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    Scales Scales Presentation Transcript

    • Skin Scales and Skeletal Muscles
      • Contents:
      • Scales
      • Types of Scales:Are all scales the same size?
      • Can scale type vary with sex?
      • Slime and Spots
      • Functions of Scales
      • How old is a fish scale
      • Fish skin
      • Function
      • Skin StructureFish and Mammalian skin
      • Skin Properties
      • Hormonal control of Skin
      • Skeletal Muscles
      • Types of Muscle
      • Skeletal Muscles function
      • Properties of Muscle
      • Structure
      • Myosin (Thick) Myofilament
      • Actin (Thin) Myofilaments
      • Sliding Filament Model of Contraction
      • Neuromuscular Junction
      • Motor Unit:
      • Contractile Machinery: Sarcomeres
      • Crossbridge formation and movemen
    • Scales
      • A rigid plate out of an animal 's skin to provide protection.
      • E volved multiple times with varying structure and function.
      • Classified as an organism's integumentary system .
      • scales usually not eaten.
    • Types of scales
      • Ganoid
      • Leptoid
      • Placoid
      • Cosmoid
      • Scales of Rohu ( Labeo rohita )
    • Ganoid Scales
      • Diamond-shaped, shiny, and hard.
      • gars (family Lepisosteidae ), reed fishes (family Polypteridae ), Sturgeons and Paddlefish
      • Similar to cosmoid but ganoin lies over the cosmine layer
    • Leptoid scales
      • Leptoid believed to derived from ganoid scales by the loss of ganoin layer
      • Single layer of bone.
      • Two forms: cycloid (circular) and ctenoid (toothed)
      • As they grow,add concentric layers.
      • Overlaping in a head-to-tail direction, like roof tiles
    • Leptoid scales
      • Jungle Perch Kuhlia rupestris
      • Paradise Fish, Macropodus opercularis
    • Leptoid scales
      • Cycloid scales
      • smooth outer edge,
      • primitive fish salmon , carp , trout, smelt, herrings and minnows
      • Ctenoid scales
      • a toothed outer edge,
      • derived fishes bass , crappie and perch
      • Kardong, Kenneth V. (1998) .
    • Placoid scales
      • also called dermal denticles, tooth like structure
      • sharks and rays
      • consists of an upper layer of enamel like substance called vitrodentine,
      • a lower layer of dentine,
      • a pulp cavity, and
      • a disk like basal plate embedded in the skin.
    • Placoid scales
      • Do not increase in size, new scales must be added as a shark grows
      • Homologous with teeth in all vertebrates.
      • Broadnose Sevengill Shark
    • Cosmoid scales
      • primitive coelacanth ( Latimeria chalumnae ) or as fossils.
      • a four-layered bony scale.
      • upper layer is enamel like vitrodentine
      • the second layer is a hard, dentine like called cosmine
      • the third layer is spongy bone, and
      • the lowest layer is dense bone
    • Cosmoid scales
      • In lungfishes, but highly modified, single-layered form.
      • Similar in structure to placoid probably arose from fusion of placoid scales
      • Queensland Lungfish
    • Cosmoid scales
      • scales of bony fishes evolved a long time ago
      • they had four layers,
      • one of dense bone,
      • one of spongy bone,
      • one of dentine and
      • one of enamel.
    • Are all scales the same size?
      • No sizes vary between species.
      • freshwater eels and tunas tiny embedded scales,
      • Coral Snappers medium sized,
      • of Tarpon, Megalops cyprinoides to be used in jewelry.
      • In Indian Mahseer, reach over 10 cm in length.
    • Can scale type vary with sex?
      • Yes. In flatfishes , males have ctenoid and females have cycloid scales
      • Sole have ctenoid scales on the 'eyed' side and cycloid scales on other side.
      • Sea Perches, have ctenoid scales above the lateral line and cycloid below
      • Not all species have scales, clingfishes are scale less.
      • Protected by a thick layer of mucous,
    • Function of Slime and Spots
      • Hydrodynamic function to reduce water friction and resistance to forward motion
      • Enzymes and antibodies as a defensive system
      • Spots size fluctuate according to nervous stimuli.
