Action and support: the muscles and skeleton

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Action and support: the muscles and skeleton. Chapter 40, pages 774-791. Muscles and Skeleton Work Together. Animals—jellyfish, earthworms, crabs, horses, and people—move using the same fundamental mechanism: - PowerPoint PPT Presentation

Transcript of Action and support: the muscles and skeleton


  • Muscles and Skeleton Work Together Animalsjellyfish, earthworms, crabs, horses, and peoplemove using the same fundamental mechanism:

    Contracting muscles exert forces on the skeleton and cause the body to change shape

    A body with muscles but no skeleton would not have coordinated movement

    A skeleton without muscles remains in one position

  • Types of SkeletonsTypes of skeletons

    Hydrostatic skeletons Exoskeletons Endoskeletons

    Coordinated movement is produced by alternating contractions of antagonistic muscles Antagonistic muscles act on each type of skeleton to provide movement

  • Hydrostatic Skeleton Worms, cnidarians and many mollusks (snails, octopuses)

    A hydrostatic skeleton is a sac or tube filled with a liquid

    Hydrostatic means to stand with water, which is how hydrostatic skeletons function

    A water-filled balloon stands up because it contains water, but if punctured it collapses The volume of the balloon is fixed, but you can change its shape by squeezing

  • Earthworm MovementAn animal with a hydrostatic skeleton controls the overall shape of its body using two sets of antagonistic muscles -circular and longitudinal

    For an earthworm to move forward it uses wavelike, alternating contractions of longitudinal and circular muscles Setae hold the front of the worm in placeThe worm first contracts its longitudinal muscles in its front end, so it becomes shorter and fatter Other longitudinal muscles in the middle and tail contract, making it shorter

    Earthworm Locomotion

  • The worm contracts circular muscles in its front half, making that half longer and thinner When the worm is fully extended, longitudinal muscles in the head contract again, fattening and anchoring the head As the wave of circular muscle contraction moves down the worm, the tail gets thin Longitudinal muscle contraction in the back half of the worm pulls the tail up toward the head This cycle is repeated over and over as the worm crawls through the soil

  • Hydrostatic Skeleton (a) Hydrostatic skeletonCircular musclescontractLongitudinalmuscles relaxCircular musclesrelaxliquidliquidLongitudinalmuscles contract

  • ExoskeletonArthropods (spiders, crustaceans) and insects, have rigid exoskeletons outside skeletons

    Movement occurs at joints of the legs, mouthparts, antennae, base of the wings, and body segments

    Thin, flexible tissue joins stiff sections of exoskeleton

    Antagonistic muscles attach to opposite sides of the inside of a joint, contraction causes movement

    Contraction of a flexor muscle bends a joint; contraction of an extensor muscle straightens a joint

    Alternating contraction of antagonistic muscles moves the joints

  • Exoskeleton (b) ExoskeletonFlexor musclecontractsExtensor musclecontractsExtensor musclerelaxesFlexor musclerelaxes

  • Molting

    The exoskeleton cannot expand, an arthropod molt its exoskeleton so that it can grow (27 times in up to 3 yrs)

  • EndoskeletonRigid structures found inside the bodies of echinoderms and chordates

    Movement also occurs primarily at joints, where two parts of the skeleton are attached to one another

    Biceps - a flexor and triceps extensor attach on opposite sides of the outside of a joint and move the joint back and forth, or rotate them in one direction or the other

  • Endoskeleton (c) EndoskeletonFlexor muscle(biceps) contractselbowExtensor muscle(triceps) relaxesFlexor musclerelaxesExtensor musclecontracts

  • Functions of Vertebrate Skeleton Provides a rigid framework that supports the body and protects its internal organs

    Allows locomotion

    Participates in sensory function

    Bones produce red blood cells, white blood cells, and platelets in red bone marrow

    Store calcium and phosphorus

  • Skeletal CategoriesThe axial skeleton, which includes the bones of head, vertebral column, and rib cage

    The appendicular skeleton pectoral, pelvic girdles and the appendages attached to them

  • Structure of Vertebrate Skeletons Three types of connective tissuecartilage, bone, and ligamentmake up the skeleton All are living cells embedded in a matrix of collage protein, with various other substances included in the matrix

    Bone - larger amounts of minerals composed mostly of calcium and phosphate, and is hard and rigid

    Cartilage contains large amounts of glycoproteins and includes elastic fibers, which make some cartilages flexible

