The Musculoskeletal System PDF

The Musculoskeletal System By Nigel Henderson 1 Musculoskeletal System Often seen as one system but actually made up from two systems: The Skeletal System The Muscular System The Skeletal System Two types of...

The Musculoskeletal System By Nigel Henderson 1 Musculoskeletal System Often seen as one system but actually made up from two systems: The Skeletal System The Muscular System The Skeletal System Two types of bone tissue found which constitute the Skeleton or Bony Framework of the body Compact bone and Cancellous bone has been identified as the hardest connective tissue of the body Bone tissue consists of microscopic systems Called Haversian Systems 2 Haversian System Each system consists of: Haversian Canal Central canal through which blood and lymph vessels along with nerves pass Lamellae Concentric plates of bone Lacunae Small inter lamellae spaces containing lymph and bone cells, osteocytes Canaliculi Small channels radiating from Haversian canal to lacunae containing lymph for nourishment of osteocytes Interstitial Lamellae Fills spaces between each Haversian system 3 4 Bone Compact bone differs from cancellous bone in its density Haversian systems not found in Cancellous bone Osteocytes in small numbers form trabeculae giving a sponge like appearance Red Bone Marrow is always present within cancellous bone Fills the spaces between the trabeculae In children all marrow is red Erythrocytes, leucocytes and thrombocytes all manufactured within red marrow Yellow Bone Marrow found in adult long bones Outer surface of bone covered with Periosteum: Outer protective covering Provides attachment for muscle tendons Gives attachment for ligaments Deeper layers possess Osteoblasts (deposit new bone material) Periosteum not found on surface of bones which form moveable joints Replaced with Hyaline Cartilage 5 Bone Bone develops from: Cartilage – long and irregular bones (Long Bones possess Diaphysis, Medullary Canal, Two epiphyses Irregular Bones compact bone surrounding cancellous bone and red marrow) Membranes – flat bones Tendons – sesamoid bones All above tissue become bone following conversion by osteoblasts called ossification Osteoblasts become osteocytes when established within lacunae 6 Typical Long Bone 7 Bone Osteoclasts reabsorb bone and are responsible for: shape maintenance of growing bone formation of medullary canal (within shaft of long bones) forms sinuses in face and skull In fetal life ossification of bone commences in primary centre of diaphysis or shaft Secondary centres occurs in epiphyses or extremities Epiphyseal cartilage responsible for increasing length, epiphyseal discs Consider repair and growth 8 Functions of Skeletal System Supportive framework Boundary forming (Cranial, Thoracic and Pelvic) Protective Joint formation for movement Attachment provision for muscles Blood cell formation in cancellous bone (Red Marrow) Storage facility for calcium salts 9 Axial Skeleton Consists of Skull Vertebral Column Ribs Sternum 10 Axial Skeleton 11 Appendicular Skeleton Consists of Shoulder girdle Pelvic girdle The appendages (upper and lower limbs) 12 Appendicular Skeleton 13  Fontanelles Joints of skull immovable and joined by sutures At birth not complete Consider advantages! Anterior and posterior Fontanelles consist of membranes Ossification occurs at 12-18 months and 2-3 months respectively 14 Fontanelles 15 Joints Fibrous or Fixed Skull sutures Cartilaginous Slightly moveable Examples include vertebrae Synovial Freely moveable Characterised by synovial membrane and fluid Ball and socket shoulder and hip Hinge elbow and knee Gliding carpal and tarsal bones Pivot proximal and distal radioulnar joints Condyloid and Saddle wrist joint 16 17 Movements Flexion bending forward and occasionally backward e.g. knee Extension straightening or bending backwards Abduction moving away from midline of body Adduction moving towards midline of body Rotation movement round long axis of bone Pronation turning palm of hand downwards Supination turning palm of hand upwards Circumduction combination of flexion, extension, abduction and adduction Inversion turning sole of foot inwards Eversion turning sole of foot outwards 18  Muscular System All movements of the skeletal system require form of mechanism to facilitate such movement. Muscular Tissue provides movement All consist of elongated cells Several types noted: Cardiac – Highly specialised, non-voluntary Striated, Striped skeletal or Voluntary Muscle Very powerful Smooth, Unstriped, Visceral or Involuntary. Not under voluntary control e.g. Vascular muscles Primary function of skeletal muscle is movement Soft Tissue movement generated by skeletal muscle Muscles allow maintenance of posture Other Role includes Heat production 25% of chemical energy only utilised for movement 75% for heat production Skeletal muscle accounts for 40-50% of Body weight 19 Muscular System Muscles do not act in isolation More than one required for movement. Such groups have integrated function Grouped into: Prime movers: initiate and maintain movement Antagonists: resists and acts in reverse of prime movers. Also decelerating movement Synergistic muscles: important where movement is variable, cancels out unwanted movements 20 Muscular System Muscles attached in two ways to bones: Origin, Relatively fixed and non moving The insertion, moves in response to contraction Attachment is via tendons Consists of white fibrous tissue also contains collagen fibres, prevents stretching Damage difficult to repair compounded by lack of blood system Muscles surrounded by connective fibrous tissue Epimysium – allows sliding over surrounding structures Perimysium - surrounds fibre bundles Endomysium – covers each fibre or muscle cell These collectively form the supporting structure 21 22 The Muscular System Sarcomeres Smallest Functional unit of the muscle Contains thin and thick filaments (myofilaments) Muscle contraction sees the thin filaments getting shorter causing the them to “slide” over the thick filaments hence shortening of filament and hence the muscle contraction Consider cross bridge and ratchet type movements between thick and thin filaments 23 24 25 Muscular System Due to elasticity also transmit force of contraction to bone, act like a spring Nerves supply each muscle Sensory Motor Sensory terminate in proprioceptors Relay information on movement and body positioning Some sensory fibres are free nerve endings Relay noxious stimuli Contraction of skeletal muscle is voluntary Nerves to muscle leave spinal column and terminate in a neuromuscular junction or muscle end plate 26 Muscular System Contraction of skeletal muscle is voluntary Nerves to muscle leave spinal column and terminate in a neuromuscular junction or muscle end plate 27 28 Summary The Musculoskeletal system made up of two systems Function together for movement and protection to be given to the body and other organs Numerous additional functions seen within both systems Functional unit of bone is the osteocytes found within Haversian systems Functional unit of the muscle is the sarcomere Seen as one system since one cannot exist and function without the other 29