fetal skull

Name the 3 main regions of the fetal skull

Base, face, vault

Name 4 main bones of the fetal skull which provide a landmark for midwives

• Frontal bones

• Parietal bones

• Occipital bone

• Temporal bones

What is the term used for the point between the eyebrows

Glabella

What is the term used for the chin

Mentum

What does the term ossification mean ?

• the process of bone formation which begins in the fetus

• Ossification between mesenchyme layers surrounding the brain

Define a suture

• Cranial joints where 2 bones adjoin

• Gaps between bones spanned by membrane which are progress ossification

Define a frontanelle

Where 2 or more sutures meet

Name the 4 main sutures of the fetal skull

• Coronal

• Frontal

• Sagital

• Lambdoidal

What are the 2 frontanelles called

• Anterior frontanelle

• Posterior frontanelle

What is the other term for the anterior frontanelle

Bregma

What is the other term for the posterior frontanelle ?

Lambda

Describe the main differences between the two frontanelles

Anterior

• diamond shaped

• 4 points

• 3 sutures meet (frontal, coronal, sagital)

• Known as bregma

Posterior

• triangle shaped

• 3 points

• 2 sutures meet (sagital,lambdoidal)

Describe what is ment by the attitude of the fetus/ fetal head

The degree of flexion/ extension of the fetal head and limbs in relation to fetal spine

What are the measurements of the longlitudal diameters of the fetal skull

• Suboccipitobregmatic

• Suboccipitofrontal

• Occipitofrontal

• Mentovertical

• Submentovertical

• Submentobregmatic

• Suboccipitobregmatic - 9.5cm

• Suboccipitofrontal - 10cm

• Occipitofrontal - 11.5cm

• Mentovertical - 13.5cm

• Submentovertical - 11.5cm

• Submentobregmatic - 9.5cm

What are the 2 transverse diameters and their measurements

• biparietal (8.5cm)

• Bitemporal (8.2cm)

Vertex presentation

• occipito- anterior position

• Well flexed head

• SOB diameter of 9.5cm

• Bi- parietal diameter of 9.5cm

Presentations- vertex (occipito posterior)

• ertect/deflexed head

• OF diameter presents (11.5cm)

• Biparietal diameter (9.5cm)

• OF diameter will descend the vagina and perineum more

Face presentation

• head completely extended

• SBM diameter(9.5cm)

• Bi temporal diameter (8.2cm)

• SMV diameter will distend (dilate/expand) the vaginal orifice (11.5cm)

Brow presentation

• partially extended head

• MV diameter 13.5cm

• Bi temporal diameter 8.2cm

• Vaginal delivery extremely unlikely as MV diameter too long

Moulding

• Bones are able to override each other at sutures

• Results in reduction in size of the presenting diameter

• But the diameter at the right angle lengthens

• Head becomes thinner but longer