10-9b Joint Structure, Function, and Mechanobiology Flashcards
two ways joints are classified
movement potential
mechanical analogy
what are the characteristics of synarthrosis and diarthrosis joints? What are the types of each?
Synarthrosis: small movement potential strong dense tissue support fibrous or cartilaginous Diarthrosis/synoavial joints: moderate to extensive movement potential
List the seven elements contained in all synovial joints
Articular cartilage
- Joint capsule
- Synovial membrane
- Synovial fluid
- Ligaments
- Blood vessels
- Sensory nerves
List the other support elements contained in some synovial joints
Intra-articular discs or menisci Peripheral labrum Fat pads Bursae Synovial Plica
What are the two ways we describe joints based on movement potential?
synarthroses
diarthroses
What are the two types of synarthrosis joints?
fibrous
cartilaginous
What is a fibrous joint? Example?
skull
interosseous membrane between radius and ulna (called syndesmosis)
strong tissue with dense collagen that prevents bones from being pulled apart
designed to disperse force
What is a fibrous joint? Example?
ex: skull, interosseous membrane between radius and ulna (called syndesmosis)
strong tissue with dense collagen that prevents bones from being pulled apart
designed to disperse force
What is a cartilagenous joint? Examples?
ex: pubic symphysis, intervertebral discs
stabilized by flexible fibrocartilage or hyaline cartilage
allow very little movement
What is the function of synarthrodial joints?
transfer forces between the bones
What is articular cartilage?
Cartilage that covers the articular surface of the bone
What is articular cartilage? What is an analogy for it? Is vascularized? innervated?
Cartilage that covers the articular surface of the bone (shiny)
cap of low-friction paint painted on end of bone
stiff
there to protect the end of the bone against forces
no vascularization or innervation
what is arthritis
when the articular cartilage starts “chipping,” “cracking,” etc.
OA
What is a joint capsule? What are its two layers?
two layers:
dense, fibrous outer layer/envelope
synovial membrane
Describe the synovial membrane:
cell layers? what do the cells secrete? analogy?
3-10 cell layers thick highly specialized cells that secrete synovial fluid folded syran wrap inside the joint pain generator: highly innervated
Describe the synovial membrane:
cell layers? what do the cells secrete? analogy? innervation? What does movement do to it?
3-10 cell layers thick highly specialized cells that secrete synovial fluid folded syran wrap inside the joint pain generator: highly innervated releases synovial fluid
Is the joint capsule innervated?
yes, stretch receptors
Is the joint capsule innervated?
yes, stretch receptors
describe synovial fluid
super slippery/lubricates the joint
helps joint surfaces glide
nourishes the joint/articular cartilage
What does OA do to the synovial fluid?
thickens it bc it releases inflammatory cells into the synovium
What are ligaments? What do they do? What are the two primary types?
connective tissue that attach between bones
prevent excessive joint movement
capsular and extracapsular
What are capsular ligaments? What do they look like? Examples?
distinct thickenings of the joint capsule
broad sheets of fibers
resist movement in multiple planes
ex: mcl of the knee
What are extracapsular ligaments?
more chord-like
resist motion in one to two planes
partially or completely separate from the joint capsule
ex. LCL
What are blood vessels’ roles in synovial joints?
penetrate the capsule and extend to the junction of the fibrous and synovial layers
What are nerve fibers’ role in synovial joints?
innervate external and internal capsular layers (pain & proprioception)
n. cells within fibrocartilage
What are intra-articular discs/menisci? What is their role? Examples?
fibrocartilage structures that have give/are spongy
shock absorbers and increase joint congruency > improves stability (provides bowl for joint to sit in/avoids shearing force across articular cartilage)
ex. in vertebrae/knee joints
What are peripheral labrum? What is their role? Examples? Analogy?
Fibrocartilage structure
Extend around the periphery of joint
Deepen joints concavity and support capsular attachment
rubber washer that surrounds and seals the joint
provides stability and deepens the cavity and has suction
in shoulder and hip (highly mobile and need extra support)
What are fat pads? What is their role? Analogy?
Reinforces capsule & fills in ‘recesses’ in the joint
Cushions surfaces to reduce forces
Often interposed between fibrous layer & synovial membrane
serves as protection/insulation, cushioning against force
ex. under patellar tendon to protect it against the tibia
What are bursae? What is their role? When are they palpable?
spaces filled with synovial fluid that provide cushion
when inflamed, fill up with fluid
Extension or outpouching of synovial membrane
Filled with synovial fluid
Cushions and prevents friction between moving tissue surfaces
extra-articular
What are synovial plicae? What is their role? What happens when they are inflamed? Why are they folded?
Redundancy or folds in synovial membrane
Redundancy is necessary to prevent undue tension during motions
can be inflamed > pathological synovial plicae (causes swelling) and causes mechanical block
to accommodate mobility/prevent tearing
only in knee
What is a hinge joint? How many axes of rotation? What is a mechanical example? Biological?
Single axis of rotation
Motion occurs perpendicular to axis of rotation
hinge
humeroulnar joint
What is a pivot joint? How many axes of rotation? What is a mechanical example? Biological?
Single axis of rotation
Rotation occurs parallel to the axis of rotation
humeroradial joint (spin)
doorknob
What is an ellipsoid joint? What is a mechanical example? Biological?
Two axes of rotation (no spin)
One side elongated concave surface & other elongated concave surface
Bi-planar motion flexion/extension & abduction/adduction
Limits spin motion at joint
the wrist
one convex and one concave
What is a ball and socket joint? What is a mechanical example? Biological?
3 axes of rotation
Spherical convex surface & cup like concave socket
Allows 3 degrees of freedom for joint angular motion
hip and shoulder
What is a plane joint? What is a mechanical example? Biological?
Lacks a definitive axis of rotation
Sliding and rotation of one surface on the other
sliding a book across a table
tarsals slide against each other
What is a saddle joint? What is a mechanical example? Biological?
2 axes of rotation
Perpendicularly oriented convex and concave surfaces
Allows ample bi-planar motion but limits spin motion (can’t rotate)
two concave shapes
saddle
thumb
What is a condyloid joint? What is a mechanical example? Biological?
Primarily 2 axes of rotation Spherical convex ball articulates with relatively flat or non-concave surface Motions vary convex ball and flat surface knee
Does the axis of rotation change? What is this called? What does this mean for the moment arm? mechanical advantage? muscle strength?
yes
instantaneous axis of rotation: axis of rotation can be different at different instances of time/it shifts
it changes as you move
mechanical advantage changes throughout the range of motion
muscles are stronger at certain ranges than others
ex. knee