      • The arrangement imbricate or mosaic
    • General Functions
      • To calculate a fish’s age
      • Dried scale of a Barramundi showing annuli.
      • Times of migration, periods of food scarcity and illness
    • How old is a fish scale?
      • As scales increase in size, growth rings called circuli visible.
      • Cooler months scale grows slowly and circuli are closer leaving a band called an annulus .
      • Source and reservoir of calcium.
    • Fish skin
      • Barrier, strong, tough and watertight,
      • Ion- and water balance
      • The scales lie in the Dermis of skin
    • Skin Structure
      • Two layers, the Epidermis (outer) layer and the Dermis .
      • Epidermis is made up of epithelial cells
      • Inter-spaced between epithelial cells are slime cells produce mucous secretions
      • Dermis consists of two layers: stratum spongiosum & stratum compactum.
      • Hypodermis
    • Comparison of Fish and Mammalian skin
    • Skin Properties
      • Mucus ->fatty acid+phospholipids
      • Pigment cells (chromatophores) under hormonal or nervous system control
      • Effector organ
      • Respond to hormones & neurotransmitters via receptors
      • Xanthophores , erythrophores and melanophores
    • Hormonal control of Skin
      • Melanin-concentrating hormone (MCH)
      • Neurotransmitter or neuromodulator
      • Sensory organs
      • Nerve endings and receives tactile, thermal, and pain stimuli e.g. teleost fish
      • Blood vessels
      • Collagen fibers
    • Types of Muscle
      • Three types of muscle:
      Skeletal muscle Smooth muscle Cardiac muscle
    • Skeletal Muscles function
      • Two groups – the axial and appendicular muscles.
      • Main function is to support the body viscera.
      • Without them animal could neither move or eat or bear young.
      • Body movement (Locomotion)
      • Maintenance of posture
      • Constriction of organs and vessel
    • Types of Muscle fiber
      • Red muscles with capillary network mitochondria and myoglobin
      • White muscles produce tensions operative for short periods
      • pink
      • Nervous Control
      • Each myomere is controlled by a separate nerve .
    • Properties of Muscle
      • Excitability : capacity of muscle to respond to a stimulus
      • Contractility : ability of a muscle to shorten with force
      • Extensibility : muscle can be stretched to its normal resting length and beyond to a limited degree
      • Elasticity : ability of muscle to recoil to original resting length after stretched
    • Structure
      • Muscles are layered rather than bundled as in other vertebrates
      • Myomere or myotome, Septa,epaxial & hypaxial
    • Structure
      • Muscle cells long and cylindrical and have many nuclei.
      • Actin and myosin with controlling proteins
      • In other vertebrates muscles connected to bone through a tendon.
      • In fish, arranged vertically throughout whole length of fish.
    • Muscle Fiber Anatomy
      • Sarcolemma - cell membrane
        • Surrounds the sarcoplasm (cytoplasm of fiber)
          • Contains oxygen-binding protein myoglobin
        • Punctuated by openings called the transverse tubules (T-tubules)
          • Narrow tubes that extend into the sarcoplasm
          • Filled with extracellular fluid
      • Myofibrils -cylindrical structures within muscle fiber
        • Are bundles of protein filaments (= myofilaments )
        • When myofibril shortens, muscle shortens (contracts)
    • Sarcomere
      • repeating functional units of a myofibril
        • About 10,000 sarcomeres per myofibril, end to end
        • Each is about 2 µm long
      • Differences in size, density, and distribution of thick and thin filaments gives the muscle fiber a striated appearance.
