Other than knowing microscopic pictures I think it is extremely essential that you know the different types of cells found in each organ system/tract. The set up of endothelial cells, epithelial cells.. how it relates to the basement membrane, what kind of lining is found in the GI system all the way from the oral cavity to all the way down the rectum, all the respiratory mucosa, inflammatory cells and what kind of enzymes they host, the different layers of arteries vs veins etc.
In my opinion, and others way disagree, having a solid background in histology makes pathology A LOT easier. Knowing the normal absolutely cold will help you make connections a lot better when you study the abnormal aka pathology. I actually refer a lot to my histology notes just to make sure I know what went wrong, where.. it helps stick better.
So, make sure you know what microscopic pictures look like and what are the key factors that differentiate them, but also follow different types of cells and where they present, and WHY they present that way.
I actually used the Ross textbook during M1 and found it very helpful for the aforementioned perspective. So needless to say, its a solid text.
