Incisal bite force direction in humans and the functional significance of mammalian mandibular translation

1978 ◽  
Vol 48 (1) ◽  
pp. 1-7 ◽  
Author(s):  
William L. Hylander
Keyword(s):  
Functional Significance ◽  
Bite Force ◽  
Force Direction

Coactivation of jaw muscles: Recruitment order and level as a function of bite force direction and magnitude

1990 ◽  
Vol 23 (5) ◽  
pp. 475-485 ◽  
Author(s):  
T.M.G.J. Van Eijden ◽  
P. Brugman ◽  
W.A. Weijs ◽  
J. Oosting
Keyword(s):  
Bite Force ◽  
Jaw Muscles ◽  
Force Direction ◽  
Recruitment Order

Electromyographic Heterogeneity in the Human Temporalis Muscle

1990 ◽  
Vol 69 (10) ◽  
pp. 1686-1690 ◽  
Author(s):  
N.G. Blanksma ◽  
T.M.G.J. Van Eijden
Keyword(s):  
Regional Differences ◽  
Bite Force ◽  
Emg Activity ◽  
Temporalis Muscle ◽  
Motor Tasks ◽  
Preferential Direction ◽  
Muscle Belly ◽  
Regional Specialization ◽  
Fine Wire ◽  
Force Direction

This study examined the possible existence of regional differences in activation of the temporalis muscle. Since the muscle is fan-shaped, its fibers pull in different directions. This suggests regional specialization for different motor tasks. EMG activity was registered by six bipolar fine-wire electrodes inserted anteroposteriorly across the muscle belly. Muscle signals were recorded during different static bite tasks for which both the direction and magnitude of bite force were specified. The results showed that the ratio of activities of the six muscle regions changed with the direction of bite force. This indicates a partitioning of the excitatory command to the muscle's motoneuron pool. Alteration in activity with changing bite-force direction was generally the smallest in the anterior-most region of the muscle, the largest in the posterior-most region, and the intermediate in the interjacent regions. Generally, all muscle regions exhibited the highest EMG activity when the bite force was in an approximately posterolateral direction. The muscle was activated uniformly only for bites in this preferential direction. Activity in the regions appeared to be scaled up or down in a linear way according to the desired bite-force level. The results indicate that the direction of pull of the muscle and the maximal force it can produce are not fixed, but depend on the direction of bite force.

Functional analysis of sabertooth cranial morphology

Paleobiology ◽  
1980 ◽  
Vol 6 (3) ◽  
pp. 295-312 ◽  
Author(s):  
Sharon B. Emerson ◽  
Leonard Radinsky
Keyword(s):  
Functional Analysis ◽  
Functional Significance ◽  
Bite Force ◽  
Cranial Morphology ◽  
Biomechanical Models ◽  
Morphological Differences

Elongate canines evolved independently at least four times among mammalian carnivores, and each time skulls were modified in similar ways. We have compared the cranial morphology of sabertooths to that of their non-sabertoothed relatives, living and extinct, and applied simple biomechanical models to elucidate the functional significance of the morphological differences. Our analysis suggests that (1) sabertooth morphology represents modification for wider gape with retention of a powerful bite force at the carnassial; (2) sabertooths probably used a throat or ventral neck slash to kill prey; and (3) elongate canines and retractile claws may have facilitated the exploitation of relatively larger prey by sabertooths compared to non-sabertooth carnivores.

A Feedback Method to Determine the Three-dimensional Bite-force Capabilities of the Human Masticatory System

1988 ◽  
Vol 67 (2) ◽  
pp. 450-454 ◽  
Author(s):  
T.M.G.J. van Eijden ◽  
J.H. Koolstra ◽  
P. Brugman ◽  
W.A. Weijs
Keyword(s):  
Three Dimensional ◽  
Bite Force ◽  
Dental Arch ◽  
Jaw Muscles ◽  
Static Contraction ◽  
Force Direction ◽  
The Subject ◽  
Feedback Method ◽  
Masticatory System

A feedback procedure is described that enables a subject to exert bite forces in certain specified directions during static contraction of the human jaw muscles. The output of a three-dimensional transducer is fed to a computer. The magnitude and direction of the resultant force are computed and visualized by a cross on the screen of the computer terminal. In a bite experiment, the subject is instructed to match this cross with a point on the screen, representing the desired bite-force direction. The procedure allows for determination of the range of possible bite-force directions and magnitudes for various locations on the dental arch and study of the concomitant recruitement patterns of the jaw muscles. Some examples of measurement are given.

Functional significance of preserved color patterns of mollusks from the Gosport Sand (Eocene) of Alabama

1988 ◽  
Vol 62 (01) ◽  
pp. 83-87 ◽  
Author(s):  
Patricia H. Kelley ◽  
Charles T. Swann
Keyword(s):  
Functional Morphology ◽  
Functional Significance ◽  
Intraspecific Variability ◽  
Color Pattern ◽  
Color Patterns ◽  
Historical Factors ◽  
Life Mode ◽  
Molluscan Fauna ◽  
Excellent Preservation ◽  
Architectural Constraints

The excellent preservation of the molluscan fauna from the Gosport Sand (Eocene) at Little Stave Creek, Alabama, has made it possible to describe the preserved color patterns of 15 species. In this study the functional significance of these color patterns is tested in the context of the current adaptationist controversy. The pigment of the color pattern is thought to be a result of metabolic waste disposal. Therefore, the presence of the pigment is functional, although the patterns formed by the pigment may or may not have been adaptive. In this investigation the criteria proposed by Seilacher (1972) for testing the functionality of color patterns were applied to the Gosport fauna and the results compared with life mode as interpreted from knowledge of extant relatives and functional morphology. Using Seilacher's criteria of little ontogenetic and intraspecific variability, the color patterns appear to have been functional. However, the functional morphology studies indicate an infaunal life mode which would preclude functional color patterns. Particular color patterns are instead interpreted to be the result of historical factors, such as multiple adaptive peaks or random fixation of alleles, or of architectural constraints including possibly pleiotropy or allometry. The low variability of color patterns, which was noted within species and genera, suggests that color patterns may also serve a useful taxonomic purpose.

Complex Vesicles, Microtubules, and Cytoplasmic Filaments in the Endothelial Cells of Normal Dog Aorta

1968 ◽  
Vol 26 ◽  
pp. 172-173
Author(s):  
C. N. Sun ◽  
J. J. Ghidoni
Keyword(s):  
Electron Microscopy ◽  
Endothelial Cells ◽  
Cross Sections ◽  
Functional Significance ◽  
Tubular Structures ◽  
Aldehyde Fixation ◽  
Cytoplasmic Filaments

Endothelial cells in longitudinal and cross sections of aortas from 3 randomly selected “normal” mongrel dogs were studied by electron microscopy. Segments of aorta were distended with cold cacodylate buffered 5% glutaraldehyde for 10 minutes prior to being cut into small, well oriented tissue blocks. After an additional 1-1/2 hour period in glutaraldehyde, the tissue blocks were well rinsed in buffer and post-fixed in OsO4. After dehydration they were embedded in a mixture of Maraglas, D.E.R. 732, and DDSA.Aldehyde fixation preserves the filamentous and tubular structures (300 Å and less) for adequate demonstration and study. The functional significance of filaments and microtubules has been recently discussed by Buckley and Porter; the precise roles of these cytoplasmic components remains problematic. Endothelial cells in canine aortas contained an abundance of both types of structures.

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