1/10/2013. Topic 10: Form and Function (COM) Newton s Laws of Motion. Newton s Laws of Motion. What are? Forces

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1 /0/203 Topic 0: Form and Function (COM) Forces exerted on vertebrate bodies How do Newton s Laws apply to vertebrate form and function? How do we study forces in functional morphology? What are Ground Reaction Forces? What are stresses and strains? How do they differ? Structural materials used to resist forces What are hydrostats? What are the types of connective tissues? What are their properties? Joints and Kinematic Chains What are the different types of joints? What are they for? What is a kinematic chain? What are the parts of a lever? What kinds of levers exist? Force acting on an object behaves as a force acting on a point COM is this point Finding the COM Hang object from two places Draw a vertical line, parallel to each gravitational vector COM Liem et al. Fig 5- Newton s Laws of Motion Newton s Laws of Motion. : A body stays in motion or at rest unless acted on by an external force P = mv 2. A force allows a body to accelerate in the force s direction. Acceleration is inversely proportional to mass 3. For every action there is an reaction Photos PJB, Drawing JF Alward Newton s 3 rd Law Locomotion is the result of the environment pushing against an animal that exerts a force on it Occurs on all substrates Animals must withstand these forces move the to exert forces on the Photos PJB, Drawing JF Alward Forces What are? Forces are vectors Animal exerts a force on the substrate, F b COM Forces can be decomposed Horizontal component Vertical component # components = # dimensions Can recompose resultant forces from component forces Vector addition F v F R FR F h Ground produces an equal and opposite force on the animal, F R (GRF) Vertical component is body being supported against gravity, F V Horizontal component is forward propulsion, F H Also lateral component, F L F b F R F H F V F L Liem et al. Fig 5-2

2 /0/203 What are stresses and strains? force exerted on an object that causes strain Yield Point Fracture the deformation of a material due to stress Young s Modulus of Elasticity Measures how well a material resists deformation High angle = Low angle = Stress (force/xs area) Young s Modulus of Elasticity Plastic Region Elastic Region Strain (deformation) Modified from Liem et al. Fig 5-4 What are stresses and strains? Stress (force/xs area) Which is which? Strain (deformation) Bone Rigid Not deformable Takes lots of stress High elastic modulus Rubber Elastic Highly deformable Takes little of stress Low elastic modulus Modified from Liem et al. Fig 5-4; photos

3 /0/203 What sorts of stresses can be applied? What are hydrostats? Rely on hydrostatic pressure Cat Humerus hydrostats Muscles make shape change Tongue, elephant trunk Helical connective tissue prevents kinking Cutaneous tendon in sharks Compression & Tension Notochord Liem et al. Fig 5-3 Photos R. Stephenson, T Gustafson, thundafunda.com What is the structure of connective tissue? Extracellular components predominate over cells Water Proteins Carbohydrates Secreted by cells Examples: Loose connective tissue Blood Cartilage Bone Loose Connective Tissue In organs, vessels, muscles, under skin: Secreted by fibroblasts Structural, high strength Collagen fibrils fibers : Elastic Ground substance Proteoglycans Other cells Macrophages White bloods cells Fat cells Adipose tissue Liem et al. 5-6A; Photo KUMC Liem et al. 5-6A; Photo histol.chuvashia.com Dense Connective Tissue Cartilage High in Collagen forms fibrils Fibrils form fibers Found throughout body Dermis (see in lab on cat) In cartilage Dermis Ligament Tendon Chondroblasts secrete matrix, allowing cartilage to grow Matrix Water Collagen Lots of proteoglycans Liem et al. 5-7 Liem et al. 5-8, photo histol.chuvishia.com

4 /0/203 Bone Types of Cartilage Cartilage High in collagen Grades into tendons Cellular Cartilage High in elastin External ear, epiglotis Cartilage Glass like End of long bones, trachea High in cells Common in Embryo Highly vascularized Highly mineralized Ossified Cartilage in canaliculi produce osteons remodel bone In older animals, stiffer High in calcium salts Hydroxyapatite (calcium salt) Laid down in lamellae (layers) Photos histol.chuvishia.com Endochondral Bone Endochondral or Cartilage Replacement bone precursor to the bone Cartilage becomes calcified Bone forms medially towards the epiphyses Epiphyseal plate is last to ossify Liem et al. 5-9; Photo KUMC How is bone remodeled? Bone is laid down by Destroyed by Allow for remodeling of bone bone bone What is membrane bone? or bone Dermal ossification What are joints? Osteoblasts gather on connective tissue Secrete osteoid matrix Produce bone trabeculae Further deposition of bone Differ in amount of movement allowed Lighter in areas of low stress Trabeculae strengthen bone where needed Liem et al. 5-3 Liem et al. 5-A Denser in areas of high stress Which bones are dermal? Liem et al. 5-9 Restrict movement Provide strength between bones Allow lots of movement Provide flexibility and function Liem et al

5 /0/203 Synarthroses No movement Periosteum forms sutural ligament Cartilage connects bones Limited movement Decreases with age Can increase with some hormones Cartilaginous connection between diaphysis and epiphysis of a long bone Images MR Villarreal; W Norman; Liem et al. 5-A Diarthroses joints Smooth motion needed Bones caped with articular cartilage Joint has capsule with fluid Meniscus adds padding and fit between bones Responsible for all major movement of bones relative to one another Images W Norman; Liem et al. 5-4C Joint Degrees of Freedom Number of unique ways a joint can move in 3D space x plane y plane z plane (angle about x) (angle about y) (angle about z) Joint Degrees of Freedom How many degrees of freedom are allowed? Elbow Joint Temporomadibular Joint Hip Joint 6 degrees of freedom are possible R Sebastian Images Jamison Orthopedic Clinic;

6 /0/203 Kinematic Chains Movement in one joint influences movement in other joints 4-bar linkage in skulls of fishes and lizards Lever rigid bar with a it pivots on section of bar in-force is applied to section of bar generating out-force All levers follow this rule: F i x L i = F o x L o Trade-off between: in-lever length Images: Westneat 2004 Liem et al. 5-6A; Pough et al B Classified by relative position of parts Class Lever Fulcrum between in & out lever Class Lever Out-lever in the middle Class In-lever in the middle Identifying the parts of a lever system What is generating the inforce? Where is the fulcrum? Where is force being output? NOTE: Textbook has error, 2 nd and 3 rd class levers are switched! Pough et al. 2004, 0-3 Liem et al. 5-6B

7 /0/203 What class levers are these? B A D C E F Pough et al. 2004, 0-3; Liem et al 5-7C; Click4Biology.info