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EMBRYOLOGY: Note #1.
Development of the Skeletal System
(3) Sutures
Sutures are fibrous joints connecting the bones of the
skull
The cranial sutures include:
o Coronal suture – connects
the frontal bone and two
parietal bones
o Sagittal suture – connects the two parietal bones
o Lambdoid suture – connects the two parietal bones to
the occipital bone
When the sutures close too early during the development
of a fetus/infant, it can cause
craniosynostosis
(4) Fontanelles
Fontanelles are open areas of the skull where
two bones
come together
These give allowance for brain growth/expansion
There are two fontanelles:
o
Anterior
o
Posterior
The posterior fontanelle closes first before the anterior
The fontanelles will bulge out if cerebrospinal fluid (CSF)
is
elevated
(B) VISCEROCRANIUM
The viscerocranium forms the bones of the face
It develops from the
pharyngeal arches, particularly the
first
The pharyngeal arches are made up of three layers:
o Outer layer – ectoderm
o Middle core – mesoderm (develops into
viscerocranium)
o Inner layer – endoderm (develops
into the primitive
pharynx)
Figure 3. Pharyngeal Arches
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