Unique tr/th/td attributes for each table class

I've been reading documentation all afternoon, and I can't seem to figure this out.

Is there a way to attach style properties to the elements of a table without having to add a class or id tag to each element?

For example, I can use

table.myclass {border:1px}
th.myclass {background-color:#888888}

and create a table with

<table class="myclass">
  <tr>
    <th class="myclass">content</th>
    <th class="myclass">content</th>
  </tr>
  <tr>
    <td>content</td>
    <td>content</td>
  </tr>
</table>

But is there a way to code it so that every table of class="myclass" will have table headers with the new color automatically, without having to add the class tag to each th tag?