FETAL SKULL SUTURES and FONTANELLES
SUTURES: -Are spaces between the bones of the skull.
- The sagittal or longitudinal suture lies between two parietal bones.
- The coronal sutures run between parietal and frontal bones on either side.
- The frontal suture lies between two frontal bones.
- The lambdoid sutures separate the occipital bone and the two parietal bones.
- It permits gliding movement of one bone over the other during molding of the head, a phenomenon of significance while the head passes through the pelvis during labor.
- Digital palpation of sagittal suture during internal examination in labor gives an idea of the manner of engagement of the head, degree of internal rotation of the head and degree of molding of the head.
A membrane-covered opening in bone or between bones. Wide gap in the suture line is called fontanel. Two are of obstetric significance:
- Anterior fontanel or bregma.
- Posterior fontanel or lambda.
Anterior fontanel –
It is formed by joining of the four sutures in the midplane. The sutures are anteriorly frontal, posteriorly sagittal and on either side, coronal. The shape is like a diamond.
Its anteroposterior and transverse diameters measure approximately 3 cm each. The floor is formed by a membrane and it becomes ossified 18 months after birth
- Its palpation through internal examination denotes the degree of flexion of the head.
- It facilitates molding of the head.
- As it remains membranous long after birth, it helps in accommodating the marked brain growth; the brain becoming almost double its size during the first year of life.
- Palpation of the floor reflects intracranial status—depressed in dehydration, elevated in raised intracranial tension.
- Collection of blood and exchange transfusion, on rare occasion, can be performed through it via the superior longitudinal sinus.
- Cerebrospinal fluid can be drawn, although rarely, through the angle of the anterior fontanel from the lateral ventricle.
It is formed by junction of three suture lines — sagittal suture anteriorly and lambdoid suture on either side. It is triangular in shape and measures about 1.2 × 1.2 cm. The posterior fontanelles ossify within 6–8 months after birth.
It is inconsistent in its presence. When present, it is situated on the sagittal suture at the junction of anterior two-third and posterior one-third. It has got no clinical importance.