Unit 2

This week we're going to finish our review material, and then also begin some new material. All we have left of the review material is the chemistry; we will be looking mainly at macromolecules to understand how they build cells.

For the new material, we will be starting off learning about epithelial tissue. Tissue is a congregation or layer of cells that, together, perform a common function. Not every cell within a tissue has to be the same-- but the function of those cells must be able to be combined for a common purpose. There are four categories of tissues commonly described:

	epithelial tissue: tissue that lines surfaces of our bodies (like lining the digestive tract or the most superficial layer of our skin)
	connective tissue: tissue that is found between other tissues, typically containing a lot of noncellular material or being more loosely organized (like fat, blood, & bone)
	muscle tissue: tissue responsible for moving parts of our bodies or moving things through our bodies (like your biceps brachii bends your arm, muscle tissue in your intestines moves the food you are digesting along, and your heart moves blood through our bodies)
	nervous tissue: tissue involved in coordinating actions of other tissues (like your brain and your spinal nerves)

The most straightforward of these four to begin learning is epithelial tissue. Most people can picture that all organs and body regions have edges to them, and epithelial tissue is just that tissue on the edges.

After learning about the many types of epithelial tissues, you will then learn one more new topic this week: skin. You see, skin covers the surface of the body, so it must have epithelial tissue on its outer surface. You will learn that skin is not just made of epithelial tissue-- skin is actually an organ. The definition of an organ is that it is made up of 2 or more types of tissue. I am just going to have you try to focus on the more superficial epithelial tissue in skin, and we'll have less emphasis on the underlying connective tissue right now. We will come back to skin later in the semester to finish it up fully.

I hope you enjoy unit 2!