filter the_content without caption

Hi there. I would like to alter the_content by adding links to certain words. I wrote a function to do that and added it as a filter to functions.php in the usual way: add_filter(‘the_content’,’function_name’);

The problem is that i want to alter only the text part of the_content, but it starts by altering pictures and captions that are placed above. Is there a way to apply the filter only to the text? Thank you for answering.