This lab is broken down into three sections: Epithelial Tissue, Connective Tissue, and Muscle & Nerve Tissue. For each section, read the background and answer any questions before you come to class, then in class sketch the specimens listed under each sketch circle. For your sketches, include the total magnification under which you viewed the specimen and be very detailed in your sketch.
Functions of Epithelium
Epithelium has two major functions: covering/lining and glandular: Epithelial tissue covers body structures or lines body spaces. One side of the epithelium is free (not attached) because it either faces outward (skin) or inward (lining). The other side of the epithelium is called the basement membrane and is attached to underlying connective tissue. Epithelia do not have their own blood supply; therefore, nutrients must diffuse through the basement membrane to reach the cells. Epithelia performing a glandular function are part of glands. Exocrine glands secrete substances into ducts which then empty onto epithelial surfaces (e.g. sweat glands, mammary glands). Endocrine glands secrete substances which then diffuse into the bloodstream (e.g. islet cells of pancreas secreting insulin).
Classification & Composition of Epithelium
Epithelium is classified by the number of cell layers and the shape of the cells in the outer layer. Number of Cell Layers Simple – only one cell layer. Stratified – more than one cell layer. Pseudostratified – “false stratified”. Nuclei have separated into two layers due to cellular compaction. Cell Shapes Squamous – like scales, wider than they are tall Cuboidal - ~cube-shaped, tall as they are wide, may be more rounded than square Columnar – column-like cells, taller than they are wide Transitional – cells that can change shape