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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