Materials Included In Kit

Additional Materials Required

Prelab Preparation

1. Set up the eight compound microscopes at eight separate lab stations.
2. Remove the identifying sticker from each slide. Using a permanent marker, write U1 on the squamous epithelium slide, U2 on the motor nerve cell, U3 on the rat blood slide and U4 on the cardiac muscle slide.
3. Using a note card, label each of the lab stations U1–U4 according to the slide which will be displayed there.
4. The slides do not need to be focused prior to students attending the lab. Allow students to focus the image to practice proper technique.
5. Assign students to a lab station and instruct students how to rotate through the stations so that every group of students visits each station U1, U2, U3 and U4.

Safety Precautions

The materials used in this lab are considered nonhazardous. Follow all standard laboratory safety guidelines. Remind students to wash their hands thoroughly with soap and water before leaving the laboratory.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. The materials used in this lab may be saved for future use. Store slides in their original container to prevent breakage.

Lab Hints

• Refresh students’ memory on the proper method to focus a microscope before beginning this activity.
• If students are using immersion oil, remind them to clean the slide and 100X objective with lens paper before rotating to the next lab station.
• Allow each student approximately 2 minutes at each lab station.
• Additional copies of the slides included in this kit are available individually for purchase.

Teacher Tips

• If the classroom has access to microscope accessories capable of displaying images on a television screen, display the slides on the television after everyone has completed the lab. Have a classroom discussion and invite students to share their observations and their method of determining the origin of the tissue sample.
• If possible, it is best to have U1–U4 on one side of the laboratory and the other identical U1-U4 set on the other side of the laboratory. Instruct students if they were originally assigned to the right side of the classroom they should rotate on the right side only.

Answers to Prelab Questions

1. What would you expect a cuboidal stratified epithelium to look like?

   More than one layer of cube-shaped cells.

2. What are the three types of muscle tissue?

   Muscle tissue can be either smooth, striated or cardiac.

Sample Data

Answers to Questions

1. Based upon your observations, identify which tissue type is present in each unknown slide.

   Unknown slide 1 consists of epithelial tissue. Specifically squamous epithelium because of its flat shape and scattered arrangement. Unknown slide 2 is nervous tissue and it appears web-like. Unknown slide 3 appeared to be a sample of blood. The erythrocytes (red blood cells) appear a light pink color and the monocytes appear purple. Unknown slide 4 is muscle tissue. It appears to be striated.

2. You are given a tissue sample that contains striated muscle. What two types of muscle tissue could it be and how would you identify which it is?

   If a muscle tissue contains striations it could either be skeletal or cardiac muscle. If the tissue contains one nucleus per segment and intercalated disks between cells then it would be cardiac muscle.

3. The structure and function of tissues are related. Explain why the web-like structure of nerves helps their function.

   Nerves carry information as electrical signals. The more they overlap, the more likely it is that information will be passed from one neuron to another.

References

Silverthorn, D. U. Human Physiology: An Integrated Approach; Pearson Benjamin Cummings: San Francisco, CA; 2004; pp 63–75.

Introduction

Assume the role of a crime scene researcher. The field agents have brought back evidence from the crime scene and it is up to the lab to compile data using the evidence. Examine four slides and determine the type of tissue present in each slide to report to the investigators.

Concepts

• Microscopy
• Tissue sample identification
• Histology

Background

Cells in the body assemble into larger units known as tissues. Tissues are collections of cells held together by connections known as cell junctions and other supportive structures. Tissues have a wide range of complexity from simple tissues containing one cell type to complex tissues containing many cell types.

Histology is the study of tissue structure and function. Histologists analyze tissue according to the following characteristics—shape and size of the cells, how the cells are arranged in the tissues, how the cells are connected to each other, and the amount of extracellular material present in the tissues. The four primary types of tissue are epithelial, connective, muscle, and neural.

Epithelial tissue or epithelia protect the internal atmosphere of the body and regulate the exchange of material between the inside and outside of the body. The upper surface of epithelial tissue may be exposed to the external environment of the body (as in skin) or an internal body cavity (as in the digestive tract). Epithilia consist of relatively flat, closely packed cells that are physically separated from underlying connective tissues by the basil lamina. The basil lamina is composed of a network of collagen and laminin filaments embedded in proteoglycans. Proteoglycans are complex or conjugated proteins consisting of peptide chains and attached carbohydrate or polysaccharide residues.

