Synovial Joints

Question 1

Discuss the relationship between mobility and stability in a synovial joint.

Answer 1

The relationship between mobility and stability in a synovial joint is a balance between the two factors. In general, the more mobile a joint is, the less stable it is, and vice versa. This is because joints with a high degree of mobility allow for a greater range of motion but have less bony support and rely more on soft tissue, such as ligaments and tendons, to maintain stability. Conversely, joints with a lower degree of mobility, such as hinge or pivot joints, are more stable because they have more bony support and less soft tissue.

Question 2

Plane joint

Answer 2

This joint allows for gliding or sliding movements between flat or slightly curved surfaces. Examples include the intercarpal and intertarsal joints.

Question 3

Hinge joint

Answer 3

This joint allows for flexion and extension movements along one plane, like a door hinge. Examples include the elbow and knee joints.

Question 4

Pivot joint

Answer 4

This joint allows for rotation around a central axis, like a pivot. Examples include the proximal radioulnar joint and the atlantoaxial joint in the neck.

Question 5

Condylar joint

Answer 5

This joint allows for flexion, extension, abduction, and adduction movements, but not rotation. Examples include the temporomandibular joint and the metacarpophalangeal joints in the fingers.

Question 6

Saddle joint

Answer 6

This joint allows for flexion, extension, abduction, adduction, and circumduction movements, similar to the condylar joint, but with a greater degree of freedom. Examples include the carpometacarpal joint of the thumb.

Question 7

Ball and socket joint

Answer 7

This joint allows for the greatest degree of mobility and includes movement in all planes, as well as rotation around a central axis. Examples include the hip and shoulder joints.

Question 8

“grade” the 6 types of joints from low mobility (plane) to highest mobility (ball & socket)

Answer 8

Plane joint
Hinge joint
Pivot joint
Condylar joint
Saddle joint
Ball and socket joint

Question 9

Identify all the possible structures that can be part of a synovial joint. Briefly understand the roles of the various structures

Answer 9

Synovial fluid= reduces friction in joint
Ligaments= resist stretching, keep bones held tightly together
Articular discs= absorb shock, cushion bones, and help make a better fit between articulating bones
Labra= provide a more articular surface area within the synovial joint capsule
Articular cartilage= cushions and pads the ends of bones
Tendon sheaths= allows a tendon to pass through an articular surface
Bursae= acts like a fluid cushion to reduce friction between the articular capsule and bone moving near capsule
Nerves and blood vessels= serves tissues and cells within the articular capsule

Question 10

Contrast extracapsular, capsular, and intracapsular ligaments in terms of location relative to the articular capsule.

Answer 10

Extracapsular ligaments are located outside the articular capsule

Capsular ligaments are located within the capsule

Intracapsular ligaments are located within the articular capsule

Question 11

Discuss how the articular capsule and capsular ligaments compare according to function, but contrast according to their structure.

Answer 11

The articular capsule and capsular ligaments have a similar function in providing stability to the joint in all directions. However, they differ when it comes to structuring. The articular capsule is a fibrous, connective tissue structure that surrounds the joint, while capsular ligaments are thickened portions of the capsule. The articular capsule is composed of two layers, an outer fibrous layer, and an inner synovial layer, while capsular ligaments are composed mainly of collagen fibers.