Joints/articulations are sites where two bones meet.
Classification of Joints:
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The body
Joints/articulations are sites where two bones meet.
Classification of Joints:
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on this image for an audio message
I. Structural Categories: material binding the bones determines the classification.
A. Fibrous: held together by bands of fibers or sheets of ligaments (dense
regular CT)
B. Cartilaginous: piece of cartilage,usually fibrocartilage, acts as a “bridge”
between the bones
C. Synovial: fluid-filled cavity between the bones.
1) Articular cartilage: hyaline cartilage at bone ends. Absorbs compression
placed on the joint and promotes movement.
2) Joint cavity: space between the articulating bones. Filled with
synovial fluid. Synovial fluid: acts as a lubricant.
3) Articular capsule:
- encloses joint cavity
- double-layered
Synovial membrane lines thecapsule internally. Produces the synovial fluid in sac.-Both serve to reduce friction thereby promoting movement.
4) Ligaments: dense regular connective tissue holding bones together, reducing movement.
II. Functional Categories: degree of movement.
A. Synarthrotic: immovable
B. Amphiarthrotic: slightly moveable, some movement
C. Diarthrotic: freely moveable, wide degree of movement.
III Examples of joints
A. Fibrous Joints:
- no joint cavity
- amount of movement determined by fiber length, but never diarthrotic
1) short ligaments between cranial and facial bones
- synarthrotic
2) short ligament betweeb tibia and fibula holds distal ends of bones together
- synarthrotic
3) short periodontal ligaments hold teeth in alveoli of mandible and maxillae
- synarthrotic
4) long ligament between radius and ulna holds diaphysis of bones together
- amphiarthrotic
B. Cartilaginous: no joint cavity
semi-solid cartilages allow movement but never diarthrotic
1) bridge of hyaline cartilage between ribs (costal cartilages)
- synarthrotic
2) fibrocartilage cartilage pad between intervertebral (discs) and pubic bones
(symphysis)
- amphiarthrotic (except pubic symphysis which is amphiarthrotic only during
late pregnancy)
C. Synovial Joint examples: most common joint type
- all are in diarthrotic functional category
1) elbow, interphalangeal, knee, shoulder and hip
- permits flexion and extension
-shoulder and hip permit adduction and abduction
2) first and second cervical vertebrae (atlas and dens of axis)
- allows rotation
- head of radius and radial notch on ulna (pronation and supination)
3) head of femur and acetabulum of pelvic girdle OR
head of humerus and glenoid fossa of scapula
IV) Selected Movements of diarthrotic joints (which are always synovial in
structure)
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a) flexion and extension
b) supination and pronation
c) dorsiflexion and plantar flexion
d ) abduction and adduction
e) elevation and depression
Helpful
Website link
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Professor Thomas M. Lancraft
Human Anatomy Courses
at St. Petersburg College
St. Petersburg/Gibbs Campus
5/2006