ZOOLOGY-LAB-2-GRP-8
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Polytechnic University of the Philippines**We aren't endorsed by this school
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BIOLOGY 1
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Biology
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Dec 19, 2024
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37
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LABORATORY ACTIVITY #2:Comparative Analysis of the Histological Structures and Functions ofEpithelial, Muscular, Nervous, and Connective TissuesEvangelista, Jhusean Zyrel D., Fabro, Erin Francheska A., Makinano, Marianne GaleH., Mujar, Ella Denise P., Pangan, Don Josef Benedict C., Pascual, Bailean M.Department of Biology, College of Science, Polytechnic University of the Philippines,Sta. Mesa, ManilaAbstract:Animal tissues are crucial to physiological processes in multicellular creatures, andthis experiment investigated their structure and functionality. Four tissue types—epithelial,connective,muscular,andnervous—werestudiedfortheirmorphologicalandfunctionalproperties.Epithelialtissues,whichcoverorgansurfacesandinteriorstructures,havedefensive, absorptive, and secretory roles. Connective tissues, including collagen, elastic, andreticular fibers, provide strength, flexibility, and support. Muscular tissues—skeletal, cardiac, andsmooth—specialize in movement. Nervous tissues in the brain, spinal cord, and nerves transmitimpulses for body communication. Students observed structural elements like nuclei, striations,and connective arrangements by increasing magnification and shifting focus. The activityenhanced their ability to identify and evaluate tissue types and grasp their structural andfunctional specialization. This aligns with histology, the study of tissue structure, and highlightsthe link between anatomy, physiology, and histology.Keywords:Histology, Tissue, Animal Tissue, Epithelial Tissue, Connective Tissue, MuscularTissue, Nervous Tissue1|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
1.INTRODUCTIONAnimal tissues are made up of clusters of cells that have similar structures andfunctions and collaborate to complete certain tasks. These tissues join to form organs,each having a specific role that helps the organism function as a whole. In multicellularorganisms, there are four fundamental tissue types: epithelial, connective, muscular,and nerve, all of which are necessary for life and homeostasis by supporting functionssuch as communication, movement, and defense.This laboratory exercise allowed students to study nineteen different specimensunder microscopes, allowing them to gain a thorough understanding of histology. Asoutlined inHistology, Microscopy, Anatomy and Disease, n.d., histology is defined asthe study of tissues and their structure. Furthermore, each tissue's structural makeup isintricately related to its function, emphasizing the close interaction between histology,anatomy, and physiology.AccordingtoMolnarandGair(2015),epithelialtissueslineinteriorbodystructures as well as cover organ surfaces. These tissues have a variety of shapes,including squamous, cuboidal, columnar, and transitional, and can be made up of singleor many layers of cells. Connective tissues, on the other hand, are composed of amatrix including both live cells and non-living ground matter. This tissue type containscollagen,elastic,andreticular fibers that provide support, flexibility, and strength.Smooth, skeletal, and cardiac muscles are specialized for contraction and movement,whereas nerve tissue is meant to transfer electrical impulses, allowing the body to2|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
communicate with itself. Furthermore, human tissue, as a type of animal tissue, is morecomplex and specialized than that of many other animals, reflecting the human body'sspecificstructuralandfunctionalrequirements.Overall,thislabactivityenabledstudents to hone their microscopy skills and gain a better grasp of tissue types andfunctionsinbothanimalsandhumans,boostingtheirtheoreticalknowledgeandpractical experience in cellular biology.2.METHODOLOGYThis section outlines the procedures and guidelines followed by the students inexaminingpre-preparedanimaltissuespecimensunderthemicroscope.Thespecimens were categorized into four tissue types: epithelial tissue, muscle tissue,connective tissue, and nervous tissue with the aim of identifying their unique structuresand understanding their functions within biological systems.2.1 MaterialsA compound microscope was obtained from the Department of Biology at thePolytechnic University of the Philippines (PUP) for use in the experiment. Nineteen (19)Pre-prepared slides of animal tissues were borrowed from the same department underthe supervision of the Department Chairperson, Ma’am Carmelita P. Mapanao, MEM,MSc. Microscopic images of the slides were recorded using a phone camera to ensureaccurate documentation and facilitate analysis. Additionally, to uphold laboratory safetystandards, appropriate protective equipment, including a laboratory gown and nitrilegloves, was utilized throughout the observation.3|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
