Ear, nose and throat (ENT) deals with disorders affecting the ear, nose and laryngopharynx, as well as with those pathologies compromising the neck and salivary glands. Disorders affecting any of these structures are particularly relevant, as they usually impair the patients' quality of life due to the severity of presenting symptoms. Furthermore, ENT disorders have a high incidence in the population. For all of these reasons, anatomic and physiologic knowledge of the organs studied by ENT, as well as comprehension of the pathologies affecting them, are of paramount importance for both laymen and healthcare professionals.
ENT focuses on the study of the nasal passages and their related structures, the laryngopharynx and the ear.
These structures, except the ear, form the upper airway, which leads inhaled air to the pulmonary alveoli. During its passage through the upper airway, air is warmed, humidified and the largest particles are filtered out. At this level inhaled particles are faced with the first immune barrier-Waldeyer's tonsillar ring, as well as the action of both lysozymes and surface immunoglobulin. On the other hand, the ear is closely related to the upper airways; because of the direct communication between the middle ear and the nasopharynx-through the Eustachian tube-the ear is considered to belong to the respiratory system. The middle ear is ventilated through this duct; therefore it is exposed to all microorganisms colonizing the upper airway.

ENT Common diseases -
1 Infectious rhinitis - It may have a viral for bacterial origin, or may be associated with specific infections.  Viral infections are the most frequent ones. Clinical symptoms of nasal mucosa inflammation include congestion, rhinorrhea, sneezing, and  nasal itching. In children, symptoms may include impaired concentration, irritability, and sleep disorders.
2 Non-infectious rhinitis- Allergic rhinitis is the most common cause of non-infectious rhinitis, characterized by congestion, nasal and ocular pruritus, watery rhinorrhea and sneezing in the presence of an allergen, due to IgE-mediated mast cell and basophil activation. Non-infectious rhinitis may be triggered not only by airborne allergens but also by food and drug allergens.
3 Rhino sinusitis – Rhino sinusitis refers to inflammation of the nasal mucosal membranes and the Para nasal sinuses, which causes collection of fluid within these cavities or the underlying bone. This condition is generally regarded as a common cold or viral sinusitis.
4 Sinusitis complications - The primary complication of sinusitis is potential chronicity, which may be caused by inadequate treatment of an acute condition or by persistence of another disease or abnormality determining its development. If inadequately treated, infection may spread to neighboring structures, such as bone or tissues surrounding the eye globe.
5 Influenza - It also known as grippe was described as a highly contagious acute respiratory disease. It is a worldwide epidemic disease affecting a large proportion of the population; its causal agent, influenza virus, is isolated from the respiratory secretions of infected patient.
6 Nasal polyposis - Nasal polyps are the most common tumors of the nasal passages; they results from an edematous degeneration of the nasal mucosa of inflammatory origin. They are a frequent finding in patients with untreated allergic rhinitis. Nasal polyp growths are round, soft, semi-translucent, pinkish-gray structures. Symptoms usually include sensation of nasal fullness without obstruction or impaired mucociliary clearance.
7 Adenoid hyperplasia and adenoiditis - Clinical symptoms of adenoid hypertrophy include nasal obstruction, oral breathing, snoring nasal voice and sometimes, watery rhinorrhea secondary to choanal obstruction by adenoid tissue, which impairs mucus clearance. A cavum X-ray is useful to determine airway obstruction by adenoid tissue. 
8 Acute tonsillitis - Tonsillitis is defined as inflammation of the palatine tonsils, in most cases, of viral etiology. Clinical symptoms include congestion of the pharyngeal mucosa with or without purulent tonsillar exudates sometimes, ulcers and blisters also develop. Group A beta-hemolytic streptococcus is the causal agent of nearly 30% of cases of pharyngotonsillitis. It usually present with fever, abdominal pain, vomiting, absence of nasal catarrh, adenopathies, glossitis or palatine petechiae.
9 Nosebleed - It also known epistaxis is most frequently observed during childhood; bleeding usually begins in the anterior septum, a hypervascularized area, known as Kiesselbach's plexus. Posterior nosebleed is more frequent in older adults.
10 Allergic rhinitis - Environmental allergens such as environmental dust, animals & domestic molds are potential triggering factors of allergic rhinitis, depending upon patient’s sensitivity. Some patients have symptom exacerbations not only upon exposure to particular allergens, but also upon changes in ambient temperature or relative humidity, or ingestion of specific foods.