lab_25 - LABORATORY 25 Animal Organization Learning...

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Unformatted text preview: LABORATORY 25 Animal Organization Learning Objectives 25.1 Epithelial Tissue 0 identify slides and models of various types of epithelium. - Tell where a particular type of epithelium is located in the body, and state a function. 25.2 Muscular Tissue ' Identify slides and models of three types of muscular tissue. 0 Tell where each type of muscular tissue is located in the body, and state a function. 25.3 Nervous Tissue 0 Identify a slide and model of a neuron. - Tell where nervous tissue is located in the body, and state a function. 25.4 Connective Tissue 0 Identify slides and models of various types of connective tissue. 0 Tell where a particular connective tissue is located in the body, and state a function. 25.5 Tissues Form Organs 0 Identify a slide of the intestinal wall and any particular tissue in the wall. State a function for each tissue. - Identify a slide of skin and any particular tissue or structure in skin. State a function for each tissue or structure. Introduction Humans, as well as all living things, are made up of cells. Groups of cells that have the same structural characteristics and perform the same functions are called tissues. Figure 25.1 shows the four categories of tissues in the human body. An organ is composed of different types of tissues, and various organs form organ systems. Humans thus have the following levels of biological organization: cells —> tissues —> organs a organ systems. The micrographs of tissues in this laboratory were obtained by viewing prepared slides with a light microscope. Preparation required the following sequential steps: 1. Fixation: The tissue is immersed in a preservative solution to maintain the tissue’s existing structure. 2. Embedding: Water is removed with alcohol, and the tissue is impregnated with paraffin wax. 3. Sectioning: The tissue is cut into extremely thin slices by an instrument called a microtome. When the section runs the length of the tissue, it is called a longitudinal section (1.3.); when the section runs across the tissue, it is called a cross section (cs). 4. Staining: The tissue is immersed in dyes that stain different structures. The most common dyes are hematoxylin and eosin stains (H & E). They give a differential blue and red color to the basic and acidic structures within the tissue. Other dyes are available for staining specific structures. 25—1 Animal Organization Laboratory 25 343 Figure 25.1 The major tissues in the human body. The many kinds of tissues in'fhe human body are grouped into four categories: epithelial tissue, muscular tissue, nervous tissue, and connective tissue. Epithelial fissue Simple columnar epithelium Muscular tissue 344 Laboratory 25 Nervous fissue ' neuroglial cell Nervous tissue neuron Connective tissue platelets white blood cells red blood cell ' osteocytes central canal fibroblast Dense fibrous protein fibers 25—3 Animal Organization Laboratory 25 345 25.1 Epithelial Tissue Epithelial tissue (epithelium) forms a continuous layer, or sheet, over the entire body surface and most of the body’s inner cavities. Externally, it forms a covering that protects the animal from infection, injury, and drying out. Some epithelial tissues produce and release secretions. Others absorb nutrients. The name of an epithelial tissue includes two descriptive terms: the shape of the cells and the number of layers. The three possible shapes are squamous, cuboidal, and columnar. With regard to layers, an epithelial tissue may be simple or stratified. Simple means that there is only one layer of cells; stratified means that cell layers are placed on top of each other. Some epithelial tissues are pseudostratified, meaning that they only appear to be layered. Epithelium may also have cellular extensions called microvilli or hairlike extensions called cilia. In the latter case, “ciliated” may be part of the tissue’s name. Observation: Simple and Stratified Squamous Epithelium Simple Squamous Epithelium Simple squamous epithelium is a single layer of thin, flat, many-sided cells, each with a central nucleus. It lines internal cavities, the heart, and all the blood vessels. It also lines parts of the urinary, respiratory, and male reproductive tracts. 1. Study a model or diagram of simple squamous epithelium (Fig. 25.2). What does squamous mean? 2. Examine a prepared slide of squamous epithelium. Under low power, note the close packing of the flat cells. What shapes are the cells? 3. Under high power, examine an individual cell, and identify the plasma membrane, cytoplasm, and nucleus. 