dextral torsion

[bunny29]

Why does a chicken embryo always have torsion on the same side? Is there a reason that the head always turns to the right?

[wildwood]

If you have a look at the temporary neck muscles that facilitate pipping you'll notice that it is pretty much one sided. As you probably know, this muscle reduces to normal size shortly after hatching. Why waste much needed energy growing more temporary muscle than you need? The ones that occasionally have their head the wrong way won't have the strength to make the initial pip in the shell, and even if they did, other health problem would soon extinguish them.

I can't be sure, but am convinced that the initial embryo position is already determined when the notachord is formed and the first heartbeats start.

[heathfield]

In the natural world, things tend to be right-handed. Even the way the normal human heart starts to form in the embryo has been found to depend on this at a molecular level.

[Peter Pedant]

I am taking this as a question of laterality.
Humans ( which arent chicks) are't symmetrical and the heart in embryo (doesnt embryology recapitulate phylogeny I hear you all chant in a kinda nineteenth century way) has to bend and twist in a pre orderd fashion.

so I googles lander dextrality

as N A Lander a surgeon in B'ham has done a bit on how laevocardia and how it arises in children
(which is kinda like why do chicks have a temp muscle on the right and not the left)

and there is a huge bibliography at
http://www.righthandlefthand.com/pdf/NOTESBOOK .PDF

and I suppose Lander's paper is at pagae 500 or somewhere.

Good reading

PP

[dundurn]

The chicken is preparing to cross the road so naturally it is set up to look right first.

Sorry - couldn't resist it!

[brachiopod]

Is all this dextral talk not sinister?