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What are the two functions of joints?
They hold the bones together securely and also give the rigid skeleton nobility.
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List and describe the three functional classifications of joints.
- Functional classification focuses on the amount of movement allowed by the joint.
- Synarthroses: immovable joints, axial skeleton
- Amphiarthroses: slightly movable joints, axial skeleton
- Diarthroses: freely movable joints, dominate in the limbs where mobility is important
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List and and give an example of the three structural classifications of joints.
- Based on whether fibrous tissue, cartilage, or joint cavity separates the bony regions at the joint.
- Fibrous: bones are united by fibrous tissue.
- EX: Sutures of the skull, irregular edges of bones interlock and are bound tightly together by connective tissue fibers allowing essentially no movement to occur.
- Cartilaginous: bone ends are connected by cartilage.
- Slightly movable (amphiarthrotic) EX: Pubic symphysis of pelvis and intervertebral joints
- Immovable (Synarthrotic) EX: Epiphyseal plates, cartilaginous joints between the first ribs and the sternum
- Synovial Joints: articulating bone ends are separated by a joint cavity containing Synovial fluid.
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What are the four distinguishing characteristics of synovial joints?
- Articular Cartilage: covers ends of bones forming the joint
- Fibrous articular cartilage: joint surfaces are enclosed by a sleeve or capsule of fibrous connective tissue, and the capsule is lined with a smooth synovial membrane.
- Joint Cavity: Articular capsule encloses a cavity, called the joint cavity, which contains lubricating synovial fluid.
- Reinforcing ligaments: The fibrous capsule is usually reinforced with ligaments.
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List the 6 types of synovial joints
- Plane Joint: articular cartilages are flat, and only short slipping movements are allowed.
- Nonaxial: gliding does not include rotation
- Intercarpal joints of the wrist
- Hinge Joint: the cylindrical end of the bone fits into a trough shaped surface on another bone.
- Uniaxial: they allow movement around one axis only
- Elbow joint, ankle joint, joints between the phalanges of the fingers
- Pivot Joint:
- the rounded end of one bone fits intoa sleeve or ring of bone (possibly ligaments)
- Uniaxial, can turn around its long axis
- Proximal radioulnar joint, joint between the atlas and the dens of the axis
- Condyle Joint: the egg shaped articular surface of one bone fits into an oval concavity in another.
- Biaxial: move side to side and back and forth, cannot rotate around its long axis
- Knuckle joints
- Saddle Joint: every articular surface has concave and convex articular surfaces, like a saddle
- allows same movements as condyle joints
- Carpometacarpal joints in the thumb
- Ball-and-Socket Joint: the spherical head of one bone fits into a round socket in another.
- Multiaxial: movement on all axis
- Shoulder and hip joints
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