4. Knowing that the diameter of field of your microscope is about 400 um, estimate the size of an epithelial cell. Figure 25.2 Simple squamous epithelium. Simple squamous epithelium lines blood vessels and various tracts. (b: Magnification X160) squamous ' epithelial cell plasma membrane nucleus b. Photomicrograph Simple Squamous Epithelium Location Walls of capillaries; lining of blood vessels; air sacs of lungs; lining of internal cavities Function _ . _ Filtration; diffusron; osmosrs 346 Laboratory 25 Animal Organization 25—4 Stratified Squamous Epithelium As would be expected from its name, stratified squamous epithelium consists of many layers of cells. The innermost layer produces cells that are first cuboidal or columnar in shape, but as the cells push toward the surface, they become flattened. The outer region of the skin, called the epidermis (see p. 361), is stratified squamous epithelium. As the cells move toward the surface, they flatten, begin to accumulate a protein called keratin, and eventually die. Keratin makes the outer layer of epidermis tough and protective, and able to repel water. The linings of the mouth, throat, anal canal, and vagina are stratified epithelium. The outermost layer of cells surrounding the cavity is simple squamous epithelium. In these organs, this layer of cells remains soft, moist, and alive. 1. Either now or when you are studying skin in Section 25.5, examine a slide of skin and find the portion of the slide that is stratified squamous epithelium. 2. Approximately how many layers of cells make up this portion of skin? 3. Which layers of cells best represent squamous epithelium? Observation: Simple Cuboidal Epithelium Simple cuboidal epithelium is a single layer of cube-shaped cells, each with a central nucleus. It is found in tubules of the kidney and in the ducts of many glands, where it has a protective function. It also occurs in the secretory portions of some glands—that is, where the tissue produces and releases secretions. 1. Study a model or diagram of simple cuboidal epithelium (Fig. 25.3). 2. Examine a prepared slide of simple cuboidal epithelium. Move the slide until you locate cube—shaped cells that line a lumen (cavity). Are these cells ciliated? Figure 25.3 Simple cuboidal epithelium. Simple cuboidal epithelium lines kidney tubules and the ducts of many glands. (b: Magnification X250) nucleus a. Drawing b. Photomicrograph Simple Cuboidal Epithelium Location Surface of ovaries; linings of ducts of glands; linings of kidney tubules Function Secretion; absorption 25—5 Animal Organization Laboratory 25 347 Observation: Simple Columnar Epithelium Simple columnar epithelium is a single layer of tall, cylindrical cells, each with a nucleus near the base. This tissue, which lines the digestive tract from the stomach to the anus, protects, secretes, and allows absorption of nutrients. 1. Study a model or diagram of simple columnar epithelium (Fig. 25.4). 2. Examine a prepared slide of simple columnar epithelium. Find tall and narrow cells that line a lumen. Under high power, focus on an individual cell. Identify the plasma membrane, the cyto— plasm, and the nucleus. Epithelial tissues are attached to underlying tissues by a basement membrane composed of extracellular material containing protein fibers. Label the location of the basement membrane in Figure 25.4. 4. The tissue you are observing contains mucus—secreting cells. Search among the columnar cells until you find a goblet cell, so named because of its goblet-shaped, clear interior. This region contains mucushwhich may be stained a light blue. In the living animal, the mucus is discharged into the gut cavity and protects the lining from digestive enzymes. 0-) Figure 25.4 Simple columnar epithelium. Simple columnar epithelium lines the digestive tract. Goblet cells among the columnar cells secrete mucus. (b: Magnification X250) mucus m. - b. Photomicrograph a. Drawing Simple Columnar Epithelium Location Lining of uterus; tubes of the digestive tract Function Protection; secretion; absorption Observation: Pseuidostratified Ciliated Columnar Epithelium Pseudostratified Ciliated columnar epithelium appears to be layered, while actually all cells touch the basement membrane. Many cilia are located on the free end of each cell (Fig. 25.5). In the human trachea, the cilia wave back and forth, moving mucus and debris up toward the throat so that it cannot enter the lungs. Smoking destroys these cilia, but they will grow back if smoking is discontinued. 1. Study a model or diagram of pseudostratified Ciliated columnar epithelium (Fig. 25.5). 2. Examine a prepared slide of pseudostratified Ciliated columnar epithelium. Concentrate on the part of the slide that resembles the model. Identify the cilia. 348 Laboratory 25 Animal Organization 25—6 Figure 25.5 Pseudostratified ciliated columnar epithelium. Pseudostratified ciliated columnar epithelium lines the trachea. The cilia help keep the lungs free of debris. (b: Magnification x250) Cilia mucus goblet cell nucleus a. Drawing b. Photomicrograph Pseudostratified Ciliated Columnar Epithelium Location Linings of reproductive system tubes and respiratory passages Function Protection; secretion; movement of mucus and sex cells Summary of Epithelial Tissue Complete Table 25.1 to summarize your study of epithelial tissue. Table 25.1 Epithelial Tissue Type Appearance Function __ Location ____—_——_—_.