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Anatomy for neurotrauma
Published in Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor, Essentials of Anesthesia for Neurotrauma, 2018
Vasudha Singhal, Sarabpreet Singh
The neurocranium houses the brain, meninges, blood supply, cranial nerves, and cerebrospinal fluid (CSF) within the cranial cavity. It has eight cranial bones—frontal, ethmoid, sphenoid, 2 parietal, 2 temporal, and an occipital bone. It is subdivided into the cranial vault or calvaria, and the basicranium or skull base. The base of the skull is further divided into three regions, corresponding to the floor of the anterior, middle, and posterior cranial fossae.
Formation of the Cranial Base and Craniofacial Joints
Published in D. Dixon Andrew, A.N. Hoyte David, Ronning Olli, Fundamentals of Craniofacial Growth, 2017
The basicranium begins its development during the 4th week as a series of discrete parasagittal condensations in the mesenchymal capsule between the ventral surface of the cranial part of the developing brain and the dorsal endodermal-lined wall of the foregut (Blechschmidt, 1976). In the rostral part of the cranium the condensations are largely the result of expansion of the cerebral vesicles and the optic cups which compress the mesenchymal cells between them (Delaire and Precious, 1987). Preceding this event, the primordia of other cranial structures have been put in place, such as the trunks of cranial nerves, major blood vessels, and the optic cups. As the chondrocranium develops it must necessarily accommodate itself to the pattern set by these pre-existing structures. This progressive change of shape converts a fundamentally simple structure into a morphologically complex one.
Studying factors influencing facial developmental instability
Published in Annals of Human Biology, 2021
In this paper we evaluated three modularity hypotheses in order to detect the developmental architecture of the human face. Regarding the performance of the modularity hypotheses, we are in agreement with Quinto-Sánchez et al. (2018) that the function-related hypothesis showed lower covariation among modules when compared to the other hypotheses, particularly the midline-related hypothesis. This indicates that the eyes, nose, mouth and facial outline are relatively independent. As expected (Linden et al. 2018), our study indicated that the facial thirds are relatively independent, since the partitions according to the three main anatomical parts of the facial area (the neurocranium, maxilla, and mandible) showed the lowest possible covariance in some age categories. This indicates that facial thirds are distinct units, and thus the developmental integrations in the face occur within units as stated by Enlow (1990). It is, however, well known that integration among anatomical regions (basicranium, facial skeleton, and cranial vault) is looser in the human skull compared to other species (Porto et al. 2009); and yet, cranial components develop in a morphologically integrated manner (Enlow 1990; Bastir et al. 2006) through numerous morphogenetic (e.g. neural) and functional (e.g. masticatory, respiratory) interactions (Lieberman et al. 2000). More importantly, as a result of independence among the modules, the effect of a stressor which leads to higher fluctuating asymmetry (Leamy and Klingenberg 2005) is transmitted less readily among modules. Our study showed a stronger theoretical dependency among vertical modules than among horizontally neighbouring modules. Thus, the effect of a stressor which leads to higher fluctuating asymmetry can be transmitted among modules more easily in a horizontal direction. This strong relationship among modules related to the midline is most likely a result of a biomechanical load of attached muscles. Moreover, this load of attached muscles can facilitate a formation of asymmetry, since it can impact both facial sides unequally. In contrast, horizontally neighbouring modules exhibited different timing of growth (particularly during adolescence) and thus these modules are less interconnected. In addition, horizontal modules originate from diverse embryonic structures, since the maxillary prominences give origin to the maxilla, os zygomaticum and a part of the os temporal, whereas the mandibular prominences give origin to the mandible (Moore and Persaud 2002).
Secular trends in cranial chord variables: a study of changes in sexual dimorphism of the North Indian population during 1954–2011
Published in Annals of Human Biology, 2019
In context to physical anthropology, the secular change may be defined as changes in the skeletal measurements of two successive populations from the same geographical region, resulting from shifts in living standards or exposure to a new environmental factor over a short timeframe (Jantz and Jantz 2000; Weisensee and Jantz 2011). These changes are usually alterations of phenotypic expression of genetic potential without any changes in gene frequencies (Rühli and Henneberg 2013). These changes may be positive (increase) or negative (decrease). The occurrence and insinuations of secular trends in the investigation of contemporary human forensic material is properly acknowledged, especially the effects of increased body size (Spradley and Jantz 2011) and cranial shape variation in sex estimation (Jantz and Jantz 2000; Jantz 2001; Wescott and Jantz 2005; Godde 2015; Marinho et al. 2018). It has been shown that secular forces affect males and females differently (Tomaljanovic et al. 2006). Changes in craniofacial measurements over time follow different patterns in different populations because each population group experiences its own exclusive combination of secular forces. Recent studies have also shown that secular forces affect each part of the skull differently. It is possible for a variable to show an increase in a recent population while other variables may show decreases or no change at all (Jantz and Jantz 2000; Jantz 2001; Wescott and Jantz 2005; Tomaljanovic et al. 2006; Godde 2015). Brachycephalization has been the most observed change in head dimensions followed by changes in the craniofacial dimensions (Nakashima 1986; Moore-Jansen 1989; Kouchi 2004; Tomljanovic et al. 2004; Hossain et al. 2005; 2011; Saini 2014; Saini et al. 2014; 2017). Smith et al. (1986) also found larger craniofacial dimensions in adult Northern European-derived offspring in comparison with their parents; they expressed an increase in the upper facial height and decrease in facial breadth. Ghosh and Malik (2007) examined a cross-sectional Indian sample of 400 fathers, 400 mothers, 292 sons and 170 daughters for secular trends in craniofacial measures with other body measurements and opined that each generation has its own set of secular forces which is different from those of their predecessors. In his study of American blacks and whites, Jantz (2001) substantiated the findings of Moore-Jansen (1989) and found that basion-bregma height and occipital chord reflected an increase in cranial vault height in both groups. In context to the Indian population, studies conducted by Saini et al. (2014) and Saini (2014) provided a glimpse of changing craniofacial and basicranium dimensions. They found that the Indian crania are going through brachycephalization and the enlargement of different craniofacial variables, including cranial length and breadth, cranial base length, basion-bregma height, etc., in both sexes of the contemporary population. In contemporary males, the maximum increase of 3.62 mm was observed in maximum frontal breadth while females showed a maximum increase of 4.28 mm in biauricular breadth. Recently Saini et al. (2017) provided data on craniofacial indices which substantiated their previous findings.