What does it mean to have hypermobility?
Double-jointed; when someone’s joints has more range of motion
What are causes of hypermobility?
- abnormally shaped ends of one or more bones in a joint
- weak ligaments (due to differences in protein structures, genetics, and/or hormone levels)
- stretched ligaments due to training
- muscle tone can influence ROM of joins (yoga exercise vs body building)
How manty joints are in the human body?
230
What is an articulation/joint?
Where 2 bones interconnect
What is the function of joints?
To hold bones together and allow movement
- each joint has a compromise between the need for strength and the need for mobility
What are the two ways to classify joints?
Structural and Functional
What are the structural classifications of joints?
Based on the structure holding bones together
- Bony fusion
- Fibrous joint
- Cartilaginous
- Synovial joints
What are the functional classifications of joints?
Based on the range of motion of joints
- synarthroses (immovable; fibrous or cartilaginous and may eventually fuse)
- amphiarthrosis (slightly/limited movable; fibrous or cartilaginous)
- diarthroses (freely movable; synovial; contains synovial fluid)
Summary of types of joints; Synarthroses
Immovable
a) sutures: dense fibrous connective tissue between the skull bones
b) gomphoses: fibrous connective tissue periodontal ligament that binds teeth to the jaw
c) synchondroses: cartilaginous rigid bridge between two bones (epiphyseal cartilage of long bones)
d) synostosis: bony fusion, two completely rigid bones fused together so that the boundary disappears (e.g. epiphyseal lines)
Summary of types of joints; Amphiarthroses
Slightly movable; collagen fibres or cartilage
a) syndesmoses: fibrous ligament between tibia and fibula
b) symphysis: fibrous cartilaginous pad between vertebrae
c) interosseous membrane: fibrous
Summary of types of joints; Diarthroses
Freely movable; fibrous articular capsule containing synovial fluid
a) synovial: ends of long bones
What are gomphoses?
Synarthroses:
Fibrous connective tissue: periodontal ligament that binds teeth to the jaw
What are synchondroses?
Synarthroses:
Rigid bridge of cartilage between two bones
What are synostoses?
Synarthroses:
Totally rigid, two bones fused together so that boundary disappears
What are syndesmoses?
Amphiarthroses:
bones connected by a ligament (made of collagen); fibrous joint
What is symphysis?
Amphiarthroses:
Bones separated by a fibrous cartilage pad
What is interosseous membrane?
Amphiarthroses:
Between diaphysis of the tibia and fibula, lots of collagen, very fibrous
What is articular cartilage?
Resembles hyaline cartilage but no perichondrium, higher water content than normal, and synovial fluid produced by synovial membranes
function: to prevent bone-to-bone contact and reduce friction
What is the joint cavity?
A synovial cavity
What lines the joint cavity?
a) Articular capsule; fibrous layer continuous with periostea of the articulating bones
b) Synovial membrane; outer layer of loose areolar connective tissue plus incomplete inner layer of synoviocytes and macrophages that do not extend over the articulating parts of the articular cartilage and menisci
What is synovial fluid?
Fluid that fills cavity and is secreted by synoviocytes of the inner layer ‘epithelium’ chemical makeup
- similar to interstitial fluid with high levels of proteoglycans
- clear and viscous
functions: lubrication to reduce friction, nutrient distribution from vessels in synovial membrane areolar tissue, shock absorption; distributing shock evenly across articular surfaces
What are the accessory structures of some synovial joints?
articular discs/menisci, fatty pads, ligaments, bursae, tendon sheath
What are articular discs/menisci?
Articular discs or menisci: wedges of fibrocartilage separating the articular surfaces
functions: channel the flow of synovial fluid
What are fatty pads?
Fatty pads: between fibrous capsule and synovial membrane or bone, covered with layer of synovial membrane
functions: protect articulating surfaces, packing material: filling in spaces as joint cavity changes shape
