Lab Animal Tissue. LEARNING OBJECTIVES: To understand the relationship between the structure and function of different animal tissues

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1 Name: Bio A.P. PURPOSE: HYPOTHESIS: NONE Lab Animal Tissue BACKGROUND: In animals, groups of closely related cells specialized to perform the same function are called tissues. There are four general classes of tissue: epithelial, connective, muscle, and nervous. In many cases tissues will associate to carry out a particular function. This structural and functional unit of associated tissues is called an organ. A group of organs that interacts to carry out a particular process is called an organ system. LEARNING OBJECTIVES: To understand the relationship between the structure and function of different animal tissues GENERAL SAFETY PRECAUTIONS: There are no major safety concerns in this lab. You may wear lab jackets and safety goggles. Do not work in the laboratory without your teacher s supervision. Talk to your teacher if you have any questions or concerns about the experiments. THE INVESTIGATIONS: This lab is a technique based lab. Be sure to follow all directions. Answer all questions and record all data in you lab journal. When drawing diagrams viewed under the microscope you need to draw your field of view and label each diagram with the structure being viewed and the total power of magnification. Remember to color your diagrams so they are as accurate as possible. Example:. Human Check Cell: Methylene blue stain 100x 1

2 Part I-Epithelial Tissue Epithelial tissues cover the internal and external surfaces of the body. These close fitting cells form a barrier between he body and its surroundings. Some epithelial cells serve the function of responding to stimuli from the environment. Others are responsible for absorption, secretion, and excretion and are often found in the walls of tubular glands such as those that product sweat, tears and saliva. Three major types of epithelial tissue can be distinguished according to shape: squamous, cuboidal and columnar. These may exist as a single layer (simple) or as more than one layer (stratified). Occasionally, the cells may seem to be stratified, but upon closer examination it is apparent that there is only one layer present; these are pseudostratified. The sheets if epithelial cells generally rest on a basement membrane, which separates them from underlying tissue. Cuboidal Squamous Columnar Simple A. Squamous Epithelium: Simple squamous epithelium consists of a single layer of flattened, polygonal cells that is easily permeable to gas and liquids. This type of tissue is found inside the lung alveoli (air sacs), in the blood vessels, and in the lining of the heart. Stratified squamous epithelium is found in areas of the body where additional protection is required, for example the skin, and in the mouth. Obtain a prepared slide squamous epithelial smear. Scan the slide for a clear section of squamous cells. Use the best magnification for a clear image of the cells. Draw and label your slide. Be sure to include the name of the slide and total power of magnification. You should be able to find and label the cell membrane and nucleus of the cells. a. What shape are the cells? b. How are they arranged? B. Columnar Epithelium: Columnar epithelium consists of a layer of closely packed columnar cells in which the length of each cell greatly exceeds its width. This type of cell is often found in the digestive-juice secreting layer of the intestine where it serves a secretory function. It is also found lining the respiratory tract and reproductive organs where the cells are ciliated. Obtain a prepared slide columnar epithelium. Scan the slide for a clear section of squamous cells. Use the best magnification for a clear image of the cells. Draw and label your slide. You should be able to find and label the cell membrane and nucleus of the cells. a. How are the cells arranged? C. Cuboidal Epithelium: When seen in cross section, cuboidal epithelial cells are shaped like cubes. These often serve a secretory function and are associated with the walls of ducts and glands. Obtain a prepared slide cuboidal epithelium. Scan the slide for a clear section of squamous cells. Use the best magnification for a clear image of the cells. Draw and label your slide. You should be able to find and label the cell membrane and nucleus of the cells. a. How are the cells arranged? 2

3 Part II-Connective Tissue Connective tissue binds other tissues together, giving substantial form and support to the organ. The cells are usually widely separated by a matrix, intercellular space filled with fluid and solid material. The relative abundance and arrangement of the cells and the character of the matrix determine the properties of a particular kind of connective tissue. A. Cartilage: Cartilage or gristle is connective tissue with a dense fibrous matrix giving it a rubbery consistence. In embryonic development of all vertebrates, cartilage serves as an initial supporting skeleton. As the organism develops, most cartilage is replaced by bone in the process of ossification. Once the last of the cartilage in a bone has disappeared, the bone can no longer grow in size. Some cartilage is never replaced by bone. Hyaline cartilage found at the ends of long bones, and at the tip of your nose, and elastic cartilage found in the ear and trachea are some examples. Distributed throughout the firm but elastic matrix of cartilage are numerous lacunae (lakes) containing cartilage cells (chrondrocytes), which secrete the matrix. 1. Obtain a prepared slide of human hyaline cartilage. Scan the slide for a clear section of cartilage. Use the best magnification for a clear image of the tissue. Draw and label your slide. On your diagram identify the following: matrix, lacunae and the chrondrocytes. 3

