Structural classifications of the body joints are based on how the bones are held together and articulate with each other. At fibrous joints, the adjacent bones are directly united to each other by fibrous connective tissue. Similarly, at a cartilaginous joint, the adjacent bones are united by cartilage. In contrast, at a synovial joint, the articulating bone surfaces are not directly united to each other, but come together within a fluid-filled joint cavity.
The functional classification of body joints is based on the degree of movement found at each joint. A synarthrosis is a joint that is essentially immobile. This type of joint provides for a strong connection between the adjacent bones, which serves to protect internal structures such as the brain or heart. Examples include the fibrous joints of the skull sutures and the cartilaginous manubriosternal joint. A joint that allows for limited movement is an amphiarthrosis. An example is the pubic symphysis of the pelvis, the cartilaginous joint that strongly unites the right and left hip bones of the pelvis. The cartilaginous joints in which vertebrae are united by intervertebral discs provide for small movements between the adjacent vertebrae and are also an amphiarthrosis type of joint. Thus, based on their movement ability, both fibrous and cartilaginous joints are functionally classified as a synarthrosis or amphiarthrosis.
The most common type of joint is the diarthrosis, which is a freely moveable joint. All synovial joints are functionally classified as diarthroses. A uniaxial diarthrosis, such as the elbow, is a joint that only allows for movement within a single anatomical plane. Joints that allow for movements in two planes are biaxial joints, such as the metacarpophalangeal joints of the fingers. A multiaxial joint, such as the shoulder or hip joint, allows for three planes of motions.
amphiarthrosis
slightly mobile joint
articulation
joint of the body
biaxial joint
type of diarthrosis; a joint that allows for movements within two planes (two axes)
cartilaginous joint
joint at which the bones are united by hyaline cartilage (synchondrosis) or fibrocartilage (symphysis)
diarthrosis
freely mobile joint
fibrous joint
joint where the articulating areas of the adjacent bones are connected by fibrous connective tissue
joint
site at which two or more bones or bone and cartilage come together (articulate)
joint cavity
space enclosed by the articular capsule of a synovial joint that is filled with synovial fluid and contains the articulating surfaces of the adjacent bones
multiaxial joint
type of diarthrosis; a joint that allows for movements within three planes (three axes)
synarthrosis
immobile or nearly immobile joint
synovial joint
joint at which the articulating surfaces of the bones are located within a joint cavity formed by an articular capsule
uniaxial joint
type of diarthrosis; joint that allows for motion within only one plane (one axis)
1. The joint between adjacent vertebrae that includes an invertebral disc is classified as which type of joint?
A) diarthrosis
B) multiaxial
C) amphiarthrosis
D) synarthrosis
C
2. Which of these joints is classified as a synarthrosis?
A) the pubic symphysis
B) the manubriosternal joint
C) an invertebral disc
D) the shoulder joint
B
3. Which of these joints is classified as a biaxial diarthrosis?
A) the metacarpophalangeal joint
B) the hip joint
C) the elbow joint
D) the pubic symphysis
A
4. Synovial joints ________.
A) may be functionally classified as a synarthrosis
B) are joints where the bones are connected to each other by hyaline cartilage
C) may be functionally classified as a amphiarthrosis
D) are joints where the bones articulate with each other within a fluid-filled joint cavity
D
1. Define how joints are classified based on function. Describe and give an example for each functional type of joint.
Functional classification of joints is based on the degree of mobility exhibited by the joint. A synarthrosis is an immobile or nearly immobile joint. An example is the manubriosternal joint or the joints between the skull bones surrounding the brain. An amphiarthrosis is a slightly moveable joint, such as the pubic symphysis or an intervertebral cartilaginous joint. A diarthrosis is a freely moveable joint. These are subdivided into three categories. A uniaxial diarthrosis allows movement within a single anatomical plane or axis of motion. The elbow joint is an example. A biaxial diarthrosis, such as the metacarpophalangeal joint, allows for movement along two planes or axes. The hip and shoulder joints are examples of a multiaxial diarthrosis. These allow movements along three planes or axes.
2. Explain the reasons for why joints differ in their degree of mobility.
The functional needs of joints vary and thus joints differ in their degree of mobility. A synarthrosis, which is an immobile joint, serves to strongly connect bones thus protecting internal organs such as the heart or brain. A slightly moveable amphiarthrosis provides for small movements, which in the vertebral column can add together to yield a much larger overall movement. The freedom of movement provided by a diarthrosis can allow for large movements, such as is seen with most joints of the limbs.