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Portrait of Cranial sutures

Anatomy · Joints & cartilage

Cranial sutures

Fibrous joints of the skull

Skull · fibrous joints

Cranial sutures are the thin seams of fibrous connective tissue that join the flat bones of the skull. They are fibrous joints that allow almost no movement in adults, but in a baby they let the skull bones override at birth and grow as the brain enlarges. The four main ones are the coronal, sagittal, lambdoid and squamous sutures.

How to spot them

  • ▸Coronal: runs from side to side across the top of the skull, between frontal and parietal bones
  • ▸Sagittal: runs front to back along the midline between the two parietal bones
  • ▸Lambdoid: at the back, between the parietal bones and the occipital bone, shaped like the Greek letter lambda
  • ▸Squamous: on the side of the skull, between the parietal and temporal bones

What to know

Joints that look like jagged seams and hardly move in adults but allow the head to squeeze through the birth canal

Cranial sutures — fibrous joints (synarthroses).

The one across the top of the skull, between the frontal and parietal bones, named for the place a crown would sit

Cranial sutures — the coronal suture.

The midline seam between the two parietal bones, named from the Latin for an arrow

Cranial sutures — the sagittal suture.

The seam at the back of the skull, shaped like a Greek letter, joining parietal and occipital bones

Cranial sutures — the lambdoid suture.

Premature fusion of them in an infant distorts the shape of the head and can raise pressure on the brain

Cranial sutures — craniosynostosis.

Key ideas

  • Growth seams: new bone is laid down at the sutural edges as the brain grows, and the sutures gradually fuse in adulthood.
  • At birth they are unfused, and the fontanelles ('soft spots') lie where several sutures meet.

Quick-fire facts

  • •Sutures are fibrous joints (synarthroses): immovable.
  • •OpenStax: the coronal and sagittal sutures are on top of the skull; the sagittal joins the lambdoid suture behind; the squamous suture is on the lateral skull.
  • •The junction of the coronal and sagittal sutures is bregma; the junction of sagittal and lambdoid is lambda.
  • •The anterior fontanelle, where the sagittal and coronal sutures meet, typically closes at around 12 to 18 months.
  • •The metopic suture between the halves of the frontal bone usually closes in infancy but persists in a minority of adults.
  • •Craniosynostosis is premature fusion of one or more sutures.
  • •Small extra bones, sutural (Wormian) bones, may lie within a suture, most often the lambdoid.
  • •The word suture is from the Latin for a seam.

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Sources