Lactation

Question 1

What are the purposes of lactation?

Answer 1

1. Provide nourishment
2. Provide immunity (colostrum)
3. Provide quick energy

Question 2

What are the locations of some of the lactating glands?

Answer 2

Pectoral region
Inguinal region
Abdominal region

Question 3

How can we categorize some of the structural arrangements of lactating organs?

Answer 3

number of glands
number of teats
number of streak canals

Question 4

What is the alveolus?

Answer 4

The basic milk secreting unit.
Composed of a lumen, epithelial cells, and myoepithelial cells.

Question 5

What is the function of the epithelial cells of the alveolus?

Answer 5

synthesize milk

Question 6

What is the function of the myoepithelial cells of the alveolus?

Answer 6

muscular cells that squeeze the alveolus to eject the milk

Question 7

Describe the arrangement of alveoli

Answer 7

they are arranged in lobes or smaller groups called lobules

Question 8

Describe the order of the flow of milk

Answer 8

Milk enters the lumen and exits from the ducts. It enters into a gland cistern, then a teat cistern before exiting the body through a streak canal.

Question 9

Describe a cow’s udder.

Answer 9

The udder is divided into four separate quarters, each independent in their milk producing function.

Question 10

Describe the growth and development of the mammary gland prior to birth.

Answer 10

The mammary streak differentiates into buds and sprouts, which later become ducts. The teats develop.

Question 11

Describe the growth and development of the mammary gland from birth to the onset of puberty.

Answer 11

Streak canal develops, further development of the teat

Question 12

Describe the growth and development of the mammary gland from the onset of puberty to the beginning of the first pregnany.

Answer 12

major ducts get larger

Question 13

Describe the growth and development of the mammary gland during pregnancy.

Answer 13

early: large ducts and development of smaller ducts
late: alveoli and lobes are forming

Question 14

Describe the growth and development of the mammary glands during lactation.

Answer 14

Alveoli begin to function and increase in number. After the peak of lactation, there is a gradual decline in the number of functioning alveoli.

Question 15

Describe the growth and development of the mammary glands after termination of lactation.

Answer 15

Alveoli and lobes regress

Question 16

What is involution?

Answer 16

The process in which secretory tissue and ductile tissue regress after the termination of lactation.

Question 17

What happens to the mammary glands during subsequent gestations and lactations?

Answer 17

The cycle of developing alveoli and involution repeats.

Question 18

How does somatotropin influence the mammary gland?

Answer 18

It is primarily responsible for mammary growth prior to puberty. The growth caused by somatotropin is isometric, meaning growth is occurring at the same rate as other body parts.

Question 19

How does estrogen influence the mammary gland?

Answer 19

It is responsible for duct and cistern growth beginning at puberty. This growth is allometric, meaning that it is growing at a faster rate than the rest of the body.

Question 20

How does progesterone influence the mammary gland?

Answer 20

It stimulates the development of the alveoli and lobes.

Question 21

What is prolactin and how does it influence the mammary gland.

Answer 21

Prolactin is a hormone released by the anterior pituitary gland. It is essential for milk formation and secretion, as well as maintaining lactation.

Question 22

How do glucocorticoids, somatotropin, and adrenocorticotropin influence the mammary gland?

Answer 22

They work with prolactin to initiate and maintain lactation.

Question 23

How does thyroxin affect the mammary gland?

Answer 23

In increases the metabolic rate of the tissue in the mammary gland.

Question 24

How does parathyroid hormone affect the mammary gland?

Answer 24

It regulates the calcium levels in the blood, and is less active when the animal is not lactating.

Question 25

How does oxytocin affect the mammary gland?

Answer 25

It causes the myoepithelial cells to contract, forcing milk ejection.

Question 26

What is parturient paresis and what is it caused by?

Answer 26

Parturient paresis is milk fever. It occurs when an animal has offspring and low parathyroid hormone levels. This prevents calcium from being mobilized in an effective manner to meat the animal's needs. Since muscles need calcium to function, not having enough of it in the blood makes it difficult for the animal to stand.

Question 27

Describe the hormonal response during gestation.

Answer 27

High levels of progesterone decrease prolactin release and decrease prolactin effect.

Question 28

Describe the hormonal response just prior to parturition.

Answer 28

Lower progesterone levels and higher estrogen levels allow for an increase in prolactin release and increases the prolactin effect.

