Introduction to Histology

Here are some learning objectives that relate to this particular topic:

- Know what histology is what the emphasis of histology is

- Know what the four primary classes of tissues are

- Know what the extracellular matrix (ECM) is (not the movie) and what it’s composed of

- Know how to properly identify tissues by observing: cellular differences, the ECM, cellular spacing, cellular size, cell numbers, etc.

Remember that histology is the study of tissues, (histo- = tissue; -ology = study of). There are a few different ways to identify tissues; the main one is by looking at the shapes and types of cells within that tissue. The shape of a cell is a great identifying characteristic, we use shapes in our everyday lives to identify things. We know that the McDonald's arch by looking at its characteristics, it looks like a large golden letter M. The same goes with the cells in our tissues; they all have distinct and unique shapes that we can use to tell them apart. Their shape also correlates with their functions; remember this because we'll talk about this as we go throughout this class. We can also tell tissues apart by how the cells are arranged; in some tissues cells are very tightly packed together such as skeletal muscle. In some tissues cells are very widely spaced, like loose connective tissue. This also plays into the function of the tissue, the loose arrangement of loose/areolar connective tissue provides a lot of space for blood vessels and nerves to grow and form networks so nearby cells can receive stimulation, nutrients, gases and omit waste products. The last thing I'll discuss on this topic is the environment of tissues. All of our tissues have unique environments that surround the cells within them. Some tissues have rubbery environments such as cartilage, some are stony in appearance such as bone because of the proteins and minerals within them, some are like clear gels (ECF is an example) etc.