RNAL and Child Health Nursing: Fetal Skull and Ossification

Course Information

• Course title: RNAL AND CHILD HEALTH NURSING
• Course code: NSG 403
• Session: 2020/2021
• Credit: 6 units
• Lecturer: R.A. Oyekale
• Department: Nursing, Faculty of Clinical Sciences

Fetal Skull

• The fetal skull is the most important part of the fetus.
• It is the most common presenting part.
• It contains the delicate brain.
• The head passes through the birth canal under pressure.
• The skull is the largest and least compressible part of the body.
• Smooth delivery is ensured after birth.
• Recognition of normal presentation and positions facilitates birth.
• Minimal trauma to mother and baby is achieved through proper understanding.

Ossification

• Bones in the fetal head originate in two ways:
  • Face: developed cartilaginous, fully ossified at birth, bones fused together
  • Vault: developed membranous, flatter and more pliable, ossifies outwards from centre.
• Ossification process is incomplete when born, leaving gaps
• Gaps become sutures and fontanelles
• Each bone has a boss/protuberance at the ossification center.

Bones of the Vault

• Five main bones:
  • Occipital bone: located at the back of the head, forms the base of the skull containing the foramen magnum: protects the spinal cord as it leaves the skull.
    • Has an occipital protuberance at its center
  • Two parietal bones: lie on either sides.
  • Ossification center of each parietal bone is called the parietal eminence.

Diagram of Bones, Sutures and Fontanelles

• Diagram shows frontal bones, parietal bones, occipital bone, sutures (coronal, sagittal, lambdoid), anterior fontanel, and posterior fontanel, with measurements.

Regions and Landmarks

• Skull divided into vault, base, and face.
• Vault: large dome-shape part above an imaginary line between the orbital ridges and nape of the neck.
• Base: comprised of bones firmly united to protect vital centers.
• Face: composed of 14 bones, firmly united, non-compressible.
• Regions described as:
  • Vertex: quadrangular area bounded by bregma and coronal sutures, lambda and lambdoidal sutures, parietal eminences.
  • Brow: area bounded by the anterior fontanelle and coronal sutures, root of nose, supra-orbital ridges.
  • Face: bounded by the root of the nose and supraorbital ridges, junction of mouth floor and neck.
  • Sinciput: area in front of the anterior fontanelle, similar to brow region
  • Occiput: limited to the occipital bone

Sutures

• Flat bones joined by non-ossified membranes (sutures).
• Four major sutures:
  • Sagittal/longitudinal suture: lies between two parietal bones
  • Coronal sutures: between parietal and frontal bones on either side.
  • Frontal suture: between two frontal bones
  • Lambdoidal sutures: divide occipital and two parietal bones.

Importance of Sutures

• Allows gliding movement during head moulding
• Important during childbirth
• Digital palpation of sagittal sutures helps assess head engagement, synclitism/asynclitism, internal rotation, and moulding degree.

Fontanelles

• Gaps in suture lines called fontanelles
• Two clinically significant fontanelles:
  • Anterior fontanelle (bregma)
  • Posterior fontanelle (lambda)
• Anterior fontanelle: diamond-shaped, formed by joining four sutures,
• Anteriorly: frontal suture, Posteriorly : sagittal suture, Coronal sutures on either sides
• Becomes ossified 18 months after birth, pathological when delayed, its palpation, helps determine the degree of head flexion and helps in moulding.
• Posterior fontanelle: triangular shape, formed by 3 sutures

Diameters of the Skull

• Engaging diameter depends on flexion/extension.
• Attitude: degree of fetal neck flexion/extension during delivery.
• Presentation: part of the fetus located at pelvic brim/lower pole of the uterus.
• Specific diameters (anteroposterior and transverse):
  • Suboccipitobregmatic, suboccipitofrontal, occipitofrontal, mentovertical, submentovertical, submentobregmatic

Moulding

• Skull bones allow slight bending. Bones can override at sutures.
• This allows for reduction in presenting diameters.

This quiz covers essential concepts regarding the fetal skull in relation to childbirth, as well as the process of ossification in the fetal head. Understand the importance of normal presentation and positions for a smooth delivery, and learn how the skull's structure facilitates childbirth. Tighten your knowledge about the anatomy of the fetal skull and its developmental processes in nursing practice.