Fetal Skull, Areas of Skull, Sutures, and Fontanelles, Diameters of Skull, (by GS India Nursing).

Fetal Skull:-

Fetal skull is to some extent compressible and mainly of thin pliable ( flat) bones forming the vault. This is anchored to the rigid and incomprehensible bones at the base of the skull.

Areas of skull:- The skull is arbitrarily divided into several zones of obstetrical importance these are.

Vertex:-

It is quadrangular area bounded anteriorly by the Bregma and coronal sutures behind by the Lambda and lambda sutures and literally by lines passing thought the parietal eminence.

Brow:-

It is an area bounded on one side why the anterior fontanelle and coronal sutures and on the other side by the root of the nose and Supra-orbital ridges of either side.

Face:

It is an area bonded on the one side by root of the nose and Supra-orbital ridges and on the other by the junction of the floor of the mouth with neck.

Sutures:-

The sagittal Or longitudinal suture:- lies between two parietal bones.

The coronal sutures:- Run between parietal and frontal bones on either side.

The frontal sutures:- lies between two frontal bones.

The Lambdoid sutures:- Separate the occipital bone and the two parietal bones.

Fontanelle:-

Wide gap in the suture line is called fontanelle. Of the many fontanelle 6 in number, two are of obstetric significance– 1. Anterior fontanelle or bregma and posterior or fontanelle Lambda.

Anterior fontanelle:-

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. It’s anteroposterior and transverse diameters measure approximately 3.cm each. The floor is formed by a membrane and it becomes ossified 18 months after birth. It becomes pathological, if it fails to ossify ever after 24 months.

Posterior fontanelle:-

It is formed by junction of three suture lines– sagittal suture anteriorly and Lambdoid suture on either side. It is triangular in shape and measure about 1.2X 1.2 cm (1/2″X 1/2″). It’s floor is membranous but become bony at term. Thus, truly it’s nomenclature as fontanelle is misnomer. It denotes the position of the head in relation to maternal pelvis.

Sagittal fontanelle:-

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.

Diameters of Skull:-

The engaging diameter of the fetal skull depends on the degree of flexion present. The Anterior-posterior diameters of the head which may engage are.

Diameters, measurement in cm, attitude of head, presentation:-

1. Suboccipito-bregmatic — extend from the nape of the neck to the center of the Bregma. Measurement in cm ( inches), 9.5 cm (3/4). — Attitude of the head, Complete flexion. Presentation, Vertex.

2. Suboccipito-frontal– extend from the nape of the neck to the anterior end of the anterior fontanelle or center of the sinciput. Measurement in cm ( inches), 10 cm (4). Attitude of the head, Incomplete flexion. Presentation, vertex.

3. Occipital-frontal — extends from the occipital eminence to the root of the nose (Glabella). Measurement in cm (inches), 11.5 cm (4/4). Attitude of the head, Marked reflexion. Presentation, vertex.

4. Mento-vertical– extend from the mid point of floor of the chin to the highest point on the sagittal suture. Measurement in cm (inches). 14 cm (5/2). Attitude of the head, partial extension. Presentation, brown.

5. Submento-vertical– extend from junction of floor of the mouth and neck to the highest point on the sagittal suture. Measurement in cm ( inches). 11.5 cm (4/2). Attitude of the head, incomplete extension. Presentation, face.

6. Submento-bregmatic– extend from junction of floor of the mouth and neck to the center of the Bregma. Measurement in cm (inches). 9.5 cm (3/4). Attitude of the head, complete extension . Presentation, face.

The transverse diameters which are concerned in the mechanism of labour are:-

Biparietal diameter:-

9.5 cm, it extend between two parietal eminence whatever may be the position of the head this diameter nearly always engages.

Super-subparietal:-

8.5 cm, it extends from a point placed below one parietal eminence to a point placed above the other parietal eminence of the opposite side.

Bitemporal diameter:-

8 cm, it is the distance between the antero-inferior ends of the coronal suture.

Bimastoid diameter:-

7.5 cm, it is the distance between the tips of the Mastoid processes. The diameter is incompressible and it is impossible to reduce the length of the bimastoid diameter by obstetrical operation.

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By GS India Nursing………..!!

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