Sighing Reinflates Collapsed Air Sacs
A sigh is a long deep breath. Physiologically it has a necessary job.
A sigh is a long deep audible breath, usually expressing relief, sadness or fatigue. It is not only emotional. Human lungs contain millions of tiny air sacs, and during quiet shallow breathing some collapse. A sigh is a breath roughly twice normal size that pops them open again, and people do it involuntarily around every five minutes whatever their mood. Without sighing, lung function measurably declines. The word is Middle English, probably a back-formation from *sighed*, itself from Old English *sican*.
- A deep breath. *A sigh of relief.*
- To breathe deeply. *Sighing heavily.*
- A soft sound. *The sigh of the wind.*
- Sigh of relief. *A sigh of relief.*
- Old English — *sican*. *The source.*
Word forms
| Form | Word | Example |
|---|---|---|
| Verb | sigh | Sighing. |
| Noun | sigh | A sigh. |
| Past | sighed | Sighed. |
| Related | sough | To sough. |
| Old English | sican | To sigh. |
- She sighed with relief.Emotion.
- We sigh every few minutes.Physiology.
- The wind sighed in the trees.Figurative.
Why the body sighs
- Alveoli are the tiny air sacs where gas exchange happens
- Shallow breathing lets some of them collapse
- A sigh is about twice a normal breath in volume
- It reopens the collapsed sacs
- A brainstem circuit triggers it automatically, every few minutes
Middle English, probably a back-formation from *sighte*, past tense of Old English *sican*, to sigh.
Why do we sigh even when we are not sad?
A sigh reopens tiny air sacs in the lungs that collapse during shallow breathing. A brainstem circuit triggers it every few minutes.
How much bigger is a sigh than a normal breath?
Roughly twice the volume, which is what makes it effective at reinflating collapsed alveoli.