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6 - Skeletal tissues - ITS - Boston College · 6 - Skeletal tissues SKELETAL TISSUE TYPES ......

Date post: 26-Aug-2018
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6 - Skeletal tissues SKELETAL TISSUE TYPES notochord cartilage bone dentine enamel ENDOSKELETON vs DERMAL SKELETON SKELETAL TISSUE USE & FUNCTION BONE SCALING
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  • 6 - Skeletal tissues

    SKELETAL TISSUE TYPES notochord cartilage bone dentine enamel

    ENDOSKELETON vs DERMAL SKELETON

    SKELETAL TISSUE

    USE & FUNCTION

    BONE SCALING

  • Excitatory vs Inhibitory Influences: Neural Integration

    EPSP: excitatory postsynaptic potential

    IPSP: inhibitory postsynaptic potential

    But also Ach,serotonin and others

  • 3

    1.EPSP: excitatory postsynaptic potential

    2. IPSP: inhibitory postsynaptic potential (GABA and glycine are the main neurotransmitters)

    Key point: An action potential in a presynaptic neuron results in a graded potential in the postsynaptic neuron.

  • 4

    NOTE: 1. The role of voltage-gated calcium channels

    2. Vesicles with neurotransmitter

    3.Neurotransmitter binding to postsynaptic receptors (often ligand-gated ion channels)

    4.Re-uptake and enzymatic breakdown of neurotransmitter

    5. At an excitatory synapse non-selective ion channels open and ions, mostly Na+ move down the gradient

    6. At an inhibitory synapse Cl- channels open

  • 5

    Real neurons receive as many as 200,000 synapses each Ion flows from all inputs summate or average at the initial segment An action potential in the postsynaptic neuron occurs if the membrane potential at the initial segment reaches threshold

    Neural integration

  • 6

  • 7

    72 kg

  • Q: What are the strengths and weaknesses of the organic and inorganic components of skeletal tissues?

    Q: What are skeletal tissue made of?

    Hydroxyapatite: Ca10(PO4)6(OH)2Collagen

  • Notochord

    (not mineralized)

  • Cartilage (chondro-)

    blast vs cyte organic components vs inorganic components

  • Bone (osteo-)

    blast vs cyte organic components vs inorganic components

  • Dermal or membranous Endochondral direct development cartilage precursor shallow location deep location protection function support function

  • Modeling endochondral ossification

    Kronenberg 2003. Nature 423:343.

  • Bone undergoes deposition and resorption by the activity of osteoblasts and osteoclasts throughout life.

  • Dentine (odonto-)

    blast vs cyte organic components vs inorganic components

  • Enamel (amelo-)

    blast vs cyte organic components vs inorganic components

  • Q: why might a single animal have more than one skeletal tissue at different times of life? In different parts of the body?

    QQ: why might some single skeletal structures be formed of more than one tissue?

  • cartilage: alcian blue

    calcified cartilage: alizarin red

  • ENDOSKELETON vs DERMAL SKELETON

  • SKELETAL TISSUE USE AND FUNCTION

    Stress vs strain

    Strain is measured as change in length relative to the original length (dimensionless)

    Stress is measured in units of force / area (Gpa)

    Q: Which skeletal tissues will strain (deform) most? Least? Q: Which skeletal tissue will break most easily? Least?

  • Stress-strain curves differ depending on the material, whether inorganic or organic

    Q: Which curve represents cartilage? bone? dentine? enamel?

    E = Youngs modulus elasticity

    ba

    c

    d

  • Q: How does bone used for different purposes vary in composition?

    Q: what is the relationship between the inorganic content and the modulus of elasticity?

    b

    a

    c

    ba c

  • Q: How might you explain the differences in mineral content among the various arm bones of a bat? http://youtu.be/rMSIauO-MJc?list=PL011EB0DA5D2CC028

    Swartz and Middleton 2007

    Glossophaga soricina

    http://www.brown.edu/Departments/EEB/EML/videos.htm

  • 5 X

    Q: Why arent large animals just bigger models of small animals?

    Support is dependent on bone x-sec, NOT bone volume.

    Q: Will the x-sec of legs increase less fast than, equally as fast as, or faster than mass ( volume)?

  • Q: Which animal was larger in life?

  • 5 X

    Q: How might we predict the factor by which the diameter of the leg bones of the small horse should increase to support the larger horse?

    Q: If linear dimensions increase by 5 ..by how much does leg cross section and volume (mass) increase if proportions are maintained?


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