Skull and bones club10/2/2023 ![]() The anterior portion develops from trabecular cartilages and orbital cartilages situated above them. The former embraces the orbital and nasal regions of the skull, and the latter embraces the occipital and aural portions. The brain case is divided into anterior (prechordal) and posterior (chordal) portions. The cerebral cranium consists of a brain case, nasal capsules (surrounding the olfactory organs), and auditory capsules (enclosing the inner ear). The cranial changes that evolved in organisms were caused by progressive development of the brain and sense organs, replacement of gill respiration by pulmonary respiration, and change in feeding habits resulting from the emergence of organisms onto land from water. The visceral, or facial, cranium is the skeleton of the anterior part of the intestine (pharynx), which originally consisted of branchial, or visceral, arches separating gills. The axial, or cerebral, cranium is the anterior continuation of the axial skeleton of the trunk that grows around the brain, olfactory organs, and inner ear. A distinction is made between the axial cranium and the visceral cranium. (also cranium), the skeleton of the head of vertebrates, including man. Earlier skulls of human ancestors, for instance, have been shown to have markedly smaller cranial capacities, as well as more powerful jaws, than do the Homo sapiens species which exist today. Study of the fossil skulls of humans and their precursors has made important contributions to evolutionary theory, and to the science of physical anthropology. The occipital bone at the base of the skull forms a complex joint with the first vertebra of the neck, known as the atlas, permitting rotation and bending of the head (see spinal column). However, the seams, or sutures, between the bones do not completely knit until the age of 20. By the age of two years, all of these fontanels have been closed over by the growing cranial bones. The remaining separations are known as fontanels, the most prominent being the soft spot atop a newborn's head. These are separate plates of bone in the fetus, but by birth they have generally grown sufficiently for most of their edges to meet. The adult human cranium, or braincase, is formed of fused skull bones: the parietals, temporals, ethmoid, sphenoid, frontal, and occipital. The mandible, or lower jaw, is not technically part of the skull. They are the lacrimals at the inner sides of the eyes, the nasals and nasal conchae of the nose, the palatines (palate), the zygomatics, or malars at the cheeks, the vomer (nasal septum), and the maxillae, or upper jaw. Among humans, some 14 bones shape the face, most occurring in symmetrical pairs. The skull houses and protects the brain and most of the chief sense organs i.e., the eyes, ears, nose, and tongue. Skull, the skeletal structure of the head, composed of the facial and cranial bones.
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