BSMLS 2 [MLS 407-LAB] PRELIMS PDF

\ 2nd Year HUMAN HISTOLOGY | MLS 407-LAB 1st Sem LABORATORY /...

\ 2nd Year HUMAN HISTOLOGY | MLS 407-LAB 1st Sem LABORATORY / DR. MILLIEM RUZZLEE REYES & DR. ICHIRO ORDANEZA Prelims 2024-2025 [TRANS] PRELIMS: ACTIVITY 1 - 4 Diopter Adjustment OUTLINE ○ Means to change focus on eyepiece so as to correct for any difference in vision between your two eyes. I. Basic Microscopy & II. Cell Division Nose Piece / Turret / Revolving Nose Piece its Use in Histology A. Introduction ○ Holds the objective lenses. A. Introduction B. Mitosis B. Definition of C. Meiosis ○ Movable hence it can revolve the objective lens as Terms III. Eukaryotic Cell you change the magnification power. C. Parts of the A. Identifying Microscope Cells in Objective Lenses D. Handling & Histology ○ Major Lenses used for specimen visualization. Storage IV. Epithelial Tissue ○ Types of Objective Lenses: Precautions A. Introduction Scanner Objective - 4x E. Procedure B. Epithelium Low Power Objective - 10x F. Troublesho oting & High Power Objective - 40x Common Oil Immersion Objective - 100x Problems Stage ○ Where the specimen is placed for viewing. BASIC MICROSCOPY & ITS USE IN HISTOLOGY ○ Contains stage clips that hold the specimen slides in place. INTRODUCTION ○ Allows the control of the slides by using the Microscope mechanical knobs and stage controls instead of ○ From the ancient Greek word “mikros” meaning moving it manually. “small,” and “skopein” meaning ”to look”. The lens inverts (image appears upside down ○ An instrument used to see objects that are too small and backward compared with the actual object) for the naked eye. the image of the object inside the microscope. ○ To magnify a small object in order to examine minute Thus, the slide must be moved in the opposite specimens that cannot be seen by the naked eye. direction that you want the image to move, so if ○ A Compound Light Microscope is used to view you move the slide to the right on stage, as you minute details of cells and primarily tissues. look through the slide appears to move left. The term compound refers to the set of lenses Aperture (ocular and objective) used simultaneously to ○ Hole on the microscope stage through which magnify the image. transmitted light from the light source reaches the The term light refers to the necessity to use a stage. light source for better viewing of the objects. Condenser ○ A microscope is a fundamental tool for laboratory ○ Used to collect and focus light from the illuminator into scientists. the specimen. The instrument has been perfected over the past ○ Plays a major role in ensuring clear sharp images that 300 years. are produced with a high magnification of 400x and It has, within its limits, allowed the invisible to above. become the visible. Diaphragm / Iris ○ For instance, these are some of the facts that may be ○ Controls the amount of light that reaches the recorded by the eye and the microscope: specimen. Shape, size, position, connections, colors, ○ Adjustable apparatus hence the intensity and size of number, texture, and chemical composition. the beam of light can be adjusted. ○ Found under the stage. PARTS OF THE MICROSCOPE Adjustment Knobs ○ Knobs used to focus the microscope. ○ Types of Adjustment Knobs: Coarse Adjustment - bring specimens to general focus. Fine Adjustment - fine tunes the focus and increases specimen details. HOW DOES A MICROSCOPE WORK? On / Off Switch ○ Turn the illuminator on or off. Brightness Adjustment ○ Adjusts the intensity of light emitted by the illuminator. Microscopic Illuminator The straight-line path is disturbed by any material of ○ Light source of the microscope. different refractive index. ○ Captures light from an external source of a low Condenser (1.515) voltage at about 100v. ↓ Base Air (1.00) ○ Acts as the support of the microscope. ↓ ○ Carries the microscopic illuminators. Slide (1.515) Head ↓ ○ Carries the optical parts in the upper part of the Mounting Media (1.515) microscope. ↓ Eyepiece / Oculars Air (1.00) ○ It is the part used to look through the microscope. ↓ ○ Found at the top. Objective (1.515) ○ Standard magnification is a 10x, but can also have 5x to 30x magnification ○ Adding Immersion Oil (1.515) fills in the air gaps/ FLG | 2B  [TRANS] PRELIMS: ACTIVITY 1 - 4 DEFINITION OF TERMS Cleaning Magnification ○ Lenses must be clean for resolution. ○ How much larger an object appears under a scope ○ Use only lens paper or gauze pad and cleaning than it actually is. solution. ○ Ability to produce an image of an object at a larger ○ Never use your fingers, handkerchief, paper towels or scale than its actual size. spit to clean the lenses. ○ Oculars are engraved with their magnifying numbers. ○ Do not remove any parts for cleaning, it only allows ○ Total Magnification Power dust to enter the microscope. This is the final magnified view of the image Putting Away brought about by the product of the magnification ○ Turn off light and center mechanical stage. power of the oculars and the objective lens used. ○ Position the nosepiece so that the lowest scanning TMP = Objective Lens Magnification x Ocular objective (4x) is in place. Lens Magnification ○ Remove the slide from the stage and put it in the proper place. TOTAL MAGNIFICATION POWER ○ Clean the stage and lenses with gauze and lens OBJECTIVE OBJECTIVE OCULAR LENS TOTAL cleaner and wipe off any oil. LENS TYPE LENS MAGNIFICATION MAGNIFICATION ○ Wrap the cord around them. MAGNIFICATION ○ Carefully carry with two hands and gently place the Scanning 4x 10x 40x microscope in the proper cabinet. Power Low Power 10x 10x 100x PROCEDURE High-Dry Power 40x 10x 400x Getting Started Oil Immersion 100x 10x 1000x 1. Get your microscope out of the cabinet in the lab, and carry it with two hands to your table. 2. Before plugging in your scope, always make sure that the voltage control is at its lowest level and the light switch is off. 3. Plug in the microscope and turn on the light source. 4. Raise the substage condenser to its top position and open the iris diaphragm all the way. 5. Turn the nosepiece so that the 10x objective is lined up with the light source. 6. Place a slide on the stage and use the mechanical stage control to move it into place. Resolution / Resolving Power 7. Turn up the light into a comfortable level. ○ The rendering of detail. Getting a Focused Image ○ High magnification without good resolution is 1. Adjust the interocular distance (distance between the worthless. oculars) by gently pressing the oculars together or ○ Light is the limiting factor of resolution. pulling them apart until you see a single circular field ○ The blue light of the scope allows resolution of 0.2 of view. microns. 2. Look through both oculars (i.e., keep both eyes open), ○ Ability to distinguish between two closely spaced but think right eye and adjust the focus until specimen points on a specimen; smallest distance between two is clear in your right eye. structures at which they can be seen as separate 3. Now think of the left eye and turn the diopter objects. adjustment (the movable ring) on the left eyepiece to ○ A Light Microscope has a resolving power of 0.2 μm. adjust the focus for your left eye. You should have a The human eyes have a resolving power of 0.2 sense of the image suddenly “popping out” at you, mm. sharp and clear. Depth of Field Optimizing Resolution and Contrast ○ The distance through which you can move the ○ Resolution is the ability to distinguish two closely specimen higher and still have it in focus. spaced points on your specimen, and it is always best ○ The magnification, the closer the objective is to the with the iris diaphragm wide open. slide and so the depth of field decreases. ○ Contrast is the magnitude of difference between light ○ Requires a more delicate technique. and dark objects, and it increases as you close the aperture of the iris diaphragm. ○ Getting the best image, then, requires that you find the right balance. ○ Slowly open and close the iris diaphragm to get a feeling for the effect this has on your image. Changing Modification ○ Always start with the lowest power objective (4x) to get oriented and locate an area of interest, and then switch to a higher power to examine interesting Field of View regions more closely. ○ It is the area a person can view through a ○ To change magnification, simply rotate the nosepiece microscope, it is represented by a circle. to bring one of the other objectives into the light path. ○ As magnification increases, the field of view Finishing Up decreases. 