Nose Anatomy and Role in Respiration and Smell

The nostrils, or nares, which let in and let out air for respiration across the mouth, are housed in the nose of vertebrates. While studying what is nose, the first thing to know is that the nose is placed in the center of the human face and functions as an alternate respiratory passage, particularly for infants throughout suckling. The olfactory mucosa and sinuses are found behind the nose.. Here, we will study the nose structure, functions of the nose, and a few other important pieces of information.

Air Treatment

A nose sense organ regulates received air as a mechanism of thermal control and filtration throughout respiration, as well as facilitating the sensory sense of smell. It acts as the very first connection between the surrounding environment and an animal's fragile internal lungs.

Hair in the nostrils cleans and filters the received incoming air, serving as the first line of protection towards dust, smoke, as well as other possible obstructions that otherwise might hinder breathing, as well as a barrier towards airborne disease. Air first passes via the pharynx, which is associated with the digestive system, before joining the rest of the respiratory system.

Mucus formed in the nose, in addition to serving as a barrier, helps the body's efforts to maintain temperature by supplying moisture to essential respiratory system components.

The nose's capillary system tends to warm and humidify the air that is entering the body; later, which in turn helps in maintaining moisture. Further, it allows alveoli throughout the lungs to efficiently exchange oxygen for carbon dioxide (respiration). The capillaries then assist in the recovery of certain moisture while exhalation, mainly as a feature of thermal control.

Structure in Air-breathing Forms

Amphibians:

• The nostrils of amphibians and lungfish expand into small sacs, which then expand into the forward roof of the mouth via the choanae. Such sacs carry a minor volume of the olfactory epithelium, that covers a range of adjacent tentacles in caecilians. 

• Despite their anatomical similarities to amphibians, lungfish do not use their nostrils for breathing; instead, they breathe via their mouths. 

• Amphibians do have a vomeronasal gland, which is covered by olfactory epithelium, however, unlike amniotes, it is normally a simple sac with no relation to the rest of the nasal system.

Reptiles: 

• The nasal chamber is normally larger in reptiles, and the choanae are situated even farther away in the top of the mouth. 

• The cavity in crocodilians is extraordinarily long, allowing the animal to breathe when underwater. 

• The anterior vestibule, the primary olfactory chamber, and the posterior nasopharynx are the three components of the reptilian nasal chamber. The top portion of the olfactory chamber is coated with olfactory epithelium, and it has a series of turbinates to maximize the sensory field. 

• In lizards and snakes, the vomeronasal organ has evolved to the point that it no longer interacts with the nasal cavity, emerging straight into the top of the mouth. In turtles, where it maintains its initial nasal relation, it is smaller, and it is missing in adult crocodilians.

Birds: 

• Birds have a nose that is similar to that of reptiles, including nostrils in the upper back portion of the beak. 

• The olfactory chamber is small though they have a weak sense of smell, however, it does comprise three turbinates, that can have a complicated system equivalent to those of mammals. 

• The nostrils of many birds, including doves and fowls, are shielded by a horny defensive shell. Based on the variety, the vomeronasal organ has been either undeveloped or entirely absent.

Mammals: 

• In mammals, all nasal cavities are merged into one. They are extraordinarily large in most animals, covering roughly half the length of the skull. 

• Nevertheless, in certain species, such as chimpanzees, bats, and cetaceans, the nose sense organ has been secondarily diminished, and all these animals have quite a weak sense of smell as a result. 

• The creation of a palate, which cuts off the entire top portion of the original oral cavity, that then becomes a component of the nose, creating the palate as the fresh top of the mouth, has widened the nasal cavity of mammals. 

• Complex turbinates in the swollen nasal cavity produce coiled scroll-like structures which serve to warm the air until it enters the lungs. The cavity also expands into adjacent skull bones, creating paranasal sinuses, which are extra air cavities.

Nose structure and function

[Image: Nose structure ]

Function of Nose

Below mentioned are some of the sense organ nose functions (function of nose):-

• Respiration: 

In the respiratory system, the human nose is the very first organ of the upper respiratory tract. Its primary respiratory purpose is to provide and clean inhaled air by heating, moisturizing, and removing particulates. Large particles are caught in the nostrils by nasal fur, which prevents them from entering the lungs.

• Sense of Smell: 

The human body nose is also an integral part of the olfactory system. It comprises a cluster of specialized cells called olfactory receptor neurons, which are responsible for the smell. Olfactory mucosa in the upward nasal passage includes olfactory glands, a kind of nasal gland that aids in olfaction. While guiding airflow to the olfactory zone, the nasal conchae often aids in olfactory function.

• Speech: 

The lungs' pressure is used to generate speech. Nasalization, or the process of adjusting airflow via the human body nose, may help with this. While enabling gases to pass from both the nose and the mouth, the soft palate is lowered to create nasal vowels and consonants. Nasal airflow is sometimes used to obtain click consonants, which are a set of nasal clicks.

Facts on Nose

• In women, the brain region responsible for smell is up to 50% larger.

• The colour of the nasal membrane is a health predictor. During nasal allergy season, subdued pink and grey appear, Pink color suggesting a healthy nasal membrane, while red indicates infection.

• Cilia are tiny hair-like structures that line the inside of your nose. Every five to eight minutes, Cilia sweeps mucus to the back of the nose.