The skull divided into; the vault, face and base. The skull divided into; the vault, face and base

The skull divided into; the vault, face and base.

• The skull divided into; the vault, face and base.

• By the time of birth the bones of the face and base are all firmly united,

• but the bones of the vault are not so well ossified, being joined only by un ossified membranes at the sutures.

• During labour the bones of the vault can undergo moulding, by which the shape of the skull can be altered by overriding the cranial bones with reduction of some of its diameters.

• The bones which form the vault are the parietal bones, and parts of the occipital, frontal, and temporal bones.

• FONTANELLES

• The points of junction of the various sutures are termed fontanelle

It is a diamond shaped area of unossified membrane formed by the junction of 4 suture.

• It is a diamond shaped area of unossified membrane formed by the junction of 4 suture.

• The suture are:-

• * Anteriorly:- frontal suture

• * Posteriorly:- sagittal suture

• * Laterally, on both side:-coronal suture.

• It is felt on fetal head surface as a soft shallow depression.

• It ossifies by 18 months after birth.

• Clinical importance:-

• 1. Degree of flexion can be assessed from its position. If on vaginal examination it is felt easily, it indicates the head is not well flexed.

• 2. It helps in the moulding of head.

• 3. From its position, internal rotation of the head can be assessed.

• 4. ICP can be roughly assessed from its condition after birth. Depression in dehydration and bulging in raised ICP.

The area of the fetal skull bounded by the two parietal eminences and the anterior and posterior fontanelles is termed the vertex .it is the part of the head which present during labour.

• The area of the fetal skull bounded by the two parietal eminences and the anterior and posterior fontanelles is termed the vertex .it is the part of the head which present during labour.

DIAMETERS OF THE FETAL SKULL

• DIAMETERS OF THE FETAL SKULL

• The diameters of the fetal skull which are important in the mechanism of labour may be divided into vertical, longitudinal, and transverse.

PROCESSES OF THE DURA MATER

• PROCESSES OF THE DURA MATER

• The great folds of the dura mater, the falx cerebri and the tentorium cerebelli, act in some degree as internal ligaments, resisting too great deformation of the fetal head both in the longitudinal and the transverse directions .

• If moulding is excessive ,or if the fetal head is subjected to severe and sudden stresses , these parts of the dura mater are liable to be torn; some of the great venous sinuses are then in danger of rupture. These are the inferior longitudinal sinus, running in the free edge of the falx cerebri and receiving the great cerebral veins of Galen from the brain, and the straight sinus running between the falx cerebri and the tentorium cerebelli.

DIAMETERS OF THE FETAL TRUNK

• DIAMETERS OF THE FETAL TRUNK

• The biacromial diameter is taken between the parts furthest apart on the shoulders and is 12cm.

• The bitrochanteric diameter measures 10cm (for breech ).