Chapter 8- Joints Flashcards
Joints (articulations)
the site where 2 bones meet
The shape of a joint determines
how much movement it allows
General functions of joints (2)
- Mobility- allow movement of various body parts
2. Stability- hold the skeleton together
Joints allow small amounts of movement are
More stable. They are less likely to dislocate and damage internal organs
In general, how are joints classified?
By structure and function
What is the structural joint classification defined by?
The type of tissue that connects bones at the articulating surface
Structural joint classifications (3)
- Fibrous
- Cartilaginous
- Synovial
Joint cavity
Only found in synovial joints. It is defined as a very small empty space between the bones that form the joint or around the joint itself. Contains synovial fluid
What is the functional joint classification defined by?
The amount of movement allowed by the joint
Functional joint classifications (3)
- Synarthroses
- Amphiarthroses
- Diarthroses
The axial skeleton typically contains which functional joint categories?
Synarthroses and amphiarthroses are prevalent in the axial skeleton.
Synarthroses are held very tightly together. We don’t want most of the bones in the axial skeleton (ribs, etc.) to move around
The appendicular skeleton typically contains which functional joint categories?
Diarthroses are prevalent in the appendicular skeleton
We want the limbs to be able to move around and want the dexterity in fingers for certain tasks
Fibrous joints
Joints composed of collagen fibers of connective tissue, contain no joint cavity. Fibrous joints have short collagen fibers, prevents movement
Fibrous joints typically include which functional joint classifications?
Mostly synarthroses, some amphiarthroses
Types of fibrous joints (3)
- Sutures
- Syndesmoses
- Gomphoses
Sutures
“Seams”- joints found only between the bones of the skull. Composed of bundles of extremely strong and short collagen fibers
The fibers are clumped/bundled together, making them strong and allowing VERY little movement
Fontanelles
Soft spots of a fetus or infant- this allows skull flexibility during birth. These areas are not ossified and the sutures of the skull are not completely formed. Large chunks of fibrous tissue separate the bone- fibrous tissue is strong and will not tear away easily
By what age will fontanelles be ossified?
18 months
Why are fontanelles important?
In fetuses, the brain grows very quickly- fontanelles allow the brain to grow without being locked in place
They also allow the infant’s head to squeeze through the pelvic bone without damage
Syntoses
What sutures form if they ossify- syntoses are not considered joints. Formation is normal, but it doesn’t happen to everyone and usually happens later in life
Syndemoses
Bones are connected to one another only by ligaments. Movement depends on the length of the ligaments. The longer the fiber, the more movement allowed.
Ligaments
bands of fibrous tissue that join bone to bone
How does the ligament between the distal portions of the tibia and fibula influence their movement?
The interosseous ligaments between the tibia and fibula in the lower leg allow them to move relative to each other but not that much- influences the amount of movement in the foot- we can kind of move the foot but can’t flip it all the way around. Short ligament= limited movement
How does the ligament between the radius and ulna influence their movement?
The ligament between the radius and ulna has longer fibers and therefore you can move the hand much more. The bones form an x when the hand is facing downward and are parallel when hand is facing up