BIOL 1030 – TOPIC 18 LECTURE NOTESTopic 18: Skeletal and Muscular Systems (Ch. 49)Ι. Uses of skeletonsA. protection of body structuresB. rigid support for body structuresC. allow movement by serving as a rigid surface for muscle attachmentΙΙ. Types of skeletonsA. hydrostatic skeleton (AKA hydraulic skeleton or hydroskeleton)1. found in soft-bodied invertebrates (such as earthworm)2. body fluids enclosed in a confined, incompressible space3. direct force of muscle against waterB. exoskeleton1. opposite muscle ends attached to hard parts on outside of body2. arthropod muscles attached to rigid chitin exoskeleton• limits size• large muscles would require excessively thick exoskeletonC. endoskeleton1. found in vertebrates and echinoderms2. most vertebrate muscles are attached to an internal bone scaffold• bone can bear more weight than chitin• bone is cellular, living tissue that can grow and be remodeled3. vertebrates have a soft, flexible exterior that stretches to accommodate movementΙΙΙ. Human skeletal systemA. composed of bones, cartilage, and ligamentsB. tendons connect muscle to boneC. over 200 bones divided into two groups, axial and appendicular1. axial – skull, backbone, rib cage, breastbone (sternum)• skull: cranium, facial, middle-ear, and hyoid bones1 of 9BIOL 1030 – TOPIC 18 LECTURE NOTES• vertebral column = spine = backbone flexible column that protects spinal cord twelve pairs of ribs protect heart and lungs (FYI, same number in both males and females)2. appendicular – attached to axial at shoulders and hips• pectoral girdle = shoulders clavicles connect shoulder blades to breastbone arms attached at shoulders• pelvic girdle = hips connects to legs major limitation in childbirthΙς. BoneA. recall: special type of connective tissueB. two types of bones: flat and long1. flat bones not modeled in cartilage first2. long bones modeled in cartilage firstC. bones also serves as calcium and phosphate reservoir and blood cells are made in the bone marrow of long bonesD. structure1. collagen fibers coated with hydroxyapatite crystals (calcium phosphate)2. result is strong but not brittle• hydroxyapatite crystals are strong and rigid but brittle• collagen matrix is flexible but relatively weak• collagen matrix redistributes stress that otherwise would easily fracture the crystals3. fibers run parallel to axis in long bones, parallel to end in joints; this helps prevent cracks from penetrating into the bone interior4. ends and interiors of long bones are an open lattice of spongy bone tissue• bone marrow found in spaces of spongy bone• bone marrow produces most blood cells5. compact bone surrounds spongy bone, gives long bones most of their strength2 of 9BIOL 1030 – TOPIC 18 LECTURE NOTESE. formation1. osteoblast cells secrete collagen fibers (cartilage model in most)2. collagen fibers become calcified; osteoblasts now called osteocytes3. osteocytes are encased in lacunae4. Haversian system – basic unit of structure for bone• Haversian canals – narrow channels that run parallel to length of the bone; they interconnect, and they carry blood vessels and nerve cells• lamellae – thin, concentric layers of bone surrounding the canals• canaliculi – openings in bone between osteocytes and the canalsF. modifications1. cartilage remains for a while at the neck of long bones, allows for continued growth until completely replaced (usually in late teens)2. articular cartilage remains at ends of bones, involved in joints3. osteoclasts can dissolve bone, allowing remodeling of bone4. new bone is formed along lines of stress, when possibleς. joints: where bones come togetherA. sutures1. nearly immovable, joined by connective tissue2. some movement in early development (fontanels of infants)3. main example: cranial bonesB. cartilaginous joints1. slightly movable; bones bridged entirely by cartilage2. main example: vertebral bones in the spine• pads of cartilage are intervertebral disks• efficient cushioning shock absorbers that allow some flexibilityC. synovial joints1. freely movable joints2. ends of bones in synovial capsule, a fibrous structure strengthened by ligaments and filled with lubricating fluid3 of 9BIOL 1030 – TOPIC 18 LECTURE NOTES3. types include ball-and-socket, hinged4. rheumatoid arthritis: degeneration of synovial joint connective tissueςΙ. tendons: where bones and muscles come togetherA. tendons are straps of dense regular connective tissueB. muscle origin attaches to stationary baseC. muscle insertion attaches to movable boneD. freely moving joints move by opposing sets of muscles1. flexors decrease joint angle (move bones closer together)2. extensors increase joint angle (move bones further apart)ςΙΙ. Muscular SystemA. specialized cells devoted produce body movement by contractionB. achieve contraction by ATP-consuming activity shifting relative positions of actin and myosin filamentsC. muscles as organs include the tissues (blood vessels, etc.) that support the muscle tissueD. three types in vertebrates, based on muscle tissue type: smooth, skeletal, and cardiacE. smooth muscle review1. tissue sheets with long, spindle-shaped, mononuclear cells2. individual myofibrils of actin and myosin not specifically aligned3. blood vessel and iris muscles contract with specific stimulation4. gut muscles contract spontaneously5. specialized for slow, maintained contraction with minimal energy useF. skeletal muscle review1. very long, multinucleate cells called muscle fibers that run in parallel2. fibers made of myofibrils; ordered structure produces striated appearance3. specialized for rapid contraction with large force4. under voluntary control by interactions with nerve tissueG. cardiac muscle review1. composed of striated fibers, orientation different than skeletal fibers4 of 9BIOL 1030 – TOPIC 18 LECTURE NOTES• chains of single, branching cells with individual nuclei• electrically coupled to neighbors by gap junctions at intercalated discs2. lattice structure critical to heart muscle function• contraction initiated at one location• spreads throughout myocardium via electrical impulses3. heart works as well-ordered system to propel blood through bodyςΙΙΙ. myofilament structureA. long chains of actin and myosin proteinsB. also contains troponin and tropomyosin proteinsC. actin1. polymer makes up thin filaments that are strings of actin "beads" 2. two filaments wind around each