Laboratory 3 Histology

Transcription

1 Laboratory 3 Histology Goals: For epithelial tissues: o discuss the major features; o classify based on simple/stratified and squamous/cubodial/columnar; o identify each type by microscopy; o identify microvilli, cilia, apical and basal surfaces, basement membrane, lumen; o describe the location in the body that each type can be found; and, o correlate structure to function. For connective tissues: o discuss the major features; o delineate the defining characteristics; o identify the different types by microscopy; o describe the location in the body that each type can be found; o compare and contrast the roles of different cell types and fibers present; and, o correlate structure to function. For muscle tissues: o discuss the major features; o elucidate the defining characteristics; o identify the different types by microscopy; o describe the location in the body each can be found; o compare and contrast the properties of the different muscle types; and, o correlate structure to function. For nervous tissues: o discuss the major features; o describe the structure and function of neurons and neuroglial cells; o identify neurons and nervous tissue by microscopy; o describe the location in the body; and o correlate structure to function. A tissue is a group of cells that are similar in structure and function with multiple tissue types represented in an organ such as the kidneys or muscles. Histology, the study of tissues, requires the use of microscopes; therefore, the first part of this laboratory exercise is familiarizing yourself with the microscope. Animal tissues are categorized into four main tissue types. Epithelial tissues form the coverings and linings of our body such as our skin or the lining of blood vessels. Connective tissue is a diverse tissue type that binds, protects, and supports organs. It includes tissues such as fat, blood, and bone. Muscle tissue is tissue that is specialized to contract. Muscle tissue is used in movement and includes skeletal muscles and the heart muscle. Nervous tissue includes the brain, spinal cord, and nerves. It is tissue that contains neurons, which are specialized cells that communicate with other cells in out body by electrochemical signals. 19

2 1. Epithelial Tissue General Features of Epithelial Tissues Epithelial tissue forms the lining of both external and internal body surfaces. Examples of epithelial tissue include the outer layer of the skin, the inner lining of the digestive and respiratory tracts, and the lining of blood vessels. It consists of tightly packed cells of one or more layers. Major functions of epithelial tissue are protection, absorption, and secretion. Further, some epithelia has specialized cells or structures that are involved in sensation. Protective functions include acting as a chemical or biological barrier, preventing water loss or dessication, and secreting protective substances. Many epithelia tissues provide surfaces for absorption of chemicals and nutrients into the body. Examples of this include exchange of oxygen and carbon dioxide in the lung epithelia and absorption of nutrients by the epithelial tissues lining the digestive tract. Secretory glands are composed of epithelial tissues. Some secretory glands are classified as exocrine glands, such as sweat glands or gastric glands, which secrete their products into the external environment. Other secretory glands are classified as endocrine glands which secrete their products into the blood. Different epithelial tissues share common features: Cells are tightly packed together with little extracellular material and minimal spaces between cells. Epithelia are supported by and rests on a layer of connective tissue called the basement membrane. Cells are polar, meaning that the two different sides of the cells have different properties. The basal surface rests on the underlying connective tissue. The apical surface is the free surface that faces either the exterior of the body or the lumen of the tubular structure. The apical surface can be specialized with cilia to aid in movement of secreted mucus or microvilli to increase the absorptive area. Most epithelial tissue is avascular, meaning they have little or no blood supply. This makes epithelia dependent on the connective tissue of the basement membrane for nutrients. Epithelia is a highly regenerative tissue with almost constant mitosis. As a covering and lining, this tissue is often subjected to abrasion and chemicals that require replacement of the cells damaged by such factors. Figure 1. Classification of epithelial tissue based upon number of cell layers and shape of cells. Classification of Epithelia Types of epithelial tissue always have two word names with the first describing the number of cellular layers and the second describing the shape of the cells. If cells are arranged in a single layer, 20

