Introduction to EumetazoaThe ‘true animals’True epithelium, definite body axes, specialized tissues                       ...
True EpitheliaEPITHELIUM – cell layer that covers surfaces, lines         internal cavities and spaces  With basal lamina,...
True EpitheliaAPICAL-BASAL POLARITY                         BASAL LAMINA                        HEMIDESMOSOMES            ...
Epidermis, Gastrodermis & GutEPIDERMIS – the outer skin; covers the surface of the                eumetazoan body         ...
Connective TissueCONNECTIVE-TISSUE COMPARTMENT – lies between           the epi- and gastrodermis   May just be the basal ...
Eumetazoan SkeletonsSkeletons can:                    Maintain body shape                 Support or protect the body     ...
Fluid SkeletonHYDROSTATIC SKELETON – water-filled skeleton,a.k.a. a hydrstat; cavity filled with water-based fluid        ...
Fluid Skeleton                         • Body wall                      strengthened by                    inelastic fiber...
Solid SkeletonPLIANT SKELETON – made of materials thatare rubbery and elastic  • Deform when stretched, spring back to ori...
Movement and Body Size  Cilia/Flagella           VS            Muscles         Only in water               Water, air, lan...
Musculature              EPITHELIOMUSCULAR CELLS:                  Arose from epithelium.               Actin-myosin micro...
Musculature   SMOOTH MUSCLE:    Contracts slowly.Tension over large range of     stretch lengths.   Contractile tentacles....
Neurons and Nervous System         Eumetazoans use nerve cells to         detect, evaluate, and respond to             env...
Neurons and Nervous SystemTransmission of a nerve impulse from neuron to neuron    or from neuron to effector (muscle) occ...
Sense Cells & OrgansEumetazoans need to obtain a dynamic picture of theirenvironment so they can respond appropriately.Res...
Gravity Receptors                    STATOCYSTS – hollow capsules                    lined with MECHANORECEPTORS          ...
Photoreceptors CILIARY and RHABDOMERIC – can be dispersed asindividual cells or, can be grouped together as EYES.         ...
DevelopmentZygote Cleavage   Blastula   *Gastrulation*   Larva                                         Gastrulation types:...
DevelopmentDIPLOBLASTIC –  adults have 2epithelial layers  (epidermis & gastrodermis)                    TRIPLOBLASTIC – a...
Growth    Solitary                VS            Modular    • Juvenile grows via               Add new, small,   general in...
Growth         Chapter 6
GrowthPOLYMORPHISM – modular growth that results in specialization of zooids with different forms and     functions (very ...
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Intro to eumetazoa2012

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Intro to eumetazoa2012

  1. 1. Introduction to EumetazoaThe ‘true animals’True epithelium, definite body axes, specialized tissues EUMETAZOA Chapter 6
  2. 2. 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
  3. 3. True EpitheliaAPICAL-BASAL POLARITY BASAL LAMINA HEMIDESMOSOMES Epithelial Junctions •AHDERING •SEALING • GAP Chapter 6
  4. 4. 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
  5. 5. 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
  6. 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
  7. 7. 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
  8. 8. Fluid Skeleton • Body wall strengthened by inelastic fibers (like collagen) • Resists aneurisms Orthogonal Crossed-helical Chapter 6
  9. 9. 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
  10. 10. 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
  11. 11. 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
  12. 12. 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
  13. 13. 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
  14. 14. 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
  15. 15. 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
  16. 16. 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
  17. 17. 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
  18. 18. DevelopmentZygote Cleavage Blastula *Gastrulation* Larva Gastrulation types: INVAGINATION EPIBOLY INGRESSION Chapter 6
  19. 19. 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
  20. 20. 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
  21. 21. Growth Chapter 6
  22. 22. 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

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