Thyroid gland answer
Pairs of somites develop along both sides of what mesodermal organ? Along what ectodermal part?
Each somite subdivides into what three parts? (one whose cells differentiate as skeletal muscle, another forms skeleton, and the third forms the inner-leathery layer of the skin).
Which of these three subdivisions then subdivides into an anterior and a posterior part? Each anterior part then fuses with the posterior part of what, so as to form what anatomical structure?
Somite cells all disperse, and later in development you can only see remnants of where they had been: Can you suggest functional or mechanical reasons why the vertebrate body is segmented by transient rather than permanent blocks if cells?
Maybe segmentation has a physical cause]
In fact, why use aggregated blocks of cells at all? People hypothesize that wave-like gradients of diffusing chemicals are what control where the somites are formed; so why not have those chemical gradients directly determine which cells will differentiate into muscle, bone and dermis. (Why not eliminate the middleman?)
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