Nose
The nose is a prominent structural element of the face that contains cells that are a part of the olfactory sensory systems (the sense of smell). The nose is also a portal or orifice to respiratory system. The nose plays an important role in both warming and filtering air before it enters the trachea, bronchi, and lungs.
Bilateral nostrils (external nares) form the external opening of the nose. Composed chiefly of skin and cartilage, the nostrils open into bilateral nasal cavities that are separated by a partition termed the nasal septum that is composed of cartilage and bone. Each of the nasal cavities is partially partitioned into three subcavities or nasal passages termed the superior, middle, and inferior nasal conchae. The passages are covered with mucous membranes and at the internal nares (openings) are continuous with the pharynx as the back of the nose. Because the nasal septum runs from the external to internal nares, any deviation (deviated speptum) or breakage can occlude the free flow of air during respiration.
The nasal passages are connected with smaller openings to the paranasal sinuses. Fluids that accumulate in the nasal sinuses drain through the openings into the nasal passages, eventually to be discharges out through the nostrils. Blockage of the passages lead to headaches and feelings of congestion.
The nasal passages are also continuous with openings to the Eustachian tubes that lead to the ears and which play an important role in equalizing pressure in the ear. Nasolacrimal ducts allow drainage of fluids from the eye region.
The mucous membrane linings of the nose are hair-like projections termed cilia that act to move mucus and other fluids from the nose. The cilia also play an important role in the filtering out of dust, dirt, and particles such as pollen from inhaled air. The increased surface area of the nasal passages also serves to warm and humidify inhaled air before the air flows down the trachea and into the bronchi and lungs. In addition to keeping these passages free of particulate obstructions, the nose serves to keep the more sensitive respiratory structures moist, and at a temperature that permits efficient gas exchange.
Each nasal cavity also contains a small area of olfactory sensory receptors. These area are not covered with cilia.
The linings of the nose are highly vascularized. The increased blood supply is important to the oxygen demanding olfactory receptors and aids in the warming of inhaled air. Because the capillaries are small, numerous, and close to the surface, even mild trauma to the nose may result in a nosebleed.
Colds, hay fever, or other allergies may cause a generalized inflammation of the mucous membrane linings of the nasal passages (rhinitis) and act to block the nasal passages.
This is the complete article, containing 449 words
(approx. 1 page at 300 words per page).
