Mammary gland development and anatomy Flashcards
Describe embryological development of mammary glands
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
Describe the microanatomy of mammary glands
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
How do IgG enter the colostrum?
Interstitial immune cells - plasma cells and lymphocytes in mammary gland
What is the annular fold?
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
Describe the macroanatomy of the mammary gland
Groups of alveoli form lobules
Groups of lobules form lobes
Label the macroanatomy of the mammary gland
Label the macroanatomy of the mammary gland
Describe the mammary layout of cows, ewes and goats
Inguinal
1 canal/cistern per teat
Describe the mammary layout of mares
Inguinal
2-3 ducts per teat
Describe the mammary layout of sows
Abdominal
2-3 ducts per teat
Describe the mammary layout of bitches and queens
Abdominal
5-6 ducts per teat
What are lactiferous sinuses?
smaller versions of the gland sinus in teats with many ducts
How many mammary glands can supply a single teat canal?
1
What are supernumery teats?
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
Describe the mammary suspension system of the ruminant udder
Medial suspensory ligament - yellow elastic connective tissue
Lateral suspensory ligaments - inelastic connective tissue
What type of growth does mammary tissue undergo from birth to puberty?
Isometric growth (everything grows at same rate)
What type of growth does mammary tissue undergo after puberty?
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
Describe mammogenesis in pregnancy
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)
Describe the cycle of mammary function
Cycles of mammogenesis, lactogenesis, weaning and involution
(involution involved apoptosis, phagocytes etc)
Why is there increased growth of mammary glands after each pregnancy?
Baselines of tissue from previous pregnancy allows further growth of glands in new pregnancy
Describe the hormonal control of mammogenesis during pregnancy in preparation for lactation
Placental lactogen acts in synergy with oestrogen:
- placental lactogen has both prolactin and GH activities
- produced by binucleate cells of placenta
Describe mammary growth during milk secretion
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
What is the blood supply to thoracic mammary glands
Mammary arteries are branches of internal thoracic and pectoral arteries
What is the blood supply to abdominal mammary glands
Mammary arteries are branches of cranial and caudal superficial epigastric arteries
What is the blood supply to inguinal mammary glands
Mammary arteries are branches of external pudendal artery
Describe blood flow of dairy cow udders
Caudal and cranial superficial epigastric veins
Large venous return => venous distension => valvular incompetency => large ‘milk veins’
Describe venous drainage of the bovine mammary gland
external pudendal veins => caudal vena cava
Perineal veins => caudal vena cava
Superficial epigastric veins (milk veins) => cranial vena cave
Describe the lymphatic drainage of the bovine mammary gland
Arises in lobules (not alveoli)
leaves gland via mammary lymph nodes
Describe the lymphatic drainage of cat and dog mammary tissue
Cranial glands => axillary and accessory axillary lymph nodes
Caudal glands => superficial inguinal lymph nodes
Describe the innervation of the bovine mammary gland
Somatic sensory innervation from tactile receptors in skin
Sympathetic motor nerves run along BVs
No parasympathetic innervation
Myoepithelial cells not innervated
