temporal aspects of 'X development' terms

[David Hill]

J Clark wrote:

>
>> Yes, the key issue here is whether you consider the vascular cord to 
>> be an is_a or a part_of the vasculature. In the case of the ureteric 
>> bud, when this term was created, I/we (I hope) thought that the 
>> metanephros represented a primordial kidney. It is defined this way 
>> in the anatomical dictionary, and I think most biologists view it 
>> this way. Same goes with the mesonephros, even though it is 
>> transient. Therefore since ureteric bud development is a part_of 
>> metanephros development, it is also a part_of kidney development. 
>> This gets into the sticky issue of lineage and when something begins 
>> to exist. In general, I think most biologists consider primordia to 
>> be the beginning of the existence of a structure. I think we will 
>> continue to be plagued by this question.
>
>
> For this bit you mean that:
>
> A structure like the kidney develops as follows:
>
> 1) kidney primordium (metanephros) forms
> 2) then kidney primordium develops into kidney.
>
>
> Then you are saying that in the past we decided that the kidney 
> primordium is a type of kidney.
>
> [i]kidney
> ---[i]kidney primordium (metanephros)
>
> Then you say that since the following is true:
>
> [i]primordial kidney (metanephros) development
> ---[p]ureteric bud development
>
> we can conclude that
>
> [i]kidney development
> ---[p]ureteric bud development
>
> The reason you're saying this is weird is because whilst 'ureteric bud 
> development' is part of the development of a primordial type of 
> kidney, and therefore part of 'kidney development', it does not occur 
> during the development of the mature kidney, which we might conclude 
> from looking at the graph.

I conclude that (here I go) an instance of 'ureteric bud development' 
[that I can look at in an embryo] is a part of some instance of the 
development of a kidney [that I can look at in an embryo]. In this case, 
it is the embryonic kidney, called a metanephros.

>
> Is that right?
>
> Jen
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