The Ear:  A good understanding of the structures in the inner ear requires that you be able to interpret the images you see under the microscope in three dimensions. Since a single section will not allow you to visualize these areas in different planes, it is important for you to refer to the pictures in your texts to acquire an appreciation for the three dimensional configuration of these structures.

• Review the general organization of the external, middle, and inner ear as shown in the diagram of Fig. 23-21.

Clincial note: Bacterial infections of the middle ear cavity (otitis media) are common complications of colds and upper respiratory tract infections in small children. If such an infection does not respond to antibiotics, the resulting fluid and inflammatory material may be drained through a perforation in the tympanic membrane. IN the image to the right the ear drum on the left is healthy, whereas the one on the right is markedly inflamed and must have hurt.

Examine a section of the inner ear (slide 121). This specimen was dissected from the skull and sectioned to best demonstrate structures within the conical, spiral-shaped cochlea (Fig. 23-30). Identify

• Portions of the spiral ganglion and spiral organ of Corti.
• Choose the best region showing the organ of Corti and identify the associated ducts (the scala vestibuli, scala media, scala tympani),
• The vestibular membrane,
• Tectorial membrane, and
• The major sensory or hair cells (Fig. 23-29).

About that ear fluid.