MSK: Bioscience

  1. 5 functions of bone: main bones of axial and appendicular skeleton: state classification according to shape
  1. composition of osseous tissue & various func. of each component
  1. compare: structure, functions and locations of compact and spongy bone
  1. interstitial growth, appositional growth and bone remodelling
  1. diff. types of bone fractures and 4 stages of fracture repair
  1. joints by structure and function
  1. various structures of synovial joint and state function of each

8 .6 diff. types of synovial joint, their movement and examples of each

  1. structure of skeletal muscle
  1. events that lead to skeletal muscle contraction and process of contraction
  1. support: provide framework. 2. protection 3. storage of minerals & triglycerides 4. blood cell protection 5. movement

BONE SHAPES: long bones: have a shaft (diaphysis) and bone ends (epiphysis) short bones: small cube shaped. patella = sesamoid bone. flat bone: thin, flat, often curved. irregular: complex shaped

AXIAL SKELETON: bones of the skull: cranial and facial. vertebral column: cervical, thoracic, lumbar, sacral and coccyx vertebrae. rib cage: sternum and ribs

APPENDICULAR SKELETON: bones of upper limb: arms, forearms, hands. lower limb: thighs, legs and feet. shoulder (pectoral) girdles. pelvic girdle

BONE STRUCTURE: contains connective tissue: osseous, adipose and hyaline cartilage(growth plates)nervous tissue: sensory neurons & muscle & epithelial tissue: blood vessels

OSSEOUS TISSUE: contains specialised cells and extracellular matrix (matrix). MATRIX: consists of ground substance,collagen fibres (provide flexibility and tensile strength) and calcium phosphate crystal (provide hardness and compressive strength). SPECIALISED CELLS: osteoprogenitor cells:stem cells differentiate into osteoblasts. osteoblasts: bone building cells (produce + secrete collagen fibres and ground substance. osteoclasts: bone resorbing cells (break down matrix & release stored minerals). osteocytes: maintain matrix

COMPACT BONE: outer layer of bone. periosteum: covers compact bone, contains blood vessels & nerves, outer connective tissue membranes. Osseous tissue arranged into osteons. osteons: runs parallel to long axis of bone CONSISTS of: - central canal (contain blood vessel and nerves) - concentric circles (hollow cylinders of matrix) - osetocytes (lie between cylinders of matrix). ACTS: as a tiny weight bearing pillar (resists force applied to ends of bone

SPONGY BONE: internal layer of bone. endosteum: internal connective tissue membrane: covers spongy bone. osseous tissue arranged into irregular latice of thin needle like structures called trabeculae. trabeculae: orientated to resist forces from all direction and transfer weight without breaking. spongy bone lighter than compact: reduces weight of skeleton - in long bones, mainly found in the proximal and distal epiphysis

INTERSTITIAL GROWTH: bones lengthen - occurs at epiphyseal plates of long bones . 1. new cartilage (hyaline) forms at top of plate 2. bone replaces old cartilage at bottom of plate 3. diaphysis lenghthen

APPOSITIONAL GROWTH bone widens - occurs at outer surface of bone 1. osteoblasts beneath periosteum secrete layers of new matrix. eventually become compact bone and bone widens 2. LONG BONES: osteoclasts slowly remove old matrix from inner surface to enlarge medullary cavity and prevent bones from being heavy.

REGULATION: childhood bone growth controlled by growth hormone(GH), thyroid hormone (TH). - adolescence bone growth requires GH, TH, estrogen & testosterone. these hormones1. promote adolescent growth spurt 2. end growth (induce epiphyseal plate closure) - rate of bone formation exceed rate of cartilage formation - cartilage eventually replaced entirely by bone - epiphyseal plate becomes epiphyseal line.

BONE REMODELLING - throughout life - maintains bone strength and mass - old matrix replaced by new - bone resorption (osteoclasts: break old matrix) and bone deposition (osteoblasts: new matrix)

BONE GROWTH & REMODELLING FACTORS - adequate amt. of calcium, phosphate and Vit, C, A, D, K and B12. - weight bearing excercise (mechanical forces stimulate osetoblast -> new matrix -> bones: thicker, stronger, more resistant to fractures.

Fracture = break/ crack in a bone and can be a - closed (simple) fracture: broken bone doesn't break skin or open (compound): broken bone protrudes skin.

5 types: 1. comminuted: bone fragrements into 3 or more pieces 2. compression fracture: bone crushed 3. greenstick: incomplete break 4. spiral: ragged break due to excessive twisting 5. epiphyseal: bone breaks along epiphyseal plate 6. transverse: bone completely breaks across diaphysis 7. depressed: broken bone pressed inwards 8. avulsion: tendon or ligament pulls off fragment of bone 9. pathological: caused by disease that weakens bone structure 10. colles: break at distal end of radius 11. scaphoid: common carpal bone fracture 12. pott's: both tibia and fibula fracture.

