Archeology, muscles and simple biomechanics Flashcards
Arthrology
Study of joints:
Anatomy
Functions
Dysfunction/disease
Treatment
What are joints?
Where 2 or more bones or cartilage and bone meet.
Function
- flexibility movement
- attachment between bones
Joint categories and 3 main types
- synovial joint- separated by a cavity
- solid/fixed- bones held together by connective tissue
- fibrous joints
- cartilaginous
- synovial
Connective tissue: skeletal muscle
Movement and joint stabilisation
Connective tissue: fibrous tissue
Forms joint capsule, muscle fascia and tendons
Connective tissue: Tendon
Continuation of muscle into bone, transmission of forces
Connective tissue: Ligament
Binds bones together for stability
Connective tissue: Cartilage
3 types
Hyaline
Fibrocartilage
Elastic
Function
- provide support and strength
- development growth of bones
- smooth, reduced friction surface at joints
Hyaline cartilage
Groups of chondrocytes in a solid/dense matrix
- found on end of long bones in synovial/cartilaginous joint
- forms part of the trachea, larynx and bronchi
- it keeps the airway open
Fibrocartilage
Dense groups of inelstic collagen fibres interspersed with chondrocytes
- tough slightly flexible
Found in
- intervertebral disc
- Meniscus of the knee
- rim of shoulder/ hip joint
Elastic Fibrocartilage
Not associated with joints
Chondrocytes lie within solid matrix of elastic fibres
- flexible tissue providing shape/ support
Found in
- pinna (ear love)
- epiglottis
- Tunica media of blood vessels
Solid joints
Bones are connected by either:
Dense fibrous connective tissue
Cartilage (mainly fibrocartilage)
Function predominantly for strength/support
Movement much more restricted than synovial joints
Fibrous joints
Syn-arthro-ses; together-joint-movement
Allow virtually no movement
Bones joined by strong fibrous tissue
3 Types of fibrous joints:
Sutures;
Gomphoses;
Syndesmoses;
Sutures
Only occur in the skull
Individual skull vault bones linked by strong connective tissue called sutural ligaments (sharpey’s fibres)
Interlocking ‘teeth’ give added strength
Wider in young children resulting in ‘soft spots called fontanelles which fuse in first year
allow minimal movement and changing shape of skull until age of approximately 20; birth and growth
becoming more fixed and immoveable and fuse by 6th decade
gomphoses
Occur between the teeth (not bone) and mandible bone
Short collagen fibres in periodontal ligament join the tooth root and bone socket in mandible
very minimal movement; over time
syndesmoses
variable but minimal movement
Bones Held together by interosseous ligament/ membrane
Examples include:
distal tibia/fibula
Distal radius/ulna
Ligamentum flavum in spine
Cartilaginous joints
Virtually no / minimal movement
Bones joined by layer of cartilage (fibro- or hyaline cartilage)
Permanent joints all in midline
2 types of cartilaginous joints:
Primary: Synchondrosis
Secondary: Symphysis
synchondroses
Connected by hyaline cartilage
No/very minimal movement
Examples include
Permanent:
sterno-costal joint of 1st rib
Sacro-coccygeal joint
Temporary:
between metaphysis and physeal plates of a growing long bone (no movement)
Physeal (growth plates)
Classed as primary synchondroses – joined by hyaline cartilage
Joint between:
Metaphysis/diaphysis and epiphysis of long bone
primary and secondary ossification centres
No movement
Allows increase in bone length; endochondral ossification
Fuses with skeletal maturity
Physeal (growth plates) zones
Reserve/germinal zone: resting daughter chondrocyte cells next to epiphysis
Proliferative zone: undergo rapid mitosis controlled by growth hormone
Hypertrophic zone: chondrocytes enlarge by taking on glycogen, lipids, and alkaline phosphatase
Provisional zone of calcification/ossification: chondrocytes apoptose (die) and calcify
Zone of ossification: osteoblasts/clasts in metaphysis replace calcification with bone
symphyses
Variable (but fairly minimal) movement
Ends of Bones covered in hyaline cartilage