————- Simple squamous Walls of capillaries, lining of blood vessels, air sacs of lungs, lining of internal cavities _ . . Stratified squamous Innermost layers are Protection, repel cuboidal or columnar; water outermost layers are flattened __—_—_—_——_———— Simple cuboidal Secretion, absorption __—_—_——_—_———— Simple columnar Columnlike—tall, Lining of uterus, tubes cylindrical nucleus of digestive tract at base __—_—__———_—————- Pseudostratified Protection, secretion, ciliated columnar movement of mucus and sex cells __—_————————— 25—7 Animal Organization Laboratory 25 349 25.2 Muscular Tissue Muscular (contractile) tissue is composed of cells called muscle fibers. Muscular tissue has the ability to contract, and contraction usually results in movement. The body contains skeletal, cardiac, and smooth muscle. Observation: Skeletal Muscle Skeletal muscle occurs in the muscles that are attached to the bones of the skeleton. The contraction of skeletal muscle is said to be voluntary because it is under conscious control. Skeletal muscle is striated; it contains light and dark bands. The striations are caused by the arrangement of contractile filaments (actin and myosin filaments) in muscle fibers. Each fiber contains many nuclei, all peripher— ally located. 1. Study a model or diagram of skeletal muscle (Fig. 25.6), and note that striations are present. You should see several muscle fibers, each marked with striations. 2. Examine a prepared slide of skeletal muscle. The striations may be difficult to make out, but bringing the slide in and out of focus may help. Figure 25.6 Skeletal muscle. Skeletal muscle is striated and voluntary. Its cells are tubular and contain many nuclei. striation nucleus l——l 20 um Skeletal muscle - has striated cells with multiple nuclei. 0 occurs in muscles attached to skeleton. - functions in voluntary movement of body. - is voluntary. 350 Laboratory 25 Animal Organization 25—8 Observation: Smooth Muscle Smooth muscle is sometimes called visceral muscle because it makes up the walls of the internal organs, such as the intestines and the blood vessels. Smooth muscle is involuntary because its contraction does not require conscious effort. 1. Study a model or diagram of smooth muscle (Fig. 25.7), and note the shape of the cells and the centrally placed nucleus. Smooth muscle has spindle—shaped cells. What does spindle-shaped mean? 2. Examine a prepared slide of smooth muscle. Distinguishing the boundaries between the different cells may require you to take the slide in and out of focus. Figure 25.7 Smooth muscle. Smooth muscle is nonstriated and involuntary. This type of muscle is composed of spindle-shaped cells. smooth- muscle cell nucleus i——I 12 um Smooth muscle - has spindle-shaped cells, each with a single nucleus. - cells have no striations. ~ functions in movement of substances in lumens of body. - is involuntary. 25—9 Animal Organization Laboratory 25 351 Observation: Cardiac Muscle Cardiac muscle is found only in the heart. It is called involuntary because its contraction does not require conscious effort. Cardiac muscle is striated in the same way as skeletal muscle. However, the fibers are branched and bound together at intercalated disks, where their folded plasma membranes touch. This arrangement aids communication between fibers. 1. Study a model or diagram of cardiac muscle (Fig. 25.8), and note that striations are present. 2. Examine a prepared slide of cardiac muscle. Find an intercalated disk. What is the function of cardiac muscle? Figure 25.8 Cardiac muscle. Cardiac muscle is striated and involuntary. Its branched cells join at intercalated disks. intercalated disk nucleus 20 um Cardiac muscle - has branching striated cells, each with a single nucleus. . occurs in the wall of the heart. - functions in the pumping of blood. - is involuntary. Summary of Muscular Tissue Complete Table 25.2 to summarize your study of muscular tissue. Table 25.2 Muscular Tissue Striations Branching Conscious Control Type (Yes or No) (Yes or No) (Yes or No) Skeletal Smooth Cardiac -———————__________—_____ 352 Laboratory 25 Animal Organization 2540 25.3 Nervous Tissue Nervous tissue is found in the brain, spinal cord, and nerves. Nervous tissue is. composed of two types of cells: neurons that transmit messages and neuroglia that largely service the neurons (see Fig. 25.1). Motor neurons, which take messages from the spinal cord to the muscles, are often used to exemplify typical neurons (Fig. 25.9). Motor neurons have several dendrites,‘ processes that take signals to a cell body, where the nucleus is located, and an axon that takes nerve impulses away from the cell body. Observation: Nervous Tissue 1. Study a model or diagram of a neuron, and then examine a prepared slide. You will not be able to see neuroglial cells because they are small and cannot be seen at this magnification. Identify the dendrites, cell body, and axon in Figure 25.9. Long axons are called nerve fibers. Explain the appearance and function of