It would be very intuitive and easier to navigate for customers if the category tree was displayed at the top of each product page. For instance:

Apparel & Accessories > T-Shirts > Men's/Unisex Tees

This would make it much more intuitive for customers to navigate back to product categories or at least see where a product is listed. Right now there is no indication of what category a product is listed in or how they got there.