Using categories to filter assets
From your example, it is a bit hard to tell how your site is organized, but it sounds like you want to set up content specific to each ministry (which is stored in the top-level of your "site_content" structure?), which will be shared across all of that ministry's sub-pages. Regardless, you will essentially want to retrieve the entry where the slider data is stored, and loop through the matrix data from there.

{% if craft.request.segment(2) == "crosstrainers" %}
    {% set entry = craft.entries.section('site_content').slug('crosstrainers') %}
    {% for block in entry.slider %}
        {# prevent error if no slider image is defined #}
        {% if block.sliderImage|length %}
            {% set image = block.sliderImage.first() %}
            &lt;img class="slider-image" src="{{ image.getUrl }}" alt="{{ entry.title }}" /&gt;
            ...
        {% endif %}
    {% endfor %}
{% endif %}