Fetal Skull

Maximum diameter of foetal head is Occipitofrontal (11.50cm) that is the engaging diameter of the occipitoposterior position. Occipito-frontal extends from the occipital eminence to the root of the nose (Glabella).
Biparietal diameter (9.5cm) extends between two parietal eminences.
Bitemporal diameter (8 cm) is the distance between the antero-inferior ends of the coronal suture.
Suboccipitobregmatic (9.5cm) extends from the nape of the neck to the anterior end of anterior fontanelle or centre of the sinciput.

Also Know:

Mento-vertical diameter is 14 cm which extends from the midpoint of the chin to the highest point on the sagittal suture.

Must know:

Submento vertical diameter: 11.5 cm. It extends from junction of floor of the mouth and neck to the highest point on the sagittal suture.

• Occipitofrontal: It follows a line extending from a point just above the root of the nose to the most prominent portion of the occipital bone. 11.5cm
• Biparietal : It is the greatest transverse diameter of the head, which extends from one parietal boss to the other. 9.5cm.
• Bitemporal: It  is the greatest distance between the two temporal sutures. 8cm.
• Occipitomental: It extends from the chin to the most prominent portion of the occiput. 12.5cm.
• Suboccipitobregmatic: It  follows a line drawn from the middle of the large fontanel to the undersurface of the occipital bone just where it joins the neck. 9.5cm.

• Occipitofrontal: It follows a line extending from a point just above the root of the nose to the most prominent portion of the occipital bone. 11.5cm
• Biparietal: It is the greatest transverse diameter of the head, which extends from one parietal boss to the other. 9.5cm.
• Bitemporal: It  is the greatest distance between the two temporal sutures. 8cm.
• Occipitomental: It extends from the chin to the most prominent portion of the occiput. 12.5cm.
• Suboccipitobregmatic: It  follows a line drawn from the middle of the large fontanel to the undersurface of the occipital bone just where it joins the neck. 9.5cm.

It does not disappear within 2-3 days

Ans. is a i.e. Brow presentation

Palpation on per vaginal examination                      Presentation

Also Know :

On palpation, difference between face and breech presentations :

Face

• Mouth and malar eminences form a triangle
• Alveolar margins hard
• Sucking effect of mouth
• No meconium staining

Breech

• lschial tuberosities & anus are in a line
• Anal margins soft
• Grip of anal sphincter
• Meconium staining on finger

A i.e.At term

Posterior fontanella closes /ossifies at At term   and anterior fontanella ossifies at 18 months

6

C i.e. 30-35

Ans. D: 18 months

The fontanelle allows the skull to deform during birth to ease its passage through the birth canal and for expansion of the brain after birth.

While the posterior and lateral fontanelles are obliterated by about six months after birth, the anterior is not completely closed until about the middle of the second year.

Full ossification starts in the late twenties and finishes before the age of 50

A sunken fontanelle indicates dehydration.

A very tense or bulging anterior fontanelle indicates raised intracranial pressure.

Ans. Collection of sero-sanguineous fluid in the scalp

The suture marked by an arrow above represents metopic suture.

• The metopic suture (also known as the median frontal suture) is a type of calvarial suture. It is often associated with frontal sinus agenesis or hypoplasia.
• This suture runs through the midline across the frontal bone from the nasion to the bregma although it may often be incomplete.
• The metopic suture is usually closed by about 6 years of age, but in rare cases it can persist  as an anatomical variant of little clinical significance but that it can be mistaken for frontal bone fracture.
• A premature fusion of the suture is termed metopic synostosis (type of  craniosynostosis) which can then result in trigonocephaly.

The largest diameter of fetal skull is occipito-mental i.e 13.5 cms.

In the picture above-

1- Submento-bregmatic 9.5 cms

2-Suboccipito-bregmatic 9.5 cms;

4-Occipito-frontal 11.5 cms

Diameter,2 shown in the fetal skull photograph above represents Biparietal diameter. The biparietal (9.5 cm), the greatest transverse diameter of the head, which extends from one parietal boss to the other.

Diameter,2 shown in the fetal skull photograph above represents Biparietal diameter. The biparietal (9.5 cm), the greatest transverse diameter of the head, which extends from one parietal boss to the other.

 “Diameter B” of fetal skull as shown in the picture above represents bitemporal diameter which measures about 8 cms.

Ans. is ‘c’ i.e., 6 years 

Infant’s skull consists of following sutures :-

1. Coronal suture
2. Saggital suture
3. Lambdoid suture
4. Metopic suture (median frontal suture).

• Coronal suture: This is placed between the frontal bone and the two parietal bones. The suture crosses the cranial vault from side to side and runs downwards and forwards.
• Sagittal suture: It is placed in the median plane between the two parietal bones.
• Lambdoid suture: It lies posteriorly between the occipital and the two parietal bones, and it runs downwards and forwards across the cranial vault.
• Metopic suture: This is occasionally present in about 3 to 8% individuals. It lies in the median plane and separates the two halves of the frontal bone. Normally it fuses at 6 years of age.