3 the epithelium is called simple; if the cells are arranged in two or more layers, the epithelium is called stratified. There are three shapes of epithelial cells: flat or squamous, cube-like or cuboidal, and tall and rectangular or columnar. Hence, simple cuboidal epithelia is comprised on a single layer of cubeshaped cells whereas stratified squamous is comprised of multiple layers of flattened pancake-looking cells. Types of Epithelial Tissue Simple Squamous Epithelium Lung 400X Appearance: Single layer of flattened cells Function: Highly permeable, often involved in passage of small molecules by diffusion or filtration Location: Alveoli of the lungs, capillaries Simple Cuboidal Epithelium Kidney 400X Appearance: Single layer of cube- like cells, the edges of the cube are rounded. Function: Actively transporting material into or out of the lumen Location: Kidney tubules, glandular ducts, thyroid Hint: You should be able to find simple squamous tissue in this image also. 21

4 Simple Columnar Epithelium Small Intestine 400X Appearance: Single row of tall, rectangular cells of approximately the same height, nuclei are at about the same level, can be ciliated Function: Absorption and secretion, often contain goblet cells for secretion, ciliated types are also involved in movement of mucus and other substances Location: Lining the most of the digestive tract (stomach through large intestines), lining the uterus Pseudostatified Columnar Epithelium Trachea 400X Appearance: Single row of tall, rectangular cells of differing height, nuclei are at different levels, staggered appearance mimics the look of stratified columnar epithelium, can be ciliated. Function: Secretion, contains goblet cells, movement of mucus and other substances. Location: Trachea and upper respiratory tract, the vas deferens in the male reproductive tract Stratified Squamous Epithelium Skin 400X Appearance: Multiple layers of cells with the cells nearer apical side appearing flattened Function: Protection from abrasion Location: Skin, inside of lips, tongue, esophagus 22

5 Stratified Cuboidal Epithelium Sweat gland 400X Appearance: Multiple layers, often two, of cuboidal cells, rare Function: Protection Location: Large ducts of sweat and salivary glands Stratified Columnar Epithelium Uterus 400X Appearance: Multiple layers of cells with the apical layer appearing columnar, the basal layer often appears cuboidal, rare Function: Protection Location: Some of the pharynx lining, Male urethra and vas deferens, Uterus Transitional Epithelium Female Urethra 400X Appearance: Looks like stratified cuboidal when not stretched and stratified squamous when stretched, apical cells are rounded Function: Stretch Location: Urinary bladder, Female urethra 23

6 Activity 1. Look at each type of tissue listed on your lab list under the microscope. Be sure to look at each tissue at all three magnifications. Exams may include images from 40X, 100X or 400X magnifications. 2. Draw each tissue at 400X magnification. Label the parts indicated on your lab list. Be sure to include the type of tissue, source and magnification on your drawing. Use colored pencils and unlined paper. 3. Connective Tissue General Features of Connective Tissue Connective tissue is the most common, and most diverse, tissue type in the human body. Types of connective tissues range from rigid bone to blood, a liquid tissue. In contrast to epithelial tissue, connective tissue has relatively sparse cells in a large amount of extracellular matrix consisting of protein fibers, proteoglycans, minerals, and water. The functions of connective tissues include structural support and protective, binding, and metabolic functions. Connective tissues not only encapsulate organs but fill and cushion the spaces between them. Bones are formed of connective tissues, offering both overall support and protection of vital organs. Connective tissues form tendons and ligaments that bind muscle to bone and bone to bone, respectively. Connective tissues also house macrophages, a phagocytic white blood cell found in tissues and an important component of the innate immune system. Adipose tissue serve as chemical energy storage units. A metabolic role is also played by osseous tissues in the hematopoiesis, synthesis of blood cells. General traits of connective tissues include: Multiple types of cells, distributed in an extracellular matrix. Major cell types include: cells which secrete the extracellular matrix, specifically fibroblasts in most connective tissues, chondroblasts in cartilage, and osteoblasts in bone. white blood cell- derived cells that function as part of our innate immune system. These include tissue macrophages which are phagocytic cells and mast cells which promote inflammation. Some tissue macrophages can become highly specialized like the osteoclast which breaks down the extracellular matrix of bone. adipocytes which store triglycerides for energy. Significant component of extracellular matrix. The extracellular matrix is composed of a variety of protein fibers and an amorphous ground substance. Fiber types are: collagen fibers. These fibers, composed of collagen, the most abundant protein in the human body, are extremely tough and provide high tensile strength. This means that they can get pulled on without breaking, with collagen fibers have greater tensile strength than steel. These fibers often appear in parallel bundles, appear white when unstained and pink in stained specimens. reticular fibers. These small fibers are also composed of collagen, but are short and this. Reticular fibers branch and form extensive fiber networks.

