FETAL SKULL

PRESENTER- NITIKA SHARMA MSC(N) 1ST YEAR

INTRODUCTION 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 without complication.

FETAL SKULL• 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)• Face• Base

VERTEXIt 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 eminences.

BROWIt 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.

FACE 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.

SINCIPUT It is the area lying in front of the anterior fontanelle and corresponds to the area of brow.

OCCIPUT It is the area limited to the occipital bone.

SUTURESFlat 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.

IMPORTANCE

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.

ANTERIOR FONTANELLE: Formed by joining four sutures in midplane.Anteriorly frontal bone-.Posteriorly saggital.On either side coronal suture. Diamond like shape.Floor is made by a membrane.Ossified at 18months after birth.

FONTANELLES

IMPORTANCE• 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 tension.

• Collection of blood and exchange transfusion, on rare occasion, can be performed through it via the superior longitudinal sinus.

• Cerebrospinal fluid can be drawn, although rare, through the lateral angle of the anterior fontanelle from the lateral ventricle.

POSTERIOR FONTANELLE:

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.

SAGGITAL FONTANELLE:- 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.

LANDMARKS• 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

side.• 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

eminences.• Bi temporal- is the distance between two lower end of coronal

suture.

DIAMETER OF SKULL

TRANSVERSE DIAMETER:-• 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

coronal suture.

LONGITUIDNAL DIAMETER

• Sub-occipitobregmatic- 9.5cm. The diameter from below the occipital protuberance to the center of the anterior fontanelle.

• 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.

Continued…..

• 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.

SUMMERIZATION

Today we discussed about the Fetal skull:-• Definition• Parts of the fetal skull• Sutures• Fontanelle• Region and landmarks of the fetal skull.• Diameters of Fetal skull

BIBLIOGRAPHYShirish 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