In a definition essay, you explain the meaning of a certain term by giving a detailed description of it, and support your definition with clear examples or facts. Such explanations are needed if a term is special, abstract, disputed or does not have a common meaning.
Dysphagia may be caused by traumatic injuries to the head, neck, or chest and result from accidents or iatrogenic causes. In the latter category, both planned and inadvertent injuries to cranial nerves are common. Many accident victims have involvement of multiple sites.
Dysphagia has many causes. First, there may be physical (anatomical) obstruction to the passage of food. Second, there may be abnormalities in the function (functional abnormalities) of the nerves of the brain, throat, and esophagus whose normal function is necessary to coordinate swallowing.