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
PROTOTHERIA: egg layers
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?
Less young but better survival!
• Protect egg!
Nourish young!
WHY MAMMARY GLANDS?
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 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 1/21
Can give to Emily, Logan, Aislinn, or me in class or send via email
.
HAVE A FANTASTIC WEEKEND!!!