TREATMENT. 1. reduction: realignment of bone ends 2. immobilisation of realigned bones 3. rehabilitation - restores functions

FRACTURE REPAIR: 1. haemotoma forms: -torn blood vessels haemorrhage - clot forms - site swollen + sore 2. fibrocartilaginous callus forms: - fibroblasts produce collage fibres - chondrocytes produce cartilage - fibrocartilaginous callus splints broken bone ends 3. bony callus forms: - fibrocartilaginous callus replaced by spongy bone - bone ends firmly united 4. bone remodelling: - compact bone replaces spongy bone at diaphysis - osteoclasts remove excess bone - bone returns to normal shape

STRUCTURALLY

FUNCTIONALLY

  1. Synarthrosis: immovable joint 2. amphiarthrosis: slighly moveable joint 3. diarthrosis: freely movable joint

1. fibrous: - fibrous connective tissue unites articulating bones - joint cavity absent - synarthrosis or amphiarthrosis 2. cartilaginous: cartilage (hyaline or fibrocartilage) unites articulating bones - joint cavity absent - synarthrosis or amphiarthrosis 3. synovial: articulating bone ends are covered in articular cartilage - joint cavity present - diarthrosis - wide range of body movements

1. articular capsule: - surrounds entire joint and encloses joint cavity. - two layers: - tough outer fibrous layer (stabilises articulating bones) - inner synovial membrane (produces synovial fluid) 2. joint cavity: -separates articulating bones and contains synovial fluid 3. synovial fluid: - shock absorption - reduces friction - supplies O2 and nutrients to articular cartilage cells (chondrocytes) and removes waste.4. articular cartilage: - covers ends of each articulating bone - shock absorption - reduces friction 5. reinforcing ligaments: - stabilise joint 6. sensory neurons and blood vessels: detect pain and monitor proprioception - blood vessels mainly supply synovial membrane

ADDITIONAL STRUCTURES. 1. menisci: discs of fibrocartilage - stabilse joint -reduce friction - shock absorption 2. muscle tendons - stabilise joint 3. bursae and tendon sheaths: - bags of synovial fluid - reduce friction between adjacent joint structures 4. fat pads: - mass of adipose tissue - cushion and protect joint structures

:

1. pivot joint allows rotation. eg: proximal radioulnar2. plane joint: allows gliding movement. eg: intercarpal joints 3. condylar joint allows flexion, extension, adduction, abduction and circumduction. eg: wrist joint 4. saddle joint allows flexion, extension, adduction, abduction and circumduction. eg: carpometacarpal joint of thumb5. hinge joint allows flexion and extension. eg: elbow joint 6. ball & socket joint allows flexion, extension, adduction, abduction and circumduction & rotation. eg: shoulder joints

composed of muscle cells (fibres), connective tissue, blood vessels and nerves

MUSCLE FIBRES: surrounded by connective tissue sheaths(membranes) 1. endomysium: surrounds each individual muscle fibre 2. perimysium: surround a bundle (fascicle) of muscle fibres 3. epimysium: surrounds entire skeletal muscle

myofibrils: - extend the entire length of muscle fibre - composed of contractile units:sarcomere sarcomeres: composed of contractile protein called thick & thin myofilaments . thick & thin myofilament: thick: composed of myosin protein. thin: composed of actin protein

SNS stimulates skeletal muscle contraction (innervated by lower motor neurons) - axon terminal of lower motor neurons form a synapse called a neuromuscular junction with a muscle fibre

EVENTS: 1. somatic motor output in form of action potential travels along axon of lower motor neuron to axon terminals 2. voltage gated Ca2+ channels open and Ca2+ enters the axon terminal 3. Ca2+ entry causes synaptic vessels to release ACh into synaptic cleft 4. ACh diffuses across synaptic cleft and binds to chemically gated ion channels (receptors) on the sarcolemma.5. Ion channels open -. influx of Na+ ions: sarcolemma depolarises - graded potential produced 6. graded potential opens voltage-gated Na+ channels in the sarcolemma -> action potential produced 7. action potential travels along length of sarcolemma 8. action potentials travels down T tubules deep into muscle fibre 9. action potential stimulates sacroplasmic recticulum Ca2+ release channels to open 10. Ca2+ flows into the cytoplasm of the msucle fibre. 11. Ca2+ binds to troponin and removes tropomyosin from the active sites on actin 12. Myosin heads bind to the active sites and contrction begins.

PROCESS: 1. myosin heads bind to actin active sites on thin myofilaments 2. myosin heads pull the thin myofilament towards the centre of the sacromere (M-line) and then detach 3. cycle repeats myosin heads bind to next actin active sites on the thin myofilament 4. myosin heads pull thin myofilament further towards the M-line and then detach.