biology

Nostril

Nostril is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Nostril rather than just read about it. In short: A nostril (or naris , pl.: nares ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities.

Key takeaways

Nostril belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Nostril to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Nostril from memory before moving on to harder problems.

Reference excerpt

A nostril (or naris , pl.: nares ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation. Fish do not breathe through noses, but they do have two small holes used for smelling, which can also be referred to as nostrils (with the exception of Cyclostomi, which have just one nostril). In humans, the nasal cycle is the normal ultradian cycle of each nostril's blood vessels becoming engorged in swelling, then shrinking. The nostrils are separated by the septum. The septum can sometimes be deviated, causing one nostril to appear larger than the other. With extreme damage to the septum and columella, the two nostrils are no longer separated and form a single larger external opening. Like other tetrapods, humans have two external nostrils (anterior nares) and two additional nostrils at the back of the nasal cavity, inside the head (posterior nares, posterior nasal apertures or choanae). They also connect the nose to the throat (the nasopharynx), aiding in respiration. Though all four nostrils were on the outside of the head of the aquatic ancestors of modern tetrapods, the nostrils for outgoing water (excurrent nostrils) migrated to the inside of the mouth, as evidenced by the discovery of Kenichthys campbelli, a 395-million-year-old fossilized lobe-finned fish which shows this migration in progress. It has two nostrils between its front teeth, similar to human embryos at an early stage. If these fail to join up, the result is a cleft palate. Each external nostril contains approximately 1,000 strands of nasal hair, which function to filter foreign particles such as pollen and dust. It is possible for humans to smell different olfactory inputs in the two nostrils and experience a perceptual rivalry akin to that of binocular rivalry when there are two different inputs to the two eyes. Furthermore, scent information from the two nostrils leads to two types of neural activity with the first cycle corresponding to the ipsilateral and the second cycle corresponding to the contralateral odor representations. In some cultures the extreme wide flaring of the nostrils accompanied by the baring of the upper teeth is often referred to as "doing the nostrils." The Procellariiformes are distinguished from other birds by having tubular extensions of their nostrils. Widely-spaced nostrils, like those of the hammerhead shark, may be useful in determining the direction of an odour's source.

See also Dilator naris muscle Nasal cycle Piriform aperture

References

External links

"nares" at Dorland's Medical Dictionary

Illustrations

Worked examples

Example 1 — a first encounter with Nostril

Start with the simplest possible case. Write down what Nostril claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Nostril before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Nostril ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Nostril

In research: Nostril appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Nostril in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Nostril is common in secondary-school and first-year university syllabi. It links to neighbouring topics Facial features, Nose, Otorhinolaryngology, so understanding it makes those chapters shorter.
In everyday life: Look for Nostril outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Nostril in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Nostril means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Nostril out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Nostril in simple terms?

A nostril (or naris , pl.: nares ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities.

Why does Nostril matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Nostril?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Nostril.