Structure and functions of nose

Introduction

The nose is an important part of the respiratory system. The nasal cavity is divided into left and right nostrils. Nostril allows the passage of atmospheric air through the openings, called nares.  The nasal cavity is well-connected with the respiratory system and a few other body systems. Because of its proximity towards the mouth, the nose touches the pharynx commonly at nasopharynx. Nasal cavities along with eyes and ears, Eusthasian tube is formed. Eusthasian tube is a triangular junction where ear nose and throat communicate with each other, although in adults it is not uncommon. The nose plays a vital role in the olfactory and respiratory systems. Olfaction is the function of the sense of smell. The olfactory system is assisted by the olfactory nerves -one of the cranial nerves. It is important to understand the anatomical and physiological aspects of the nose. Nose is the mix of bones, muscles, cartilaginous tissues, blood vessels and nerves together assisting in its respiration and olfaction. Nose also serves an aesthetic function as it plays a significant role in the facial appearance. Let us understand some of the anatomical and physiological aspects of the nose.

 

Nasal anatomy 

1. Anterior nares

The respiratory system begins with the nose and completes at the alveoli. The first part of the respiratory system is the nose. The human nose is made up of both hard and soft tissues mostly having bones and cartilaginous tissues. The bony and cartilaginous tissues are also supported by muscles e and thin mucous membranes into which sinuses open. On the visible side, 2 nares are clearly visible. The anterior nares are lined with fine hair-like projections along with the mucus membrane nourished with a very rich blood supply. Nasal hair and mucus help in trapping the pollen and other allergic substances. The nose is so shaped, it does not usually allow the foreign material, allergens, and dust inside.

 

 

2. Nasal bones and cartilages

Bones and cartilages provide strong protection for the nose. Behind the vestibule along each outer wall of the nasal passages, there are 3 elevations known as nasal concha. Nasal concha assist in olfactory function – smell. There are several muscles helping in the movements of the nose. The arrangement of the cartilages makes the nose flexible while inhaling and exhaling the air.  Nasal Bones form the roof of the mouth made up of both the nose and nasal palatine area. Nose is supported by the maxilla, frontal bone as well as a few smaller bones. The uppermost bony portion of the nose is formed by the frontal bone( one of the skull bone) that runs in between the eyebrow ridges towards the nasal notch( junction between the nose and frontal bone). The lateral bones of the nose are the left and right nasal bones. The cribriform plate is a flat structure providing a connection to the nose and the internal roof of the nasal cavity. It is a perforated area sloped into the sphenoid bone of the skull. Nasal septum divides the nasal cavity into 2 equal halves; left and the right nostrils. In addition to these, 2 maxillary bones join at the middle part of the mouth forming the base of the nose.

 

3. Nasal cartilages

They are of 3 types of nasal cartilages, septal, lateral major alar, and minor alar. Nasal cartilages extend from the nasal bones into the midline, then they run posteriorly towards the bony part of the septum. From the septum, it passes along the floor of the nasal cavity. Nasal Cavity is a hollow space that runs from the tip of the nose till the nasopharynx. The nasal mucous membrane is very sensitive, highly vascular(more blood supply). In addition to the filtering and trapping of dust, it helps in moistening and warming the air entered inside.

 

4. Nasal sinuses

The sinuses are the cavities forming the air-filled pockets, near the nasal passage. The sinuses are small holes lined with mucous membranes. Sinuses help in. The sinuses help in lightening the skull so that a balance is maintained. It also improves our voices, but their main function is to produce a mucus help in moisturizing the nasal mucus membrane of the nose. There are 4 types of sinuses, ethmoid sinuses, frontal sinuses, maxillary sinuses, and sphenoid sinuses. They are named based on the bones that they attached to. The ethmoid sinus is found proximal to the bridge of the nose. Maxillary sinus is also located inside the face, around the area of the cheeks. The frontal sinus is located in the area of the forehead. Frontal sinuses do not develop until the age of 7 years. Sphenoid sinus is located around the base of the skull, behind the nose.

 

Physiology of nose  

  1. Nose help in many ways. First and foremost, it helps in the respiration through inhalation and exhalation. Inhalation is the process of taking air in and leaving the carbon dioxide out.  Nasal concha provides a channel of communication between the nose and the air by advancing itself till the nasopharynx. From the nasopharynx, the air then enters the oropharynx to reach into the lungs via larynx, trachea, and bronchi.

  2. Nose also assists in purifying and moisturizing the dry air by secreting viscous fluid by its mucus membrane. Dry air might damage the delicate surface of the nasal mucosa, hence, moistening is important. The hair found in the nares help in filtering the air. The most important function of the nose is the sense of smell by the olfactory area.

  3. The olfactory area has nerve endings that receive the signals to smell many substances.

  4. Another major function of the nose is the sense of smell or olfaction. Olfaction is carried out through the olfactory epithelium, in the upper nasal cavity. Olfactory epithelium has a close connection with the specialized olfactory cells help in sensing the smell.

  5. The nose is also involved in the speech by involving in the nasalization process. Nasalization is the process of producing of nasal consonants.

 

Blood supply

The blood supply to the nose is provided by branches of the ophthalmic, maxillary, and facial arteries – branches of the carotid arteries. The roof of the mouth is supplied by the branches of the ophthalmic artery, anterior and posterior ethmoidal arteries, and the dorsal nasal artery. The branches of the maxillary artery supplies some parts of the maxilla. The outer walls of the nasal cavity is supplied by the sphenopalatine artery and the ethmoid arteries. The skin of the alae is supplied by the septal and lateral nasal branches of the facial artery.

 

Related topics

1        

Structure of tongue

2

Structure of respiratory system

3

Structure of human teeth

4

Anatomy and physiology of stomach

 

Questions

  1. Explain the nasal bones and cartilages.
  2. What are nasal sinuses. Name the different nasal sinuses and explain the functions.
  3. Explain the physiology of nose .
  4. What is olfactory function? Explain the role nose in sense of smell.

 

 



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