joined by fibrocartilage disc
strengthened by surrounding ligaments
Occur in midline
Examples include:
intervertebral discs between vertebrae in spine
symphysis pubis in pelvis
Intervertebral discs
Inferior / superior endplates of vertebrae covered by thin layer of hyaline cartilage
Joined by fibrocartilage disc
connected to vertebrae though strong fine collagen fibres (sharpey’s fibres)
Compressible and strong
Roles include:
Shock absorber
hold vertebrae together
Permits minimal movement (rotation/flexion/extension/sideways bending)
Increase in size from superior to inferior
Intervertebral discs: Fibrocartilage disc formed of:
Anulus fibrosis:
outer fibrocartilage and collagen ring
arranged in lamellar (onion skin) layeRS
Nucleus pulposis:
gelatinous centre
Dehydrates and shrinks as we age
Synovial joints
Main classification of joints; where most movement occurs
Movement varies according to type of synovial joint
Highly specialised according to required function
Basic structure includes:
End of bones covered by protective layer of articular (hyaline) cartilage
Space in between layers of cartilage filled with synovial fluid
Bones joined by Surrounding fibrous capsule continuous with periosteum
Capsule lined by synovial membrane which secretes lubricating fluid
Synovial joint components: Main features + Accessory structures
Main features
Joint cavity
Two bones
Hyaline cartilage
Joint capsule
Synovial membrane
Fibrous capsule
Synovial fluid
Accessory structures
Menisci (articular discs)
Fat pads
Bursae
Synovial sheaths
Tendons / muscles
Ligaments
Sesamoid bones
Bones / Hyaline cartilage
Two opposing bones covered by hyaline (articular cartilage)
Prevent bone-on-bone contact
Protection and reduced friction
Normally not seen on X-ray (joint space)
Thickness dependent on forces acting on joint
Thinning caused by arthritis
Synovial membrane
Lines inner part of joint capsule enclosing joint cavity between edges of hyaline cartilage
Does not cover articulating surfaces (i.e. where cartilage present)
Pink (highly vascular) Smooth, slippery membrane
Produces synovial fluid
Helps to remove debris from joint as derived from monocyte cells
Also found in outside joints in synovial sheaths and bursae
Synovial fluid
Viscous fluid produced by synovial membrane
Components include:
Hyaluronic acid
Lubricin
Proteinases / collagenases
Phagocytic cells
Similar in consistency to egg white
Fills joint cavities within synovial membrane and forms very thin layer between articular cartilages
Roles include:
Friction reduction
Shock absorption; becomes more viscous the more pressure it undergoes (opposite of ketchup!)
Nutrient/waste diffusion to cartilage (avascular)
Removal of microbes / particles debris from degeneration of cartilage
Fibrous capsule
Dense fibrous connective tissue external to synovial membrane
Enclose all intra-articular aspects of a joint
Blends with periosteum in articulating bones
Perforated by nerves / blood vessels
Parts may be thickened to form stabilising ligaments (further supported by ligaments outside of capsule)
Menisci (articular discs)
Fibrocartilage discs within larger joints; knee
Intra-capsular (articular) structures
Roles include:
Increase concavity / joint surface of articulating bones (stability)
Additional shock absorption
Provide additional support on certain movements (increase range)
May be prone to injury
Bursae / synovial sheaths
Occur at sites and of most friction between extra-articular structures such as:
Tendon / bone
Muscle / bone
Ligament / bone
Skin / bone
Closed sack of synovial membrane: bursa (bursae)
Length of synovial membrane surrounding tendon: tendon sheath
Normally contain minimal synovial fluid (except if inflamed - bursitis)
Sesamoid bones
Form within tendon (or muscle) at site of stress (or normal variant)
Improves mechanical efficiency to transmit force by acting as a fulcrum /pulley for tendons to slide over
Stability of synovial joints
Bony articulations inherently unstable; articular surfaces a minor component in joint strength
