Joints

Joints Now that we know all of the bones we need to look at the joints of the skeleton Joints, also called articulations, have two main functions They hold bones together securely They give the rigid skeleton mobility

Classification of joints Joints are commonly classified in two manners Functionally -- how they work Structurally -- how they are constructed and shaped.

Functional Classification The functional classifications focus on the amount of movement allowed by the joints With this system we have 3 main categories Synarthroses Amphiarthroses Diarthroses

Synarthroses Synarthroses joints are joints that are immoveable Most commonly located in the axial skeleton Ex: joints of the large bones of the cranium like the tempro-parietal joint

Amphiarthroses Amphiarthroses are joints that are slightly movable. These joints, like synarthroses are mostly located in the axial skeleton where rigidity is important to the function of the bones.

Diarthroses Diarthroses are joints that are freely movable These are mostly found in the appendicular skeleton, whose main function is mobility and manipulation.

Structural Classification We can also classify the joints by there structural classifications We also have 3 structural classifications Fibrous Cartilaginous Synovial

Fibrous Joints Fibrous joints are joints that are united by fibrous tissue The best examples of this type of joint are the sutures in the skull In sutures we have the jagged edges bound tightly together with connective tissue fibers

Fibrous joints Sutures are not the only place for fibrous joints There are some places where the connecting fibers are larger and longer to allow more “give” These are called syndesmoses An example is between the distal end of the fibula and tibia

Cartilaginous Joints These are the joints connected by cartilage Examples of this type of joint are usually slightly moveable The joints between the vertebrae are cartilaginous joints

Synovial Joints Synovial joints are those in which the articulating surfaces are seperated by a joint cavity containing synovial fluid All Synovial joints have 4 distinguishing features.

Features of synovial joints Articular cartilage Fibrous articular capsule Joint Cavity Reinforcing Ligaments

Types of synovial joints There are 6 types of synovial joints Plane Hinge Pivot Condyloid Saddle Ball-and-Socket

Plane Joint A plane joint can be seen in your carpals It moves very limitedly

Hinge joint A hinge joint can be found in your humerus where it connects to the ulna This allows motion similar to a hinge of a door

Pivot joint Pivot joints can be found in your radius and ulna as well as your vertebrae They allow for twisting motion

Condyloid joint Condyloid joints provide motion to the sides like a joystick An example would be your metacarpals and metatarsals

Saddle joint A saddle joint is shaped like a saddle and provide for motion back and forth and side to side An example would be where your metacarpal 1 meets your carpals

Ball and socket joint Ball and socket joints provide the most movement out of all the joints They allow for nearly 360 degrees of rotation They can be found in the heads of your humerus and femur