ANAT2341 Lab 6 - Postnatal

Introduction

Fetal Head (12 weeks) showing bone and cartilage

The Skull is a unique skeletal structure in several ways: embryonic cellular origin (neural crest), form of ossification (intramembranous and endochondrial) and flexibility (fibrous sutures).

The cranial vault (which encloses the brain) bones are formed by intramembranous ossification.
While the bones that form the base of the skull are formed by endochondrial ossification.
The bones enclosing the brain have large flexible fibrous joints (sutures) which allow:

the head to pass through the birth canal
postnatal brain growth

ossification continues postnatally, through puberty until mid 20s.
in old age the sutures separating the vault plates are often completely ossified.
Flexible fibrous sutures allow growth of the brain to be accomodated by calvarial plate growth.
Recent molecular studies have show that noggin (a BMP antagonist) is involved in closure of these sutures.

Postnatal Skull

Skull CT Vertex, later and basal views.^[1]

rapid brain growth in the early years of life (growth of the neurocranium stopping at about 7 years of age).
fontanels usually close by the second year of life
- posterior fontanel by about 3 months.
- anterior fontanel by about 20 months.
Complete sutural fusion occurs after the third decade of life.

Sutures and Fontanels