2.2 Animal Tissue ObservationToobserveanimaltissues,pre-preparedslidesofAdiposetissuesection,Striated Muscle, Pseudostratified columnar epithelium, Stained bone, Nerve, CardiacMuscle, Columnar Epithelium, Cerebrum, Frog Striated Muscle, Mammal Spinal Cord,Human Urinary Bladder, Human Squamous Epithelium Smear, Cross Section FrogStomach, Cuboidal Liver, Columnar Cross Section Frog Stomach, Transitional HumanUrinaryBladder,CuboidalCrossSectionFrogKidney,FrogSimpleSquamousEpithelium, and Cuboidal Epithelium X.S were used. From a box container, the slideswere then carefully taken out and inspected to ensure they were free from dust orsmudges.Following tissue identification, the magnification was progressively raised to 10xand then 40x in order to study the material more closely. The course and focus knobswere adjusted as needed during the observation to maximize clarity. As a result, certainstructures—likecellnuclei,musclefiberstriations,orconnectivetissuearrangements—were able to become more noticeable and distinct. Finally, the slideswere then observed and photographed under the two magnifications for further analysisand reference.2.3 Animal Tissue CategorizationUnder a microscope, the observed animal tissue specimens were categorizedinto four types: epithelial, muscular, connective, and nervous tissue. Each specimenwascategorizedaccordingtoitsuniquemorphologicalfeaturesandfunctional4|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
characteristics such as shape, numbers of layers, type of contraction, existence ofstriations, their neurons, and more.Images taken throughout the procedure were examined to verify the distinctivecharacteristics of each tissue type, and microscopic observations were cross-checkedwith reference materials on the internet to guarantee accuracy.3.RESULTS AND DISCUSSIONSThis section examines the findings and discussions from the experiment. In thisstudy, nineteen (19) specimens were examined under the microscope and classifiedinto four tissue types: epithelial, muscle, nervous, and connective. The following figuresillustrate these classifications and provide a detailed analysis of the observations.According to Cleveland (2024), muscles are pieces of soft tissue throughout yourbody, they move, support, and protect your organs. They help in performing locomotoractivities performed by the body. There are different types of muscles found in differentkinds of organisms and in this experiment, we found four. Namely,epithelial, muscle,nervous, connective, and skeletal muscle tissue. These types of muscle each have theirown roles in enabling essential bodily functions.Epithelial tissues form protective layers on the body’s surface, serving as a shieldfor the outer skin, aiding in the absorption of molecules, and providing sensory functionsto the organism. Nervous tissues, made up of neurons, transmit signals that helpcoordinateandprocessinformationbetweenthebrain and the rest of the body.Connective tissues offer structural support, protecting bones and other internal organs.5|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
Lastly, skeletal muscle tissue, connected to bones through tendons, enables movementlike walking and other physical actions.3.1 Epithelium TissuesEpithelial tissues, recognized as one of the four primary tissue types, line thebody's inner and outer surfaces (Vasković, 2023). They also form part of glandulartissues responsible for producing and secreting mucus and proteins (Tarantino, 2022).These tissues composed of epithelial cells take on different shapes and arrangementsaccording to location and function (Cleveland Clinic, 2021). Epithelial tissues have threemain structural domains: the apical region, which is the exposed upper surface facingthe exterior of the cell; the basal area, which connects to the underlying connectivetissue;andthelateralregion,whichformsextensionsbetween adjacent cells toincrease the surface area for fluid transfer (Soffar, 2020). Furthermore, these tissuesform numerous junctions and membranes, each having a specific function (Byjus, n.d.).Notably, the body has several types of epithelial tissues, which will be further discussed.Figure 1.Pseudostratified ciliatedcolumnar epithelium under LPO.Figure 2.Pseudostratified ciliatedcolumnar epithelium under HPO.6|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
