Musculoskeletal system

Musculoskeletal system

1. Joints

   • Connection between 2 or more bones
     • Irrespective of whether movement occurs between the bones
   • Synovial joints
     • Plane joints
       • e.g. acromioclavical joint
       • Articular surfaces are flat
       • Joint capsules are tight
       • Sliding movements in planes of articular surfaces
     • Hinge joints
       • e.g. elbow joint
       • Permits flexion and extension only
     • Saddle joints
       • e.g. carpometacarpal joint of thumb
       • Articular surfaces are convex and concave
       • 2 axes of movement
       • Permits flexion, extension, abduction, adduction and circumduction
     • Condyloid joints
       • Similar to saddle joints
       • Movement in 2 axes, but one is usually restricted
       • Permits flexion, extension, abduction, adduction and circumduction
       • e.g. metacarpophalageal joints of fingers
     • Ball and socket joints
       • e.g. hip joint
       • Spherical and concave articular surfaces
       • Multiple axes of movement
       • Permits flexion, extension, abduction, adduction, circumduction and rotation
     • Pivot joints
       • e.g. atlanto-axial joint of cervical spine
       • Rotation around a central axis
     • Bones united by joint capsule enclosing a joint cavity
       • Joint capsule = outer fibrous layer and inner serous synovial membrane
       • Joint cavity = potential space containing lubricating synovial fluid
       • Bones are covered by hyaline cartilage
     • Allow free movement between the bones they join
     • Majority of limb joints are synovial
   • Fibrous joints
     • Bones are united by fibrous tissue
     • There is no joint cavity
     • Amount of movement depends on length of the fibres
     • e.g. sutures of cranium
       • Fibrous joints with essentially no movement betwene them
     • e.g. interosseus membrane between radius and ulna of forearm
       • A partially moveable fibrous joint
   • Cartilaginous joints
     • Bone united by cartilage
     • Primary
       • Bones united solely by hyaline cartilage
         • Provides some flexibility
       • e.g. attachment of ribs to sternum
     • Secondary
       • Bones are covered with a layer of hyaline cartilage
         • Then united by fibrocartilage
           • This provides strength
       • e.g. joints between vertebral bodies
   • The knee joint
     • Most complex joint
     • Synovial hinge joint
       • Articulations between lateral and medial condyles of the distal femur, the later and medial condyles of the tibia and patella
         • Due to forces placed through the knee joint during weight bearing activity, articulating surfaces need protection
           • Medial and lateral menisci
             • Made of fibrocartilage and hyaline cartilage
               • Fibrocartilage helps with shock absorption
               • Hylaine cartilage covers articulating surfaces to allow smooth movements
       • External support is required to prevent injury to articular capsule and internal structures
         • Each side of knee = strong ligaments
           • Lateral and medial collateral ligaments
           • Bands of fibrous connective tissue
           • Stabilise the femur and tibia in the coronal plane
             • When a lateral force is applied, the knee joint does not open out excessively
             • A lateral force applied to the knee will open out the medial angle and strain/tear the Medial Collateral Ligament
             • A medial force applied to the knee will open out the lateral angle and strain/tear the Lateral Collateral Ligament
         • 2 further ligaments that prevent excessive movements in the sagittal plane
           • ACL
             • Anterior cruciate ligament
             • Attaches the posterior aspect of the lateral condyle of the femur and to the anterior part of the tibial plateau
             • Because of its position, it prevents excessive forward movements of the tibia in relation to the femur
           • PCL
             • Posterior cruciate ligament
             • Arises from the posterior tibial plateau and attaches to the anterior part of the medial condyle of the femur
             • Prevents excessive movements of the femur anteriorly in relation to the tibia
           • Mechanisms of injury
             • ACL - Excessive twisting / anterior movement of tibia when fully weight bearing
             • PCL - Excessive forward movement of the femur on the tibia (usually when flexed)

2. Muscles

   • Cardiac muscle
     • Makes up heart
     • Has unique histological and physiological features
     • Fibres
       • Striated
       • Tubular
       • Branched
       • Uninucleated
     • Has involuntary action
   • Smooth muscle
     • Involuntary functions
       • Digestion
       • Blood pressure control
       • Micturition
       • Temperature control
     • Occurs widely throughout body
       • Walls of hollow organs
       • Bowel
       • Bladder
       • Uterus
       • Blood vessels
       • Skin
     • Controlled by autonomic nervous system
     • Narrow, tapered rod-shaped cells
     • Non-striated, uninucleated fibres
   • Skeletal muscle
     • Under voluntary control
     • Function = to move skeleton for locomotion, feeding etc.
     • Has 2 or more attachments to bony skeleton
       • Usually at least 1 joint between attachments
     • Contraction of the muscle will pull attachments closer together and cause a movement at the joint
       • Muscle attachment that moves the least = the ORIGIN of the muscle
         • The origin has quite a small area of fusion to the bone
         • Made of very strong tendon
           • This widens out into the belly of the muscle
             • A second tendon forms to carry the contractile force to the insertion
       • Attachment that moves the most = the INSERTION
     • Muscle fibres themselves do not attach to bone - there is always an intervening tendon
     • Types of muscle
       • Fusiform
         • Biceps brachii
       • Parallel
         • Rectus abdominis
       • Convergent
         • Pectoralis
       • Unipennate
         • Palmar interosseous
       • Bipennate
         • Rectus femoris
       • Multipennate
         • Deltoid
       • Circular
         • Orbicularis