Mandibular canal and the arrangement of the neurovascular bundle exit routes in divergent populations

Aim: In face anatomy and surgery, variation in the presence, number, location, and size of the mental foramen is discussed. Knowledge of the location of the mental foramen canal, which may led due to the possibility of accidental injury of the neurovascular bundle passing through this canal may lead to anesthesia. This study aimed to present selected anatomical features of human mandibles, focusing on the morphology of the mandibular canal and its neurovascular bundle exit in populations with different socio-economic status. Material and methods: Selected well preserved and unharmed human skulls (N= 169) (50.3% males, 49.7% females) from two populations (rural and outskirts) from Poland were used. Populations differed in socio­economic statuses. Results: Obvious dimorphic differences in each analyzed population were stated and inter-population differences were observed as well. In an outskirt population sexual dimorphism was more evident. Those differences should be considered when approaching the mandibular canal during anesthetic, surgical and forensic procedures. Discussion: The occurrence of the mental foramen is relatively constant, but location is variable, and thus, each individual may exhibit a different arrangement of bundle exits. Both the position and the direction of the exit of the neurovascular bundle were similar to other European population. However, differences in localization between those two investigated populations were observed. This may suggest that not only genetic but also environmental factors, such as living conditions and diet (which affects developmental stability), may influence the morphology of the mandibular features.

The asymmetry of dermatoglyphic finger ridge counts and the geographic altitude of the Jujenean population in northwest Argentina

Asymmetry is omnipresent in the living world and therefore is a measure of developmental noise and instability. The main stressing agent in high-altitude ecosystems is hypobaric hypoxia. The variation in bilateral dermatoglyphic symmetry in populations from the Province of Jujuy in northwest Argentina is analyzed, and these results are compared to those for other populations with different ethnic and environmental backgrounds. Fingerprints were collected from 310 healthy students (140 males and 170 females) aged 18-20 years from three localities in Jujuy Province-Abra Pampa (3484 m above sea level), Humahuaca (2939 m above sea level), and San Salvador de Jujuy (1260 m above sea level). Asymmetry by sex was assessed based on radial and ulnar ridge counts to determine its pattern of variability (directional asymmetry [DA], fluctuating asymmetry [FA] and antisymmetry), and asymmetry and diversity indices were calculated. A bivariate plot and principal component analysis (PCA) were used to compare these indices with those for other populations. Homogeneity was found between populations and sexes when radial and ulnar ridges were counted. FA values did not show significant differences by locality or side (ulnar and radial), but significant differences were found by finger and sex, with males showing significantly greater FA values. The asymmetry and diversity indices clearly group the Andean populations and separate them from populations of different ethnic and geographic origin. Only the diversity index showed significant differences by locality in males, which suggests a substantially different genetic component in Abra Pampa male samples.

An Applied Anatomical Study of the Ethmoidal Arteries: Computed Tomographic and Direct Measurements in Human Cadavers

Computed tomography (CT) images have been used in very few studies on distances to the ethmoidal arteries in the orbit. Most other studies have included direct measurements on cadavers and frequently quote the 24-12-6 mm rule to describe distances from the anterior lacrimal crest to the anterior and posterior ethmoidal foramina (AEF and PEF), optic canal (OC), respectively. However, the large interindividual variation of distances renders absolute values less applicable in a clinical setting. Preoperative measurements on CT images may provide more precise distances than absolute rules and thus lead to safer orbital surgery. The authors hypothesize that the distances to the ethmoidal arteries and the length of the medial wall are positively correlated and that measurements of the distances from the posterior lacrimal crest (PLC) on CT images are feasible with a low intra- and interobserver variability.Fifty intact orbits from 25 Caucasian cadavers were exenterated and examined. In additional, high-resolution CT scans of 48 orbits from 24 other Caucasian nonexenterated cadavers were examined. Distances were measured from 4 different anterior landmarks to the AEF and PEF and the OC.Distances from the most anterior landmarks to the arteries were positively correlated with the length of the medial wall. Measurements of the distances from the PLC to the ethmoidal arteries on CT images were feasible with a low intra- and interobserver variability. In conclusion, iatrogenic damage to the ethmoidal arteries in the orbit may be best avoided by using CT measurements in presurgical planning.

Moderate climate signature in cranial anatomy of late holocene human populations from Southern South America

OBJECTIVE

The aim of this study is to analyze the association between cranial variation and climate in order to discuss their role during the diversification of southern South American populations. Therefore, the specific objectives are: (1) to explore the spatial pattern of cranial variation with regard to the climatic diversity of the region, and (2) to evaluate the differential impact that the climatic factors may have had on the shape and size of the diverse cranial structures studied.

MATERIALS AND METHODS

The variation in shape and size of 361 crania was studied, registering 62 3D landmarks that capture shape and size variation in the face, cranial vault, and base. Mean, minimum, and maximum annual temperature, as well as mean annual precipitation, but also diet and altitude, were matched for each population sample. A PCA, as well as spatial statistical techniques, including kriging, regression, and multimodel inference were employed.

RESULTS

The facial skeleton size presents a latitudinal pattern which is partially associated with temperature diversity. Both diet and altitude are the variables that mainly explain the skull shape variation, although mean annual temperature also plays a role. The association between climate factors and cranial variation is low to moderate, mean annual temperature explains almost 40% of the entire skull, facial skeleton and cranial vault shape variation, while annual precipitation and minimum annual temperature only contribute to the morphological variation when considered together with maximum annual temperature. The cranial base is the structure less associated with climate diversity.

CONCLUSION

These results suggest that climate factors may have had a partial impact on the facial and vault shape, and therefore contributed moderately to the diversification of southern South American populations, while diet and altitude might have had a stronger impact. Therefore, cranial variation at the southern cone has been shaped both by random and nonrandom factors. Particularly, the influence of climate on skull shape has probably been the result of directional selection. This study supports that, although cranial vault is the cranial structure more associated to mean annual temperature, the impact of climate signature on morphology decreases when populations from extreme cold environments are excluded from the analysis. Additionally, it shows that the extent of the geographical scales analyzed, as well as differential sampling may lead to different results regarding the role of ecological factors and evolutionary processes on cranial morphology.