Figures 1 and 2 depict the pseudostratified ciliated columnar epithelium, whichseems to be layered due to its tight arrangement, giving the nuclei the appearance ofbeing on different levels. This creates the illusion of being stratified. However, theaddition of "pseudo" to its name indicates that this is not the case. This form of epithelialtissue consists of a single layer of epithelial cells of varying heights that may or may notreach the apical surface but are in direct contact with the basal region below (Bhatia,2023). Its epithelial cells appear like rectangles as they seem to be taller than theirwidth, which is expected from columnar types (Harvey, 2023). It also possesses cilia, amicrotubule-based structure that drives particles such as pathogens and dust in acertain direction (Biology Dictionary Editors, 2019). This type of tissue is usually foundin the respiratory system and is often called the respiratory epithelium, with the functionof protecting, secreting, and moving mucus (Ocran, 2024).Figure 3.Cuboidal Liverunder LPO.Figure 4.Cuboidal Liverunder HPO.In Figures 3 and 4, cube-shaped liver cells are observed to be uniform, withnearly identical width, height, and depth. Their nucleus is spherical and prominent,7|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
located in the center of the cell. These cuboidal cells, known as cholangiocytes, line thebile ducts and play an essential role in bile modification and substance transportbetween the bile and blood (O’Hara et al., 2012).Figure 5.Columnar Cross SectionFrog Stomach under LPO.Figure 6.Columnar Cross SectionFrog Stomach under HPO.In the cross-section of a frog stomach, the columnar cells seem rectangular andsomewhat elongated, with continuous layers. The image shows the existence of theconnective tissue called lamina propria. The mucosal epithelial layers are visible andpossess multicellular gastric glands that release pepsinogen enzymes (Karki, 2020).Figure 7.Transitional HumanUrinary Bladder under LPO.Figure 8.Transitional HumanUrinary Bladder under HPO.8|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
The transitional human urinary bladder is made up of multiple layers of large andflattened or rounded cuboidal epithelial cells that vary according to whether the bladderis empty or full (Sapkota, 2023c). The presence of lamina propria is evident, as is thenucleus, which is spherical and visible. One of its main functions is to act as animpermeable barrier through which water and most small molecules cannot penetrate,making it resistant to osmotic pressure (Biology Dictionary Editors, 2017c). It alsoprotects the underlying tissues from toxic substances found in acidic or alkaline urine(Taylor, 2024).Figure 9.Cuboidal Cross SectionFrog Kidney under LPO.Figure 10.Cuboidal Cross SectionFrog Kidney under HPO.Figures 9 and 10 display a photomicrograph of a cuboidal cross-section of a frogkidney. It has a spherical nucleus at the center of cube-like epithelial cells. Kidneystructures like the proximal and distal convoluted tubules and the thick portion of theLoop of Henle are made up of this type of epithelial tissue (Menefee et al., n.d.). Themain purpose of these cells is to be utilized in the process of generating urine throughselective secretion and reabsorption (Biology Dictionary Editors, 2017a).9|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
Figure 11.Frog Simple SquamousEpithelium under LPO.Figure 12.Frog Simple SquamousEpithelium under HPO.In Figures 11 and 12, the cells in the frog simple squamous epithelium appear tobe irregularly formed polygons with a large, prominent, rounded nucleus located in thecenter. This tissue is composed of one layer of closely packed squamous cells and iscommonly found in areas where material absorption and movement are essential, suchas diffusion, osmosis, and filtration (Biology Dictionary Editors, 2017b).Figure 13.Cuboidal Epithelium X.Sunder LPO.Figure 14.Cuboidal Epithelium X.Sunder HPO.The cross-section of the Cuboidal Epithelium appeared to be a series of slightlysimilarcubecellsarrangedinauniformcombinationoftubularandcircular10|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
arrangement. According to Megías et al. (2019), Cuboidal Epithelium is a layer ofcube-like cells whose nucleus is rounded and located centrally or slightly basal in thecell. The apical surface of the cell also often shows cilia, flagella, or microvilli. They alsostated that these epithelium acts as a lining in different ducts and tubes in the body suchassecretoryepithelium,excretoryducts,andprotectionsurfaces.TheCuboidalEpithelium is efficient protection, secretion of biologically active fluids, and absorption ofsubstances into or out of the tube or follicle they line (Sapkota, 2023a).Figure 15.Columnar Epitheliumunder LPO.Figure 16.Columnar Epitheliumunder HPO.The columnar epithelium is another type of epithelia, with column-shaped cells,columnar epithelium are taller than they are wide in an orderly arrangement, forming asmooth lining. Columnar epitheliums typically have elongated nuclei, which can be seenin the photomicrographs as dark purple dots caused by the stain. This type of epitheliumis usually for absorption and usually has apical cilia or microvilli, or the finger-likestructures on the surface of the epithelial cells, that help better absorb substances(Cleveland Clinic, 2021a). Additionally, columnar epithelium also secretes molecules,11|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
