Chapter 8 - Joints Flashcards
Define joints and what they do.
Joints or articulations, are the sites where two or more bones meet.
Joints give the skeleton mobility.
Joints hold the skeleton together.
Joints can play a protective role.
What are the 3 structural categories of joints?
- Fibrous
- Cartilaginous
- Synovial
The structural classification of joints focuses on the material binding the bones together and whether or not a joint cavity is present.
What are the functional classifications of joints?
- Synarthroses - immovable joints (largely restricted to the axial skeleton)
- Amphiarthroses - slightly moveable joints (largely restricted to the axial skeleton)
- Diarthroses - freely moveable joints (these predominate in the appendicular skeleton)
Functional classification of joints is based on the amount of movement allowed at the joint.
Fibrous Joints
- Bones in these joints are connected by the collagen fibers of connective tissue.
- No joint cavity is present.
- Most fibrous joints are immovable
What are the 3 types of fibrous joints?
- sutures
- syndesmoses
- gomphoses
Sutures (fibrous joint)
- literally they are “seams”
- Occur only between the bones of the skull.
- The immovable nature of sutures are a protective adaptation to prevent cranial bones from moving/damaging the brain.
Syndesmoses (fibrous joint)
- In syndesmoses, bones are connected exclusively by ligaments, cords or bands of fibrous tissues.
- If the fibers of this joint are short, little or no movement is allowed. If the fibers are long, a large amount of movement is possible.
Gomphoses (fibrous joint)
- A peg-in-socket fibrous joint.
- Only example is the articulation of a tooth with its bony alveolar socket. Teeth are embedded in their socket.
- The fibrous connection in this case is called the short periodontal ligament.
Cartilaginious joints
- In these joints the bone is connected by cartilage.
- Cartilaginous joints lack a joint cavity.
- The joints are not highly moveable.
- The two types of cartilaginous joints:
1. Synchondroses
2. Symphyses
Synchondroses (cartilaginous joint)
- A bar/plate of hyaline cartilage unites the bones at a synchondrosis joint.
- Virtually all of these joints are immovable.
- ex: The epiphyseal plates on long bones of children.
Symphyses (cartilaginous joint)
- Symphysis unite bones with fibrocartilage.
- Fibrocartilage acts as a shock absorber and permits limited movement at the joint.
- Hyaline cartilage is also present in symphyses in the form or articular cartilages on bony surfaces.
- ex: Intervertebral joints and pubic symphysis.
Synovial joints
- Synovial joints have a fluid filled joint cavity.
- This arrangement permits substantial freedom of movement.
- Nearly all joints of the limbs and most joints of the body fall into this class.
What are the 6 distinguishing features of synovial joints?
- Articular cartilage
- Joint cavity
- Articular capsule
- synovial fluid
- Reinforcing ligaments
- Nerves and blood vessels
Articular cartilage of synovial joints
- This cartilage covers opposing bone surfaces (as hyaline cartilage).
- They absorb compression placed on the joint (keep bone ends from being crushed)
Joint cavity of the synovial joints
- The joint cavity contains a small amount of synovial fluid.
- The cavity is normally nonexistent but is there so that it can expand if fluid accumulates (i.e. during inflammation).
Articular capsule of the synovial joints
- Articular capsule is 2 layers that enclose the joint cavity.
- Inner layer of the joint capsule is called the synovial membrane. Its function is to make the synovial fluid.
Synovial fluid of the synovial joints
- Derived by filtration of blood flowing through the capillaries in the synovial membrane.
- This fluid provides a slippery weight-bearing film that reduces friction between the cartilages.
- Weeping lubrication lubricates the free surfaces of the cartilages and nourishes thier cells.
Reinforcing ligaments of the synovial joints
- Synovial joints are reinforced and strengthened by a number of bandlike ligaments (most often capsular ligaments).
Nerves and blood vessels of the synovial joints
- Synovial joints are richly innervated
- Nerves can detect pain, and monitor joint position and stretch.
- Synovial joints are richly vascularized
- Blood vessels su
Bursae and Tendon Sheaths
- Often found closely associated with synovial joints
- Bags of lubricant, acting as ball bearings to reduce friction between adjacent structures during joint activity.
- Bursae - flattened fibrous sacs containing synovial fluid.
- Tendon sheath - an elongated bursa that wraps completely around a tendon subjected to friction. (ex the wrist)
Factors influencing the stability of synovial joints…
- Because synovial joints are constantly stretched and compressed, they must be stabilized so as not to dislocate. This stability depends on 3 factors:
1. The shapes of articulation surfaces - these shapes determine what movements are possible at a joint.
2. The number and positioning of ligaments - the more ligaments a joint has, the stronger it is.
3. Muscle tone - tendons are kept under tension by the tone of their muscles. This tone is extremely important in reinforcing the shoulder and knee joints and the arches of the foot.
Gliding movement
- Occurs when one flat or nearly flat bone surface glides or slips over another without angulation or rotation
- Occurs at: intercarpal joints, intertarsal joints, between articular processes of vertebrae.
Special Movements: Supination and Pronation
- Supination (turning forward) and Pronation (turning backward) refers to movements of the radius around the ulna.
Special Movements: Dorsiflexion and Plantar Flexcion
- Dorsiflexion and Plantar Flexion of the foot: The up and down movements of the foot at the ankle;
- Dorsiflexion: bending foot towards shin
- Plantar Flexion: pointing toes.
Special Movements: Inversion and Eversion
- Inversion is where the sole of the foot faces medially
- Eversion is where the sole of the foot faces laterally.
Special Movements: Protraction and Retraction
- Protraction is where the mandible juts out.
- Retraction is where the mandible is pulled towards the neck.
Special Movements: Elevation and Depression
- Elevation is where the body part is lifted superiorly (eg. shrugging shoulders)
- Depression is the lowering of the body part (eg. opening of jaw)
Special Movements: Opposition
- Opposition is the movement of the thumb.
eg. Touching thumb to the tips of other fingers.
Plane Joint
Hinge Joint
Pívot Joint
Condylar Joint
Saddle Joint
Ball-and-Socket Joint
