Abstract
The course of the Chorda tympani in relation to the malleus, tensor tympani tendon, annulus, and facial nerve in the middle ear was investigated in 30 human temporal bones.
The temporal bones were fixed in 10 percent formalin solution, decalcified in 5 percent trichloroacetic acid solution, and dissected under an operating microscope.
The tympanic membranes with the malleus, a part of the chorda tympani, and facial nerve were dissected. Sudan black B stain was applied to the dissected tympanic membranes and their surrounding tissues.
After entering the middle ear cavity, the chorda tympani runs forward along the lower margin of the posterior mallear fold.
The following measurements were made and results were obtained:
1. The mean distance between the lowest point of the articular surface of the malleus and the chorda tympani was 0.7mm.
2. The mean diameter of the chorda tympani on the neck of the malleus was 0.4mm.
3. The mean distance between the chorda tympani and the tendon of the tensor tympani was 0.3mm.
4. The mean diameter of the tendon of the tensor tympani was 0.7mm.
5. The mean length of the chorda tympani between the facial nerve and the annulus was 8.8mm.
6. The mean shortest distance between the chorda tympani and the tympanic annulus was 0.9mm.
7. The mean angle between the chorda tympani and the tympanic annulus was 30°.
8. The angle between two lines, one perpendicular to the axis of the malleus at the umbo and the other connecting the umbo and the point where the chorda tympani crosses the annulus, was 15°.