1. Turn down the illumination. As you switch from scanning (40x) to high power 2. Turn off the power. (100x), the area you see through the microscope 3. Switch back to the 4x objective. gets smaller. 4. Remove your slide. We can see better detail with high powers of 5. Unplug the power cord and wrap it around the base of magnification, but we cannot see as much of the the scope. image. 6. Lower the stage to hold the cord in place. 7. Return your scope to the cabinet. TROUBLESHOOTING & COMMON PROBLEMS TROUBLESHOOTING MICROSCOPE PROBLEMS HANDLING & STORAGE PRECAUTIONS Image is too dark. Carrying ○ Adjust the diaphragm, make sure light is on. ○ Always carry your microscope with two hands, one There’s a spot in the viewing field, even when the slide grasping the arm or back slot and the other is moved, the spot stays in the same place. supporting the base. ○ The lens is dirty. ○ Carry the microscope upright, otherwise the ○ Use lens paper, and only lens paper to carefully clean eyepieces may fall out. the objective and ocular lens (the ocular lens can be Table Placement removed to clean the inside). ○ Set the microscope on a flat, solid support and in a ○ The spot is probably a spec of dust. position where it will not easily be knocked off. Nothing cannot be seen under high power. ○ Coil the cord to avoid tripping over it. FLG | 2B  [TRANS] PRELIMS: ACTIVITY 1 - 4 ○ If a specimen can’t be focused under scanning and G1 Phase then low power, nothing would also be focused under The first growth phase of the cell cycle, it is the resting high power. stage during which some cell organelles increase in size, ○ Start again with scanning magnification and walk and the cells rapidly synthesize the different types of RNA through the steps again. and proteins. Centrioles begin to duplicate during the late Only half of the viewing field is lit, it looks like a G1 phase. half-moon is present. The time gap between mitosis and the beginning of DNA ○ Objective must not have been fully clicked into place. replication. Cell volume that was reduced by half during mitosis, COMMON MICROSCOPE PROBLEMS returns to its previous size in this phase. Microscope Out-of-Focus / Poor Image Quality Start (G1 / S) Checkpoint ○ The slide is upside down. ○ Make sure cell nutrition, size, and environment is ○ The stage height stop is set too low. favorable. ○ The coverslip is missing or is too thick / thin. ○ DNA should be intact. ○ A dry objective has oil on it – common with 40x (clean ○ Preparation for DNA replication and entering S off the oil) Phase. ○ No oil or insufficient oil contact when using 100x objective. G0 Phase ○ The condenser is too low or the iris is closed. The phase where cell cycle activities are temporarily / Microscope Does Not Stay in Focus permanently suspended. ○ The slide is not lying flat on the stage. ○ The tension adjustment needs to be tightened. S Phase ○ The nosepiece is not fully engaged. Dirt / Dust in Field of View The DNA synthesis phase during which the genetic ○ If debris moves when the eyepiece is rotated, then the material present in the nucleus gets copied to produce two dirt is on the eyepiece. identical sets of chromosomes. The centrioles / ○ If there is a diminished view under one objective, then centrosomes complete their duplication during this phase. that objective has debris on it. ○ The top of the condenser or lamphouse has debris on G2 Phase it. The gap between DNA duplication and the next mitosis. Seeing Double Image / Headache While Using Second gap or resting phase during which the synthesis of Microscope RNA and proteins from the G1 phase continues. During ○ Microscope could be out of alignment if bumped or this period, cells store energy as ATP to be utilized during dropped and needs repair mitosis. At the end of this stage, cells enter the stage of ○ The focusing eyepiece is all the way up or down mitotic division. (make sure it is set at zero position). G2 / M Checkpoint ○ DNA should be completely replicated and enter mitosis. CELL DIVISION INTRODUCTION Most cells went through various