Joint and Muscle Structure and Function Flashcards
Synarthroses
Reinforced by combo of fibrous and cartilaginous connective tissues
Permit slight to no mvt
More for stability than mobility
Allows forces to be dispersed across relatively large area of contact, thereby reducing injury
Bind to bones together and transmit force from one bone to the next w/ min jt motion
Fibrous Joint
Synarthrodial joint
More for stability than mobility
Dense CT, not a lot of mvt
Ex: sutures of skull, distal tibiofibular joint, interosseous membrane
Cartilaginous Joint
Synarthrodial joint
More for stability than mobility
Fibrocartilage, hyaline cartilage
A little bit of mvt
Ex: intervertebral discs, pubis symphysis
Diarthroses
Possess synovial fluid-filled cavity
Permit moderate to extensive mvt
Ex: GH, facet, tibiofemoral, taloacrual
Synovial Joint Elements (ALWAYS)
Synovial fluid
Synovial membrane
Articular Cartilage
Joint Capsule
Blood vessels
Nerve endings
Ligaments
Synovial Joint Elements (SOMETIMES)
Fat pad
Mensci
Bursa
Labrum
Synovial plicae
Diarthrodial Subclasses (Uniaxial)
1 DOF
Hinge - elbow
Pivot - humeroulnar/radial
Diarthrodial Subclasses (Biaxial)
2 DOF
Condyloid Joint
Biaxial
Shaped so that concave surface of one bony component is allowed to slide over convex surface of another component in two directions (concave surface is more shallow)
3rd DOF is restricted by ligaments
Ex: MCP joints, tibiofemoral joints
Ellipsoid Joint
Biaxial
Convex elongated surface in one direction that is matched on concave side (deeper concavity medially and laterally)
No rotation
Ex: radiocarpal
Saddle Joint
Biaxial
Each side of saddle joint has two surfaces, one convex and one concave
M/L - convex; A/P - concave
Ex: CMC joint
Diarthrodial Subclasses (Triaxial)
3 DOF
Ball-and-socket
Plane - can have multiple mvts (SC joint)
Connective Tissue Makes Up…
Ligament
Tendon
Bone
Capsule
Articular and fibrocartilage
Connective Tissue Has…
Cells
Extracellular matrix (ECM) - fibrous proteins and ground substance
Connective Tissue Cells
Fibroblast - basic cell of most CT (ligaments, tendons, other periarticular CT)
Chondrocytes - hyaline and fibrocartilage
Tenocytes - tendon
Osteocytes - Bone
Manufacture and secretes ECM
Connective Tissue ECM
Part of CT outside of cells
Determines tissue function
Fibrous proteins and ground substance
ECM (Fibrous Component)
Contains 2 major classes of proteins: collagen and elastin
Collagen
ECM fibrous component
Most abundant protein in body
Strength similar to steel (tensile strength)
Responsible for integrity of tissue and response to forces
Collagen Types
Type I - tendons, ligaments, fibrocartilage, jt capsules (stiff, strong, little elongation, good for binding/supporting b/w 2 bones)
Type II - cartilage and intervertebral discs (thinner, less tensile strength, maintains shape of complex structures in body)
Elastin
ECM fibrous component
Uncoils when stretched
Found in all jt structures
Make up smaller component of ECM than collagen
Found in structures that require more “give”
Ex: aorta, ligamentum nuchae
ECM Ground Substance
Non-fibrous component
Fibrous proteins embedded in ground substances
Composes of: glucosaminoglycans (GAG’s), water, solutes
Types of Connective Tissues
Dense CT (ligaments, external layer of jt capsule, tendons)
Articular cartilage (hyaline cartilage)
Fibrocartilage (mensci, labra, discs)
Dense Connective Tissue
High in Type 1 collagen
Limited blood supply
Irregular (capsule) and regular (ligament/tendon) classification
Regular CT - tissue fibers are aligned in one direction b/c they resist forces in one direction
Irregular CT - withstand multiple directions of mvt
Ligaments
Dense CT
Attach bone to bone
Small amounts of cells, large ECM
Mainly Type I collagen
Densely packed, arranged in direction of tensile force
Arrangement of fibers allows for mobility and stability
Stiffen as it approaches bone (common site for degeneration)
Tendons
Dense CT
Bone muscle to bone
Small amount of cells, large ECM
Primarily Type I collagen (adapted to larger tensile forces)
Collagen fibrils bundle (larger bundle, larger tensile force is can handle)
Cartilage
Composition
- Small number of cells (chondrocytes)
- Solid matrix of collagen and proteoglycans
- Water
Types
- Elastin (ears)
- Fibro- (intervertebral discs, labra, TMJ disc, mensci)
- Hyaline/articular (covers synovial jt surfaces)
Articular Cartilage
Distributes load every over surface (disperse forces)
Provide shock absorption
Reduce friction
Lacks perichondrium (covers most cartilage that supplies blood supply) - limited blood supply, limited ability to self-repair after damage
Line each joint
Bone Structure
Nonhomogenous (not uniform in structure throughout)
Compact - outer layer - hard, dense, provide structure
Cancellous - inner layer - spongy, not as dense (trabecular bone)
Bone Composition
Organic material - mostly collagen (Type 1)
Water
Inorganic (minerals) - most
Forces on MS System
3 primary types of forces (loads): tension, compression, shear
Combo of 2: bending, torsion
Shear Force
Translators force (mid-shaft skier)
Bending
One side is distracted and one side is compressed
Bones do better under bending than shearing forces
Stress
Force (internal resistance) per cross-sectional unit of material (F/A)
Ex: finger vs. palm
Strain
