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!!!