cycles of macromolecular synthesis (growth) and division before differentiating (mitosis). The cell cycle is the regular series of occurrences that results in the division of new cells. Growth, repair, and renewal in all multicellular organisms depend on the formation of new cells by division of pre-existing cells. There are 2 mechanisms of cell division, and they have many features in common but they differ in the behavior of chromosomes during the early stages in cell division. ○ Mitosis - occurs in somatic cells. ○ Meiosis - confined to the developing germ cells. The process of meiosis and mitosis is dynamic and continuous but is subdivided into phases. Essentially, a duplication of the chromosomes during cell division takes place, and they are distributed to the daughter cells. Limits to Cell Growth: ○ Large cells means more nutrient demands. ○ Would cause DNA overload. ○ Surface Area : Volume Volume increases faster than Surface Area. Exchange of nutrients and water is dependent on the Surface Area. TYPES OF CELL DIVISION MITOSIS MEIOSIS 2 Cells produced known as 4 Cells produced known as Daughter Cells. Daughter Cells. Daughter Cells are Diploid. Daughter Cells are Haploid. Daughter Cells are genetically Daughter Cells are genetically identical to each other and to the different from each other and the Parent Cell. Parent Cell. 1 Cell Division occurs. 2 Cell Division occurs. MITOSIS Prophase It is the only cell cycle phase that can easily be recognized The nucleolus disappears and the replicated chromatin under a light microscope. condenses into discrete threadlike X-shaped The process where a single parent cell divides to make 2 chromosomes, each consisting of duplicate sister identical (same chromosomal set) daughter cells / diploid chromatids (becomes increasingly shorter and thicker) cells. joined at the centromere by kinetochore protein complexes. INTERPHASE The two centromeres with their now-duplicated centrioles Used to refer to the lengthy interval between mitoses. separate and migrate to opposite poles of the cell and The cell grows in size and replicates its DNA to prepare organize the microtubules of the mitotic spindle. for cell division. Later in Prophase, lamins and inner nuclear membrane are phosphorylated, causing the nuclear lamina and nuclear pore complexes (nuclear envelope) to FLG | 2B  [TRANS] PRELIMS: ACTIVITY 1 - 4 disassemble and disperse in cytoplasmic membrane vesicles. The nucleolus gradually disintegrates. The chromosomes begin to migrate towards the center of the cell, marking the end of prophase. Telophase It is the last recognized phase of mitosis marked by the end of the daughter chromosome’s migration to the opposite poles. The two sets of chromosomes are at the spindle poles and begin reverting to their decondensed state. The spindle depolymerizes and the nuclear envelope begins to reassemble around each set of daughter chromosomes. A belt-like contractile ring of actin filaments associated with myosin develops in the cortical cytoplasm at the cell’s equator. ○ The chromosomes decondense, transcription Metaphase resumes, nucleoli reappear, and the nuclear lamina and nuclear envelope reassemble. It is the second phase of mitosis and is marked with the During cytokines at the end of telophase, constriction of complete disappearance of the nuclear envelope that had this ring (F-actin bundle) produces a cleavage furrow and started during prophase. progresses until the cytoplasm and its organelles are The chromosomes, which are at their shortest and thickest divided into two daughter cells, each with one nucleus. stage with two sister chromatids, get attached to the Nuclear envelope redevelops around each group of spindle fibers present at the opposite poles. chromosomes to form daughter nuclei. Chromosomes condense further and protein complexes Mitotic apparatus disappears with a reduction in the called kinetochores at each centromere attached to the viscosity of cytoplasm, followed by the synthesis of RNA. mitotic spindle. The nucleolus reappears with the chromosomes becoming The cell is now more spherical, and the chromosomes are slender and extended. moved into alignment at the equatorial plate as a