        • A bands : a dark band; length of thick filaments
          • M line - protein to which myosins attach
          • H zone - thick but NO thin filaments
        • I bands : a light band; from Z disks to ends of thick filaments
          • Thin but NO thick filaments
          • Extends from A band of one sarcomere to A band of the next sarcomere
        • Z disk : filamentous network of protein. Serves as attachment for actin myofilaments
        • Titin filaments : elastic chains of amino acids; keep thick and thin filaments in proper alignment
    • d) myofibril c) muscle fibre b) muscle fibre bundle a) Muscle belly Components of skeletal muscle
    • Nerve and Blood Vessel Supply
      • Motor neurons: stimulate muscle fibers to contract. Nerve cells with cell bodies in brain or spinal cord; axons extend to skeletal muscle fibers through nerves
      • Axons branch so that each muscle fiber is innervated
      • Capillary beds surround muscle fibers
        • Muscles require large amts of energy
        • Extensive vascular network delivers oxygen and nutrients and carries away metabolic waste produced by muscle fibers
    • Myosin (Thick) Myofilament
      • elongated molecules like golf clubs.
      • Single filament contains 300 molecules
      • Molecule consists of two heavy myosin wound together to form a rod and two heads that extend laterally.
      • Myosin heads
        • Can bind to active sites on the actin molecules to form cross-bridges. (Actin binding site)
        • Attached to the rod portion by a hinge region that can bend and straighten.
        • Have ATPase activity:
    • Actin (Thin) Myofilaments
      • Thin Filament : 3 major proteins
        • F (fibrous) actin
        • Tropomyosin
        • Troponin
      • Two strands of fibrous (F) actin form a double helix extending the length of the myofilament; attached at either end at sarcomere.
        • Composed of G actin monomers each of which has a myosin-binding site Actin site can bind myosin during muscle contraction.
      • Tropomyosin
      • Troponin three subunits:
        • Tn-A : binds to actin
        • Tn-T :binds to tropomyosin,
        • Tn-C :binds to calcium ions.
    • Sliding Filament Model of Contraction
      • Thin filaments slide past the thick ones so that the actin and myosin filaments overlap to a greater degree
      • In the relaxed state, thin and thick filaments overlap only slightly
      • Upon stimulation, myosin heads bind to actin and sliding begins
    • Sliding Filament Model of Contraction
      • Each myosin head binds and detaches several times during contraction, acting like a ratchet to generate tension and propel the thin filaments to the center of the sarcomere
      • As this event occurs throughout the sarcomeres, the muscle shortens
    • Neuromuscular Junction
      • The neuromuscular junction is formed from:
        • Axonal endings, which have small membranous sacs (synaptic vesicles) that contain the neurotransmitter acetylcholine (ACh)
        • The motor end plate of a muscle, a specific part of sarcolemma that contains ACh receptors and helps to form the neuromuscular junction
      • Axonal ends and muscle fibers are always separated by a space called the synaptic cleft
    • Neuromuscular Junction Figure 9.7 (a-c)
    • Motor Unit: The Nerve-Muscle Functional Unit
      • A motor unit is a motor neuron and all the muscle fibers it supplies
      • The number of muscle fibers per motor unit can vary from a few (4-6) to hundreds (1200-1500)
    • Motor Unit: The Nerve-Muscle Functional Unit Figure 9.12 (a)
    • Contractile Machinery: Sarcomeres
      • Contractile units
      • Organized in series ( attached end to end)
      • Each myosin is surrounded by six actin filaments
      • Projecting from each myosin are tiny contractile myosin bridges
      Longitudinal section of myofibril (a) At rest
    • Contractile Machinery: Crossbridge formation and movement
      • Cross bridge formation: - a signal comes from the motor nerve activating the fibre
      • - the heads of the myosin filaments temporarily attach themselves to the actin filaments
      • Cross bridge movement:
      • - similar to the stroking of the oars and movement of rowing shell
      • - movement of myosin filaments in relation to actin filaments
      • - shortening of the sarcomere
      b) Contraction Longitudinal section of myofibril
    • Contractile Machinery: Optimal Crossbridge formation
      • Sarcomeres should be optimal distance apart
      • optimal distance is (0.0019-0.0022 mm)
      • At this an optimal number of cross bridges is formed
      • If stretched farther apart :
      • - fewer cross bridges can form  less force produced
      • If the sarcomeres are too close together:
      • - cross bridges interfere with one another  less force produced
      Longitudinal section of myofibril c) Powerful stretching d) Powerful contraction
    • Any questions …….. Don’t shy