Sutures are cranial joints and are formed where two bones adjoin. A fontanel is formed when two or more sutures meet.

Types of Sutures

  • The lambdoidal suture is shaped like the Greek letter 'lambda' and separates the occipital bone from the two parietal bones.
  • The sagittal suture lies between the parietal bones
  • The coronal suture separates the frontal bones from the parietal bones, passing from one temple to the other.
  • The frontal suture runs between the two halves of the frontal bone.

    In summary:
  • Frontal suture - between the two frontal bones.
  • Sagittal suture - between the two parietal bones.
  • Coronal suture - between the parietal and frontal bones
  • Lambdoid suture - between the parietal and occipital bones.
  • Temporal suture - between the inferior margin of the parietal and temporal bones.

Types of Fontanel

a) The posterior fontanel or lambda: is a diamond shaped space situated at the junction of the lambdoidal and sagittal sutures and it can be recognised vaginally.
b) Anterior fontanel (bregma) - is located at the junction of coronal, sagittal and frontal sutures (3 by 3 cm;, ossifies at 18 months); it can be felt or recognised vaginally

The sutures and fontanels consist of membranous spaces that allow for a degree of overlapping of the skull bones (moulding) during labour and delivery.

Moulding

  • Occurs with the descent of the foetal head into the pelvis to reduce the head circumference.
  • Frontal bones slip under parietal bones.
  • Parietal bones override each other.
  • Parietal bones slip under the occipital bone.
(The anterior fontanel is larger than the posterior fontanel)
Last modified: Tuesday, 21 February 2017, 4:06 PM