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Germinal Layers

A human embryo starts out as three layers of tissue known as the ectoderm, mesoderm and endoderm. Most of us know, if we know anything about embryology at all, that the ectoderm becomes the nervous system and skin, the mesoderm becomes the bones and muscle, and the endoderm becomes the gut. But let's get more specific.

What layer originates the parenchyma of the tonsils and thymus?
Ectoderm? Mesoderm? or Endoderm??

endoderm

The lymph and lymph vessels?
mesoderm

What layer forms the epithelium of the tympanic cavity, antrum and auditory tube?
endoderm

What layer is the origin of the mammary glands?
ectoderm
yep: skin, nerves, brain and boobs

What TWO layers form the adrenals?
medulla is ecto
cortex is meso

What layer originates the ovaries, testes and genital ducts?
mesoderm

What layer forms the thyroid and parathyroid?
endoderm

What TWO layers become the pituitary?
posterior<--ecto
anterior<--????

What layer forms connective tissue and serous membranes?
mesoderm

What layer forms the LIVER and pancreas?
endoderm

What layer forms the spleen, blood and blood vessels?
mesoderm

The heart?
mesoderm
plus neural crest cells for the SA and AV nodes, bundle of his, purkinje fibers etc.

The epithelium of the bladder, most of the urethra?
endoderm

The kidneys?
mesoderm

The lungs?
endoderm

Get the pattern?
I don't.
Grouping now to see if there is a pattern I can grasp:

SUMMARY

ECTODERM:
CNS, PNS, retina of eye, sensory epithelia of ear, nose
posterior pituitary and adrenal medulla
all of the above are neuro
epidermis and appendages including the breasts

MESODERM:
CT, cartilage
bone & bone marrow, blood & lymph (vessels and cells), spleen
muscle (incl heart and smooth muscle of GI), serous membranes
kidneys, adrenal cortex
ovaries, testes, genital ducts
??anterior pituitary???????

ENDODERM:
gastric and respiratory epithelium (lungs!)
parenchyma of tonsils, thymus
glandular cells of thyroid, parathyroid, liver, pancreas
??anterior pituitary???????
epithelial lining of bladder, most of urethra
epithelial lining of tympanic cavity, tympanic antrum, auditory tube

Comments

( 2 comments — Leave a comment )
kellamaste
Jul. 29th, 2009 08:45 pm (UTC)
Was looking over your journal hoping to find clarity on something and saw this. The anterior pituitary comes from the Ectoderm as well. It arises from the Buccal or surface ectoderm, while the posterior arises from the neroectoderm.

You had big ?'s around it so I thought I'd figure it out as I was wondering too! I'm sure you already know the answer though. :)
liveonearth
Jul. 30th, 2009 04:14 pm (UTC)
=-] Yeah, actually it was just yesterday that I finally looked it up. Lots to know....
( 2 comments — Leave a comment )

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