1), where the flat bones are held together by a thin layer of dense fibrous material. Functionally sutures are an example of synarthrosis, as there should be no movement of the joint when formed.
.
Figure 1 Section across the sagittal suture in the skull.
As well as sutures, fibrous joints also make up gomphoses. Gomphosis is a joint in the form of an articulation by the insertion of a conical process into a socket; this is not seen in any joints between bones, but is seen in the as of the roots of the teeth, this is an example of a synarthrosis since the joint should not be movable unless damage has occurred. Finally fibrous joints also form syndesmoses where bones are held together by a sheath of fibrous tissue, this can be seen in the radio-ulnar joint (fig 2). Syndesmoses are examples of ampiarthrosis since there is some movement possible. Fibrous joints have evolved to fulfill the role of holding bones very close together, allowing little or no relative movement of the bones achieving this by attaching bones with dense fibrous connective tissue, tending to form either synarthroses or amphiarthroses. The collagenous nature of these joints allows them to fulfill their role of allowing little or no movement due to the high strength of collagen fibers.
.
Figure 2 the radio-ulnar joint held together by dense connective tissue.
There are two types of cartilaginous joints, primary (sychondroses) and secondary (symphyses). Sycondroses are found at the junction between the epiphysis and the diaphysis (between the ossifying centers) of growing long bones and another example is the cartilaginous connection between the ends of the first pair of vertebrosternal ribs and the sternum. The joint is formed by hyaline cartilage. The hyaline cartilage holds the epiphysis and diaphysis together tightly and is thus a synartharthrosis, allowing no movement. The joint acts like a rigid, cartilaginous bridge between two articulating bones.
