Suturae

A suture is a type of fibrous joint that is only found in the skull (cranial suture).

The bones are bound together by Sharpey's fibres.

A tiny amount of movement is permitted at sutures, which contributes to the compliance and elasticity of the skull.

These joints are synarthroses.

It is normal for many of the bones of the skull to remain unfused at birth.

The fusion of the skull's bones before birth is known as craniosynostosis.

The term "fontanelle" is used to describe the resulting "soft spots".

The relative positions of the bones continue to change during the life of the adult (though less rapidly), which can provide useful information in forensics and archaeology.

In old age, cranial sutures may ossify (turn to bone) completely.

The joints between the teeth and jaws (gomphoses) and the joint between the mandible and the cranium, the temporomandibular joint, form the only non-sutured joints in the skull.

Types of sutures

Plane sutures – edges of the bones are flush with each other as in a normal butt joint. Eg: Internasal suture.

Limbous sutures – edges are bevelled so the plane of the suture is sloping as in a mitre joint. Eg: Temporo-parietal suture.

Schindylesis – formed by two bones fitting into each other similar to a bridle joint. Eg: Palatomaxillary suture.

Denticulate sutures – the edges slot into each other as in a finger joint. Eg: Lambdoid suture.

Serrate sutures – similar to a denticulate suture but the interlocking regions are serrated rather than square. Eg: Coronal suture.

List of sutures Cranial sutures viewed from top of head

Most sutures are named for the bones they articulate, but some have special names of their own.

Visible from the side

Coronal suture – between the frontal and parietal bones Lambdoid suture – between the parietal and occipital bones and continuous with the occipitomastoid suture Occipitomastoid suture – between the occipital and temporal bones and continuous with the lambdoid suture Sphenofrontal suture Sphenoparietal suture Sphenosquamosal suture Sphenozygomatic suture Squamosal suture – between the parietal and the temporal bone Zygomaticotemporal suture Zygomaticofrontal suture

Visible from the front or above

Frontal suture / Metopic suture – between the two frontal bones, prior to the fusion of the two into a single bone

Sagittal suture – along the midline, between parietal bones

Visible from below or inside

Frontoethmoidal suture Petrosquamous suture Sphenoethmoidal suture Sphenopetrosal suture