result of their attachments to the dynamic microtubules of the mitotic spindle organized by the centrosomes. Metaphase / Anaphase Checkpoint ○ Make sure DNA is intact, and chromosomes are attached to the mitotic spindle. ○ Beginning of chromatid separation and preparation for cytokinesis. Cytokinesis This is the process where the cytoplasm is divided to produce two independent daughter cells, each containing a complete set of chromosomes. Cytokinesis begins at the anaphase stage and continues through telophase and into the interphase. In the end, mitosis results in two genetically identical daughter cells, each having diploid (2n) number of Anaphase chromosomes. Sister chromatids (now called chromosomes) separate and move toward opposite spindle poles (centrosome) by a combination of microtubule motor proteins and dynamic changes in the lengths of the microtubules as the spindle poles move farther apart. It starts by splitting each paired chromosome into two sister chromatids, now known as daughter chromosomes, then are pulled towards the opposite end of the cell due to the contraction of the spindle fibers. At the end of this phase, each pole contains a complete set of chromosomes. MEIOSIS It is the process by which two successive cell divisions result in gametes (sperm and egg cells), which have half of the chromosomes of somatic cells to maintain the DNA. Produces 4 haploid cells. FLG | 2B  [TRANS] PRELIMS: ACTIVITY 1 - 4 The nuclear envelope is formed around the chromosome, and the spindle fibers disappear. The chromosomes uncoil and become less dense with the nucleolus appearing within the nucleus. Cytokinesis 1 It involves the division of the cytoplasm to produce two MEIOSIS 1 individual daughter cells. In most cells, cytokinesis occurs at the same time as Synaptic pairs separate toward two daughter cells at the telophase. first meiotic division. At the end of cytokinesis I, two different daughter cells are formed, each with half the number of chromosomes as the Prophase 1 parent cell (having 23 chromosomes having 23 pairs of Unique, extended period in which homologous chromatids). chromosomes pair and undergo genetic recombination Meiosis is thus also called the reduction division. during the process called synapsis. The duplicated chromosomes condense, resembling an X-shaped structure with two sister chromatids that become distinctly visible within the nucleus. The homologous chromosome pair comes closer and associates along the entire chromosome length, forming a tetrad (with four chromatids each), then they exchange DNA parts with each other (crossing over). Spindle fibers originate from the centrioles on either side of the cell, getting attached to each chromosome’s centromere. The last step of prophase involves the breakdown of the MEIOSIS 2 nuclear envelope, then the chromosomes start moving The second meiotic division occurs with no intervening S towards the middle of the cell. Phase and separates the sister chromatids into two final cells that are haploid. Prophase 2 The nuclear membrane initiates to break down, and the spindle fibers appear again. Each centriole divides, forming two pairs of centrioles. Chromosomes do not replicate any further in this phase of meiosis and begin migration towards the center of the cell. Metaphase 1 Homologous chromosomes align along the center of the cell. The centrioles reach the opposite poles of the cell with the spindle fibers extending from them. The centromeres orient themselves towards the opposite poles of the cell. Metaphase 2 Chromosomes arrange on the equator of the cell with the help of the spindle fibers. The centrioles are now at opposite poles in each of the daughter cells. Centromere divides, producing two sister chromatids, now known as daughter chromosomes, with the spindle fibers Anaphase 1 attached to each chromosome. The chromosomes with two sister chromatids are separated, and they begin to migrate to the opposite poles. This separation is achieved because of the contraction of the spindle fibers attached to each chromosome’s centromere. The homologous chromosomes start to migrate to the opposite poles. Anaphase 2 The daughter chromosomes are pulled towards the opposite poles