    Ligaments hold bones together at joints and have small amounts of elastic fibers

  • Cartilage plays many rolesProvides flexible support and connections In some fishes (sharks and rays) the entire skeleton is composed of cartilage

    During embryonic development, the skeleton (except for skull and collarbone) is first formed as cartilage, and later replaced by bone

  • Skeletal Development

  • More Cartilage FunctionsCovers the ends of bones at joints

    Supports the flexible portions of the nose and external ear

    Provides the framework for the larynx, trachea, and bronchi of the respiratory system

    Forms the tough, shock-absorbing intervertebral discs between the vertebrae of the backbone

  • Cartilage StructureChondrocytes are the living cellsSecrete the glycoproteins and collagen that make up the matrix No blood vessels penetrate cartilage To exchange wastes and nutrients, chondrocytes rely on diffusion of materials through the collage matrix Cartilage cells have low metabolic rate, damaged cartilage repairs itself slowly, if at all

  • BoneHard outer shell of compact bone encloses spongy bone Compact bone is dense and strong, provides an muscle attachment site Develops as small tubes called osteons with collagen and calcium phosphate surrounding a central canal containing blood vessels

    Spongy bone is an open network of bony fibers Porous, lightweight, rich in blood vessels Red bone marrow is found in the cavities of spongy bone

  • Cartilage and Bone compactbonespongybone(containsmarrow)cartilagechondrocytescollagenmatrixosteonosteocytescentralcanalblood vessels

  • Bone CellsThere are three types of bone cells: Osteoblastsbone-forming cells Osteocytesmature bone cells Osteoclastsbone-dissolving cells

    Early in development, when bone replaces cartilage in the skeleton, osteoclasts invade and dissolve the cartilage Ostoblasts secrete a hardened matrix of bone and gradually become entrapped within it

  • As bones mature, the trapped osteoblasts mature into osteocytes Not capable of enlarging a boneEssential to bone health because they rework the calcium phosphate deposits, preventing excessive crystallization that would make the bone brittle

  • Bone Remodeling Allows skeletal repair and adaptation to stressEach year, 5% -10% of your bone is dissolved.

    Replaced by the coordinated activity of osteoclasts that secrete acid and dissolve small amounts of bone, and osteoblasts that secrete new bone This process allows the skeleton to alter its shape in response to demands placed on it Bones that carry heavy loads or are subjected to extra stress become thicker, providing more strength and support

  • Bone remodeling varies with age Early in life, the activity of osteoblasts outpaces that of osteoclasts, allowing bones to become larger and thicker as a child grows

    In the aging body, however, the balance shifts to favor osteoclasts, and bones become more fragile as a result Although both sexes lose bone mass with age, this is typically more pronounced in women

  • Broken Bone RepairThe ultimate bone remodeling occurs after a fracture healing takes about 6 weeksTypically, the ends of the broken bone are put back into proper alignment

    A clot is formed surrounding the broken endsCartilage replaces the clotBone replaces the cartilageCompleted when mature bone completely replaces cartilage, etc.

  • Bone Repair Blood fromruptured bloodvessels forms aclot surroundingthe ends of thebroken bone1 Healing beginswhen a callus ofcartilage replacesthe clot2 Bone gradually replaces thecartilage in thecallus3 When maturebone completelyreplaces the callusand the originalshape of the bonehas been mostlyrestored, thefracture is healed4largebloodclotcompact bonespongy bone

  • Muscles produce force by contracting A muscle can only contract or not contract

    Muscle lengthening is passive, occurring when muscles relax and are stretched by other forces such as: contractions of other musclesweight of a limbpressure from food

    Coordinated movement is produced by alternating contractions of muscles with opposing actions by antagonistic muscles

  • Structures of Vertebrate Muscles The muscles of all animals have striking similarities in both the cellular components that produce contractions and in the structural arrangement of these components The details of muscle structure and function, however, show a tremendous range of adaptations For example, clams possess a special type of muscle that holds their shells tightly closed for hours using very little energy Some flies have flight muscles that can contract 1,000 times per second

  • Types Vertebrate MuscleSkeletal, cardiac, and smooth

    All work on the same basic principles but differ in function, appearance, and control

  • Skeletal muscle Moves the skeletonCells are striated MultinucleateVoluntary or conscious control Contractions range from quick twitches to powerful, sustained tension Many nuclei located just beneath the cells plasma membrane; largest fibers have seve