the parts of a motor neuron: 5“!" a. Dendrites b. Cell body 0. Axon il' Figure 25.9 Motor neuron anatomy. (b: Magnification X200) cell body nucleus '1 . i ._ '2' x. ‘R‘ l " \—————— dendrite ii . .! neuroglial cell axon myelin sheath <—impulse Nervous Tissue Location Brain; spinal cord; nerves Function Conduction of nerve impulses a. Drawing 25—11 Animal Organization Laboratory 25 353 25.4 Connective Tissue Connective tissue joins different parts of the body together. There are four general classes of connective tissue: connective tissue proper, cartilage, bone, and blood. All types of connective tissue consist of cells surrounded by a matrix that usually contains fibers. Elastic fibers are com— posed of a protein called elastin. Collagenous fibers contain the protein collagen. Observation: Connective Tissue There are several different types of connective tissue. We will study loose fibrous connective tissue, dense fibrous connective tissue, adipose tissue, bone, cartilage, and blood. Loose fibrous connective tissue supports epithelium and also many internal organs, such as muscles, blood vessels, and nerves (Fig.125.10). Its presence allows organs to expand. Dense fibrous connective tissue contains many collagenous fibers packed together, as in tendons, which connect muscles to bones, and in ligaments, which connect bones to other bones at joints (Fig. 25.11). 1. Examine a slide of loose fibrous connective tissue, and compare it to Figure 25.10. What is the function of loose fibrous connective tissue? Figure 25.10 Loose fibrous connective tissue. Loose fibrous connective tissue supports epithelium and many internal organs. ground _ . substance fibroblast elastic fiber collagenous fiber a. Drawing b. Photomicrograph Loose Fibrous Connective Tissue Location Between muscles; beneath the skin; beneath most epithelial layers Function Binds organs together 354 Laboratory 25 Animal Organization 25712 2. Examine a slide of dense fibrous connective tissue, and compare it to Figure 25.11. What two kinds of structures in the body contain dense fibrous connective tissue? Figure 25.11 Dense fibrous connective tissue. Dense fibrous connective tissue is found in tendons and ligaments. (b: Magnification X250) fibroblasts —__..-_-=__ _ collagenous .1- fibers b. Photomicrograph a. Drawing Dense Fibrous Connective Tissue Location Tendons; ligaments Function Binds organs together; binds muscle to bones; binds bone to bone 25—13 Animal Organization Laboratory 25 355 Observation: Adipose flame: In adipose tissue, the cells have a large, central, fat-filled vacuole that causes the nucleus and cytoplasm to be at the perimeter of the cell (Fig. 25.12). Adipose tissue occurs beneath the skin, where it insulates the body, and around internal organs such as the kidneys and heart. It cushions and helps protect these organs. 1. Examine a prepared slide of adipose tissue. Why is the nucleus pushed to one side? 2. Examine Figure 25.17 (see p. 361), and state a location for adipose tissue in the body. What are two functions of adipose tissue at this location? Figure 25.12 Adipose tissue. Adipose tissue is composed of cells filled with fat droplets. (b: Magnification X250) nucleus of - ' adipose cell - plasma membrane . llat a. Drawing b. Photomicrograph Adipose Tissue Location Beneath the skin; around the kidney and heart; in the breast Function Insulation; fat storage; cushioning and protection 356 Laboratory 25 Animal Organization 25_14 Observation: Compact Bone Compact bone is found in the bones that make up the skeleton. It consists of ostemiljs [Haversian system) with a central canal, and concentric rings of spaces called laminae, which are cormeCIed by tiny crevices called canaliculi. The central canal contains. a metro and blood vessels, which service bone. The lacunae contain bone cells called osteocytes, whose processes extend into. the canaliculi. Separating the lacunae is a matrix that is hard because it contains minerals, notably calcium salts. The matrix also contains collagenous fibers. 1. Study a model or diagram of compact bone (Fig. 25.13). Then look at a prepared slide and identify the central canal, lacunae, and canaliculi. 2. What is the function of the central canal and canaliculi? Figure 25.13 Compact bone. Compact bone contains osteons in which osteocytes within lacunae are arranged in concentric circles. (b: Magnification X320) osteon osteon " .' -— canaliculi osteocyte inlacuna central canal b. Photomicrograph a. Drawing Compact Bone Location Bones of skeleton Function Support; protection Observation: Hyaline Cartilage In hyaline cartilage, cells called chondrocytes are found in twos or threes in lacunae. The lacunae are separated by a flexible matrix containing weak collagenous fibers. 1. Study the diagram and photomicrograph of hyaline cartilage in Figure 25.14. Then study a pre— pared slide of hyaline cartilage, and identify the matrix, lacunae, and chondrocytes. 2. Compare Figures 25.14 and 25.13. Which o...
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