Is it possible for me to define custom output for links and images?

[tendstofortytwo]

For example, images are currently rendered as:

<img src="url" alt="text" />

And I want to render them as:

<figure><img src="url" alt="text" /><figcaption>text</figcaption></figure>

Is it possible to change the HTML output for a particular kind of Markdown element? If so, how? Thanks!