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!!• Huge female expenditure for

something outside their own body!• Develop offspring/ species survival!

GIVE A 1 WORD DEFINITION FOR

THIS COURSE!

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)!

MAMMALS• WHAT ARE 2 DISTINCT

FEATURES OF MAMMALS?

•HAIR?•MAMMARY GLANDS!

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

Duckbill Platypus

Mammary gland:• no teats• tubules

• myoepitelial cells• milk forced onto hair

• Female lays eggs 2 weeks post mating• 10 - 14 day incubation period

• 1-2 eggs• Young: 350 mg at birth; 3-4 mo.- 1/2 adult wt.

WHY MAMMALS?

WHY MAMMARY GLANDS?

• Protect egg!

Less young but better survival!

Nourish young!

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

HAVE PLACENTA!

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

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!

Why is > 3 important?

• Can have embryo in utero• Lactation results in delayed growth• Prolactin inhibits luteal function/ P4

• What a baby machine!!!

MARSUPIALS

• ~ 275 SPECIES!

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!

EUTHERIAN

EUTHERIAN

FUTURE THOUGHTS• What do mammals have in common:

- hair

- mammary glands

* development and tissue

* secretion products

EUTHERIAN

What do boy and girl mammary glands have in common?

AS 337 LACTATION BIOLOGYEXTRA 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 1/23Can give to Mackenzie, Kali, Melissa, Brittany , or me in class or

send via email .HAVE A FANTASTIC WEEKEND!!!