4 B. Bone Long bones of the skeletal system are not solid structures. Rather, they are constructed to provide the maximum strength with minimum weight. This is accomplished by surrounding the outer portion of the bone with heavy compact bone to provide strength. A marrow cavity in the center of the bone of the shaft and spongy bone at the ends of long bones reduces the weight. Bone consists of a dense matrix made up of calcium salts and protein secreted by the bone forming cells called osteoblasts. Bone is constantly being remolded by osteoclasts, cells that break down bone structure, and the continued synthesizing activities of the osteoblasts. Mature osteoblasts (osteocytes) become trapped in lacunae. Haversian canal Lamella Haversain System Canaliculi Osteoblast within the lacunae 1. Obtain a prepared slide of human compact bone. Scan the slide for a clear section of bone. Use the best magnification for a clear image of the tissue. Draw and label your slide. On your diagram identify the following: Haversian system, Haversian canals, canaliculi, lacunae, matrix, and osterocytes. 2. Obtain a prepared slide of vertebra-fetus. Scan the slide for a clear section of the tissue. Use the best magnification for a clear image of the tissue. Draw and label your slide. a. How do you suppose that a broken bone heals? b. Does the vertebra-fetus resemble bone or cartilage? Explain. 4

5 C. Loose and Dense Connective Tissue Connective tissue is responsible for the attachment of skin to muscle, muscle to bone (tendons) or bone to bone (ligaments). Loose connective tissue or areolar tissue connects organs and tissues. Dense connective tissue is more compact and shows a more or less orderly arrangement of its fibers, depending on its function. Such tissue is found in the periosteum covering bones, the dermis of skin and as part of ligaments and tendons. Loose connective tissue is composed of two types of fibers: white collagenous fibers and yellow elastic fibers embedded in a semisolid ground substance. Fibroblasts secrete both the matrix and the fibers. White blood cells (macrophages) may also be seen wandering through the tissue 1. Obtain a prepared slide of areolar tissue. Scan the slide for a clear section of the tissue. Use the best magnification for a clear image of the tissue. Draw and label your slide. On your diagram identify the following: fibroblasts, elastic fibers (yellow and branched), collagen fibers (white and un-branched). a. Do you see any white blood cells? What purpose do you think is served by these cells wandering around the connective tissue of your body? D. Blood Blood is a connective tissue because its cellular components are suspended in a fluid matrix (plasma). Mammalian blood consists of 55% plasma and 45% formed elements (cells). Plasma consists of water (90%) plus dissolved solids, metabolic waste, digested food material, hormones, antibodies, and dissolved gases. 1. Obtain a prepared slide of human blood smear. Scan the slide for a clear section of the tissue. Use the best magnification for a clear image of the tissue. Draw and label your slide. On your diagram identify the following: erythrocytes, leucocytes, and platelets. a. How many different types of white blood cells do you find? b. Compare the structure of the white blood cells to the red blood cells. c. What is the general shape of the red blood cells? Do they contain a stained nucleus? 2. Obtain a prepared slide of frog blood. Scan the slide for a clear section of the tissue. Use the best magnification for a clear image of the tissue. a. Do the blood cells of a frog have nuclei? b. Did your red blood cells have nuclei? c. What distinguished the red blood cells of mammals from those of other vertebrates? 5

6 E. Muscle Tissue Most muscle is composed of cylindrical or spindle shaped muscle cells called fibers, each of which contains many microscopic elongated parallel myofibrils. These fibers are composed of the protein actin and myosin. If alternating dark and light cross bands (striations) are seen under the microscope the muscle is said to be striated. Skeletal and cardiac muscle are striated. Smooth (visceral) muscle contains myofibrils but so not show striations Skeletal muscle (striated or voluntary muscle) makes up the muscle masses, which are attached to and move the bones of the body. Skeletal muscle is made up of several elongated cylindrical cells fused to form a multinucleated un-branched muscle fiber. The nuclei are located along the periphery of the fiber. Cardiac muscle is found only in the heart wall. They are cylindrical and striated. Unlike other muscle, the fibers are branched. Individual cells are separated by transverse membranes called intercalated disks, which appear as dark bands crossing over the fibers. Nuclei are centrally located. Smooth muscle is found in the walls of the alimentary tract, the urinary and genital tracts, and the walls of arteries and veins. Smooth muscle fibers are spindle shaped cells with no striations. There is a single, elongated central nucleus in each cell. 1. Obtain a prepared slide of skeletal muscle. Scan the slide for a clear section of the tissue. Use the best magnification for a clear image of the tissue. Draw and label your slide. On your diagram identify the following: nuclei and striations. 2. Obtain a prepared slide of smooth muscle. Scan the slide for a clear section of the tissue. Use the best magnification for a clear image of the tissue. Draw and label your slide. On your diagram identify the following: nucleus and muscle fiber. F. Nervous Tissue The basic structural unit of the nervous system is the individual nerve cell or neuron. The function of the neuron is the conduction of a nerve impulse (action potential) to another neuron of to a muscle fiber. Only about 10% of the cells in the nervous system are neurons. The remainder are glial elements and sheath cells whose function is to sustain neurons and support them. Neurons consist of three major sections: the cell body, dendrites and the axons. The cell body contains the nucleus and organelles. Cellular extensions of fibers that conduct nerve impulses toward the cell body are dendrites. Axons conduct the impulses away from the cell body. 1. Obtain a prepared slide of motor neuron. Scan the slide for a clear section of a single motor neuron. Use the best magnification for a clear image. You DO NOT have to draw this slide. a. Can you see an entire motor neuron in the slide? Why or why not? b. Where would you find the longest nerve cell in your body? 6

7 Note: When you have completed this lab you should have the each of the following diagrams: Simple squamous epithelium Columnar epithelium Cuboidal epithelium Human elastic cartilage Human compact bone Vertebra-fetus Areolar tissue Human blood smear Frog blood Skeletal muscle Smooth muscle 7