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EVOLUTION OF THE MAMMARY GLAND AND SECRETIONS. Why is the mammary gland really a gland of reproduction?. MAMMARY GLAND. Gland of Reproduction Development is tied to hormones and physiology of reproduction. Purpose is to nuture young!!

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Evolution of the mammary gland and secretions

EVOLUTION OF THE MAMMARY GLAND AND SECRETIONS

Why is the mammary gland really a gland of reproduction?


Mammary gland
MAMMARY GLAND

  • Gland of Reproduction

  • Development is tied to hormones and physiology of reproduction.

  • Purpose is to nuture young!!

  • Huge female expenditure for something outside their own body!

  • Develop offspring/ species survival!



Mammals
MAMMALS

  • mamma: latin word - breast / milk gland

  • Kingdom: Animals

  • Phylum: chordata

  • Sub phylum: vertebrae

  • Class: mammalia

  • > 4400 species ( good info on ~150)

  • Evolved 250 million years ago (dinosaurs- 65)!


Mammals1
MAMMALS

  • WHAT ARE 2 DISTINCT FEATURES OF MAMMALS?

  • HAIR?

  • MAMMARY GLANDS!


Subclass prototheria
SUBCLASS: PROTOTHERIA

  • NO PLACENTA

  • Egg laying mammals

  • Lactation preceded placentation!

  • One order: Monotremata

  • 3 species?

  • Mammary glands: no teats!

  • Tubules with myoepithelial tissue

  • Young have strong forepaws/ poorly developed hindlimbs



Evolution of the mammary gland and secretions

  • Mammary gland:

  • no teats

  • tubules

  • myoepitelial cells

  • milk forced onto hair


Evolution of the mammary gland and secretions


Evolution of the mammary gland and secretions

WHY MAMMALS?

Less young but better survival!

  • Protect egg!

Nourish young!

WHY MAMMARY GLANDS?


Echidna
ECHIDNA

  • Lay eggs but transfer to temp. brood pouch

  • 10 day incubation

  • 3-4 month lactation

  • special areas called areola in pouch: tubules


Subclass theria
SUBCLASS: THERIA

HAVE PLACENTA!


Metatheria
METATHERIA

  • Give birth to live young but not a true placenta: chorio-vitelline

  • One order: Marsupials

  • Pouched animals

  • 3-4 week gestation

  • Embryo born w/ highly dev. forepaws

  • Adaptation: animals move/ forage


Evolution of the mammary gland and secretions

Why is > 3 important?

  • Young born and crawl up into pouch

  • Latches on teat for months (breathes!)

  • Can have 2 in pouch, 1 latched, 1 not

  • Different milk in each teat!


Evolution of the mammary gland and secretions

Why is > 3 important?

  • Can have embryo in utero

  • Lactation results in delayed growth

  • Prolactin inhibits luteal function/ P4

  • What a baby machine!!!


Marsupials
MARSUPIALS

  • ~ 275 SPECIES!


Eutherian
EUTHERIAN

  • > 95 % OF ALL MAMMALS

  • TRUE PLACENTA!

  • Extract nutrients from maternal blood!

  • 21 orders ( see Dr. Anderson paper)

  • Born more mature

  • Lactations from 4 days to years!




Future thoughts
FUTURE THOUGHTS

  • What do mammals have in common:

    - hair

    - mammary glands

    * development and tissue

    * secretion products


Eutherian3
EUTHERIAN

What do boy and girl mammary glands have in common?


Evolution of the mammary gland and secretions

AS 337 LACTATION BIOLOGY

EXTRA CREDIT QUESTION 1 (10 PTS)

Are the SUBCLASSES / orders we talked about in class (monotremes / marsupials/ 21 orders for eutherians) all there or are there some lost subclasses / orders looking for a home? Can you find a lost subclass / order and if so, state what it is and where you found it! (paper or website!) Or any other interesting evolution facts?

DUE ON OR BEFORE CLASS NEXT THURS 1/23

Can give to Mackenzie, Kali, Melissa, Brittany , or me in class or send via email .

HAVE A FANTASTIC WEEKEND!!!