EVOLUTION OF THE MAMMARY GLAND AND SECRETIONS
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Transcript of EVOLUTION OF THE MAMMARY GLAND AND SECRETIONS
LACTATION
SYNTHESIS / SECRETION OF MILK
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!
Which came first? Dinosaur or mammals?
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!
By definition: all mammals produce milk(this example is a pouched bandicoot)
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
PROTOTHERIA: egg layers
• 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 1/21
Can give to Emily, Logan, Aislinn, or me in class or send via email .
HAVE A FANTASTIC WEEKEND!!!