Fetal Skull: Sutures of Fetal Skull, Fontanels and Diameter of Fetal Skull

Fetal Skull

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Introduction:

The fetal skull is made of flat bones. Fetal skull is larger than compared to any other part of the fetal body. The fetal skull consists of a vault, face and base.

Fetal Skull

Areas of Skull:

    ❑ Vertex

The area midway between the anterior fontanel (bregma), the two parietal bones and upto posterior fontanel (lambda).

    ❑ Brow

The area from the nose and supra-orbital ridges to the anterior fontanel and coronal suture.

    ❑ Face

The area from the junction of the floor of the mouth or mentum to the root of the nose and supraorbital ridges.

    ❑ Sinciput

The area lying in front of the anterior frontanel and corresponds to the area.

    ❑ Occiput

The area between the base of skull and posterior fontanel. Occipit is limited to occipital bone.

Sutures of Fetal Skull:

The joints between two cranial bones are known as sutures.

    A. Sagittal Suture

It is found between two parietal bone. It is also know longitudinal suture.

    B. Coronal Suture

It is found between the frontal and parietal bones of fetal skull.

It is 2 in number.

    C. Frontal Suture

It is found between two frontal bones of fetal skull.

    D. Lambdoid Suture

It separates the occipital bone and the two parietal bone.

    E. Squamous Suture

It is found between parietal bone and temporal bone.

FONTANELS:

A wide gap in the suture line is called fontanel.

    1. Anterior Fontanel

It is also known as Bregma.

It is found at the junction of the frontal and two parietal bones.

It is formed by the junction of one frontal suture, two coronal sutures and one sagittal suture.

It is diamond shaped.

Its length is about 3-4 cm.

Anterior Frontanel close at the age of 1½ year or 18 months of baby (after birth).

    2. Posterior Frontanel

It is also known as Lambda.

It is and found at the junction of two parietal bones and one occipital bone.

It is formed by the junction of the one sagittal suture anteriorly and lambdoid suture on transversely.

It is triangular shaped.

It's length is about 1-1.5 cm.

Posterior Frontanel close at the age of 1½ months or 6 week of baby (after birth).

DIAMETERS OF SKULL

> Anteroposterior Diameters

    ○ Suboccipitobregmatic ➝ 9.5 cm: Extends from the nape of the neck to the center of the bregma.

    ○ Suboccipito-frontal ➝ 10 cm: Extends from the nape of the neck to the anterior end of the anterior fontanel or center of the sinciput.

    ○ Occupitofrontal ➝ 11.5 cm: Extends from the occipital eminence to the root of the nose (Glabella).
    ○ Mento-vertical ➝ 14 cm: Extends from the midpoint of the chin to the highest point of sagittal suture.
    ○ Sabmentovertical ➝ 11.5 cm: Extends from the junction of the floor of mouth and neck to the highest point of sagittal suture.
    ○ Submentobregmatic ➝ 9.5cm: Extends from junction of floor of the mouth and neck to the center of bregma.

Fetal Skull Youtube Video:

> Transverse Diameter

■ Biparietal Diameter ➝ 9.5 cm: It extends between two parietal eminences.

■ Super-subparietal  ➝ 8.5 cm: It extends from a point place below parietal eminence to a point place above the other parietal eminence of opposite side.

■ Bitemporal Diameter ➝ 8 cm: Extends the distance between the antero-inferior end of the coronal suture.

■ Bimastoid Diameter ➝ 7.5 cm: Distance between the tips of the mastoid processes.

CIRCUMFERENCES:

✓ Complete flexion Biparietal ➝ Biparietal-suboccipitobregmatic (almost round) ➝ 27.5 cm

✓ Deflexed ➝ Biparietal-occipito-frontal (oval shape) ➝ 34 cm

✓ Incomplete extension  ➝  Biparietal-mento-vertical (bigger oval shape) ➝  37.5 cm

✓ Complete extension ➝ Biparietal-Submentobregmatic (almost round shape) ➝  27.5cm

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REFERENCE: DC Dutta’s Textbook of OBSTETRICS