Human Body Bones 4

The skull (from the Greek κ? Ανίον kranion and Latin cranium) is a bony case that protects and contains the brain primarily. The human skull consists of 8 huesos1 joint, forming an open cavity of variable thickness and ovoid, with an approximate capacity of 1,450 ml (adults).

The skeleton of the head, or solid neo-facial skeleton is the set of skull bones (ossa cranii PNA) and the bones of the face (ossa faciei PNA), known colloquially as the skull, but anatomically is the head bone, the skull being a part of the head. It is common to designate the whole skull head bone, which is inappropriate in the study of anatomy. However, in other areas (embryology, biology, etc..) Is considered synonymous with the skull of the head skeleton.

The distinction between the skull and face is very clear: the skull houses the brain, primarily the neurocranium, while the face provides attachment for the muscles of facial expression and mastication and houses some of the sense organs. The skull plays an important role, as they contain all the worries of the central nervous system, except for the core.

The skull, as a cavity, can be seen from inside the cavity as endocranium, or from the outside as exocráneo. In turn, together, can be divided by a horizontal section passing through the middle frontal eminence and the external occipital protuberance, into two parts:

a top, the skull and cranial vault (calvaria PNA), a bottom, the base of the skull (basis cranii PNA).

This division is not arbitrary. Part of different embryological origin of the bony structures: endochondral ossification for the bones of the skull base, and intramembranous ossification for the bones of the skull.

The vault is formed by the parental (vertical part), the parietal, temporal scales and the occiput (top). It is covered by the scalp, bones are joined by a few joints called sutures: coronal suture frontoparietal, between the frontal and parietal, interparietal or sagittal suture between the two parietal or parietooccipital and lambdoidal suture between the occipital and parietals.

Cranial cephalic structures originate from mesenchymal cells derived from neural crest and paraxial mesoderm. The bones that form the skull does not have the same origin, so is the difference between the regions of the cranial vault and base.

Membranous Neurocráneno - cranial vault

The bones of the skull are flat bones of coating. These are generated by the process of intramembranous ossification from sheets of fibrous connective tissue (mesenchyme) surrounding the brain. Thus, centrifugally develop (ossify) a flat amount of membranous bones. At birth, the bones of the skull are not fused nor totally ossified, leaving interosseous spaces covered by fibrous tissue (sutures and fontanelles).

Cartilaginous neurocranium (chondrocranium) - base of skull

The bones of the skull base are developed through the process of endochondral ossification from the chondrocranium, a structure consisting of several separate nuclei and cartilaginous osteosteogénicos widespread throughout the region (prechordal chondrocranium originated from the neural crest, and chordal chondrocranium paraxial mesoderm originated from )

Fontanelles and sutures - Skull of a newborn

At birth, the flat bones of the skull are not fully ossified and are separated by spaces occupied by fibrous connective tissue (derived from neural crest) that further contribute to the final formation of bones and their articulation (sinfibrosis) . Thus these spaces are the metopic suture, coronal, sagittal and lamdoidea. At sites where more than two bones articulate, sutures are wide and six fontanels are:

two odd and middle: anterior and posterior fontanelles, and two lateral pairs: posterolateral (mastoid) and anterolateral (sphenoid).

The sutures and fontanelles have importance in labor, as a mechanical support of overlap between the bony plates of the skull (modeling) that allows the passage of the fetal head through the birth canal. During the postpartum period, the bones back to their original position. During childhood, palpation of the anterior fontanelle to verify the normality of development and ossification of the skull as well as intracranial pressure.

Growth and consolidation

The sutures and fontanelles ossify take years to complete and achieve total coaptation between the pieces of the skull bone. The growth of the bones of the vault that continues into adulthood is at the expense of the fibrous material of the sutures and fontanelles. This mechanism allows a certain complacency of the braincase for brain growth and adaptation according to the development and craniofacial growth. The cranial capacity is reached to complete the 5 years.



Bones of the human body