Joint structure Flashcards
Synarthrotic joint (fibrous)
-little to no movement
-Stable
Ex: sutures in the skull, of the joint between the teeth and the mandible (gomphosis)
Synarthrotic joint (cartilaginous)
little to no movement
Pubic symphysis and the intervertebral discs
Diarhrotic joint
moderate to extensive motion
ex the hip, shoulder, knee
Basic structures that are always in a diarthrotic joint
- synovial fluid
- articular cartilage
- joint capsule
- synovial membrane
- ligaments
- blood vessels
- sensory nerves
what is synovial fluid
-hyaluronan (hyaluronic acid)
-Lubricating glycoprotein
-Coats articular cartilage
-Reduces friction
-Assist articular cartilage nutrition
What is articular cartilage
found at the end of bones to provide cushion
Lines the ends of bones and acts as shock absorbers
what is a joint capsule (and what are the layers)
-sheath to give stability (encloses the joint) and is lined with synovial membrane
-The outer layer is called the stratum fibrosum and -the inner layer is called the stratum synovium
What is a synovial membrane?
stratum synovium
produces synovial fluid for lubrication (inner membrane)
what do ligaments do?
reinforce the joint capsule and add additional stability
What are structures that are sometimes present
intra-articular discs or menisci
peripheral labrum
fat pads
bursa
synovial plica
what are intra-articular discs or menisci
menisci are found in the knee and are circular or semicircular for additional shock absorber
what are peripheral labrum?
found in the shoulder and the hip to deepen the socket, made from fibrocartilage
where are fat pads in joints
in/around the surrounding tissue
what are bursa
fluid filled sacs or areas of high friction
Ex: occurs under a tendon and bone
what is a synovial plica
a redundancy or fold in joints → a common problematic place this occurs is in the knee
what is periartiular CT
capsule
ligaments
tendons
articulate cartilage
fibrocartilage
bone
Explain periarticular CT/what they do
Capsule: that is made up of the inner and outer layers
Ligaments: provide stability for the joint
Tendons: transmits a force across the bone
Articular cartilage: lines the ends to reduce friction and acts as shock absorbers
Fibrocartilage: ex mensci
Bone
What are the fundamental components of periarticular CT (on a molecular level)
Cells: they excrete an extracellular matrix
extracellular matrix: made up of fibrous proteins and ground substances
what types of tissues have MORE fibroblasts
tendons, joint capsules, and ligaments
what types of tissues have MORE chondrocytes
articular cartilage and fibrocartilage
Collagen Type 1 explain?
found in tendons, ligaments, and joint capsules
Excreted as a triple helix
Thicker and resist tension
collagen type 2 explain
Thinner than type 1
Associated with higher GAGS meaning these will hold onto more water
glycosaminoglycans (GAGS)
-have a high affinity for water and will keep it in place
-Proteoglycan attaches to a hyaluronan core and -becomes a proteoglycan macromolecule and will hold and abide fluid
What is ground substances composed of
-GAGS
-water: a significant component in articular cartilage since you cannot compress water
-solutes: Na, K, Ca
-the fibrous proteins are embedded in the ground substances
What does the dense classification of CT mean
a lot of collagen fibers and not as many ground substances
a joint capsule has what kind of CT?
