Joints, Cartilage, Synovium Flashcards
Joints
(3 main types)
Provide articulation between bony elements
Main types:
•Synovial joints (synovial fluid-filled cavity)- can be a lot of fluid or not much
-Elbow, shoulder, stifle, hip, etc.
•Fibrous joints (~ligamentous tissue in gap)
- Sutures of skull
- Syndesmoses between equine metacarpal bones
- Gomphosis holds tooth to bone of socket
•Cartilagenous joints (cartilage in gap)
- Synchondroses at growth plate between epiphysis and diaphysis
- Symphyses at midline (mandible, pelvis) and between vertebral bodies: cartilage on bone and fibro(cartilageno)us in middle
*what is different is what is in the gap between the two bones
Suture Joints
Sites of skull growth
-Fiberous tissue between the gap!
- Membranes grow
- Bone grows into membrane at suture
Allow some flexibility during parturition (giving birth)
In most species (not mice!) tend to close in adults: becomes bone
That is why a mouse can get through a hole the size of a standard biro pen
Sydesmosis and Gomphosis
(Fibrous Joints)
- Bands of short ligaments holding structures tightly together
- A syndesmosis is a slightly movable fibrous joint in which bones such as the tibia and fibula are joined together by connective tissue.–> (e.g. between horse metacarpals…2 and 4 are held tightly on the sides of the 3rd main digit)–>The syndesmosis between equine metacarpals can ossify (turn into bone/bony tissue) - this may be inflammatory and painful.
- A gomphosis, also known as a dentoalveolar syndesmosis, is a joint that binds the teeth to bony teeth sockets in the maxillary bone and mandible. Forming articulation between tooth and mandible–> collectively gomphosis. (periodontal ligament)
Synchondrosis
(Cartilaginous Joint)
- an almost immovable joint between bones bound by a layer of cartilage
- Cartilagenous joint between epiphysis and diaphysis (growth plate)
- Epiphyseal Plate (Growth plate) is a synchondrosis
Epiphyseal Plate
(growth plate)
- The epiphyseal plate (or epiphysial plate, physis, or growthplate) is a hyaline cartilage plate in the metaphysis at each end of a long bone.
- This ‘growth plate scar’ can persist for some time in young adult animals, after growth in length has stopped. Its main relevance to you is that it can look like a fracture radiographically, and fractures (Salter Harris types) can occur in this weak spot.
- When a child’s bones are done growing (called reaching skeletal maturity), the growth plates ossify (harden) and the epiphysis fuses with the metaphysis, forming one complete bone
Symphysis
(cartilaginous Joint)
- Mandibular: hold mandible together in the middle
- In some animals mobile for mastication (chewing where food is crushed by teeth)
- In most relatively stiff joint- rabbits it is quite mobile
- Common traumatic injury in cats is mandibular symphysis fracture –> when cats fall and hit head/hit chin on ground, usually heals fine
- Pelvic
- Another common cat fracture site (with the sacroiliac joint, but that’s an unusual synovial joint)
- Becomes softer/separated prior to parturition under influence of relaxin (from corpus luteum or placenta, depending on species–> cows and female humans)- sometimes even stays loose after
- What about birds?
–>Birds & reptiles don’t have a complete pelvis with ventral midline fusion (as mammals do), which aids in the laying of eggs.
- Symphysis ossification may occur with age and especially so in males.
Synovial Joint
(range of motion)
6 different shapes
Range of motion
•Defined in large part by shape of articular surfaces
A.Plane
B.Hinge (metacarpal/phalangeal joint- like surfaces of cylinder and opposite to cylinder –> can only rotate in that one plane, stops joint from going medial laterally)
C.Pivot
D.Condylar (e.g. knee, similar in that it stays in one plane or it may rupture. With a fracture of these joints, can note that movement becomes abnormal)
E.Ellipsoidal
F.Saddle
G.Spheroidal (e.g. hip is ball and socket joint–> needs to move in many different directions so needs spherical interface)
Motion of Synovial Joints
*IMPORTANT*
Main Kinds of Movement
- Flexion / extension / hyper(over)extension: opening and closing angle of a joint
–> when a horse is standing, it’s in a hyperextended position, especially when galloping. Fully extended would be just a straight limb (180 degrees) *Remember which side to measure angle on- point of flexion*
- Adduction / abduction
- Circumduction
- Rotation:
—>Pronation & supination
Flexion of joint
closing the angle of a joint
Extension of a Joint
Opening the angle of a joint
Adduction/Abduction
Adduction: moving towards midline/sggital plane
Abduction: moving away
Effective Mechanical Advantage of Joints
-turn small musclular motions into large limb motions
Effective mechanical advantage
- Leverage provided by joint configuration
- Ground reaction force (relates to mass of animal) vs. muscular force (muscle force must be relatively greater than the GRF to balance out the weight of animal bc the lever arm) - advantage is you get MUCH more movement
- GRF: weight of animal causes a moment around the joint (being driven by external force(s) to cause the rotation
example: calf muscle provides force (F)
Lever arms: (see-saw example)
- r = distance from muscle insertion to fulcrum (the point against which a lever is placed on which it turns or is supported)
- R = distance from contact point to fulcrum
fulcrum acts on opposite side of two forces that are working opposite
- can have muscle closer to the fulcrum than where the work is happening in some joints
- muscles can actually be distant from joints and lever arm. work can be done in muslce and change in shape of that muscle is minimal but causes a great movement of the limb
EMA
(Effective Mechanical Motion)
EMA= r/R
r= distance from muscle insertion to fulcrum
R= distance from contact point to fulcrum
- Crouched animals have lower EMA (big R is bigger) and therefore less GRF-resisting moment. But, they tend to be more agile.
- Large animals tend to adopt a less crouched or upright posture to increase EMA (by reducing R),
Synovial Fluid
The lubricant of synovial joints
- Water
- Hyaluronic acid
- Glycoproteins
- Surface active phospholipids
- A few mononuclear leukocytes (WBCs)
- glucose and electrolytes occur in concentrations similar to those in plasma (equilibrium with plasma)
- Produced mainly by type B synoviocytes
- Cartilage’s extracellular fluid: Transport of metabolites, waste, signaling molecules
-articular cartilage with metabolic transport
