AUni Axial Synovial Joints

(1) In uni-axial synovial joints, motion occurs in only one plane. The joints of the fingers (interphalangeal) flex and extend in the sagittal plane. These are commonly referred to as hinge joints.

(2) If a single rotatory (rotational) motion occurs around a post-like structure, the joint is a pivot joint. The atlas vertebra rotating around the dens (tooth like projection) of the axis vertebra at the top of the neck (base of the skull) is a pivot joint.

b. Bi-Axial Synovial Joints. In bi-axial synovial joints, motion between the bones occurs in two planes. Here the surface in contact is curved or rounded in two directions.

(1) The proximal phalanx of a finger can flex and extend and move from side to side on the rounded head of the metacarpal bone. This is the MP or metacarpophalangeal joint.

(2) When the two surfaces are curved in directions at right angles to each other, a shape similar to that of a cowboy's saddle is formed. This type of synovial joint is called a saddle joint. In the human body, the saddle joint is located at the base of the thumb.

STRUCTURE

TISSUE(S)

FUNCTION(S)

1.

BONE

BONY

(a) Serves as site of attachment for the skeletal muscles.

(b) Serves as lever of motion.

2.

ARTICULAR CARTILAGE

HYALINE CARTILAGE

Serves as smooth surface, over which motion takes place.

3.

FIBROUS CAPSULE

DENSE FCT

Encloses articulation.

4.

SQUAMOUS

(b) Secretes synovial fluid into synovial space.

5.

SYNOVIAL SPACE

-

Frees articulation for motion.

6.

SYNOVIAL FLUID

SEROUS FLUID

Lubricates articulation.

7.

LIGAMENT

(VERY) DENSE FCT

Holds the bones together.

8.

MUSCLE

FIBERS

Applies force to produce motion.

Table 4-1. The tissues and functions of structures of a "typical"

synovial articulation.

Table 4-1. The tissues and functions of structures of a "typical"

synovial articulation.

c. Multi-Axial Synovial Joints. In multi-axial joints, motion is possible in all three planes of space.

(1) The ball-and-socket-type synovial joint has the freest motion in all directions. A spherically rounded head (ball-like) fits into a receiving concavity (socket). The hip joint is an example of the ball-and-socket type, with the spherical head of the femur fitting into the cup or socket (acetabulum) of the pelvic bone.

(2) In the plane joint, the contact surfaces of the bones are essentially flat. These flat surfaces slide on one another (also called translatory motion). The acromioclavicular joint of the shoulder region is an example of a plane joint.

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Responses

  • Sandra Conti
    Which of the following is NOT a type of synovial joint in the human body?
    5 years ago

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