Cranial bones

Anatomically the nervous system is subdivided into the Central Nervous System (CNS), that which is encased in the cranial bone tissue and surrounded by the bone and cartilage, that is, the brain and spinal column, respectively. The function of the CNS is to control and integrate afferent and efferent signals. The network of neurons in the soft tissues of the bodies, impinging on organs and musculature is the Peripheral Nervous System (PNS). We will discuss the CNS in more detail later. For now, let us consider the PNS. 

Anders are cranial bone growths that occur within the Cervidae, or deer family (Figure 6.12). Only the males of most species carry anders, with the exception of caribou and reindeer, where they appear on both males and females. Antlers are used by these animals for defense and for display, which... 

Silicon appears to be required for the normal synthesis of the organic matrix of bone and for its normal calcification. The silicon in the blood serum occurs entirely as silicic acid. Osteoblasts may contain the highest concentrations of silicon of all the cells of the body. Within these cells, silicon occurs mainly in the mitochondria. Silicon deficiency in animals results in bones with abnormal structures. These abnormalities include thinner oc rtical bone, reduced bone flexibility, and flattened cranial bones. Silicon deficiency also affects cartilage, and results in a dramatic reduction in the ividth of the epiphyseal cartilage (Carlisle, 1985). 

Large complex shapes require computer aided design and computer-aided manufacturing to fit the anatomical constraints. Mechanical strength has been optimized in terms of curvature, thickness, width, and porosity (Ono et al. 1998) and further employed for large complex cranial bone defects (Ono et al. 1999). The porosity serves the purpose for bone ingrowth, as explained in the next section. 

The divisions of the cranial central nervous system include the cerebral hemispheres, the diencephalon (thalamus and hypothalamus), the brainstem (midbrain, pons and medulla oblongata) and the cerebellum (Fig. 1.2). Each cerebral hemisphere occupies one half of the cranial vault and can be subdivided into four lobes (frontal, parietal, temporal, occipital), the insula and the limbic lobe. The first four lobes are named for the cranial bones that overlie them. With respect to the floor of the cranial cavity, the frontal lobes lie in the anterior cranial fossa the brainstem and cerebellum occupy the posterior cranial fossa the remaining structures are found either in the middle fossa or within the portion of the cranial vault above the tentorium cerebelli. The insula is covered by the temporal lobe and is not observable unless the temporal lobe is retracted. The hmbic system is a continuous interior... 

Piskin E, Isoglu A, Bolgen N, Vargel I. In vivo performance of simvastatin-loaded electrospun spiral-wound polycaprolactone scaffolds in reconstruction of cranial bone defects in the rat model. J Biomed Mater Res A 2009 90 1137-51. 

Albo, D., Long, C., Jhala, N. et al., 1996. Modulation of cranial bone healing with heparin-hke dextran derivatives. Journal of Craniofacial Surgery 7 19-22. 

In the newborn, the cranial musculature is poorly developed, allowing surface coil spectroscopy of neonatal brain without additional localization. An extremely broad peak underlies the spectrum, from relatively immobile P nuclei in cranial bone, but this can be removed in postacquisition processing. As... 

Dr. Wang and his coworkers set out to investigate the role of the 3D kinematics and macro/micro structures of beak and cranial bones in avoiding impact injury to a woodpecker s head. They used high-speed video cameras and scanned the birds skulls to obtain 3D simulations. The idea was to quantify the effect of pecking forces on the birds heads. After 3 years of research, they discovered why the brains of woodpeckers are not affected by the constant blows. 

Among the alterations caused by vitamin A deficiency in animals, bone growth retardation is one of the most characteristic. It affects long, epiphyseal, and flat bones. The retarded growth of the cranial bone is followed by degeneration of the cranial nerves, and sometimes lesions in the white and grey matter of the brain also develop. Vitamin A undoubtedly affects bone growth directly or indirectly because, as we shall... 

Leiggener, C.S., Curtis, R., MiiUer, A.A., Pfluger, D., Gogolewski, S., Rahn, B.A., 2006. Influence of copolymer composition of polylactide implants on cranial bone regeneration. Biomaterials 27, 202—207. 

Szpalski, C., Barr, J., Wetterau, M., Saadeh, P.B., Warren, S.M., 2010. Cranial bone defects current and future strategies. Neurosurg. Focus 29, e8. 

The cranial bones in the frontal plane are cut using long, thin scissors. 

Failure modes for each fastener system were also different. The major failure mode for Bioplate metal screws tested with both sawbone and canine cranial bones was screw pull-out. Occasionally, the sawbone was broken before the screw pulled out. The Biomet Lactosorb PLA/PGA screws, however, failed Just below the screw head when tested with sawbone, but pulled out of cranial bone with little or no damage to the threads or screw head. The failure mode for the rivet/pins was pull-out from both the sawbone and cranial bone. 

William Gamer Sutherland was another student of Still. When the grooves in the suture of a temporal bone caught his eye, he was led to believe that the cranial bones mnst be capable of motion. He likened them to the "gills of a fish." He thns began the stody of cranial osteopathy and spent many years developing its theories and techniqnes, nsed today as a specialized form of osteopathy. 

Structure of the cranial sutures allows various types of motion between contiguous bones. The nature of the sutures is discussed further in Section X, Chapter 102, as is the motion characteristics of the various cranial bones. 

The newborn skull has no interlocking sutures. The only fully formed joint in the cranium is that between the condyles of the occiput and the atlas. A newborn s cranial bones develop within dura, and the shape of the skull is maintained by dura, by fluid, and by the central nervous system s motion within. Developmentally before bone formation, membranes provide shape and protection and also guide and limit motion. 

The external layer of dura is the internal periosteum of cranial bones, the pericranium. Pericranium is continuous with periosteum of sutures and foramina, and with the external periosteum of the cranial bones. Compressive and tensile forces generated on the dura by the growing brain stimulate the membranous connective tissue to form bone between these layers of the dura. Therefore, the bones of the cranium develop within iayers of dural membrane. 

The periosteum of all cranial bones is continuous with all the dura. All adjacent membranous and fascial structures are continuous with each other. The dura and bone of the skull are examples of the continuity of connective tissues of differing densities. 

Study of the embryological development of cranial bone provides important information regarding their form and function. Compressive forces early in development create a cartilaginous matrix in the area that becomes the cranial base. Tensile forces create membrane in the area that develops into the cranial vault. Dr. Sutherland considered the motion in the cranial base primary, the motion in the vault being accommodative to the base. 

No cranial bone moves independently. Restriction originating in any part of the cranium will cause changes in the motion of the entire cranium. The patterns of both functional and dysfunctional motions presented in this section should be considered in the context of variability that may influence the overall motion that presents itself. This approach provides an excellent basis for deepening understanding of the varieties of patterns that may present clinically. 

---