Some people get nosebleeds rather often, and others rarely get them. There may be just a trickle of blood or a strong stream. If people swallow the blood, they often vomit it because blood is irritating to the stomach. Swallowed blood may pass through the digestive tract and appear in the stool as black tarry stools.
Worldwide, about half a billion people (almost 8% of the world's population) have hearing loss. More than 10% of people in the United States have some degree of hearing loss that affects their daily communication, making it the most common sensory disorder. The incidence increases with age. Although less than 2% of children under 18 have a permanent hearing loss, hearing loss during infancy and early childhood can be detrimental to language and social development. Over one third of people over 65 years and over half of people over age 75 are affected.
The middle ear consists of the eardrum (tympanic membrane) and an air-filled chamber containing a chain of three bones (ossicles) that connect the eardrum to the inner ear (see Middle Ear). The middle ear acts as an amplifier of sound, whereas the inner ear acts as a transducer, changing mechanical sound waves into an electrical signal that is sent to the brain via the nerve of hearing (statoacoustic nerve).
Cancers of the mouth, nose, and throat develop in almost 65,000 people in the United States each year. These cancers are more common among men because male smokers continue to outnumber female smokers and because oral human papillomavirus (HPV) infection is more frequent in males. Most affected people are between the ages of 50 and 70. However, the cancers caused by HPV, which are primarily oropharyngeal cancers, occur more often in younger people.
The upper part of the nose consists mostly of bone. The lower part of the nose gains its support from cartilage. Inside the nose is a hollow cavity (nasal cavity), which is divided into two passages by a thin sheet of cartilage and bone called the nasal septum. The bones of the face contain the paranasal sinuses, which are hollow cavities that open into the nasal cavity (see Nose and Sinuses).