Venous hyperemia model in the frog tongue

Use the frog from the previous session after rinsing its tongue with saline solution. To model venous hyperemia, tie ligatures around the veins in the tongue root. There are two pairs of large parallel blood vessels in the root of the tongue: the lateral vessels are veins, whereas the medial ones are arteries. To tie a ligature around the vein, pull the tongue by its tip with forceps and insert a needle with the ligature between the vein and the artery, then bring it out. After this, the procedure is repeated on the second vein. Tie both ligatures to form a loop on each side but do not fasten the knots tightly. Study the normal circulation at low magnification (x10). Then, without moving the preparation, pull one of the tied ligatures’ ends and fasten the knot. Note the changes in the size of the vessel lumen, the blood velocity, the separation of the lumen into axial and marginal plasmatic strata and the number of functioning capillaries. Then tie firmly the second ligature and inspect the preparation microscopically. Note the microcirculatory changes taking into consideration the same parameters. Also pay attention to the outward appearance of the tongue (colour, size, etc).

Observe the microcirculation changes after the ligatures on both sides have been removed.