of the cells with the help of the spindle Telophase 1 fibers. The chromosomes stop migrating with each pole At the end of anaphase II, each end of the cell contains a containing a haploid number of chromosomes. complete set of chromosomes. FLG | 2B  [TRANS] PRELIMS: ACTIVITY 1 - 4 IDENTIFYING CELLS IN HISTOLOGY CELL SIZE Telophase 2 The nuclear membrane forms around each chromosome with the disappearance of the spindle fibers. Nucleolus reappears as the cell prepares for the second round of cytoplasmic division. Cytokinesis 2 This step is identical to cytokinesis I, involving the second cytoplasm division, resulting in the formation of two individual daughter cells. THE EUKARYOTIC CELL Cells are the building blocks of all living things. The fact that all cells are made of the same substances and perform similar tasks demonstrates the relationships of all life on earth. Eukaryotic Cells ○ Cells found in plants and animals which are structurally complex. Prokaryotic Cells CELL SHAPE ○ Have simpler organization, like bacterias. SHAPE EXAMPLES MICROSCOPIC VIEW All the cells have the same fundamental metabolic Round - Lymphocytes principles as other cells, employ the same methods to - Erythrocytes generate proteins, and contain DNA as their genetic material. The neurons of giant squid and tiny bacteria are two examples of different-sized cells. They differ in function, from free-living amoebae to muscle cells in an animal to sperm cells inside the pollen grain of a plant. Cuboidal - Cells in the Cells also differ in their role in the environment, from food ovary makers to predators to decomposers that eat the dead. - Cells in the kidney tubules Based on their basic chemistry, structure, and hereditary materials, all cells fall into one of the three groups, as if the family tree of life on earth split into three main branches, called domains. Eukarya - plants, animals, fungi, and plants. Columnar - Goblet cells Bacteria - familiar, single-celled microorganisms, - Cells in the some of which are useful to humans and some of stomach and which cause human disease. intestines Archaea - single-celled microorganisms found in all types of environments but first discovered in extreme environments, such as hot springs. FLG | 2B  [TRANS] PRELIMS: ACTIVITY 1 - 4 Pyramidal - Neurons (in NUCLEUS LOCATION the cerebral cortex and NUCLEUS EXAMPLES MICROSCOPIC VIEW amygdala) LOCATION Central - Adipocyte / fat cells - Epithelial cells Stellate - Astrocytes (a glial cell) Eccentric - Plasma cells Spindle - Smooth muscle cells - Fibroblasts Basal - Columnar epithelial cells Polygonal / - Squamous Polyhedral cells STAINING REACTION STAINING REACTION EXAMPLES Basophilic - Nucleus - DNA - Rough endoplasmic reticulum NUCLEUS SHAPE Eosinophilic - Cytoplasm SHAPE EXAMPLES MICROSCOPIC VIEW - Collagen - Mitochondria Circular - Epithelial cell Chromophobic - Some cytoplasm components (Clear) - Intercellular spaces Amphophilic - Cytoplasm of certain cells (Both) - Neutrophils Kidney-Bean - Monocyte / white blood cell Lobed / Lobulated - Eosinophil / / Segmented white blood cells EPITHELIAL TISSUE INTRODUCTION The dynamic functions within our body are attributed to the specialized functions of minute cells that as a group comprise the “tissues.” There are four basic types that exist and function in close association with one another. Anucleated - Platelets OVERVIEW ON TISSUES TISSUE CELLS EXTRACELLULAR MAIN FUNCTIONS MATRIX NERVOUS Elongated cells Very small Transmission of with extremely amount nerve impulses fine processes EPITHELIAL Aggregated Small amount Lining of surface Elongated - Skeletal polyhedral cells / body cavities; muscle cells glandular secretion MUSCLE Elongated Moderate Strong contractile cells amount contraction; body movements CONNECTIVE Several types of Abundant Support and mixed and amount protection of wandering cells tissues / organs FLG | 2B  [TRANS] PRELIMS: ACTIVITY 1 - 4 EPITHELIUM An epithelium is a layer / sheet of cells that covers a surface or lines a cavity. Epithelial tissue, or epithelium, consists of sheets of cells that cover the external surfaces of the body, line the internal cavities, and the organs, form various organs and glands, and line