7 elastic fibers. These fibers, composed of elastin, are elastic (think rubberband- like). These stretch in response to tension and recoil when the tension is released. These are commonly found in tissues that need to stretch and return to size such as lungs and blood vessels. Ground substance is composed of: water proteoglycans (proteins that are heavily glycosylated) inorganic minerals, most notably bone. Most connective tissues are well- vascularized EXCEPT cartilage and dense regular connective tissues. Most connective tissues regenerate well EXCEPT cartilage. Classification of Connective Tissues Connective tissues break down into five major categories with some of these categories breaking down further: Loose connective tissue has loosely woven fibers, large number of accessory cells, and fibroblasts embedded directly in the matrix. The types are: Areolar characterized by all three major types of fibers. Adipose characterized by numerous, closely packed adipocytes filled with large lipid droplets Reticular similar to areolar connective tissue but only reticular fibers. Dense connective tissue has densely packed fibers, fewer cells visible that in loose connective tissue, and fibroblasts embedded directly in the matrix. The three types are: Regular characterized by large number or parallel collagen fibers. Irregular characterized by large number of collagen fibers without apparent order. Cartilage - has chondrocytes (mature chondroblasts) surrounded by chambers called lacunae, no blood vessels or nerves are present. The three types are: Hyaline gel- like amorpous matrix with prominent lacuanae. Elastic similar to hyaline but many small elastic fibers throughout. Fibrocartilage similar to hyaline with parallel collagen fibers throughout. Osseous (bone) has hard matrix composed of inorganic calcium deposits, osteocytes (mature osteoblasts) reside in lacunae. Blood the only fluid tissue consisting of bone marrow derived blood cells in a liquid matrix, plasma. Fibers only form during blood clotting. 25

8 Types Connective Tissue Areolar Connective Tissue Areolar Connective Tissue 400X Appearance: All three fiber types present in a loose network. Fibroblasts, macrophages and mast cells present. Function: Cushions, houses cells of innate immune system, diffusion of nutrients into tissues. Location: Most widely distributed connective tissue, under epithelia of body including skin. Adipose Connective Tissue Adipose 400X Appearance: Packed with adipocytes. These cells are large, with a centralized fat droplet taking up most of the cellular space pushing the nucleus and organelles to the periphery of the cell. Function: Cushions, insulates, stores energy in the form of triglycerides, Location: Under skin, in abdomen including around kidneys, behind eyes.. Reticular Connective Tissue Reticular Connective Tissue 400X Appearance: Similar to areolar but with predominantly small, short reticular fibers. Function: Loose support for other cell types. Location: Lymphatic tissues 26

9 Dense Regular Connective Tissue Tendon 400X Appearance: Parallel collagen fibers with some fibroblasts apparent between the fiber bundles. Function: Withstands tensile strength, attaches bone to muscle or bone. Location: Tendons and ligaments. Dense Irregular Connective Tissue Human Dermis 400X Appearance: Irregularly arranges collagen fibers with fibroblasts apparent between bundles. Function: Structural support Location: In the dermis of skin, and fibrous capsules of joints and organs. Hyaline Cartilage Hyaline Cartilage 400X Did you see any of this tissue earlier? Appearance: Amorphous gel- like matrix with chondrocytes present in lacunae. Function: Supports, involved in bone growth and remodeling. Location: Epiphysis of long bones, costal cartilages, nose cartilage, cartilage in trachea 27

