What does skull ossification mean?
The bones of the skull are formed in two different ways; intramembranous ossification and endochondral ossification are responsible for creating compact cortical bone or spongy bone. These two terms account for the bones of the face and the bones of both the cranial base and the cranial vault respectively.
Which bones develop from the chondrocranium?
Our description of two anatomical regions of the chondrocranium, the braincase floor cartilages and the cartilages of the pre-occipital lateral wall and roof, and their associations with the early development of the frontal, parietal, basioccipital, and exoccipital bones reveals distinctive patterns in developmental …
When did chordates develop skulls?
Cambrian explosion
Chordates first acquired and developed the head compartment during the Cambrian explosion, a major evolutionary event related to the origin and diversification of body plans in animal phyla [6].
What is neurocranium and dermatocranium?
The neurocranium/chondrocranium includes the box that encloses the brain and the capsules surrounding the sense organs. It protects the brain. 2. The splanchnocranium is the visceral portion of the skull that supports the gills and contributes to the jaws. 3.The dermatocranium is the dermal bone that is believed to.
Is the Dentary part of the dermatocranium?
The dermatocranium comprises the skull roof, the facial skeleton (usually excluding the dentary), and—in fishes—the opercular bones.
Why does the skull have sutures?
Sutures allow the bones to move during the birth process. They act like an expansion joint. This allows the bone to enlarge evenly as the brain grows and the skull expands. The result is a symmetrically shaped head.
How do sutures develop?
Sutures are formed during embryonic development at the sites of approximation of the membranous bones of the cranial bones and as a flexible fibrous tissue uniting the adjacent bones10). The site of suture formation corresponds to the location of major dural reflections.
What is the function of chondrocranium?
The chondrocranium is the large single element of the head skeleton (Figure 3.2). It surrounds and provides support for the brain and sense organs. The scoop-like rostrum projects anteriorly and contains the precerebral cavity.
What did Chordata evolve from?
Then, chordates were thought to have evolved from an ancestral chordate tadpole larva that underwent paedomorphosis and now retains adult characteristics with the larval tail (13). Chordates have also been thought to evolve from a pterobranch-like ancestor (reviewed in refs.
Where did chordates evolve from?
It is thought that chordates evolved from a common ancestor of deuterostomes (echinoderms, hemi- chordates and chordates) by organizing these characteristic features.