The nose, the site of the sense of smell is the organ through which mammals take in air. It is supported by cartilage and bone, covered with skin, lined with a mucous membrane, and provided with muscle. A nasal septum divides it into passages, each of which begins with a vestibule and contains a respiratory and olfactory region. The lining of the vestibule is continuous with the skin and contains hairs, sweat glands, and sebaceous (oil producing) glands.
The respiratory region includes nearly all of the septum and the lateral walls of the nose. Goblet cells, which produce and secrete a watery mucus, are present in the lining, as is a type of erective tissue, composed of large, thin-walled veins whose blood supply serves to warm incoming air. The olfactory region is located on the superior concha and adjacent septum. Olfactory cells are present in its lining and have delicate, slender process (modified cilia) at their free surface. Odors from chemicals in the air are received by these processes. Nerve cells that impinge upon the olfactory cell convert the chemical information into nerve impulse and convey the sensory information to the brain.
The nose is divided by the septum into two cavities, each containing three called cnchae and lined with a mucous membrane. Air taken in through the nostrils is filtered by the cilia small hairs in the mucous membrane, mostened by the mucus, and warmed by the blood vessels of the superior conchae and adjacent part of the septum, contains olfactory cells, nerve cells sensitive to odors. Airborne chemicals interact with the ciliated endings of these cells; nerve impulses then are carried by the olfactory nerve to the brain.


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