This section deals with diseases of the head and neck—but not the brain, which is covered in the section on the nervous system (Section XV). The main rationale of including such diverse organs as the oral cavity, salivary glands, ear, nose, pharynx, and larynx in one section is that they are included in the surgical specialty of otolaryngology. Diseases of the teeth (dental pathology, Chapter 31: The Oral Cavity & Salivary Glands) and eyes (ophthalmic pathology, Chapter 33: The Eye) form the rest of this section. The oral cavity, nose, pharynx, and larynx form the common opening of the respiratory and gastrointestinal systems and are often collectively called the upper respiratory tract.