Why don't elephants get embolisms?

[victor]

Well lets look at the first problem, how does the elephant breathe at all as their lungs are below the surface.
To do it they expand their chest cavity against the outside preasure until the preasure in their lungs is less than 1 atmosphere. Then air flow in.

Thus across the lung walls the preasure is at 1 atmosphere the same as at the surface therfore no embolism here.

How can they do this. Well elephants do not have a pleural cavity, the lungs attach directly to the chest wall and the diaphragm. Respiratory movements are dependent on chest musculature (not on inflating lungs by negative pressure in the pleural cavity, as is usual in mammals) see http://elephant.elehost.com/index.html

So how hard does the chest have to work?
When they are swimming their shoulders are at the surface thus the top of their lungs will only be about 2 or 3 feet below the surface. While I am sure the constriction on their chests makes breathing more difficult the muscles of the diaphragm and chest must be strong enough to overcome the preasure or the would not be able to breathe at all.

Now Giraffes walking in deep water, they would have real problems with their lungs about 15ft under ater.

 

[Kim]

I agree Victor.....they need strong muscles to breath at all. However......their cardio vascular system is all MUCH deeper than the surface, so it's not really the problem of how they breath at all I'm highlighting here......it's the pressure differential at the blood/lung interface I'm talking about. The program I watched was about elephants, but I wouldn't be surprised at all if giraffes were similar.......in fact they'd have to be or they couldn't enter water. (DO giraffes enter water like that?)

 

[fisherdvm]

Hey...come on! When have you ever seen a 3.3 tall elephant!!!

Anyway....Let's see if others chime in on this. I only posted it because I thought it was interesting. I actually already know the answer....I just watched a National Geographic program that talked about it. I thought it would be interesting to post like this though, and make people think about pressure in a slightly unusual way.

OK, 6.6 ft tall elephant - at least down to lung level. That would make it 1.2 ATM. Smart*****

 

[Kim]

OK, 6.6 ft tall elephant - at least down to lung level. That would make it 1.2 ATM. Smart*****

LOL.....that's still a pretty small elephant! Remember...when they are swimming it's just the top of their heads and eyes, plus trunk, that breaks the surface. With a large elephant that means that the deepest part could be what...10...12 feet below the surface? That means the entire vascular system has to be at THAT pressure in order to pump blood to the extremities.
The lung has to remain at 1ATA the whole time (or VERY close) as it's snorkeling 1ATA air from the surface.
It's not like their blood pressure can be higher in one part of their body than in others (unless there are constrictions blocking blood flow). Vascular systems are open circuit.

 

[Spongebobscubasteve]

Ah! But what if an elephant did take up scuba and did need to be put in a deco chamber?
Do you think he would fit?

 

[Kim]

Ah! But what if an elephant did take up scuba and did need to be put in a deco chamber?
Do you think he would fit?

Oh come on...be serious! How far do you think an elephant would get on an AL80? :no

 

[fisherdvm]

LOL.....that's still a pretty small elephant! Remember...when they are swimming it's just the top of their heads and eyes, plus trunk, that breaks the surface. With a large elephant that means that the deepest part could be what...10...12 feet below the surface? That means the entire vascular system has to be at THAT pressure in order to pump blood to the extremities.
The lung has to remain at 1ATA the whole time (or VERY close) as it's snorkeling 1ATA air from the surface.
It's not like their blood pressure can be higher in one part of their body than in others (unless there are constrictions blocking blood flow). Vascular systems are open circuit.

Not true... The entire vascular system has the same physics as a column of water. That's why your blood pressure is measured at the level of the heart. If you were standing up, your blood pressure at the ankle would be equals to your height from your heart to the ankle, divided by 33, times by 760, then added to the blood pressure at the chest.

 

[fisherdvm]

You forget that the lung has a separate circuit than the body. It is pressurized by the right ventricle.

Physiologically, the body can pressurize each system separately. That explains why folks with sleep apnea can develop pulmonary hypertension over time.

I am not an exercise physiologist, but my guess is that the elephant simply pressurize his pulmonary circulation to exceed that of the alveolar pressure - what ever it might be.

The body does amazing things.

 

[Kim]

Not true... The entire vascular system has the same physics as a column of water. That's why your blood pressure is measured at the level of the heart. If you were standing up, your blood pressure at the ankle would be equals to your height from your heart to the ankle, divided by 33, times by 760, then added to the blood pressure at the chest.

So you think that someones blood pressure in their ankles is more than at their heart?

 

[fisherdvm]

I don't think - I know. Just like you say, the vascular system is an open circuit (only the artery side).

It works like a pressurized column of water. Low at the head, high at the ankle. The venous system is almost an open system, with the exception of simple flap valves along the way.

That explains why older folks or those with bad genes gets varicose veins. Puncture one of those, and blood will be spurting out for hours, unless you get a pressure bandage on it.

You are welcomed to check the blood pressure on your ankle. You will need a doppler device or someone with a sensitive finger to check for your pedal pulses. Compare that to your heart height, and it simply is a column of water (blood, actually).