Epithelial tissues are classified according to their cell shape and cell layers. Epithelial cells may be found as simple stratified or psuedostratified. Simple epithelia have cells arranged in a single layer (see Table 1). Stratified epithelia are classified as cells arranged in two or more layers. The height and width of cells vary from one layer to another. Pseudostratified epithelium is an intermediate between simple and stratified epithelium. It consists of one layer of cells of irregular size and shape attached to the basil lamina. In addition to classifying epithelial tissue by the number of layers of cells, the latter may also be classified by shape. Columnar cells are much taller than they are wide. Cuboidal cells are approximately equal in length and width. Squamous cells are flat and irregular in shape. See Table 1 for a summary of epithelial tissue classification.

The second major tissue type is connective tissue. Connective tissues provide structural support and sometimes a physical barrier that aids in defending the body against foreign bacteria. Examples of connective tissue include blood, which supports tissues for the skin and internal organs, as well as cartilage and bone. Connective tissue consists of a gel-like matrix with proteoglycans and water plus insoluble fibrous protein fibers. Therefore a connective tissue consists of elastic fibers, collagen fibers, fibroblasts (cells that secrete matrix proteins), macrophages, and ground substance.

There are five main classifications of connective tissue. Loose connective tissue has an abundance of cells distributed among loosely arranged fibers of proteoglycans within a gelatinous ground substance. Dense connective tissue has few cells among a dense network of fibers with minimal ground substance (see Figure 1). Cartilage exhibits cells among fibers in a firm gelatinous ground substance. Bone consists of cells distributed among abundant fibers in a solid ground substance containing minerals (see Figure 2). Blood is also considered a connective tissue and is comprised of blood cells and platelets distributed in a matrix known as blood plasma (see Figure 3). Both muscle and neural tissues are known as excitable tissues due to their ability to generate electrical signals. Both tissue types have a minimal extracellular matrix, usually consisting of basal lamina.

Muscle tissue has the ability to contract as well as produce force and movement. There are three types of muscle found in the body—cardiac muscle, which is found in the heart, and skeletal and smooth muscles, which are found in internal organs. Cardiac muscle is striated and has a single, centrally located nucleus (see Figure 4). Cardiac muscle also has intercalated disks that bridge cells together. Skeletal muscles are attached to bone and allow movement of the body. They consist of long cylindrical cells with bands that run perpendicular to the length of the cell. The cells in skeletal muscle tissue are multinucleated, meaning they contain many nuclei (see Figure 5). Smooth muscle consists of cells with one centrally located nucleus. The cells are elongated with tapered ends and are not striated (see Figure 6). Neurons carry information from one part of the body to another via chemical and electrical signals. Although neurons are concentrated in the brain and spine, they are found in virtually every part of the body. A neuron consists of a cell body, dendrites, and an axon (see Figure 7). Neural tissue samples contain a large nucleus with a distinct nucleolus. Nervous tissue samples often appear somewhat web-like as the neurons are intertwined on a slide. Tissue samples serve as key evidence in accurately solving crimes. The main reason they are valuable is they can be used to obtain deoxyribonucleic acid (DNA). DNA can indisputably link specific individuals to a crime scene and solve the case.

Experiment Overview

Examine each of the four slides from the crime scene and determine the type of tissue present.

Materials

Prelab Questions

1. What would you expect a cuboidal stratified epithelium to look like?
2. What are the three types of muscle tissue?

Safety Precautions

The materials used in this laboratory activity are considered nonhazardous. Please follow all laboratory safety guidelines.

Procedure

1. You will be assigned to one of the compound microscopes set up throughout the classroom.
2. Each microscope is labeled U1–U4 and contains the corresponding unknown slide. Note: Microscopes with the same label contain the same unknown slide.
3. Focus the image on the slide using the 4X objective. Adjust the coarse and fine focus knobs as needed to clearly view the cells.
4. Once the image is focused, switch to the 10X objective. Adjust the coarse and fine focus knobs as necessary.
5. Switch to the 40X objective to view the fine details of the cell and adjust the fine focus knob to view the image clearly.
6. After viewing with the 40X objective, continue with the oil immersion objective if available. Note: The fine focus knob should be used to clarify the image when the objectives are changed to 40X and 100X. Do not use the coarse focus knob with the 100X objective.
7. Record detailed observations of the cells and tissue on the Investigating Tissue Microscopy Worksheet. Be as specific as possible, describing key distinguishing features of the cells and cell junctions. Draw a sketch of the cells and identify the type of tissue present.
8. Return the microscope to 4X objective, lower the microscope stage, and, if necessary, wipe clean all objective lenses and the prepared microscope slide using lens paper.
9. Rotate through the workstations as designated by your instructor (the slides may be viewed in any order). Repeat steps 1–8 with the three remaining workstations.

Student Worksheet PDF

11025_Student1.pdf