mucus, and enzymes, forming the lining of some sections of the digestive system andparts of the female reproductive tract (Betts et al., 2022).Figure 17.Human Urinary Bladderunder LPO.Figure 18.Human Urinary Bladderunder HPO.Figures 17 and 18 displays a photomicrograph of the Human Urinary Bladderconsists of different layers of the transitional epithelium lining, loose connective tissues,and smooth muscles (Ling & Gillespie, 2022). Observing the photomicrograph, theepithelial layer is located above the smooth muscles, appearing darker in color. Theepithelial layer that lines the human urinary bladder allows the bladder to increase anddecrease in size or volume to carefully accommodate the flow of urine inside thebladder when it fills or releases it (Bolla et al., 2023).12|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
Figure 19.Human Squamous EpitheliumSmear under LPO.Figure 20.Human Squamous EpitheliumSmear under HPO.In figures 19 and 20, the Human Squamous Epithelium Smear, sometimesreferred to as the Pavement Epithelium because of its recognizable appearance to tiles,seems to be dispersed or smeared in a disorganized way. The specimen staining givesthe individual cells a polygonal appearance, with distinct cytoplasmic borders and adarker-looking central nucleus. According to Nuovo (2013), one of the main roles ofsquamous cells is to protect the skin from external factors that could pierce it as well asfromevaporation.Additionally,theyplayanessentialpartinthemovement andabsorption of substances as well as the secretion of fluids like mucus, which serves asa lubricant to prevent inevitable friction (Sapkota, 2023b).13|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
Figure 21.Cross Section Frog Stomachunder LPO.Figure 22.Cross Section Frog Stomachunder HPO.When viewed in cross-section, the frog stomach seems to feature long, wave-likeridges known as rugae or gastric folds. Similar to theS. Infraimmaculata, a frog species,all kinds of frogs also show a series of epithelial cells. One of them is the columnarepithelium, an epithelial cell that consists of tall, cylindrical cells (Akat, 2018). Thisepitheliallayerplaysacrucialroleinsecretion and absorption, as described byDonahue-Taylor (n.d.), who highlighted that the digestive system’s general structureincludesathin,simplecolumnarepitheliallayeroptimizedforthesefunctions.Epitheliumtissueslikethecolumnarepitheliumoftenhaveunique characteristicsincluding microvilli or cilia, that can improve their absorptive function and assist inmovements (Vasković, 2023).3.2 Muscle TissuesThe experiment revealed various types of muscles, each with unique microscopicfeatures that reflect their specific roles. According to the study of Gash et al. (2023),Striated muscle fibers contain actin and myosin filaments that power contraction and are14|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
organized into repeating arrays, called sarcomeres. Striated muscles also have multiplenuclei and mitochondria located nearby to supply the energy needed for contraction.Similarly, cardiac muscles depict striated fibers but also have intercalated discs. Thesediscs allow the cardiac muscle cells to contract in a wave-like pattern so that the heartcan work as a pump (Libretexts, 2022) ensuring efficient and rhythmic blood pumping.These findings highlight the distinct functions of each muscle type.Muscle tissue is made up of cells that may shorten or contract, causing physicalmovements. This tissue is tightly packed with cells and is well-vascularized (NationalCancer Institute, 2019). This type of tissue seems striated under a light microscope,with many nuclei pushed along the membranes (Biga et al., 2019a). The human body,for example, comprises various muscle tissues with specialized tasks that contribute tothe body’s function as a whole. This laboratory experiment identified four types ofmuscle tissues: striated muscle, frog striated muscle, cardiac muscle, and cross-sectionfrog stomach. Despite being classified as muscle tissue, they have significant variations,ranging from their appearance under a microscope to the roles they perform in the body.Figure 23.Striated Muscleunder LPO.Figure 24.Striated Muscleunder HPO.15|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
