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Fig. 1. Schematic dorso-ventral representation of the tongue of Python
molurus and its extrinsic muscles. (A) Abbreviations: cbr,
ceratobranchial; m, mandible; dsh, distal tongue ensheathing; ggl, m.
genioglossus; hgl, m. hyoglossus; psh, proximal tongue ensheathing; sh, tongue
sheet. The dental bone forms the local coordinate system of the head. Although
the head is highly deformable during feeding, the lower jaws do not deform
during tongue flicking. The position of the ceratobranchials is assumed to be
fixed to the skull during tongue flicking (e.g.
Bels et al., 1994). The mm.
genioglossi and the mm. hyoglossi are able to protract and retract the tongue
relative to the mandibles and ceratobranchials. Proximally on the tongue, the
mm. hyoglossi are ensheathed. This tubular tongue sheet encloses the tongue
distally up to the tongue tips, inverts into itself and connects to the tongue
at the distal tongue ensheathing
(McDowell, 1972). The outer
tongue sheet is connected to the muscles and connective tissue of the mouth
floor. The inverted inner part is protruded while the tongue elongates. (B)
Radio-opaque marker positions at rest: 1–5, local coordinate system
fixed (glued) to the jaws (skin); 6, fold of the tongue sheet at maximum
tongue retraction – the outer layer of the tongue sheet is fixed to the
connective tissue of the mouth floor; 7, point of bifurcation (marker
injected); 8, proximal tongue ensheathing (marker glued after manual
protrusion of the tongue); 9, 10, tongue base (markers injected). (C)
Hypothetical displacements of the markers indicating the relative translation
and elongation of the soft tissues.
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