Laboratory 2: Epithelia and Integument
Exercises 6 and 7
The objectives of Lab 2 are: 1. Learn histology and 2. Learn the location and function of epithelial tissue and integument. On the lab practical you will be asked to recognize tissues under the microscope. Quiz yourself or another student by blindly selecting slides and identifying each one.
Exercise 6 is long and detailed, covering 19 types of tissue. Exercise 6 will be completed over two lab periods. During Lab 2 you should learn the basic structure of epithelial tissues (e.t.) and the histology, location, and function of the following:
6. Transitional e.t.
(Note: we will not examine stratified cuboidal e.t. or stratified columnar e.t. Know the locations and functions of these tissues. You will not be asked to recognize them.) In Lab 3 we will study connective tissues.
Epithelial tissues cover surfaces including the lining of the stomach, the lining of ducts, and the skin. Epithelial tissues are named according to two structural characteristics:
1. Number of cell layers
2. Cell shape
For example, simple cuboidal e.t. has one cell layer thick (simple) with cube shaped cells (cuboidal). Stratified squamous e.t. has multiple cell layers (stratified) with flattened, irregularly shaped cells (squamous).
Two types of epithelial tissue, pseudostratified columnar e.t. and transitional e.t., seemingly defy this classification scheme. Pseudostratified columnar e.t. is a simple tissue (one cell layer thick) and the cells are columnar in shape. The height of the cells and the location of the nuclei within the cells give the appearance of multiple cell layers. Hence the name pseudostratified. Transitional e.t. is a stratified tissue (multiple cell layers thick), but the shape of the cells varies from squamous to cuboidal. As cells progress from the basement membrane to the apical surface, there is a transition in cell shape, from squamous to cuboidal.
The skin has two distinct layers.
1. The superficial epidermis is composed of stratified squamous e.t.
2. The deeper dermis consists of dense irregular connective tissue (2nd half of Ex. 6) and several structures including glands and hair follicles. Both the dermis and the epidermis may, themselves, be broken down into several layers.
Use Figs. 7.1 and 7.2 and prepared slides to learn them.
Stratum corneum (superficial)
Use the microscope pointer to practice identifying layers. Note: in most of our slides, only the deepest and most superficial layers of the epidermis are clearly distinguishable (S. basale and S. corneum, respectively). You will not be asked to identify any of the central layers, but know them all, in order.
Within the dermis, examine exocrine and apocrine glands as well as hair follicles.
Skip: Figs. 7.3, 7.4 (b) and (c), 7.5, and Plotting the Distribution of Sweat Glands