Striatedmuscle,alsoknownasskeletalmuscle(ClevelandClinic, 2021b),appeared to be irregularly round but is organized as it forms a pattern. Small dot-likestructuresthatrepresentthenucleusareobservedand visible on the side. Themyofibers are the cellular elements that form this tissue (Cretoiu et al., 2018). In muscledevelopment, nuclei shift from the center of the myofiber to its periphery (Rosen &Baylies, 2017). It is responsible for voluntarily producing force and contract supportingrespiration, locomotion, and posture (Shadrin et al., 2016).Additionally, skeletal muscleis vital for thermoregulation—the equilibrium between heat production and heat loss(Miller, 2009). It helps maintain temperature homeostasis by producing heat throughshivering and nonshivering thermogenesis (Periasamy et al., 2017).Thermoregulationisthethermophysiologicalprocessresponsibleforhomeostasis, in which it is responsible for the balance between heat gain and lossthrough heat exchange with the environment (latent or sensible) to maintain a relativelyconstant body temperature (Crucianelli, L., et al., 2024). When we engage in physicalactivity, our skeletal muscles produce heat. In cold environments, some organismsshiver, using their skeletal muscles to generate heat and maintain a stable internaltemperature, a process called thermoregulation. In contrast, when it’s warm, sweatglands depend on small smooth muscles in their ducts to push sweat onto the skin’ssurface. As the sweat evaporates, it removes heat and cools the body. Thus, musclesplay a key role in thermoregulation by either generating heat in the cold or aiding insweat production to cool the body in the heat, helping maintain balance in the body’stemperature.16|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
Figure 25.Frog Striated Muscleunder LPO.Figure 26.Frog Striated Muscleunder HPO.On the other hand, the frog striated muscle, though similar in being classified asstriated muscle, showed a difference as it was observed to have displayed an elongatedstructure. Nuclei are not prominent in this type of frog tissue. However, their presence isexpected as all muscles comprise cells called myocytes, which contain nuclei (Baxter,2016; Ripa, 2022). According toDavidson (2015b), frog-striated muscles are made upof narrow and wide elongated fibers, giving them a striped appearance. The author alsomentioned that this type of tissue enables frogs to leap long distances. In another work,Davidson (2015a) stated that striated muscle is the most common muscle type in frogs,which makes up a large proportion of their total body weight.17|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
Figure 27.Purkinje fiber -Cardiac Muscle under LPO.Figure 28.Purkinje fiber -Cardiac Muscle under HPO.As for the cardiac muscle, it appeared to be striated and exhibited smaller,several small dot-like structures that represent the centrally located nuclei. According toEske(2019), the stripes are formed by alternating filaments of myosin and actinproteins, and most cardiac muscle cells have a nucleus that houses all of the cell’sgenetic material. It is responsible for the heart’s rapid, involuntary contraction andrelaxation,ensuringbloodispumpedefficiently.Itsstructureallowscoordinatedcontraction and resistance to fatigue (Saxton et al., 2018).Figure 21.Cross Section Frog Stomachunder LPO.Figure 22.Cross Section Frog Stomachunder HPO.18|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
Moreover, the cross-section of the frog stomach has shown curved folds thatappear smooth and exhibit a wavy pattern. The histological structure of the frog’sdigestive mucosa changes in the esophagogastric junction. The pseudostratified ciliatedmucosalepitheliumoftheesophagustransformsintoasimplemucus-secretingepithelium of the gastric type. The glands straighten, the muscularis mucosa becomes afulllayer,andthe muscularis becomes thicker (Huidobro & Pastor, 1996). Thesechanges are important as the stomach is highly acidic, which is different from how theesophagus works. The esophagus is a muscular tube that transports food from thethroat to the stomach (National Cancer Institute, 2011b). While the stomach holds thefood and mixes it with acid and enzymes that continue to digest it (University ofMichigan Health, 2019).The structural differences between these muscle types highlight their uniqueroles in the body. Some muscles are striated and contain multiple nuclei, allowing forquickand efficient physical movements. Others have spindle-shaped cells withoutstriations, enabling slower, controlled contractions essential for tasks like regulatingblood flow and other internal processes. Cardiac muscles, with their branched fibersand intercalated discs, are specially designed for synchronized, rhythmic contractionsthat keep the heart beating. These distinct structural features ensure each muscle typeis perfectly suited to its specific function, contributing to the overall harmony of theorganism.Theobservablecharacteristicsof skeletal and cardiac muscles reflect theirspecific functions. Skeletal muscles have organized sarcomeres, seen as striations,19|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
