Fetal skull

Obstetrics

2. FETAL HEAD
The skull is made up of the base of
skull and the vault or cranium.
The vault is made of occipital bone
posteriorly, the two parietals at the
sides ,and the temporal bones and
frontal bones anteriorly.
These bones at birth are thin,easily
compressible and joined by
membrane.

3. SUTURES
Sagittalsuture
Frontal suture
Coronal suture
Lambdoidalsuture

4. Clinical significance
1)Sutures make mouldingpossible and some amount
of mouldingis needed for vaginal delivary.
2)In hydrocephalus, there is suturalseperation,
resulting in .‘islets of bone in a sea of membranes.’
3)Palpation of the sagittalsuture during vaginal
examination gives an idea of the degree of internal
rotation.

5. FONTANELLES
Fontanellesare the membrane-filled spaces at the meeting point of
the sutures.
•ANTERIOR FONTANELLE OR BREGMA
* Meeting point of sagittal,coronaland
frontal sutures .
*Diamond shaped
*Measures 3×2 cm.
*Ossifies by one and a half years.
•POSTERIOR FONTANELLE OR LAMBDA
*Junction of sagittalsuture and the two lambdoidalsutures
*Smaller than the anterior fontanelle
*Y shaped
*Closes at 6-8 weeks

7. Clinical significance
1.Palpation of posterior fontanelleduring vaginal
examination denotes position of the head.
2.Palpation of the anterior fontanellewill denote the
degree of flexion of the head .
3.After birth ,fontanelleare useful to asses the
condition of the baby .
4.The fontanellesremain membraneousfor some time
after birth . This helps to accomadatethe marked
growth of the brain.

8. BONY LANDMARKS
oOcciputis the area occupied by the occipital bone and is
behind and below the posterior fontanelle.
oVertexis the area bounded by the two fontanellesand the
parietal eminences.
oSinciputor brow is the area bounded by the bregmaand
coronal sutures superiorly and inferiorly by the orbital
ridges.
oGlabellais the raised area between the orbital ridges.
oNasionis the root of the nose.
oParietal bosses are the two eminences on the side of each
parietal bone.

9. DIAMETERS OF FETAL SKULL
ANTERO-POSTERIOR DIAMETERS
1)Suboccipit0bregmatic diameter (9.4 cm) extends
from the undersurface of the occipital bone where it meets
the neck,tothe centre of the anterior fontanelleor
bregma.Itis the diameter that presents when the head is
well flexed and in occipitoanteriorposition.
2)Occipitofrontaldiameter(11 cm) extends from the
external occipital protruberanceto the glabellaand
presents when the head is deflexed as in occipitoposterior.
3)Suboccipitofrontal(10.5 cm) is another presenting
diameter in occipitoposterior.

11. 4) Verticomental(13.5 cm) extends from the vertex to
the chin and It is the longest antroposteriordiameter
of the head and the diameter in which brow presents.
5)Submentobregmatic(9.4 cm) extends from the
junction of the neck and lower jaw to the centre of the
anterior fontanelleand is the diameter in face
presentation.

12. TRANSVERSE DIAMETERS
1)Biparietal(9.4 cm) is the largest transverse diameter
in all cephalic presentations. The head is said to be
engaged when the biparietaldiameter has passed
through the pelvic brim. It extends between the two
parietal bosses.
2)Bitemporaldiameter(8 cm) is the shortest
transverse diameter and is between the two
temporals.
3)Supersubparietal(8.5 cm) extends from a point
below one parietal eminence to another placed above
the opposite parietal eminence.

14. RELATIONSHIP BETWEEN THE
FOETUS AND PELVIS
1)LIE; relationship between the long axis of fetal ovoid
to the long axis of uterine ovoid.

15. PRESENTATION;partof the fetus that lies over the
pelvic inlet and ccupiesthe lower pole of uterus.

16. PRESENTING PART; dependent part of the fetus which
is felt first on vaginal examination.
ATTITUDE;relationof the fetal parts to each other.
The main attittudesare flexion and extension.

17. DENOMINATOR ;arbitrarily chosen point on the
presenting part of the fetus, which is used to describe
the position.
POSITION;relationship of the denominator to the four
quadrants of maternal pelvis.