Lactation

monotremes marsupials placental mammals

egg laying mammals lack teats milk is secreted from tubular glands onto stiff mammary hairs where it is consumed by the young no storage of milk

pouched animals although not all have pouches short gestation- 13-40 with very simple placental development live young are born and travel to pouch where they attach to a teat and lactation is stimulated

teats on the abdomin, ex dogs, pigs

teats on the chest, ex. humans, chimps, elephants

between the rear legs, ex. cows, horses, sheep goats

55-65%

25-60lbs

modified skin, and it lies outside the body cavity

skin, connective tissue, and suspensory ligaments

-lack of ligament, no intramammary groove, heavy sagging udder -median suspensory ligament forms intramammary groove -lateral suspensory ligament

-forms fore udder attachment to abdominal wall

no hair or sweat glands on the teats usually 4,sometimes more

extra teats (>4), mostly non functional

front: 6.6 cm, rear: 5.2 cm

front: 2.9 cm, rear: 2.6

-barrier between the outside world and the sterile world of the udder, main barrier against infection - the name of the opening by which milk exits the teat -lengths by a small amount with subsequent lactations

keratin

this keratin plug seals the canal and has antimicrobial properties

-storage cavity -space between the annular folds and streak canal

between teat and gland cistern

-alveoli (alveolus)= basic milk production unit (storage of milk) -1 mill/cubic in -bill/udder -separate blood supply to each alveolus

-opens to teat cistern -storage structure for milk

-contractile cells that squeeze the alveoli -are responsible for milk let down -respond to oxytocin(tells animal to release milk)