The blue nuclei are quite obvious here.

At first glance, you might think that all that is pink is cytoplasm. If you do, and draw imaginary lines you might get a picture like the lower one.

Stop! Notice the sizes and shapes of the nuclei. They are small, flat and certainly not euchromatic. If this is the case, what are such small nuclei doing in such huge cells?

Once again, the size and shape of a nucleus is a clue to the size and shape of the cell it belongs to. If the nuclei are flat, the cells are flat as well. Indeed, the cells are rather thin. Which means that the major part of the pink material is intercellular substance! Could this be the matrix of a connective tissue?

You can correlate the following with knowledge you will gain in the lecture next Monday. In connective tissue matrix, the ground substance is barely visible (does not stain well, and a lot of it is washed out by water). Reticular fibres are not visible with H&E stain. Elastic fibres are thin and usually scattered. The only component that appears as a pink mass can be thick, densely packed collagen!

This, then, is dense fibrous connective tissue with lot of collagen and flat, mostly inactive cells.

Collagen is quite tough, and not easy to cut sections through. The result is that tears are likely to appear in sections. See the large tear along the lower end of the picture. The rest of the tissue also shows a 'scratchy' appearance for the same reason.

We shall see more of such tissues in Week 2.

The cell in the oval has two nuclei in this section. It is difficult to decide in this picture if the nuclei are euchromatic. But that is not the issue here. The cell between the oval and the letter X has three nuclei.

Whatever the number of nuclei, note that they are not central in location! Each nucleus is very close to the cell membrane.

In three dimensions, these cells could be polyhedral (solids with many surfaces) or they could long, like sticks. We shall understand later that these cells are indeed like sticks.

The point is : if a 5 μm section can have two or three nuclei, the entire cell is likely to have many, many more! As a matter of fact, a complete cell of this kind can have many dozens, even a few hundred nuclei. We shall learn later that these are cells of skeletal muscle.

The thin, clear spaces among these cells are the result of shrinkage of muscle cells during preparation of this material for sectioning.