and posterior mammary veins

- prevents pinching off when lying down

Question 32

Lymph in the udder

Answer 32

• lymph travels from the udder to the thoracic duct and empties into the blood system

Question 33

Skin of udder

Answer 33

• soft, thin and pliable

- covered with fine hair

Question 34

Escutchion

Answer 34

• the region on the caudal surface of the udder where the hair is directed dorsally

Question 35

Median Intermammary Groove

Answer 35

• divides right and left glands