Usuario:Spirit-Black-Wikipedista/Taller PD
El cráneo humano se encuentra conformado por ocho huesos, sin tomar en cuenta piezas óseas que se conocen bajo el nombre de huesos suturales. Estos ocho huesos integran parte de una única conformación, en conjunto con la cara, conocida como cabeza. Es común que el término cráneo sea usado para designar a la totalidad de la cabeza ósea, lo cual es impropio en el estudio de la anatomía. Sin embargo, en otros ámbitos (como la embriología, biología y demás) se considera el cráneo como sinónimo de esqueleto de la cabeza. En este artículo se refleja la composición del mismo cráneo y los elementos anatómicos que se encuentran en cada uno de los huesos, así como las características mismas y el desarrollo que presenta, cubriendo todos los aspectos relacionados con su estudio anatómico.
Origen y desarrollo[editar]
El cráneo es una estructura compleja; sus huesos están formados tanto por osificaciones intramembranosas como endocondriales.
The skull is a complex structure; its bones are formed both by intramembranous and endochondral ossification. The skull roof, comprising the bones of the splanchnocranium (face) and the sides and roof of the neurocranium, is formed by intramembranous (or dermal) ossification, though the temporal bones are formed by endochondral ossification. The endocranium, the bones supporting the brain (the occipital, sphenoid, and ethmoid) are largely formed by endochondral ossification. Thus frontal and parietal bones are purely membranous.[1] The geometry of the cranial base and its fossas: anterior, middle and posterior changes rapidly, especially during the first trimester of pregnancy. The first trimester is crucial for development of skull defects.[2]
At birth, the human skull is made up of 44 separate bony elements. As growth occurs, many of these bony elements gradually fuse together into solid bone (for example, the frontal bone). The bones of the roof of the skull are initially separated by regions of dense connective tissue called "fontanels". There are six fontanels: one anterior (or frontal), one posterior (or occipital), two sphenoid (or anterolateral), and two mastoid (or posterolateral). At birth these regions are fibrous and moveable, necessary for birth and later growth. This growth can put a large amount of tension on the "obstetrical hinge", which is where the squamous and lateral parts of the occipital bone meet. A possible complication of this tension is rupture of the great cerebral vein of Galen. As growth and ossification progress, the connective tissue of the fontanelles is invaded and replaced by bone creating sutures. The five sutures are the two squamous, one coronal, one lambdoid, and one sagittal sutures. The posterior fontanel usually closes by eight weeks, but the anterior fontanel can remain open up to eighteen months. The anterior fontanel is located at the junction of the frontal and parietal bones; it is a "soft spot" on a baby's forehead. Careful observation will show that you can count a baby's heart rate by observing his or her pulse pulsing softly through the anterior fontanel.
- ↑ Carlson, Bruce M. (1999). Human Embryology & Developmental Biology. Mosby. pp. 166-170. ISBN 0-8151-1458-3.
- ↑ Derkowski, Wojciech; Kędzia, Alicja; Glonek, Michał (2003). «Clinical anatomy of the human anterior cranial fossa during the prenatal period». Folia morphologica 62 (3): 271-3. PMID 14507064.