Adv. Biology Chapter 4: Tissues

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Epithelial Tissue
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Pseudostratified columnar epithelium- nuclei at different levels - locations: urethra, respiratory passages (trachea, bronchi)Stratified squamous epithelium- flat with deep layers of cuboidal and columnar cells - function: protects underlying tissues in areas subject to abrasion - locations: nonkeratinized is the lining of the esophagus, mouth, and vagina; keratinized type is the epidermis of the skinStratified cuboidal epithelium- very rare, only found in two layers - found in ducts of sweat glandsStratified columnar epithelium- found in urethra and milk ducts of mammary glandsTransitional epithelium- found in areas subject to variations in internal pressure - locations: ureters, urinary bladderAdhesions of epithelial cells1. CAM: cell adhesion molecules 2. Intracellular cement: composed of protein-polysaccharide mixtureIntercellular connections of epithelial cells1. Tight/Occluding Junctions: adhesion belt, fits together like ridges of a zipper 2. Gap Junctions: cell-to-cell communication, provide a direct route 3. Desmosomes: spot desmosomes - forms a small disc, hemidesmosomes - attach cells to extracellular structuresMicrovilliFingerlike extensions of plasma membrane, increase surface area, aid in absorptionCiliafound on columnar epithelium that needs to move secretionsBasement membraneLayer between epithelium and underlying connective tissueGeneral characteristics of connective tissue1. most abundant tissue in the body 2. all formed by embryonic mesenchyme 3. characterized by varieties of widely scattered cells (extracellular material) 4. the amount of structure of each component correlates with the functionembryonic mesenchymeloose spongy tissueIntracellular matrixmold in which the cells live (connective tissue)Fibrous intracellular substance- contains collagen fibers - elastic fibers - reticular fibersCollagen fibers- large in diameter - straight or wavy, very tough but flexible - may be loose or dense, regular or irregular - formed by fibroblastsfibroblasts- forms all the fibers that will be found in the cells (CT) - large, flattened cells with tapered ends - old fibroblasts are called fibrocytes, contains many of themelastic fibers- long, thin, cylindrical, or flat ribbons - homogenous and not fibrous - yellowish color due to elastin - concentrated in elastic ligaments and arterieselastinprotein that the elastic fibers are made ofreticular fibers- made of tiny collagen fibers - never found in bundles - branches - found in loose connective tissueAmorphous intercellular substance- provides a medium for tissue fluids - comes from the cells (secreted) - made of proteins, glycoproteins, carbohydrates, lipids, and waterMacrophages- any cell that goes through endocytosis - essential to the immune system - similar in appearance to fibroblasts - glandular - irregularly shaped - nuclei are an indented oval - amoeboid movementAdipocytes- they are mature fat cells, contains large droplets of lipid - amount varies with the type of CTMast cells- large oval cells with spherical nuclei - related to blood basophils - mobile - filled with chemicals to help defend the body after injury or infectionMeloncytespigment cellsLoose connective tissueareolar, adipose, reticularAdipose CT- closely packed - reticular fibers are common - made of adipocytes - locations: subcutaneous layer, bone marrow, mesentery, around kidneysReticular CT- meshlike framework - produce reticular fibersAreolar CT- loosely arranged, fibro-elastic CT (looks like styrofoam) - packs and anchors blood vessels, nerves and binds other tissues - flexible - ground substance is fluidDense connective tissueregular and irregularIrregular CT- direction is random - high tension areas - arranged in sheets - high density of collagen fibers - locations: fascia, dermisRegular CT- dense array of collagen fibers that lay parallel (enhances strength and resistances, dominates space) - locations: tendons, ligamentsCartilagehyaline, elastic, fibrocartilageHyaline cartilage- translucent, bluish white - cells exist in a lacunae - locations: fetal skeleton, surfaces of joints, nose, trachea, bronchi - strong, flexible - most common cartilage - made of collagen fiberselastic cartilage- provides support with flexibility - made of elastic fibers - locations: external ear, epiglottis, auditory tubeFibrocartilage- tough support and tensile strength - locations: intervertebral disks, symphysis pubis, tendon insertionsGeneral characteristics of cartilage1. more resistant to stress 2. has cells, fibers, and ground substances 3. very slow healing due to no blood cells 4. locations: walls of trachea, bronchi, larynx, nose, ears, ribsCells of boneosteoblasts, osteocytes, osteoclastsosteoblastsresponsible for the formation and growth of new boneOsteocytes- mature bone cells surrounded by matrix - aid in maintenance of bone tissue - connect to other osteocytes by canaliculi - cells trapped in lacunaeChondrocytescartilage cellsLacunaespace or pocket cells occupyOsteoclastsgiant cells active in bone reabsorption during remodelingBone matrixinorganic material, organic material, highly vascularized so easier healinginorganic material- 65% of mass - primarily calcium phosphate and calcium carbonate - forms crystal and hydroxyapatiteorganic material- mostly collagen fibers - very little ground substance - hardness and rigidityblood- cells do not produce a ground tissue - three types of cells surrounded by a fluid intracellular plasma (red, white, platelets)membranes- epithelial and CT combine to form 4 types of membranes - mucous - serous - cutaneous - synovialMucous membrane- line cavities that communicate with the exterior, including the digestive, respiratory, reproductive, and urinary tracts - kept moist all the time - lined with simple epithelial that absorb and secreteSerous membrane- line the ventral body cavity - there are 3 each: pleura - pleural cavity and lungs, peritoneum - abdominal cavity, pericardium - pericardial cavity and heartCutaneous membrane- skin - stratified squamous and underlying dense connective - thick, waterproof, drySynovial membrane- line joints cavities that surround bone - loose connective tissue and incomplete layer of epithelia - ends of bone covered by hyaline and separated by thick synovial fluidMuscle functions1. movement 2. protection 3. support 4. heat protection 5. specific contractible functions In the cardiac, vasomotor, gastrointestinal tract, urogenital areasMuscle properties1. Excitability (irritability) - respond to environment 2. Contractility 3. Conductivity - transport an impulse 4. Elasticity (stretchability)Types of musclesstriated, smooth, cardiacStriated muscle- cylindrical - striations - multi-nucleated (20 per cell) - organized as individual muscles - voluntary control (except reflexes)Smooth muscle- spindle-shaped - no visible striations - only one nucleus per cell - located in walls of viscera and blood vessels - under involuntary ANS (autonomic nervous system) controlCardiac muscle- cylindrical and branching - visibile striations - bi-nucleated - only in heart - involuntaryNervous tissue- carries electrical impulses to the body - brain, spinal cordTwo types of nervous tissue1. Neurons 2. Neuroglia (supporting cells)Neurons- communicate through impulses - longest cells in body - cannot repair (can't divide by mitosis)Neuroglia- physical support for neurons - maintains chemical composition - supply nervous with nutrients - defend from infectionNeuron structure1. cell body - contains a large nucleus 2. dendrites - numerous branching projections, receive info 3. axon (nerve fibers)- only one per cell, carry info, long and slender, ends at synaptic terminalMesenchymal Cellsa multipotent adult stem cellTypes of connective tissueproper, supportive, fluidTypes of proper connective tissue- loose: adipose, areolar, reticular - dense: regular, irregularTypes of supportive connective tissue- hyaline cartilage - fibrocartilage - elastic cartilage - boneTypes of fluid connective tissue- blood - lymph