type 1 collagen fibers lined in different directions making it dense irregular
-movement in the joint capsule will encourage more GAGS to be made
What type of CT is a ligament
Type 1 collagen - dense regular
Reinforce the joint capsule
Prevent certain forces (MCL will prevent the knee from going inward)
Type 1 but will be arranged in a parallel fashion so that it can prevent force in one direction
what type of CT is a tendon
dense regular
Transmits force in one direction
Type 1 collagen in parallel
what type of CT is in fibrocartilage
Menisci → can be pinched/shock absorbers and therefore will have more type 1 with more ground substances than normal
what type of CT makes up articular cartilage
cushion and stick absorber so it has more type two fibers and high amount of water
Explain the zones of articular cartilage
Tangential (superficial):
Helps to resist shearing forces
Fibers are arranged in parallel to the surface (horizontal)
Articulate with other bone on the same layer
Transitional:
Fibers in different directions
Cells are a little bigger
Increased ground substances (GAGS)
Resist compression and multidirectional tensile forces (fibers in multiple directions)
Radial:
Column arranged perpendicular to the surface (more vertical to keep it on the bone)
Fibers anchored to tidemark
Resist compression and tensile forces (primary)
Tidemark: where we start to see calcification
Calcified:Ground substance is calcified and starting to lead to the bone
Subchondral bone:
First layer of the bone
Thin cortical bone
Gets nutrition from synovial fluid
Growth rate is slow and decreases with age
Pain with degenerative process only after significant destruction of more superficial layers (these are the more shock absorbing layers)
Subchondral layer exposed to more harmful stress (osteoarthritis)
Explain the toe region in the collagen stress curve
the collagen fibers will start to straighten out and not a lot of load will be needed to get it to change shape
Gets the “crimp” out of the tissues
explain the elastic region in the collagen stress curve
when they are stretched passed being fully straightened and start to slide → if stress is removed it will return to normal shape
Tissue starts to deform
explain the plastic region in the collagen stress curve
the fibers are connected by crosslinks and that will limit how far they can slide past each other but they can slide too far and cause a strain?
Start to tear cross links at around 4%-6% of strain
Microstrain
It is not recoverable at this length
explain what the failure portion of the collagen stress curve
tear of tissue
At around 8% of strain it will tear causing complete failure
Uniaxial joint
one axis and one degree of freedom
examples:
-hinge (ginglymus) - humerus and ulna joint
-pivot (trochoid) - radius and the capitulum of the humers
biaxial joint
two axes and two degrees of freedom
examples:
1. ellipsoid: axial and carpal joint
2. saddle: carpal and metacarpal joint in the thumb
3. condyloid: metacarpal and pharangyeal
triaxial
three axes and three degrees of freedom
examples:
1. ball and socket (enarthrodial) : glenohumeral
2. plane: functional the movement is limited by adjacent bones such as in the metacarpals and the hamate joint
Muscles spindles
-located in parallel with the muscle fibers
-activated with tension
-dynamic response (primary-rate-strong)
-static response (secondary-length-weak)
-CNS sends a signal back to contract
-if muscle experiences a rapid stretch the muscle spindle is activated and sends a sign to the dorsal side of the spinal cord to a motor neuron to contract
Golgi tendon organs
-located in series at the muscle-tendinous junction (with muscle fibers and tendons)
-force sensor
-inhibit muscle contraction activated by excessive contraction or stretch
can stimulate 1 B fibers and inhibit muscles if it senses it will be over stretched
pain receptors
located in the capsule, muscles, skin
-not found in hyaline cartilage/limited in cartilaginous joint structures (fibrocartilage mensci)
-respond to chemical (inflammation) or mechanical stimuli (strained or compressed)
-may trigger other defense mechanisms
mechanoreceptors
located in the capsule
respond to vibration, compression and tension
recognize and monitor status of joint and where it is in space
Osteokinematics
gross rotational motion that can be measured with a Goni
arthrokinematics:
accessory motion
-motion between joint surfaces
roll, glide/slide, spin
-these are needed for the osteokinematics to occur
rotation
is like a tire on a street
slide/glide
is like hitting the brakes and the tires slide
spinning
a toy top on a table
When you have convex moving on concave
the roll and the glide will happen in opposite directions
-an upward roll and then glides down (shoulder abduction)
when you have concave on convex
the roll and glide happen in the same direction
what are open pack positions
-they are positions of joints where there is the most slack
-there is more space between the bones of the joint (they are less congruent)
-this causes a decrease in pressure in the joint
-it is called “resting position” (because it must less tension on the muscles and tendons
-it is usually the midrange of the joint
what is a a closed pack position
-when the joint surfaces are more congruent meaning there is less space between the bones of the joint
-this causes the joint capsule to be tight and increases pressure on the joint
-there is less movement between joint surfaces
-normally the end ranges (there are typically two)
open kinematic chains
distal end is free tome
-independent movement of segments
-non-weight bearing
closed kinetic chain
distal end is fixed
-movement in one segment results in movement in another segment