10 Elastic Cartilage Epiglottis 400X Appearance: Similar to hyaline cartilage with elastic fibers present. Function: Flexible support Location: External ear and epiglottis Fibrocartilage Fibrocartilage 400X Appearance: Similar to hyaline cartilage with thick collagen fibers present. Function: Shock absorption Location: Discs between the vertebrae, disc in the knee, and the pubic symphis. Osseous Tissue Compact bone, ground 400X Appearance: Hard, organized matrix with collagen fibers but extensive mineral deposits Function: Supports and protects body organs Location: Bones. 28

11 Blood Human blood smear 400X Appearance: Red and white blood cells in a fluid matrix Function: Transport of nutrients, respiratory gases, wastes, and hormones throughout the body. Location: Within blood vessels Activity 1. Look at each type of tissue listed on your lab list under the microscope. Be sure to look at each tissue at all three magnifications. 2. Draw each tissue at 400X magnification. Label the parts indicated on your lab list. Be sure to include the type of tissue, source and magnification on your drawing. Use colored pencils and unlined paper. 4. Muscle Tissue General Features of Muscle Tissue Muscle tissues are specialized for contraction. The cells, called myocytes, are elongated with many cells organized roughly parallel. Myocytes compose of contractile proteins that allow the myocytes to contract, become shorter and thicker. Myocytes are also excitable, responding to contract due to a stimulus. Following contraction, muscle cells are elastic returning to normal length following after contraction is over. Classification of Muscle Tissues Skeletal muscle tissue comprises skeletal muscles attached to bone. This tissue is under voluntary control and is stimulated by motor neurons. Skeletal myocytes are long, cylindrical, and multinucleate (having more than one nucleus in the cell). Additionally, this type of tissue has striations within each large cell. Cardiac muscle tissue is found in the heart. Similar to skeletal myocytes, cardiac myocytes are striated. In contrast, however, cardiac muscle cells are unicellular with only one nucleus per cell. Cardiac myocytes are branching and connect with other cardiac myocytes at intercalated discs. Interacalated discs contain both desmosomes to strengthen the attachment between individual cardiac muscle cells and gap junctions that lead to the individual cardiac myocytes contracting as an unit. Cardiac muscle is not voluntarily controlled. Smooth muscle tissue lack striations and are composed of smaller myocytes than either skeletal or cardiac myocytes. Each smooth muscle cell is spindled shape and involuntarily 29

12 controlled. Smooth muscle forms the structure of hollow organs such as the gastrointestinal tract or blood vessels. Types of Muscle Tissue: Skeletal Muscle Tissue Skeletal Muscle 400X Appearance: Multinucleate, striated, long cylindrical cells. Function: Voluntary contraction. Location: Skeletal muscle attached to bones. Cardiac Muscle Tissue Heart 400X Appearance: Uninucleate, striated, branching cells with intercalated discs. Function: Involuntary contraction of the heart. Location: Heart. 30

13 Smooth Muscle Tissue Smooth muscle 400X Appearance: Spindle- shaped cells, uninucleate Function: Involuntary contraction of internal organs. Location: Walls of hollow organs such as the gastrointestinal tract or blood vessels. Activity 1. Look at each type of tissue listed on your lab list under the microscope. Be sure to look at each tissue at all three magnifications. 2. Draw each tissue at 400X magnification. Label the parts indicated on your lab list. Be sure to include the type of tissue, source and magnification on your drawing. Use colored pencils and unlined paper. 5. Nervous Tissue General Features of Nervous Tissue Nervous tissue is composed of nerve cells, also called neurons, and supporting cells, collectively referred to as neuroglia. Neurons have a cell body containing many branches that relay electrochemical cells. A neuronal cell body, also called the soma, receives this signal through small, branched dendrites, and passes this signal to the next cell through longer axons. Axons can be nearly 1 meter long, running from your spinal cord to your toes, for example. Neuroglia are supporting cells that help with protection, metabolism, and signaling of neurons. 31