Ligaments:
Add to strength of fibrous capsule
More ligaments, more stability
Minimal elasticity; prone to tearing under severe strain
Muscles/tendons:
Muscle tone most important to joint stability (continuous passive partial contraction)
Maintains posture and alignment
Muscle groups work in combination
Important part of physiotherapy/rehabilitation in trauma/disease
Basic biomechanics
Mechanics is the study of forces and their effects
Biomechanics relates mechanics in living things; in particular the msk system
Lever; bones
Pivot/fulcrum; joints (and the supporting ligaments)
Force; muscles
Resistance; weight of body/force applied or opposing muscles
Lever systems 1,2, or 3 dependent on the position of the pivot in relation to the force/resistance
Basic biomechanics
Almost no 2nd lever systems in body (tmJ)
Most combination of 1st/3rd lever systems working together
3rd lever systems most common to flex joint
Longer the lever arm (pivot to resistance), larger the force required to counter
Muscle insertions close to joint allow more control but more force to move lever
Types of synovial joint
Type determined by structure and Range of movements:
Condylar / ellipsoid
Plane / gliding
Hinge
Ball and socket
Saddle
Pivot
Almost all synovial joints allow more than one axis of movement (maybe small); some overlap between types
Movement definitions
Abduction – movement away from the midline
Adduction – movement towards the midline
Rotation – turning around an axis
Circumduction – circular movement around a joint (combination of the above)
FLEXION - reducing angle of joint (bending)
EXTENSION - increasing angle at a joint (extending)
SUPINATION – turning upwards (towards NAP)
PRONATION – turning downwards (away from NAP)
INVERSION – turning the sole of the foot medially
Eversion – turning the sole of the foot laterally
Synovial condylar/ellipsoid joint
biaxial; movement in two directions/axes at right angles
Rounded (condyloid) surface sites within cup-shaped (concave) surface
Varies but may include all directions
Examples include:
wrist joint (radio-carpal)
Metacarpo-phalangeal joints (MCPJ)
Metatarso-phalangeal joints (MTPJ)
Temporo-mandibular joint (TMJ)
Synovial ball and socket joints
multiaxial; movement in more than two directions/axes
Ball (head) of one bone sits within deep socket of other bone
Similar to condylar but deeper and wider range of movement
Allows flexion, extension abduction, adduction, rotation, and circumduction
Examples include:
Hip joint
Shoulder joint
Synovial saddle joint
biaxial; movement in two directions/axes
Allows flexion, extension abduction, adduction, and rotation
Articular surfaces like person sitting on a saddle
Similar to condyloid joint
Examples include:
Ankle joint
Sterno-clavicular joint (SCJ)
Thumb carpo-metacarpal joint (cmcJ)
Synovial plane/gliding joint
Uniaxial; movement in one direction/axis
Articular surface flat/slightly curved
Allows gliding only
Least movement of all synovial joints
Often Work in groups (eg foot, spine)
Examples include:
Sacro-iliac joint (SIJ)
Proximal tibio-fibular joint
Acromio-clavicular joint (acj)
Inter - Carpal / tarsal joints
Vertebral facet joints
Synovial pivot joint
uniaxial; movement in one direction/axis
Allows rotation only
Long process on one bone sits within hole/arch of other bone/ligament
Examples include:
Proximal radio-ulna joint
Distal radio-ulna joint
Synovial hinge joint
Uniaxial; movement in one direction/axis
Allows flexion / extension
Articular surfaces fit like door hinge
Examples include:
Elbow joint
Inter-phalangeal joints
Joint Abnormalities
Disruption of normal joint articulation:
Dislocation; complete loss of apposition of joint surfaces
Subluxation; partial loss of apposition of joint surfaces (partial dislocation)
Diastasis; widening (pulling apart of joint surfaces)
Unable to see underlying soft tissue damage on X-ray (remember where the strength is)
Fracture-dislocation when both fracture and dislocation present
Need for two-views for true assessment
