In order to understand histology and anatomy of penguins, one needs to have a base knowledge. Before you go on to read about the histology of penguins, read the following discussion of cell types. I'm not going to enter a discussion of what a cell is comprised of, but I will ask you to note the presence of a nucleus (cell center containing DNA) in penguin cells.

    There are four types of tissue in penguins. There is nervous tissue, muscle, epithelial tissue, and connective tissue. Everything that is natural to the penguin, i.e. that which is created by the penguin, is composed of one or more of these types of tissue. Cells are classified as any of the above depending on their location and characteristics. It should be obvious what nervous tissue is; it is composed of the cells that create neurons, glial cells (neuron helpers) and other brain tissue. Muscle is divided into skeletal, cardiac, and smooth. Skeletal muscle most often attaches to the skeleton and helps the penguin perform voluntary movements like walking, swimming, and vocalizing. Cardiac muscle is the muscle found in the penguin heart. Smooth muscle is the muscle that lines portions of the digestive system. All these muscle types have one thing in common: they are contractile in nature. That is, they contract! They create movement, whether voluntary or involuntary. (The heart and gi system move involuntarily -- at the unconscious level of control.)

    The other two tissue types are less obvious. Epithelial cells are the cells that line organs and tissues where they come in contact with the external environment or line the internal cavities. There are many types. Here are a few.

    The first cell type is simple squamous epithelium. It consists of a single layer of flat cells. These cells line the inside of blood vessels or the external surfaces of organs like the heart, liver, or lungs. "Squamous" refers to cells that have no particular shape but remain flat in all situations. Simple squamous cells do not receive direct blood supply, so the oxygen and nutrients they need must travel through other cells to reach the squamous layers. Simple squamous cells are very common and renew fairly frequently.

    Stratified squamous epithelium is similar to simple squamous epithelium. This tissue is composed of the same cells, but unlike simple squamous, stratified squamous epithelium has multiple layers of squamous cells. Stratified squamous epithelium lines the outside of the skin, portions of the oral cavity and the region where the skin meets the cloaca. As you might imagine, stratified sqamous epithelium doesn't have a direct blood supply either, despite the fact that it is several layers thick. It receives oxygen and nutrients the same way. It renews fairly frequently and is good barrier.

    Though there are several other types, the last type I will discuss is pseudostratified columnar epithelium. It's called pseudostratified columnar because it looks like a columnar epithelium (column-shaped cells) that is stratified like the stratified squamous epithelium. However, each cell of pseudostratified columnar epithelium touches the bottom, or basement membrane. Pseudostratified columnar epithelium lines most of the respiratory system. Wedged inbetween these pseudostratified columnar cells are goblet cells. Goblet cells look like goblets (of course!) under the microscope and they secrete mucus (can be seen as that thin layer in the image). Mucus helps trap particles that shouldn't get into the lungs of the penguin.

    The anatomy of penguins should be equally interesting as the histology of penguins. Unlike penguin cells, we can actually see parts of the penguin anatomy. Remember, as you flip through these pages, ask the question: Why is the anatomy of the penguin like this? Try to answer that question yourself. If you can't think of it, check the FAQ. Or, you can e-mail me.