Mammary gland development and anatomy

Question 1

Describe embryological development of mammary glands

Answer 1

Mammary ridges (thickened epidermal tissue) give rise to primary mammary bud
Primary buds push into dermis => secondary mammary bud
Secondary buds branch out and canalise to form lactiferous ducts

Question 2

Describe the microanatomy of mammary glands

Answer 2

Epithelial/alveolar cells surround spherical lumen (alveolus)
Myoepithelial cells surround each alveolus and the duct
Contraction of myoepithelial cells propels milk out of alveoli into ducts
Ducts empty into gland cistern

Question 3

Answer 3

Question 4

How do IgG enter the colostrum?

Answer 4

Interstitial immune cells - plasma cells and lymphocytes in mammary gland

Question 5

What is the annular fold?

Answer 5

Thickening of tissues at base of gland cistern of mammary tissue
Suckling neonates press down on base of teat and close it
Tongue presses up to squeeze milk into mouth

Question 6

Describe the macroanatomy of the mammary gland

Answer 6

Groups of alveoli form lobules
Groups of lobules form lobes

Question 7

Label the macroanatomy of the mammary gland

Answer 7

Question 8

Label the macroanatomy of the mammary gland

Answer 8

Question 9

Describe the mammary layout of cows, ewes and goats

Answer 9

Inguinal
1 canal/cistern per teat

Question 10

Describe the mammary layout of mares

Answer 10

Inguinal
2-3 ducts per teat

Question 11

Describe the mammary layout of sows

Answer 11

Abdominal
2-3 ducts per teat

Question 12

Describe the mammary layout of bitches and queens

Answer 12

Abdominal
5-6 ducts per teat

Question 13

What are lactiferous sinuses?

Answer 13

smaller versions of the gland sinus in teats with many ducts

Question 14

How many mammary glands can supply a single teat canal?

Answer 14

1

Question 15

What are supernumery teats?

Answer 15

Extra teats formed from mammary ridge - not connected to sinus
Needs to be removed in dairy heifers as can get in way of milking machine

Question 16

Describe the mammary suspension system of the ruminant udder

Answer 16

Medial suspensory ligament - yellow elastic connective tissue
Lateral suspensory ligaments - inelastic connective tissue

Question 17

What type of growth does mammary tissue undergo from birth to puberty?

Answer 17

Isometric growth (everything grows at same rate)

Question 18

What type of growth does mammary tissue undergo after puberty?

Answer 18

allometric growth:
- complete and rapid growth of ducts in presence of prolactin and GH
- during oestrus ducts branch under effects of oestrogen
- alveoli formed under influence of progesterone in pregnancy

Question 19

Describe mammogenesis in pregnancy

Answer 19

Terminal alveoli grow into lobules due to P4 dominance
Prolactin, adrenal cortical hormones and placental lactogen allow synthesis of milk (relaxin from CL in pigs)

Question 20

Describe the cycle of mammary function

Answer 20

Cycles of mammogenesis, lactogenesis, weaning and involution
(involution involved apoptosis, phagocytes etc)

Question 21

Why is there increased growth of mammary glands after each pregnancy?

Answer 21

Baselines of tissue from previous pregnancy allows further growth of glands in new pregnancy

Question 22

Describe the hormonal control of mammogenesis during pregnancy in preparation for lactation

Answer 22

Placental lactogen acts in synergy with oestrogen:
- placental lactogen has both prolactin and GH activities
- produced by binucleate cells of placenta

Question 23

Describe mammary growth during milk secretion

Answer 23

Milk yield keeps increasing up until 3 weeks - demand for milk increases as neonates get bigger so milk yield increases - weaning behaviours start after this

Question 24

What is the blood supply to thoracic mammary glands

Answer 24

Mammary arteries are branches of internal thoracic and pectoral arteries

Question 25

What is the blood supply to abdominal mammary glands

Answer 25

Mammary arteries are branches of cranial and caudal superficial epigastric arteries

Question 26

What is the blood supply to inguinal mammary glands

Answer 26

Mammary arteries are branches of external pudendal artery

Question 27

Describe blood flow of dairy cow udders

Answer 27

Caudal and cranial superficial epigastric veins
Large venous return => venous distension => valvular incompetency => large ‘milk veins’

Question 28

Describe venous drainage of the bovine mammary gland

Answer 28

external pudendal veins => caudal vena cava
Perineal veins => caudal vena cava
Superficial epigastric veins (milk veins) => cranial vena cave

Question 29

Describe the lymphatic drainage of the bovine mammary gland

Answer 29

Arises in lobules (not alveoli)
leaves gland via mammary lymph nodes

Question 30

Describe the lymphatic drainage of cat and dog mammary tissue

Answer 30

Cranial glands => axillary and accessory axillary lymph nodes
Caudal glands => superficial inguinal lymph nodes

Question 31

Describe the innervation of the bovine mammary gland

Answer 31

Somatic sensory innervation from tactile receptors in skin
Sympathetic motor nerves run along BVs
No parasympathetic innervation
Myoepithelial cells not innervated