their ducts. Epithelium is not supplied by the blood vessels and is therefore nonvascular. The basement membrane is what separates the epithelium from the connective tissue. There are two functional types of epithelium: lining epithelium and glandular epithelium. LOCATION Tight Junctions JUNCTION Zonula Occludens Major Transmembrane - Occludins Link Proteins - Claudins - ZO proteins Cytoskeletal Components - Actin FIlaments FUNCTIONS Major Functions - Seals adjacent cells to one Transportation (transcellular) of molecules from one another. epithelial surface to another occurs by various processes. - Controlling passage of molecules Absorption occurs via endocytosis or pinocytosis;. between them. Secretion of various molecules (hormones, mucus, - Separates apical and basolateral proteins, etc.) occurs by exocytosis. membrane domains. Protection from abrasion and injury is provided by the Medical SIgnificance - Defects in occludins may epidermis; the epithelial layer of the skin. compromise the fetal blood-brain barrier, leading to neurologic disorders. CELL POLARITY Asymmetric distribution of proteins, organelles, or cytoskeleton within groups of cells for them to carry out Adherent Junctions their functions. JUNCTION Zonula Adherens Major Transmembrane - E-cadherin Link Proteins - Catenin complexes Cytoskeletal Components - Actin FIlaments Major Functions - Provides points linking the cytoskeletons of adjacent cells. - Strengthens and stabilizes nearby tight junctions. BASAL DOMAIN Medical SIgnificance - Loss of E-cadherin in epithelial cell Directed towards the underlying connective tissue. tumors (carcinomas) promotes tumor invasion and the shift to Basement Membrane malignancy. All epithelial cells in contact with subjacent connective tissue have at their basal surfaces a specialized, fellike Desmosome sheet of extracellular material referred to as the basement JUNCTION Macula Adherens membrane. Major Transmembrane - Cadherin family proteins Thin extracellular sheet of macromolecules. Link Proteins (desmogleins, desmocollin) Structural support and anchoring of the epithelial tissue to the connective tissue. Cytoskeletal Components - Intermediate filaments (keratins) Scaffold for repair and regeneration. Major Functions - Provides points of strong Mediates cell to cell interactions and cellular migration. intermediate filament coupling Made up by the basal lamina (secreted by epithelial cells) between adjacent cells, together with the underlying layer. strengthening the tissue. Medical SIgnificance - Autoimmunity against desmoglein I leads to dyshesive skin disorders characterized by reduced cohesion of epidermal cells. Hemidesmosomes JUNCTION Hemidesmosomes Major Transmembrane - Integrins Link Proteins Cytoskeletal Components - Intermediate filaments Major Functions - Anchors cytoskeleton to the basal LATERAL DOMAIN lamina. Directed towards adjacent cells. Medical SIgnificance - Mutations in the Integrin-β4 gene Composed of intracellular adhesion and other junctions. are linked to some types of Allows communication between adjacent cells through epidermolysis bullosa, a skin blistering disorder. specialized attachment areas. FLG | 2B  [TRANS] PRELIMS: ACTIVITY 1 - 4 Gap Junctions molecules (mesothelium) JUNCTION Nexus Appearance Major Transmembrane - Connexin Link Proteins Cytoskeletal Components - N/A Microscopic View Major Functions - Allows direct transfer of small molecules and ions from one cell to another. Medical SIgnificance - Mutations in various connexin genes have been linked to certain types of deafness and peripheral neuropathy. APICAL DOMAIN Directed towards the exterior surface of the lumen of an enclosed cavity / tube. Composed of special surface modifications and features. Simple Cuboidal Epithelium TYPE Simple Cuboidal Description - Single-layer of cube-shaped cells Location - Lining of the ovaries - Lining of the thyroids - Lining of the distal tubule in kidney - Lining of ducts in some glands Major Functions - Covering - Secretion Appearance Cilia Cilia are motile structures found on certain cells in the uterine tubes, uterus, efferent ducts in the testes, and conducting tubes of the respiratory system. Microscopic View