Is there a vacuum anywhere inside the human body?

[wow_its_science]

I have a question - is there a vacuum anywhere inside the human body? Of course, the spaces between cells are filled with interstitial fluid, but what about hollow organs, like for example stomach, bladder, bowels, uterus? 

[studiot]

3 minutes ago, wow_its_science said:

I have a question - is there a vacuum anywhere inside the human body? Of course, the spaces between cells are filled with interstitial fluid, but what about hollow organs, like for example stomach, bladder, bowels, uterus? 

Depends what you mean by a vacuum.

If you mean a complete void   -  empty space with nothing in it, not even air the no there isn't.

But if you adopt a polular (also scientific) notion as being any region where the gas pressure is below atmouspheric then yes.

This is often called a partial vacuum and can be measured as so many milliletres or inches of mercury below atmouspheric pressure.

 

As a sports scientist I hope you realise that the old phrase Nature abhors a vacuum is nonsense.
Most of the Universe is empty space.
Your lungs do not suck air into them when you breathe in.
The outside air pressure pushes air in when you expand your lungs by lowering the diaphragm.
This lowers the air pressure within your lungs to below atmouspheric.

There is no such thing as suction.

 

[Doogles31731]

I would  think that the nearest you would get to lower than air pressure in any region of an air-breathing animal, is in the chest cavity on expiration, simply because of the elasticity in healthy lungs. If pneumothorax  occurs for any reason, animals have great difficulty breathing.

[TheVat]

A true vacuum would lower the boiling point of water to room temperature.  This suggests that a true vacuum anywhere in or  around a body would be catastrophic for the person.   Cells would burst and their contents would vaporize.  

Anyplace in the GI tract would equalize pressure with the external environment since the tract is technically not separate from the exterior and has no hermetic seals at larynx or anus.  A slightly higher pressure in the tract, from methane and hydrogen formation,   results in burps or farts,  or  bloat if those don't happen due to temporary food blockages or constrictions of sphincters.  And then there's this fact, one which I am mostly encouraged not to share at social functions:  prolonged sitting in a chair can compress the anal sphincter to where it effectively seals the colon.    

In theory,  you could,  say, eat a bag of white flour,  with some water,  then sit for a prolonged period,  then induce vomiting while in the seated  position followed by laryngeal compression and you might achieve (and "achieve" is really the word here, eh?) a small partial vacuum in your GI tract for a brief period.   

[mistermack]

It can only be a partial vacuum. But that's what you produce in your mouth when you suck up a drink through a straw. 

On 10/27/2021 at 7:31 PM, studiot said:

There is no such thing as suction.

I know what you're saying, but actually, suction just means creating a partial vacuum in normal parlance. We say that a vacuum cleaner sucks air, even though it's really the weight of the atmosphere pushing air into the hose because the fan causes a pressure difference. So I would say that there is such a thing as suction, but the mechanism isn't what a lot of people imagine.

It's just word preference really.

[bangstrom]

6 hours ago, Doogles31731 said:

I would  think that the nearest you would get to lower than air pressure in any region of an air-breathing animal, is in the chest cavity on expiration, simply because of the elasticity in healthy lungs. If pneumothorax  occurs for any reason, animals have great difficulty breathing.

A low pressure would be in the lungs on inhalation or in the eustachion tubes when air pressure is rising or in the joints as when "cracking" knuckles.

 

[studiot]

8 hours ago, mistermack said:

It can only be a partial vacuum. But that's what you produce in your mouth when you suck up a drink through a straw. 

I know what you're saying, but actually, suction just means creating a partial vacuum in normal parlance. We say that a vacuum cleaner sucks air, even though it's really the weight of the atmosphere pushing air into the hose because the fan causes a pressure difference. So I would say that there is such a thing as suction, but the mechanism isn't what a lot of people imagine.

It's just word preference really.

Its more than juast word preference.
It determines the lift of some pumps.

6 hours ago, bangstrom said:

A low pressure would be in the lungs on inhalation or in the eustachion tubes when air pressure is rising or in the joints as when "cracking" knuckles.

 

I agree totally. +1 for the  information additional to the lungs.

 

 

What a pity the OP hasn't been back as he has reeceived some excellent answers.

[Doogles31731]

18 hours ago, bangstrom said:

A low pressure would be in the lungs on inhalation or in the eustachion tubes when air pressure is rising or in the joints as when "cracking" knuckles.

 

I could be wrong, but my take on respiration is that inhalation occurs when the diaphragm contracts. This results in expansion of the lungs with normal air pressure entering through the nose or mouth. A negative pressure within the lungs does not seem to be necessary.

And would it be fair to say that the middle ear is dependent on eustachian tube patency to equalise its pressure with the environment during flight. I imagine that there would be periods during aeroplane ascents when the normal pressure of the middle ear is greater than that outside of the middle ear, resulting in slight pain, and lower during descent.

The 'crackling' knuckles intrigues me though. How does air get into a joint to cause 'crackling'?

[swansont]

24 minutes ago, Doogles31731 said:

I could be wrong, but my take on respiration is that inhalation occurs when the diaphragm contracts. This results in expansion of the lungs with normal air pressure entering through the nose or mouth. A negative pressure within the lungs does not seem to be necessary.

Why would air move, without a pressure difference?

PV = nRT is approximately correct. If the lungs expand, V goes up, P goes down.

[Doogles31731]

Swansont, doesn't that formula apply to a closed system? The lungs are an open system.

My analogy for this is in pulling back the plunger of a syringe to fill it with water. The pressure of the water does not change. Where is the evidence that the air pressure changes when we breathe in? The air pressure stays the same.

On the other hand, if we do not have a partial vacuum in the pleural cavity, the lungs will not expand when the diaphragm contracts.

I'll see if I can find any practical research experiments on this.

Did you have any ideas on 'cracking' knuckles?

Swansont, I found a couple of articles that agree with you -- eg https://www.britannica.com/science/human-respiratory-system/The-mechanics-of-breathing. 

The authors of these do not provide any experimental measurements, but they do use use Boyle's law as an explanation. They imply that the lungs expand first, thus creating at least a temporary lower pressure for the incoming air to equalise. That may be so, but I think that any such time lag would be minimal during resting breathing.

During my early years as a practicing veterinary surgeon, I attended many animals experiencing pneumothorax, so I can assure everybody that we need a partial vacuum in the pleural cavity to ensure normal expansion of the lungs on inspiration. Otherwise we experience severe dyspnoea.

[wow_its_science]

Wow, thank you for all the amazing answers here! Totally helped me clear my doubts