Intro to eumetazoa2012
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Intro to eumetazoa2012






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      Intro to eumetazoa2012 Intro to eumetazoa2012 Presentation Transcript

    • Introduction to EumetazoaThe ‘true animals’True epithelium, definite body axes, specialized tissues EUMETAZOA Chapter 6
    • True EpitheliaEPITHELIUM – cell layer that covers surfaces, lines internal cavities and spaces With basal lamina, apical-basal polarity, cell-cell junctions, immobileAllows for establishment of regulated compartments (connective tissue, gut lumen, coelom) Epithelial cells control passage of materialsEnvironment under the epithelium can be chemically controlled Chapter 6
    • Epidermis, Gastrodermis & GutEPIDERMIS – the outer skin; covers the surface of the eumetazoan body Secretory Absorptive ImpermeableGASTRODERMIS – stomach skin; epithelial layer that lines the gut and joins the epidermis at the mouthGUT – internal, epithelia-lined cavity; it is a regulated compartment • GUT LUMEN (CAVITY) – also regulated compartment • Allows EXTRACELLULAR DIGESTION • Secretes digestive enzymes and absorbs products Chapter 6
    • Connective TissueCONNECTIVE-TISSUE COMPARTMENT – lies between the epi- and gastrodermis May just be the basal lamina of the two epithelia May be very thickCONNECTIVE TISSUE – consists of ECM and cells; no collective term for cells of the ECM Sponges – mesohyl Metazoans – blastocoel Cnidarians – mesoglea Bilateria – simply called ‘connective tissue’ Chapter 6
    • Eumetazoan SkeletonsSkeletons can: Maintain body shape Support or protect the body Transmit force of muscle contraction Be internal or external Be mineral, organic or both Be fluid or solid Chapter 6
    • Fluid SkeletonHYDROSTATIC SKELETON – water-filled skeleton,a.k.a. a hydrstat; cavity filled with water-based fluid **This is a eumetazoan innovation!!** • Surrounded by muscles (circular and longitudinal) • Muscles contract and pressurize the fluid • Water is incompressible •CIRCULAR CONTRACTION – lengthens hydrostat and stretches longitudinal muscles • LONGITUDINAL CONTRACTION – shortens hydrostat and stretches circular musclesUtility  inflate body, extend parts, locomotion, burrowing Chapter 6
    • Fluid Skeleton • Body wall strengthened by inelastic fibers (like collagen) • Resists aneurisms Orthogonal Crossed-helical Chapter 6
    • Solid SkeletonPLIANT SKELETON – made of materials thatare rubbery and elastic • Deform when stretched, spring back to original shape • Proteins, polysaccharides, water • Use as CT in comb jellies, mesoglea in jellyfish, hinges of bivalvesRIGID SKELETON – made of materialsthat resist a change of shape (bone/shell)Insect framework, terrestrial and flying invertebrates, and fast moving crustaceans of the ocean Chapter 6
    • Movement and Body Size Cilia/Flagella VS Muscles Only in water Water, air, land Associated with surface Associated with volumearea (effective when S/V is Locomotion, can move large) body parts with respect to Small, lilliputian other body parts (ALL invertebrates ANIMALS DO THIS) Prone to surface friction Effective when S/V is and viscous drag from small environement Momentum stops whenciliary/flagellar beat stops Chapter 6
    • Musculature EPITHELIOMUSCULAR CELLS: Arose from epithelium. Actin-myosin microfilaments allowed some to become contractile. MYOEPITHELIAL CELLS: Contractile fibers isolated in independent cells but are still part of the epithelium. Outside the basal lamina MYOCYTES: True muscle, contractile cells below basal lamina. No longer epithelial. Chapter 6
    • Musculature SMOOTH MUSCLE: Contracts slowly.Tension over large range of stretch lengths. Contractile tentacles.CROSS-STRIATED MUSCLE: Contracts rapidly.Tension over limited range. Snapping jaws or claws. OBLIQUELY-STRIATED:Intermediate of the other two. Extensible animals that can make quick movements. ANTAGONISTIC Chapter 6
    • Neurons and Nervous System Eumetazoans use nerve cells to detect, evaluate, and respond to environmental stimuli. NEURONS - respond to stimuli by transmitting information as a wave of depolarization to the target cells Sensory receptors and neurons arose from epithelia (like muscle cells). They became specialized and migrated to a connective-tissue compartment Chapter 6
    • Neurons and Nervous SystemTransmission of a nerve impulse from neuron to neuron or from neuron to effector (muscle) occurs via: Electrical junctions – gap junctions that join cells so that membrane depolarization (action potential) spreads uninterrupted; no organismal control SYNAPSE – gap between two cells (synaptic cleft) through which the action potential is carried by chemical neurotransmitters Chapter 6
    • Sense Cells & OrgansEumetazoans need to obtain a dynamic picture of theirenvironment so they can respond appropriately.Response to different stimuli like: Electromagnetic Mechanical Chemical Magn etic Direction and distance to the source of the stimuli are so important to each eumtezoan Simple: sensory neuron-effector Complex: multiple stimuli, whole-body response, accessory structures, CNS Chapter 6
    • Gravity Receptors STATOCYSTS – hollow capsules lined with MECHANORECEPTORS and with a dense, heavy STATOLITH at the center.Gravity pulls the statolith against the bed of mechanoreceptorswhich then causes alterations of the depolarization pattern. Chapter 6
    • Photoreceptors CILIARY and RHABDOMERIC – can be dispersed asindividual cells or, can be grouped together as EYES. OCELLUS:PIGMENT SPOT PIGMENT CUP – EVERTED or INVERTED Chapter 6
    • DevelopmentZygote Cleavage Blastula *Gastrulation* Larva Gastrulation types: INVAGINATION EPIBOLY INGRESSION Chapter 6
    • DevelopmentDIPLOBLASTIC – adults have 2epithelial layers (epidermis & gastrodermis) TRIPLOBLASTIC – adults have 3 epithelial layers (addition of mesothelium) MESODERM – located between ecto- and endoderm and can arise from either Chapter 6
    • Growth Solitary VS Modular • Juvenile grows via Add new, small, general increase in size identical units (module – • ALLOMETRIC – different ZOOID)body parts grow at different Clonal budding rates All zooids form a colony • Surface > Volume Favorable SA:V• Gills, lungs, gastrodermis ISOMETRIC – similar • Associated with growthlocomotion and increasing Colony is considered complexity on one body one individual axis Self repair, higher • Self repair, often killed survival if preyed upon Chapter 6
    • Growth Chapter 6
    • GrowthPOLYMORPHISM – modular growth that results in specialization of zooids with different forms and functions (very common in Cnidarians) Exemplifies the replication- specialization- integration pattern of metazoans Chapter 6