Question 29

Describe the processes of milk synthesis.

Answer 29

1. Filtration (water) 2. Selective absorption (minerals, vitamins) 3. Cell metabolism (casein, lactose, milk fat)

Question 30

What are the blood precursors to lactose synthesis in a monogastric?

Answer 30

glucose in the blood

Question 31

What are the blood precursors to lactose synthesis in a ruminant?

Answer 31

glucose from blood and liver via gluconeogenesis using propionic acid gluconeogenesis is a necessary step because most of the glucose is converted into VFA's, and not much of it is in the blood

Question 32

What is the blood precursor to milk lipids in monogastrics?

Answer 32

blood lipids and glucose

Question 33

What is the blood precursor to milk lipids in ruminants?

Answer 33

blood lipids and acetic acid

Question 34

What is lactose synthase?

Answer 34

an enzyme found only in lactating tissue; derived from alpha-lactalbumin lactose is the milk solids component most closely tied to yield

Question 35

How are vitamins and minerals acquired for milk production by monogastrics and ruminants?

Answer 35

Minerals are mainly absorbed, and so are vitamins. Ruminants can synthesize their own supply of the B complex vitamins and Vitamin K

Question 36

What are the phases of milk secretion?

Answer 36

1. Synthesis 2. Secretion 3. Rest and regeneration

Question 37

How does intramammary pressure relate to milk flow?

Answer 37

fast: low pressure slow: moderate pressure stop: high pressure Frequent milk removal will keep the pressure low so that there is a fast rate of secretion.

Question 38

How are casein and lactose released from a lactating mammary cell?

Answer 38

Vesicles merge to form larger vesicles. They then become continuous with the cell membrane, and the micelles are released from the cell.

Question 39

How are fat globules released from a lactating mammary cell?

Answer 39

The cell membrane envelops the fat globule, and it pinches off from the cell, leaving part of the cell membrane surrounding the fat globule.

Question 40

Describe milk let-down.

Answer 40

Stimuli: hypothalamus tells posterior pituitary to release oxytocin in response to suckling, sound, etc Oxytocin travels through the bloodstream to the udder to stimulate the release of milk.

Question 41

What can inhibit milk let-down?

Answer 41

Disturbing the cow could cause epinephrine to be released, inhibiting milk let-down.

Question 42

How is milk removed?

Answer 42

suckling hand milking mechanical milking

Question 43

Describe the metabolic burdens of lactation during all of its stages

Answer 43

Beginning: negative energy balance, fat is mobilized Mid-Lactation: zero energy balance (energy intake = energy outtake) Late Lactation: positive energy balance (weight gain) Management schemes are designed to minimize negative energy balance at the beginning of lactation and prevent obesity at the end of lactation.

Question 44

What is persistence? What trends exist with it?

Answer 44

How well an animal maintains her milk production level throughout lactation. Older animals tend to have higher peak production but are less persistent than younger animals.

Question 45

What is mastitis?

Answer 45

Mastitis is an inflammation of the mammary gland. It's usually caused by infection, and it is the most costly issue in the dairy industry since it usually results in lower milk production.

Question 46

What ligament separates the mammary into right and left halves?

Answer 46

median suspensory ligament

Question 47

How can bacteria enter the mammary system most easily?

Answer 47

teat opening

Question 48

For each pound of milk produced, how many pounds of blood must pass through the udder?

Answer 48

400 lbs. of blood

Question 49

What three major items pass through the inguinal canal?

Answer 49

blood vessels lymphatic tissues and vessels nerves

Question 50

Do arteries or veins have thicker walls?

Answer 50

arteries

Question 51

What are some functions of the lymphatic system?

Answer 51

It returns interstitial fluid to the bloodstream and aids in killing bacteria.

Question 52

Near the time of parturition, animals often accumulate large quantities of lymph in their mammary systems. What is this condition called?

Answer 52

Udder adema

Question 53

The streak canal streaks what fibrous protein that helps prevent the invasion of mastitis-causing organisms?

Answer 53

keratin

Question 54

What closes the teat end between milkings?

Answer 54

a muscular sphincter

Question 55

Where does milk collect between milkings in the alveolus?

Answer 55

the lumen

Question 56

What might cause the release of epinephrine into the blood stream of an animal and decrease the effectiveness of oxytocin?

Answer 56

fright, rough handling, stress, unusual circumstances