Exam 4 - Mammary Systems Flashcards
Mammary Origins
Mammary gland is the distinguishing characteristic of all mammals (‘mamma’ = breast or milk gland in Latin)
Amniotes
An animal whose embryo species of mammals develops in an amnion; AMNIOTES mammals, birds and reptiles
Mammals
Origins of lactation trace to over two hundred million years ago with the appearance of mammals from the same evolutionary branch as birds and reptiles
The two dominant theories of lactation and mammary development
- Prolonged maternal care
- Maintain moisture and nourishment of egg
Prolonged maternal care decreases the need for hatched young to be self-reliant quickly (i.e. _________________________).
Female no longer required to leave the nest to find food for hatched young (implications for ___________ and ____________ ________________). This buffers against ___________ in food availability
Do not need to go out and find food on own; protection; temperature regulation; fluctuations
Maintain moisture and nourishment of eggs has a ________ shell and due to _______ _________ there is a limited ability to lay eggs near water
Porous; climate changes
The three main classes of mammals
- Monotremes
- Marsupials
- Placentals
Monotremes
Egg-laying mammals, lack teats and instead have still mammary hairs that are licked by young, no milk storage
Marsupials
Simplistic placenta, “pouched” animal, birth live, embryonic young, only teat the joey attaches to will secrete milk, as joey grows and leaves pouch mother will conceive another that travels to the patch after birth, milk composition and amount is unique to each teat
Placentals
90% of extant mammals, birth live young classified as altricial or precocial, distinguished by a complex placenta in relation to marsupials and therefore they have a greater investment in gestation.
Three types of teat location and examples
Abdominal (pigs, cats, dogs) Pectoral (elephants, primates) and Inguinal (cows, sheep, horses)
Mammary gland
Modified skin that exists external to the body cavity