which enable rapid and forceful voluntary movements. Their long, multinucleated fiberssupport repair and growth, making them ideal for activities like locomotor functions.Cardiac muscles, also striated, have branching fibers and intercalated discs that allowsynchronized,rhythmiccontractionsandefficientelectricalsignaling,ensuringcontinuous, involuntary pumping of blood. These structural adaptations demonstratehow each muscle type is perfectly designed to meet its functional demands, withskeletal muscles excelling in strength and precision, and cardiac muscles sustainingendurance and synchronization.3.3 Connective TissuesConnective tissue is a type of tissue that connects and provides cohesion of thebody’s shape and organs. It is primarily made out of cells, fibers, and a gel-likesubstance (National Cancer Institute, 2011a). This tissue type comes in different formsand has specialized functions in the human body. Connective tissue includes bones,ligaments, tendons, cartilage, and adipose tissue (Fawcett, 2019). They are essential inthe human body, as they support and link the body’s many tissues and organs and canbe found throughout the body. Two connective tissues were examined in the laboratoryexperiment: an adipose tissue section and stained bone. Under the microscope, eachtissue was observed to distinguish and compare the structural characteristics of thesetissues. This will provide students with a better understanding of their roles in the body.20|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
Figure 29.Adipose Tissueunder LPO.Figure 30.Adipose Tissueunder HPO.The adipose tissue section appeared unorganized, as it did not follow a patternor form a shape. Additionally, small dot-like structures are observed in an irregularmanner, which indicates that the presence of the nuclei is scattered. Tallitsch andGuastaferri (2021) described adipose tissue as a loose, irregular connective tissueconsistingofadipocytes—buildingblocksofadiposetissue.Thelipidinmatureadipocytes fills the cell, pushing the nucleus to the periphery of the cell membrane,producing a thin ring within the cell (Gomillion & Burg, 2011). This tissue is found underthe skin, between internal organs, and even in the inside cavities of bones. Additionally,it is essential for energy storage, protection against extreme temperatures, cushioningsurrounding soft organs, and communicating through hormone signals with other organsthroughout the body (Cleveland Clinic, 2022).21|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
Figure 31.Stained Boneunder LPO.Figure 32.Stained Boneunder HPO.As for figures 31 and 32, the stained bone, it exhibited various shapes, includingcircular structures that resemble tree trunks. Small dot-like structures are also evident inthis tissue type. Biga et al. (2019b) described bone tissue under a microscope as ahighly structured structure of concentric circles. Each set of concentric circles forms themicroscopic structural unit of compact bone known as an osteon—a cylindrical structureof concentric layers of bone known as lamellae (Walker, 2020). Osteocytes are the mostabundant type of cell in mature bone tissue (Augustyn et al., 2020) whose nucleus canbe found on the vascular side, facing the bone surface (Marahleh et al., 2023). Bonetissue can be found throughout the body. It is crucial for protecting internal organs,supporting other tissues, allowing movement by helping muscle attachment, and playinga significant role in producing red and white blood cells (Chesnutt & Enzor, 2019).3.4 Nervous TissuesNervous Tissues are essential in the human body. They help our body functionproperly by transmitting electrical impulses and information around the body. It is the22|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
one accountable for the coordination and managementof many activities in the body.And out of all four types of tissues, Nervous Tissue is the most complicated one as it isvery complex and it lacks intercellular substance (Zhang, S. X., & Zhang, S. X., 1999).Thistissue is found in peripheral nerves throughout the body and in central nervoussystem organs like the brain and spinal cord (Admin, 2020). Out of 19 slides, 3 wereidentified as nervous tissue: the Nerve, Cerebrum, and Mammal Spinal Cord. Figures 1and 2 show cross-sections of the Nerve under two different magnifications, LPO andHPO. Figures 3 and 4 depict the Cerebrum in LPO and HPO, respectively. Lastly,Figures 5 and 6 present the Mammal Spinal Cord in LPO and HPO, respectively.Figure 33.Nerveunder LPO.Figure 34.Nerveunder HPOIn the Nerve Cross section under the Low Power Objective (LPO), there is whitematter, epineurium, and perineurium that could be seen. The outermost layer, theepineurium, is tough, mechanically resistant, and provides structural support (Stewart,2023). Beneath it lies the perineurium, a smooth, transparent layer made of concentric,flatperineurialcells,withitsthicknessvaryingbynervelocation(Perineurium|23|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