14 Nervous Tissue Example: Nervous Tissue Motor Neuron 400X Appearance: Round- ish cell body with long, narrow processes. Presence of smaller supporting cells. Function: Transmitting electrochemical signals throughout the body. Location: Brain, spinal cord, nerves. Activity 1. Look at each type of tissue listed on your lab list under the microscope. Be sure to look at each tissue at all three magnifications. 2. Draw each tissue at 400X magnification. Label the parts indicated on your lab list. Be sure to include the type of tissue, source and magnification on your drawing. Use colored pencils and unlined paper. 6. Putting it all together Tissues do not exist in isolation of each other. Many of the sections that you will look at through out this laboratory assignment have multiple tissue types in them. Activity 1. Try to identify different types of tissues when looking the trachea, kidney, and skin. 2. Look at the mouse tibia/femur. You should be able to identify hyaline cartilage, fibrocartilage skeletal muscle, dense regular connective tissue, and adipose tissue. 7. Histology Notebook Instructions: Histology drawings should be done on unlined white paper and should be done with colored pencils. The provided template is optional but recommended. Lined paper is NOT acceptable. You should place four drawings per page and on one side of the paper only. Drawings should be based on what you see under the microscope at 400x. Each drawing should be clearly labeled. When your drawings are ready to turn in, staple them together. Put a cover sheet on the front with your name on it. You must include a cover sheet. Don t use notebooks or folders, please. 32

15 Grading Rubric will vary by instructor, but full credit requires: Correct title, magnification and tissue source (from the slide, include species) A correct and recognizable picture All required labels present and correct Colored pencils No lined paper Name of drawing Labels to include Tissue source 1. Simple squamous Lumen, nucleus, cell Lung (mouse) or Kidney (mouse) epithelium 2. Simple cuboidal Lumen, nucleus, cell Tubules of kidney (mouse) epithelium 3. Simple columnar Lumen, nucleus, cell Small intestine (mouse) epithelium 4. Pseudostratified, Lumen, nucleus, cell Trachea (mouse) ciliated, columnar epithelium 5. Stratified squamous Lumen, nucleus, cell Esophagus (mouse) epithelium 6.. Transitional Lumen, nucleus, cell Urinary bladder (human) epithelium 7.. Areolar connective Fibroblasts, collagen fibers, elastic fibers Areolar Connective tissue tissue 8. Adipose connective Adipocytes, cell membrane and nucleus Tibia/Femur (mouse) or Adipose tissue tissue 9. Dense irregular Fibroblast, collagen bundles Human skin, Non-pigmented connective tissue 10, Dense regular connective tissue Fibrocytes and collagen fibers Tibia/Femur (mouse) or Dense Regular Connective Tissue 11. Hyaline cartilage Chondrocytes, nucleus, lacunae Tibia/Femur or trachea (mouse) or Hyaline Cartilage 12. Elastic cartilage Chondrocytes, nucleus, lacunae, elastic fibers Epiglottis (human) 13. Fibrocartilage Chondrocytes in lacunae, collagen fibers Tibia/Femur (mouse) or Fibrocartilage 14. Bone Osteocytes in lacunae, central canals, Compact Bone, ground (human) canaliculi, lamellae 15. Blood Red blood cell, white blood cells Human blood smear 16. Smooth muscle Smooth muscle cells, nuclei, Human smooth muscle 17. Skeletal muscle, Muscle fibers(cells) nuclei, striations Human skeletal muscle longitudinal section 18. Cardiac muscle Muscle cells, nuclei, striations Human cardiac muscle 19. Nervous tissue- Cerebrum Neuron, nuclei, cell body(soma), axon and dendrites, and glial cells Cerebrum, Golgi 33

16 Attribution of images used in this document: Figure 1. National Cancer Institute (n.d.). [Types of epithelium]. SEER Training Modules, Epithelial Tissue. Retrieved May 7, 2012 from (alternative citation: SEER Training Modules, Epitheliels. U. S. National Institutes of Health, National Cancer Institute. 7, May 2012 (of access) < 2: Wikimedia Commons, user Arcadian. All other images: Green, P.S. and Long, G. (2011). [Various microscopic images]. Tacoma Community College. 34

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