Fetal skull

Landmark of Fetal skull 

Occiput:- is the occipital bone/external occipital protuberance.

Sinciput:- is the forehead region of fetal head.

Parietal eminences:- are the eminences of parietal bone on either side.

Mentum:- is the chin.

Vertical point:- is the center of sagittal suture.

Frontal point:- is the root of nose.

Sub occiput:- it is the junction fetal neck and Occiput.

Sub mentum:- it is the junction between neck and chin.

Bi parietal:- is the transverse distance between two parietal eminences.

Bi temporal :- is the distance between two lower end of coronal suture

SUTURES : SUTURES : 

Sagittal suture:- 

This lies in between two parietal bone.

Coronal suture:- 

This lies in between the frontal and parietal bone on either side.

Frontal suture:- 

This lies in between two frontal bone.

Lambdoid suture:- 

It lies in between the parietal and occipital bone on either side.

CLINICAL IMPORTANCE OF SUTURE

These suture permit gliding movement of one bone over  other during moulding of the head in the vertex presentation , as a result the diameter of the head get smaller so passage of head through the birth canal become easier.

Position of fontanelle and sagittal suture can identify attitude and position of vertex.

From the digital palpation of the sagittal suture during labour, degree of internal rotation and degree of moulding of the head can be noticed.

In deep transverse arrest, this sagittal suture lies transversely at the level of the ischial spines.

Area of skull

A. Vertex:- 

It is the quadrangular area bounded anteriorly by the bregma and coronal sutures behind by the lambda and the lambdoid sutures and laterally by the line passing through the parietal eminences.

B. Brow:- 

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

C. Face:- 

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

Diameter of skull

The engaging diameter of the fetal skull depends on the degree of the flexion of the presenting part. 

A. The antero-posterior diameter which may be engaged are:-

1.Sub-occipito bregmatic:-

It extends from the nape of the neck to the centre of anterior fontanelle.

Length:-9.5cm

Attitude:-complete flexion

Presentation:-Vertex.

Clinical importance:- 

Smallest diameter.

FETAL SKULL CHANGES IN LABOUR

Moulding:-It is the changes in shape of the head in vertex presentation during labour while passing through the resistant birth canal.

Mechanism:-  

1. Overlapping of cranial bones at the membranous joints due to compression of the engaging diameter of the head.

2. It is physiological, harmless and disappears within a few hours after birth.

GRADING

Grade 0:- the bones lies side by side having an intervening membrane.

Grade +:- the bone touching but not overlapping

Grade++:- overlapping but easily separated by pressure.

Grade+++:- fixed overlapping and cannot be separated.

CAPUT SUCCEDANEUM

It is localized area of edema on fetal scalp on vertex presentation due to pressure effect of dilating cervical ring and vaginal introitus.

Characteristics:-

It is physiological, present at birth and disappears within 24 hours.

It is soft, diffuse and pits on pressure.

No underlying skull bone fracture.

Cephalhematoma

It is a collection of blood between periosteum and skull bone which is limited by the periosteal attachments at the suture lines.

Characteristics:-

Appears after 12 hours of birth.

Limited by suture lines.

Tends to grow larger.

Disappears within 6-8  weeks.

It is circumscribed, soft and non pitting.

May be associated with skull bone fracture.

Treatment:- No treatment  required. The blood is absorbed and the swelling subside. 

DIFFERENCES