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MSC(N) 1ST YEAR
The fetal head is large in relation to the fetal body
compared with adult.
Adaptation between the skull and the pelvis is necessary
to allow the head to pass through the pelvis during labour
• The skull bones encases and protect the brain.
• Fetal skull is compressible, and made mainly of thin
pliable tabular(flat) bones forming the vault.
• The fetal skull has three major parts :
• Vault of the cranium (Roof)
It is a quadrangular area bounded anteriorly by the bregma
and coronal suture behind by the lambda and lambdoidal
sutures and laterally by lines passing through the parietal
It is an area bounded on one side by the anterior fontanelle
and coronal sutures and on the other side by the root of the
nose and supra-orbital ridges of either side.
It is the area bounded by the root of the nose and supra-
orbital ridges and on the other, by the junction of the floor of
the mouth with neck.
It is the area lying in front of the anterior fontanelle
and corresponds to the area of brow.
It is the area limited to the occipital bone.
Flat bones of the vault are united together by the non-
osssified membranes attached to the margins of the
bones. These are called sutures.
THE SAGGITAL SUTURE:
Lies b/w two parietal bones.
THE CORONAL SUTURES :
Run b/w parietal and frontal bones on either sides.
THE FRONTAL SUTURE :
Lies b/w two frontal bones.
THE LAMBDOIDAL SUTURES :
Separate the occiput bone and two parietal bones.
It permits gliding movement of one bone over the other
during moulding of the head.
Digital palpations of sagittal suture during internal
examination in labour gives an idea of the manner of
engagement of the head, degree of internal rotation of the
head and degree of moulding of the head.
Wide gap in the suture line is called fontanelle.
Formed by joining four sutures in midplane.
Anteriorly frontal bone-.
On either side coronal suture. Diamond like shape.
Floor is made by a membrane.
Ossified at 18months after birth.
• Its palpation through internal examination denotes the
degree of flexion of the head.
• It facilitates moulding of the head.
• As it remains membranous long after birth, it helps in
accommodating the marked brain growth, the brain
becoming almost double its size during first year of life.
• Palpation of the floor reflects intracranial status-
depressed in dehydration, elevated in raised intracranial
• Collection of blood and exchange transfusion, on rare
occasion, can be performed through it via the superior
• Cerebrospinal fluid can be drawn, although rare, through
the lateral angle of the anterior fontanelle from the lateral
Formed by junction of three sutures.
Saggital suture anteriorly.
Lambdoidal suture on either side.
Triangular in shape.
Measure about 1.2 x1.2cm.
Its floor is membranous but become bony at 3months.
It is inconsistent in its presence. It is situated on the
saggital suture at the junction of anterior to two-third
and posterior one-third.
It has got no clinical importance.
• Occiput- is the occipital bone/external occipital protuberance.
• Sinciput- is the forehead region of fetal head.
• Parietal eminences- are the eminences of parietal on either
• Mentum- it is the chin.
• Vertical point- it is the center of saggital suture.
• Frontal point- is the root of nose.
• Sub occiput- 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
• Bi temporal- is the distance between two lower end of coronal
DIAMETER OF SKULL
• Bi parietal Diameter-
Measure about 9.5cm.
It extends between two parietal eminences.
• Bi-temporal diameter-
Measure about 8cm.
It is the distance between anterio-inferior ends of the
• Sub-occipitobregmatic- 9.5cm. The diameter from
below the occipital protuberance to the center of the
• Sub-occipitofrontal- 10cm. The diameter from below the
occipital protuberance to the center of the frontal suture.
• Occipitofrontal-11.5cm. The diameter from the occipital
protuberance to the glabella.
• Mentovertical-13.5cm. The diameter from the point of
the chin to the highest point on the vertex, slightly nearer
to the posterior than to the anterior fontanelle.
• Submentovertical-11.5cm. the diameter from the point
where the chin joins the neck to the highest point where
the chin joins the neck to the highest point on the vertex.
• Submentobregmatic-9.5cm. The diameter from the point
where the chin joins the neck to the center of bregma.
Today we discussed about the Fetal skull:-
• Parts of the fetal skull
• Region and landmarks of the fetal skull.
• Diameters of Fetal skull
Shirish S Sheth,“Essential of Obstetrics”, 1st Edition,
Jaypee Brothers Medical Publishers, New Delhi,2004,
page no.: 102 - 104.
Diane M, “Myles textbook for Midwives”, 14th edition,
Elsevier Publisher, London, 2008, page no: 157-160
Dutta D.C, “Textbook of obstetrics” 7thedition Published
By New Central Book Agency, page 86-89