Complete Anatomy, n.d.). In the brain and spinal cord, white matter consists of axonbundlescoatedwithmyelin,alipid-proteinmixturethatfacilitatesnervesignalconduction and protects the axons (Team, 2020). Since this slide is viewed under LPO,some details of these structures are not visible.Under the HPO, based on the observation, the slide shows the perineurium,endoneurium, axons, and schwann cells. The endoneurium, composed of longitudinallyarranged collagen fibrils (Kim, et. al, 2012), surrounds axons, which are long, tail-likestructures (Vandergriendt, C., 2022). Schwann cells, a type of glial cell, form the myelinsheath on axons outside the brain by wrapping around individual segments, creating aprotective, multilayered coating (Lee, et. al, 2011). Some cells are still not visible andstill require a higher magnification.Figure 35.Cerebrumunder LPO.Figure 36.Cerebrumunder HPOIn the slide of Cerebrum, viewed under the microscope using LPO lens, it couldbe observed that it has an observable axon, gray matter, white matter, and pia mater.Gray matter contains neuronal cell bodies and short, branching dendrites that connect24|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
with nearby neurons for communication (Driemeyer et al., 2008). While the pia mater isa thin, delicate layer that closely adheres to the brain and spinal cord, following theircontours (McLaren, n.d.). Some details are still hard to describe and point out as itrequires a much higher magnification. While when it is viewed under HPO lens, it couldbe seen that ithas an observable satellite cell. Satellite glial cells (SGCs), a type of cellfound in the peripheral nervous system (PNS), surround sensory neurons in the dorsalroot ganglia and have a flattened, circular shape resembling a "tortilla" (Madhusudanan,et. al, 2017). Some details could also be seen, such as the axons, the white, and graymatter.Figure 37.Mammal SpinalCord under LPO.Figure 38.Mammal SpinalCord under HPOIn the glass slide of Mammal Spinal Cord under the microscope using a LowPower Objective, a White and Gray matter could be visibly observed, while a centralcanal could also be seen. White matter, found in the outer regions of the spinal cord,consists of nerve fibers that transmit information both upward and downward. Graymatter, located at the center of the cord, contains cell bodies and is recognizable by its25|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
butterflyshape.Thecentralcanal,situatedinthemiddleofthecord,holdscerebrospinal fluid (Nervous System Lab, n.d.).Using a microscope that has a High Power Objective, the oligodendrocytes,axon, dendrites, and astrocytes are clearly visible. Oligodendrocytes have a roundnucleusandacytoplasmrichinorganelles,aGolgi complex, microtubules, andglycogen (Oligodendrocytes | Complete Anatomy, n.d.). While astrocytes is a major celltype in the central nervous system (CNS), comprising 20% to over 50% of CNS cells,depending on the species (Hasel, P., & Liddelow, S. A., 2021). Oligodendrocytes andastrocytes are found in the spinal cord because they are both glial cells that performimportant functions in the central nervous system (CNS). These are typically seen alongwith the white and gray matter that was already visible under the LPO.4.CONCLUSIONIn conclusion to this second lab experiment, it has successfully enabled thestudents to achieve its goal in enhancing their microscopy skills through identifying thedifferent tissue types present in the several specimens used, its parts, and its functions.In the beginning of the experiment, the students were given nineteen specimens tostudy. Each specimen was examined under a compound light microscope using boththe High Power Objective and the Low Power Objective lenses. The specimens werethen grouped into four types of tissue: epithelial, connective, muscular, and nerve.Additional details, like squamous, cuboidal, columnar, and transitional, were noted todescribe the shapes of the samples.26|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
Through their research and analysis, the students described the four muscletypes present in the experiment. Epithelial tissue, a protective lining on organ surfaces,wasidentifiedalongside connective tissues, which provide support, structure, andconnection within the body. Muscle tissues were classified into three: skeletal musclesfor voluntary movements, cardiac muscles found in the heart, and smooth muscleslocated in the walls of organs such as blood vessels. Additionally, nerve tissues,composed of neurons, were observed for their role in transmitting signals from the brainand spinal cord to muscles, enabling physical activity. A variety of tissue shapes werealso observed, including squamous (flat and scale-like), cuboidal (cube-shaped forabsorption and secretion), columnar (tall and rectangular), and transitional tissues,which change shape from squamous to cuboidal during muscle expansion. This activityhas successfully enhanced their practical and theoretical understanding of animal tissuemicroscopy.5.REFERENCESAdmin.(2020).Nervoustissue-characteristics,structure,function.BYJUS.https://byjus.com/biology/nervous-tissue/Akat,E.(2018).Histologicalandhistochemical study on stomach of Salamandrainfraimmaculata(amphibia:Urodela).CelalBayarÜniversitesiFenBilimleriDergisi, 14(1), 13–16. https://doi.org/10.18466/cbayarfbe.40799727|Evangelista, Fabro, Makinano, Mujar, Pangan, & Pascual_BSBIO 1-2_GROUP8
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