The image at the right is a cross section of a mouse tongue. The snout of the mouse has been cut so that you are looking "into"
the oral cavity, i.e., it's a "frontal" section plane.
The top of the image is the dorsal side, the bottom ventral; the tongue is the large oval structure in the center. The space around it is the oral cavity.
The dorsal surface of the tongue is covered with specialized lingual papillae (see below). The entire tongue is covered with stratified squamous epithelium. Not much detail can be see in this low power image, but a closer look will reveal the way the muscle bundles are laid out.
In
this higher magnification view, the muscle bundles and their arrangement can be
seen clearly. This organization of muscle bundles is one of the identifying features
of the tongue.
One set runs parallel to the screen from upper left to lower right; a second set runs at a right angle to these from lower left to upper right. The third group is cut in cross section, as it runs in and out of the plane of the screen; it's therefore at right angles to both the other two. The bundles are thus set into X, Y, and Z axes.
This arrangement gives the tongue its amazing flexibility and controllability. The muscle bundles play off against one another, and by controlling the tension it's possible for the tongue to assume many shapes. This requires exquisite neural control, and the tongue has that.
It's common to see nerve fibers running between the bundles, and small salivary glands here and there. The muscles are controlled by motor fibers from cranial nerves; there are fibers for general touch sensation (quite a few of them) and those serving the taste buds on the dorsal surface. Sympathetic and parasympathetic fibers innervate the salivary glands.
Monkey tongue; H&E stain, 1.5 µm plastic sections, 20x and 40x