Long, highly motile apical structures. Larger than the microvilli. Abundant on cuboidal / columnar cells. Microvilli Microvilli are small, non motile projections that cover the surfaces of all absorptive cells in the small intestine and the proximal convoluted tubules in the kidney. Apical cytoplasmic projections. Uniform in length. Found in cells lining the small intestine. “Brush / striated border” Simple Columnar Epithelium Stereocilia Stereocilia are long, nonmotile, branched microvilli / TYPE Simple Columnar projections that line the cell surfaces in the epididymis and Description - Single-layer of tall, rectangular vas deferens. cells Less common and is seen in the lining of the male - May contain specialized apical reproductive system and inner ear sensory cells. structures It increases surface area, facilitates absorption, and Location - Lining of the the intestine and motion-detecting function. stomach - Lining of the gallbladder - Lining of the excretory ducts in LINING EPITHELIUM some glands The epithelium is classified according to the number of cell Major Functions - Protection layers and the morphology / structure. - Lubrication Cell Layers: - Absorption ○ Simple - Secretion ○ Stratified Appearance ○ Pseudostratified Cell Morphology: ○ Squamous ○ Cuboidal ○ Columnar Simple Squamous Epithelium Microscopic View TYPE Simple Squamous Description - Single-layer of flattened cells Location - Lining of the blood vessels (endothelium) - Lining of the peritoneum and pleura (mesothelium) - Serous lining of cavities - Alveoli in the lungs Major Functions - Facilitates movement of viscera (mesothelium) - Active transport by pinocytosis (mesothelium and endothelium) - Secretion of biologically active FLG | 2B  [TRANS] PRELIMS: ACTIVITY 1 - 4 Pseudostratified Ciliated Columnar Epithelium Appearance TYPE Pseudostratified CIliated Columnar Description - May appear as many layers because of the different levels of Microscopic View the nuclei - Not all cells reach the free surface, but all rests on the basement membrane - Single layer only - An intermediate type that appears stratified but really is one cell layer thick Stratified Cuboidal Epithelium Location - Lining of the trachea, bronchi, and TYPE Stratified Cuboidal nasal cavity - Lining of excretory ducts in parotid Description - Multiple layers of cube-shaped glands cells Major Functions - Protection Location - Lining of sweat glands - Secretion - Developing ovarian follicles - CIlia-mediated transport of Major Functions - Protection particles trapped in mucus out of - Lubrication the air passages - Absorption - Conduit for particle movement - Secretion Appearance Appearance Microscopic View Microscopic View Stratified Squamous Epithelium Stratified Columnar Epithelium TYPE Stratified Squamous Keratinized TYPE Stratified Columnar (Dry) Description - Multiple layers of rectangular cells Description - Multiple layers of flattened cells Location - Lining of large excretory ducts in - Cells near the basement some glands membrane are moved - Lining of cavernous urethra progressively on the skin surface, - Conjunctiva becoming thin, inactive, and lacking nucleus. Major Functions - Protection Location - Epidermis of the skin Appearance Major Functions - Protection - Prevention of water loss Appearance Microscopic View Microscopic View Transitional Epithelium TYPE Transitional Description - Multiple layers of cube-shaped to flattened cells with a superficial TYPE Stratified Squamous layer of large, dome-like cells called “umbrella cells” Nonkeratinized (Moist) - Also called as “urothelium” Description - Same as the Stratified Squamous - Line cavities in the urinary tract, Keratinized Epithelium but does which may be distended, and the not contain the protein keratin. thickness of the epithelium varies Location - Mouth, esophagus, and larynx with the degree of distention - Vagina and anal canal Location - Lining of minor and major calyces Major Functions - Protection - Lining of pelvis - Secretion - Lining of ureters and bladder of the - Prevention of water loss urinary system Major Functions - Protection - Distensibility FLG | 2B  [TRANS] PRELIMS: ACTIVITY 1 - 4 Appearance Microscopic View FLG | 2B