Percentage of change in length or cross-section of structure
Change from original point to final point
Load Deformation Curve
Elastic region
Plastic region
Ultimate failure point
Elastic Region
Between A and B
Structure will return to normal once load is removed
Function in this region all the time
Plastic Region
Beyond elastic region
Will not immediately return but may with time
Beyond functional stress
Continue to pull, won’t return to original length
Deformation is permanent
Ultimate Failure Point
After C
Force exceeds strength of tissue/ligament - tears
Stress-Strain Curve
Elastic region - when force is releases there is no permanent change (deformation) in shape
Yield point - transition point b/w elastic and plastic region
Plastic region - increasing in strain w/ little change in stress, force results in permanent deformation
Ultimate failure point - final rupture of material
Viscoelasticity
Combo of elasticity and viscosity
Elasticity is structure’s ability to return to original length or shape
Viscous materials is resistant to flow
High viscosity tissue has high resistance to deformation (honey), less viscous deforms easily (water)
Creep
Force remains constant, length changes over time (continued deformation of material over time with constant load)
Ex: textbook
Stress-Relaxation
Force decreases over time, length remains the same
Muscle Structure
Belly - group of fascicles
Fascicle - group of fibers
Fibers - group of myofibrils
Myofibril - group of myofilaments
Myofilaments - made up of contractile proteins (action/myosin)
Muscle Morphology
Shape of muscle causes function and force production
Fusiform
Fibers run parallel to one another and to central tendon
Ex: biceps
Pennate
Fibers that approach their central tendon obliquely
Most muscles
Generate large force
Unipennate, bipennate, multipennate
Physiologic Cross-Sectional Area
Reflects amount of active proteins available to generate contraction of force
Maximal force potential is proportional to sum of cross-sectional area of all its fibers
Thicker muscle generates more force
Total amount of active proteins that performs contraction force
Increases in area - greater force - more active proteins are present to generate force
Pennation Angle
Angle of orientation b/w fibers and tendon
If parallel - angle is 0 degrees (all force transmitted to tendon)
If greater than 0 (oblique) - less of the force is transmitted to the tendon (more fibers in a given length of muscle - more cross-sectional area)
Passive Length Tension
Stretching whole muscle elongates both parallel and series elastic components generating springlike resistance
Resistance back from stretched muscle
Ex: hamstrings
Critical length - max stretch
Tension going to increase if stretch increases
Created by non-contractile forces
Serves to move or stabilize (stretched muscle stores part of energy created by end of stretch and can be used when muscle is contracted)
Active Length Tension
Active force generation depends on instantaneous length of muscle
Sarcomere lengthening/shorting from resting length decreases number of cross bridges and thus force generation
At resting length, max force (allows greatest # of cross-bridge attachments)
Total Length-Tension Curve
Below resting length: total force = active force
Passed resting length
- Total force increases b/c passive and active tension sum
- Most of tension is passive
Types of Contraction
Concentric - muscle contracts, internal torque exceeds external torque
Eccentric - muscle lengthens, external torque exceed internal torque
Isometric - length of muscle unchanged, internal and external forces matched
Velocity and Contraction
Concentric - force prod. is inversely proportional to velocity of muscle shortening (faster you go, less force you are able to produce)
Eccentric - force prod. is directly proportional to velocity of muscle lengthening (generate more force when going fast - don’t function in top left because body is protecting us from getting injured)
Isometric - generate more force than concentric
Power and Work
Power - rate of work; product force and contraction velocity (power = force x velocity)
Concentric = positive work (power generation)
Eccentric = negative work (power absorption)
Factors Influencing Force Production
Muscle size (PCSA)
Muscle moment arm
Stretch of muscle
Velocity
Level of muscle fiber recruitment
Motor unit types composing muscle
Passive Insufficiency
Inability to move through entire available range b/c of passive restrictions from opposing soft tissue
Ex: hamstring on stretch
Active Insufficiency
Inability of a muscle to shorten enough to pull limb through it’s complete ROM
Muscle can’t pull through normal ROM
Ex: on stomach, hip ext., bend knee, can’t generate more force b/c hamstrings are short
Task Analysis using Biomechanical Model
Phases of mvt - break down mvt
Joint motion/sequencing - how much joints are moving
Muscle activity - primer movers, concentric, eccentric
Alignment - how someone does a certain mvt
Hypothesis generation - what causes what
- Stability vs. mobility
- Follow up testing vs. confirmation from examination findings
Task Analysis using a Headman Model
Doesn’t break down to phases
Look at mvt as whole
Starting posture, environment context?
Initial conditions - preparation - limitations - execution - termination - outcomes
