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Cell Physiology 3140A Lecutre 3.docx

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Physiology 3140A
Anita Woods

CELL PHYSIOLOGY 3140A SEPTEMBER 13, 2013 LECTURE 3 TISSUES AND THEIR EXTRACELLAR MATRIX - Extracellular Matrix is a complex network of secreted macromolecules. This matrix that we see around cells are generally product of those cells. Ex. Cartilage cells will secrete a cartilage type matrix. They secrete a matrix that they will “live” in. It is like building houses for you to live in. That matrix and that cell type will make that tissue type. The matrix has a lot of important functions. 1. The matrix holds cells and tissues together. There are a lot of tissue that needs the external support. Tissue types also undergo mechanical stress. Ex. Muscles are always contracting so the matrix needs to hold them together. Skin needs matrix to keep those skin cells together. Joints, cartilage and bone need extracellular matrix. 2. The matrix are there to organize an environment for cells to move and interact. The matrix provides a ladder or stairway for cells to interact. It also prevents the cells from getting away from it’s tissue type. The matrix organizes events for tissues to work together. 3. The matrix is bidirectional. This means that when a cell is sitting in a ECM, it can sense what the matrix is and it tells the cell “this is who you are, how long you’ve been here” etc. The cell itself will have information that will sense the matrix and it will make molecules appropriately. If the cell is sitting in a matrix with less collagen, the cell will make more collagen. All in all, the ECM regulates proliferative capacity, differentiation and survival. What is the Matrix? - The matrix is a meshwork of proteins and polysaccharides. There are multiple sugar units strung together. Cells that are currently in the matrix or cells that has come before have secreted the matrix. Ex. The growth plate is a specific type of structure where cells previously existed secreted a matrix. Those cells die and the new cells came in to take advantage of the matrix. The old cells set up like a template for their “children”. The matrix is bidirectional. Compare and Contrast Between Epithelial Tissue and Connective Tissue - See package - There are 5 different tissue types. In those tissue types, those tissues have different composition of matrix. The 2 most different types of tissues are epithelial tissue (ET) and connective tissue (CT). The epithelial tissues are the skin, lining of gastrointestinal tract and the lining of the respiratory system. The connective tissues are tendons, bones and cartilage. When thinking about those 2 tissue types, the way the matrix functions and how much there is, is very different. The first difference between the 2 is: ET has a very rare ECM. They have very little ECM. Ex. In the gastrointestinal tract, there are very little ECM, they re mostly cellular. In CT there are more ECM. The 2 difference is: the ET has existing matrix called the basal lamina. Similar to a Toblerone bar. In ET, you have this mat of ECM and they have these nice little cells sitting on top. The cellular portion faces the inside of the organ, so they face the internal structure of the organ. Ex faces the internal structure of the stomach, the lumen. The basal lamina faces the body, so the inner structures of the body. That basal lamina has lots of proteoglycans and collagen. The connective tissue are rich in proteoglycans and collagen. Depending on the type of connective tissue you are, you will have different composition of proteoglycan and collagen. Those are the main two types of ECM proteins. The 3 difference is ET has lots of cell-cell adhesion. The tissues and cells are stacked beside each other. In CT, you have a lot of matrix and cells are found throughout and they are not connected together. Ex. Tangerine in jello. The 4 difference is ET has cells tightly bound into sheets called epithelia. There is a high necessity for cells to interact with each other. For CT, direct attachment between cells is rare. Because of the way these tissues are structured, there are difference responsibilities of the ECM. Because the ET, the cell to cell adhesion are what keeps the cells together, anchored by ECM. 5 difference: Those cell-cell adhesions bear most of the mechanical stress. Ex. When you ar
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