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Morphology of the jaw-closing musculature in the common wombat (Vombatus ursinus) using digital dissection and magnetic resonance imaging.

Sharp AC, Trusler PW - PLoS ONE (2015)

Bottom Line: The masseter and medial pterygoid muscles are greatly enlarged compared to other marsupials.This, in combination with the distinctive form and function of the dentition, most likely facilitates processing a tough, abrasive diet.The broad, flat skull and large masticatory muscles are well suited to generate a very high bite force.

View Article: PubMed Central - PubMed

Affiliation: School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria, Australia.

ABSTRACT
Wombats are unique among marsupials in having one pair of upper incisors, and hypsodont molars for processing tough, abrasive vegetation. Of the three extant species, the most abundant, the common wombat (Vombatus ursinus), has had the least attention in terms of masticatory muscle morphology, and has never been thoroughly described. Using MRI and digital dissection to compliment traditional gross dissections, the major jaw adductor muscles, the masseter, temporalis and pterygoids, were described. The masseter and medial pterygoid muscles are greatly enlarged compared to other marsupials. This, in combination with the distinctive form and function of the dentition, most likely facilitates processing a tough, abrasive diet. The broad, flat skull and large masticatory muscles are well suited to generate a very high bite force. MRI scans allow more detail of the muscle morphology to be observed and the technique of digital dissections greatly enhances the knowledge obtained from gross dissections.

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Related in: MedlinePlus

The arrangement of the jaw muscles as visualized from the MRI.The legend indicates the colour for each muscle group as well as non-muscle anatomy. The location for each MRI slice is indicated on the lateral view of the skull.
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pone.0117730.g002: The arrangement of the jaw muscles as visualized from the MRI.The legend indicates the colour for each muscle group as well as non-muscle anatomy. The location for each MRI slice is indicated on the lateral view of the skull.

Mentions: One adult female specimen was scanned by X-ray computed tomography (CT) and magnetic resonance imaging (MRI) at the University of Melbourne Veterinary Hospital for construction of a 3D model. The MRI was set to proton density (PD)-weighted and scanned with a 3.0 mm slice thickness and 0.625/0.625 pixel spacing in the frontal plane, and 2.5 mm slice thickness and 0.55/0.55 pixels for the horizontal and sagittal planes. The CT scans have a 0.6 mm slice thickness, 0.3 mm interslice distance and 0.3125/0.3125 pixels. The CT (S1 Movie) and MRI (S2 Movie) data are available as movie files in the supplementary information. The CT and MRI data were imported into the image visualisation and processing software program Avizo (Visualization Science Group), in which manual segmentation using the paintbrush tool (the process of selection and isolation of the structure of interest) was used to isolate the craniodental morphology and individual muscles into separate materials. Muscle origin and insertion sites (Fig. 1) for V. ursinus were identified for each muscle based on dissections and MRI scans (Fig. 2). Each muscle was selected first in the coronal plane and then edited in the remaining two planes for biological accuracy (sagittal and horizontal plane). When each muscle, and the cranium and mandible were assigned to separate materials, a 3D surface model was produced using the Avizo “SurfaceGen” module, which constructs a mesh of triangles and nodes that represent the continuum structure. The volume for each muscle was obtained from the 3D model using the Avizo “MaterialStatistics” module, and the percentage of each muscle of the total volume was determined.


Morphology of the jaw-closing musculature in the common wombat (Vombatus ursinus) using digital dissection and magnetic resonance imaging.

Sharp AC, Trusler PW - PLoS ONE (2015)

The arrangement of the jaw muscles as visualized from the MRI.The legend indicates the colour for each muscle group as well as non-muscle anatomy. The location for each MRI slice is indicated on the lateral view of the skull.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4338273&req=5

pone.0117730.g002: The arrangement of the jaw muscles as visualized from the MRI.The legend indicates the colour for each muscle group as well as non-muscle anatomy. The location for each MRI slice is indicated on the lateral view of the skull.
Mentions: One adult female specimen was scanned by X-ray computed tomography (CT) and magnetic resonance imaging (MRI) at the University of Melbourne Veterinary Hospital for construction of a 3D model. The MRI was set to proton density (PD)-weighted and scanned with a 3.0 mm slice thickness and 0.625/0.625 pixel spacing in the frontal plane, and 2.5 mm slice thickness and 0.55/0.55 pixels for the horizontal and sagittal planes. The CT scans have a 0.6 mm slice thickness, 0.3 mm interslice distance and 0.3125/0.3125 pixels. The CT (S1 Movie) and MRI (S2 Movie) data are available as movie files in the supplementary information. The CT and MRI data were imported into the image visualisation and processing software program Avizo (Visualization Science Group), in which manual segmentation using the paintbrush tool (the process of selection and isolation of the structure of interest) was used to isolate the craniodental morphology and individual muscles into separate materials. Muscle origin and insertion sites (Fig. 1) for V. ursinus were identified for each muscle based on dissections and MRI scans (Fig. 2). Each muscle was selected first in the coronal plane and then edited in the remaining two planes for biological accuracy (sagittal and horizontal plane). When each muscle, and the cranium and mandible were assigned to separate materials, a 3D surface model was produced using the Avizo “SurfaceGen” module, which constructs a mesh of triangles and nodes that represent the continuum structure. The volume for each muscle was obtained from the 3D model using the Avizo “MaterialStatistics” module, and the percentage of each muscle of the total volume was determined.

Bottom Line: The masseter and medial pterygoid muscles are greatly enlarged compared to other marsupials.This, in combination with the distinctive form and function of the dentition, most likely facilitates processing a tough, abrasive diet.The broad, flat skull and large masticatory muscles are well suited to generate a very high bite force.

View Article: PubMed Central - PubMed

Affiliation: School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria, Australia.

ABSTRACT
Wombats are unique among marsupials in having one pair of upper incisors, and hypsodont molars for processing tough, abrasive vegetation. Of the three extant species, the most abundant, the common wombat (Vombatus ursinus), has had the least attention in terms of masticatory muscle morphology, and has never been thoroughly described. Using MRI and digital dissection to compliment traditional gross dissections, the major jaw adductor muscles, the masseter, temporalis and pterygoids, were described. The masseter and medial pterygoid muscles are greatly enlarged compared to other marsupials. This, in combination with the distinctive form and function of the dentition, most likely facilitates processing a tough, abrasive diet. The broad, flat skull and large masticatory muscles are well suited to generate a very high bite force. MRI scans allow more detail of the muscle morphology to be observed and the technique of digital dissections greatly enhances the knowledge obtained from gross dissections.

Show MeSH
Related in: MedlinePlus