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For most of the long bones head is the proximal end, but for metacarpals and Ulna, head is the distal end. Why are their distal ends called as heads?

What's the criteria for calling an end as head end?

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    $\begingroup$ Why voted to close? I have searched on internet but could not find any literature about it, all I see is " head is usually the proximal end" .So I asked it here. What should I mention in the section MY attempt in the question? $\endgroup$ – JM97 Jul 19 '17 at 6:37
  • $\begingroup$ Because it's easy to google, but I'm answering it anyway. $\endgroup$ – anongoodnurse Jul 19 '17 at 6:41
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Here is a head and a neck:

enter image description here

Anatomy is fairly straightforward. regarding individual long bones, "heads" are curved ends of bones distal to a narrowing called a neck of a bone. Take the radius:

enter image description here

See how the radial head (curved) is just distal to a narrowing (neck)?

The ulnar head, though, is at the opposite end, because the proximal end isn't rounded, but the distal end is.

Metacarpal heads are distal (see blue area):

enter image description here

The humeral head is probably most obvious:

enter image description here

So, the head of a long bone is not determined by the position (it can be proximal or distal) but by the contiguous shapes.

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    $\begingroup$ When will you answer about chassaignac's tubercle? $\endgroup$ – JM97 Jul 19 '17 at 6:51
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    $\begingroup$ @JM97 - I don't appreciate your pushiness. I would have thought you'd have accepted that I'm no longer involved in that thread. You're welcome for my answering this, btw.a completely voluntary activity. $\endgroup$ – anongoodnurse Jul 19 '17 at 7:26
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    $\begingroup$ You were the only person to say that you know about it, so i was eager to know about that. $\endgroup$ – JM97 Jul 19 '17 at 7:32

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