The document summarizes key aspects of the fetal skull, including its bones, sutures, and fontanelles. The fetal skull is dome-shaped and composed of bones that fuse together over time. It has several soft spots called fontanelles that allow the skull to change shape during birth. The largest fontanelle is the anterior fontanelle, located at the junction of the frontal and parietal bones, which usually closes between 12-18 months. Premature fusion of skull bones can cause craniosynostosis disorders that deform the skull.

1. Foetal Skull
Sameeullah Azeem
PG 2nd Year
AIIMS Rishikesh

2. Contents
• Regions of foetal skull
• Bones
• Sutures
• Fontanelles
• MCQs

3. Introduction
• At birth, the calvaria is large in proportion to
other skeletal parts, reflecting cerebral
maturation.
• The facial region is relatively small and
constitutes only about one-eighth of the
neonatal skull, whereas it constitutes about
half of the adult skull.

4. Introduction
Adult Skull Fetal Skull

5. Adult and Fetal Skull

6. Fetal Skull
• Skull bones encase
and protect the
brain
• Major 3 Parts
Vault
Face
Base

7. Bones of the Vault
2 Frontal Bones
2 Parietal Bones
1 Occipital Bones
2 Temporal Bones

8. Vault
• Large, dome shaped part above an imaginary
line drawn between the orbital ridges and
nape of the neck
• Base
Base comprises bones that firmly united to
protect the vital centers in the medula
oblangata
Face
Comprises of 14 bones that are firmly united and are
non-compressible

9. 2 Frontal Bones
• Form the forehead or
Sinciput
• The ossification center
of each bone is frontal
eminence
• Fuse into single bone by
8 years of age.

10. 2-Parietal Bones
• Lie on either side
and occupy most
of the skull
• Parietal
eminence(Ossificat
ion Centre)

11. Occipital Bone

12. Temporal Bone

13. Fontaneles
• The fibrous membrane that
forms the calvaria remains
unossified at the six angles of
the parietal bones, producing
six fontanelles:
• Two single midline (anterior
and posterior) and
• Two lateral pairs
(sphenoidal/anterolateral and
mastoid/posterolateral).

14. Fontanelles

15. Anterior Fontanelle
• Largest and Rhomboid
• 4 cm AP
• 2.5 Transverse
• Formed between Sagittal,
Transverse and Frontal
Suture
• Closes at 12-18 months.

16. Clinical
• Palpation of fontanelle
is useful clinically.
• Sunken fontanelle
indicates dehydration
• Tense or bulging
anterior fontanelle
indicates
raised intracranial
pressure. E.g
Meningitis ,
Hydrocephalus

17. Posterior Fontanelle
• Triangular
• Between sagital and
lambdoid suture
• Closes at 6-8 weeks
• Delayed closure
suggests
Hyperthyrodism

18. Anteriolateral Fontanelle
• Sphenoidal Fontanelle
• Lies at sphenoidal angle
of Parietal Bone between
the sphenoid, parietal,
temporal, and frontal
bones
• Fuses at 6 Months

19. Posteriolateral Fontanelle
• Mastoid Fontanelle
• Bilateral soft
membranous gaps at the
junction of
the parietomastoid, occi
pitomastoid,
and lambdoid sutures
• Fuse at 6-18 months
• Persists as Asterion

20. Sutures

21. Metopic Suture
• Also known as median
frontal suture
• Vertical fibrous joint that
divides the two halves of the
frontal bone runs cross the
frontal bone from
the nasion to the bregma.
• Fusion 3-9 months

22. Metopic Synostosis
• Premature fusion of the
metopic suture
• Results
in Trigonocephaly.

23. Coronal Suture
• Cranial suture formed
between the two parietal
bones and the frontal
bone.
• Junction of the Anterior
Fontanelle
• Fuses at 24 years of age

24. Oxycephaly
• Craniosynostosis in which
top of the skull is pointed or
conical due to premature
closure of the coronal
suture.
• Most severe form of
craniosynostosis.
• Characterised by
• 8th cranial nerve lesion
• Optic nerve compression
• Mental deficiency

25. Plagiocephaly
• Flat Head Syndrome
• Asymmetric premature
closure of the coronal
suture/lambdoid suture.
• Widespread form is
characterized by a flat
spot on the back or one
side of the head caused
by remaining in a supine
position for prolonged
periods

26. Sagittal Suture
• Midline articulation that
joins the two parietal
bones
• Normal fusion at 22
years.

27. Scaphocephaly
• Most common form
of craniosynostosis
• Premature closure of
the sagittal suture
• Results in an impediment
to the lateral growth of
the skull while
anteroposterior growth
continues, producing a
narrow and elongated
skull.

28. Squamosal Sutures
• Arches backward from
the pterion and connects
the temporal squama
with the lower border of
the parietal bone
• May not completely
close until 60 years of
age.

29. Lambdoid Suture
• Junction between the
superior border of
the occipital bone and the
posterior borders of the
right and left parietal bones
• Fuses at approximately 26
years

30. Sphenofrontal Suture
• Between Frontal and Sphenoid Bone
• Anteriorly suture appears on the roof of the
bony orbit.
• Laterally as meeting point of inferior posterior
edges of frontal bone and anterior, superior
edge of the greater wing of the sphenoid bone
• Fuses at 15 years of age.

32. Questions

33. • 1) At what age the anterior fontanelle fuse?
a) 12-18 Months
b) 18-36 Months
c) 6-12 Months
d) 3-6 Months
Ans : A

34. • 2) A mother bought her 1 month old baby in the OPD
with the complaint of fever. The physician did the
physical examination and found raised intracranial
pressure. Which of the following fontanelles suggest
the same after proper palpation ?
a) Anterior
b) Posterior
c) Sphenoidal
d) Mastoid
Ans : A

35. 3) Trigonocephaly results from which of the
following Synostosis?
a) Lambdoid
b) Sagital
c) Coronal
d) Mitopic
Ans: D

36. Bibilography
Grays Anatomy 41st Edition
Radiopedia