how to access the child control in update panel?

in my master page, i am using update panel,inside update panel i use child control like label box,drop down and text boxes.
all controls are placed in a panel, now how to get the panel id.
<asp:UpdatePanel ID="up1" runat="server">
<ContentTemplate>
 <asp:TabContainer ID="TabContainer1" runat="server" ActiveTabIndex="1">
<asp:TabPanel ID="tab3" runat="server" HeaderText="3.Give Traveller Name(s)">
<ContentTemplate>
<table>
<tr>
<td>
<asp:Panel ID="Panel1" runat="server">
<asp:Label ID="Label5" runat="server">Adult1</asp:Label>
<asp:DropDownList ID="ddl" runat="server">
<asp:ListItem>thiri</asp:ListItem>
</asp:DropDownList>
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
</asp:Panel>

c ...