chickens and eggs

[indian]

How do chicken manage to form an egg inside themselves?

[Clanad]

It turns out the chicken has little to do with the formation of an egg's shell -- the egg actually grows the shell around itself! It does this using processes that are also seen in bones and seashells.

Around the egg is a membrane, and evenly spaced on the membrane are points where columns of calcite (a form of calcium carbonate) form. These columns stack together side by side to form the shell. According to an incredibly interesting book called "Made to Measure" by Philip Ball:

The nucleation points are defined protein nodules called mammillary protrusions, and the mineral is first deposited as particles of aragonite with random orientation of the crystal planes. On top of these aragonite piles, columns of oriented crystalline calcite begin to grow upward.
The calcite is basically floating in solution around the shell, and it deposits on the shell like a forming crystal. The egg grows its own shell!

(Thanks to How Stuff Works)

[commoner]

..mm....I believe the egg is soft until it makes contact with the outside world and gets it's typical "egg shape" as it is actually laid.............commoner

[MargeB]

commoner is correct.

[Clanad]

Sorry to disagree, but having raised laying hens the fact is that the egg is layed in a hard condition... there are some shell-less eggs layed, but these are rare...

See here:

http://www.afn.org/~poultry/egghen.htm

[spudqueen]

Female humans also form eggs inside themselves, albeit smaller and without a 'shell'!

[MargeB]

Clanad, that only occurs when the hen is exposed to green socks during pregnancy.

[Clanad]

Actually, MargeB, most commercial egg factory hens never see (or experience) a male of the species, green socks or not...