Unit Two: Lecture Content

Name and describe the characteristics and functions of at least six (6) different categories of typical synovial joint structures.

-Synovial Joints have a joint cavity which is a space between bones for lubrication.

-They are all diarthroses which means they are involved with a lot of movement.

-Some types of synovial joints are ball and socket joints, pivot joints, hinge joints, and plane joints.

1. There is articular cartilage which does exactly what it says in the name. It helps create a smooth surface for the articulating regions of bones. The tissue type for this is hyaline cartilage.

2. There is a synovial cavity that houses the synovial fluid. It is simply a space between bones that is filled with synovial fluid.

3. The synovial fluid is the real star of the show and the synovial cavity is simply just a backup dancer. The synovial fluid has a slimy egg-white consistency that is constantly being replaced and is filled with nutrients and wastes. It lubricates the joint to prevent friction and nourishes the articular cartilage since cartilage has no blood supply.

4. Next there is the big boy which has not one but two layers and surrounds the joint cavity. This is the JOINT CAPSULE.

THE FIRST LAYER;

-the outer layer with an alias known as the fibrous capsule
-its tissue is dense connective tissue that conveys strength in ALL directions. Since it has strength in all directions it can run continuously from periosteum #1 of bone to periosteum #2 of bone- and across the joint cavity. 

-The first layer binds bones together, and creates a strong protective wrapping around outside edges of the joint cavity.

THE SECOND LAYER;

-The inner layer with an alias known as the synovial membrane. Once again synovial stealing the attention away. But it is really important for lubrication so its okay.

-The inner layer is the little guy so instead of having the strong dense connective tissue it has the loose connective tissue.

-It secretes and produces synovial fluid.

5.)Reinforcing ligaments

-Dense Regular CT; Connect bone to bone

-Binds tissues together (holding bones together)

-This is the strictler who limits the range of motion and defines the range of motion of a joint.

-Since it is dense regular tissue it can only convey strength in ONE direction. It does though, convey strength in plpaces where it is needed.

-It is located in extrascapular ligaments which means they are outside of the joint capsule (ex collateral ligaments)

-It is also found in intrascapular ligaments (inside the joint capsule)

6.) Bursae/Tendon Sheaths:

1. Bursae/Tendon Sheaths

   • optional (are found where they are needed)

   • FX = lubricating to prevent friction between non-moving and moving parts outside joint capsule

   • Bursa CH = membrane bound sac of synovial fluid outside joint cavity

   • Tendon Sheath CH = membrane bound sac of synovial fluid outside joint cavity, wrapped around a tendon to function in multiple planes

2. Fat Pad

   • optional

   • FX = cushion; fill-in space in a joint

   • CH = TISS = adipose CT

3. Articular Disc

   • optional

   • CH = pad of fibrocartilage (TISS)

   • FX = absorb shock

   • LOC = knee (meniscus); temperomandibular joint (TMJ) = jaw

Compared to a fibrous joint(sutures, gomphoses, and syndesmoses)

-Fibrous joints are connected by dense connective tissue and have little to no movement. 

-Composed of mainly collagen fibers with no joint cavity or synovial fluid present.

-These joints provide strength and stability however, they do lack movement.

-Can be found in the sutures of the skull

Compared to a cartilaginous joint(synchondrosis or symphyses)

-There is no synovial fluid or joint cavity similar to the fibrous joint.

-Mostly hyaline cartilage

-symphyses, such as the pubic symphysis or intervertebral discs, fibrocartilage provides cushioning and allows slight movement.

-In synchondroses, bones are united by hyaline cartilage (epiphyseal plates in growing long bones)

-Less movement than synovial joints but more movement than a fibrous joint.