Digestion Confusion

[nonzerosum]

I ran into this line the kaplan book on digestion: the body of the esophagus lies within a negative thoracic cavity and abdominal cavity has a positive pressure gradient. So without normal defense mech, the pressure will favour reflex.

I am utterly confused on this. What do they mean by positive pressure gradient? Does the negativie thoracic cavity mean negative pressure? How do these 2 related?

thank you

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[Charles_Carmichael]

I ran into this line the kaplan book on digestion: the body of the esophagus lies within a negative thoracic cavity and abdominal cavity has a positive pressure gradient. So without normal defense mech, the pressure will favour reflex.

I am utterly confused on this. What do they mean by positive pressure gradient? Does the negativie thoracic cavity mean negative pressure? How do these 2 related?

thank you

The thoracic location of the esophagus means that intraesophageal pressure is equal to intrathoracic pressure. When they say negative pressure, they mean that it's negative compared to atmospheric pressure. For example, if the pressure is -10 torr, it means that the pressure is 750 torr (since atmospheric pressure is 760 torr and 750 - 760 = -10).

What this means is that the intraesophageal pressure is lower than abdominal pressure (ie. the abdominal pressure is not as negative as intrathoracic/intraesophageal pressure; I can't recall its actual value off the top of my head but it might be positive relative to atmospheric pressure).

So, the problem is that there's a pressure gradient between what's in the abdomen (ie. the stomach) and the esophagus since the pressure is lower at the esophagus. Since stuff goes from an area of high pressure to an area of low pressure, it would mean that keeping gastric contents out of the esophagus is something to worry about (and keeping air from coming in from the top, where the pressure is higher...ie. atmospheric pressure). The job of the upper esophageal sphincter is to prevent air from coming in and the job of the lower esophageal sphincter to prevent gastric contents from entering the esophagus.

Hope this helps.

 

[Baboo Bhaiya]

The thoracic location of the esophagus means that intraesophageal pressure is equal to intrathoracic pressure. When they say negative pressure, they mean that it's negative compared to atmospheric pressure. For example, if the pressure is -10 torr, it means that the pressure is 750 torr (since atmospheric pressure is 760 torr and 750 - 760 = -10).

What this means is that the intraesophageal pressure is lower than abdominal pressure (ie. the abdominal pressure is not as negative as intrathoracic/intraesophageal pressure; I can't recall its actual value off the top of my head but it might be positive relative to atmospheric pressure).

So, the problem is that there's a pressure gradient between what's in the abdomen (ie. the stomach) and the esophagus since the pressure is lower at the esophagus. Since stuff goes from an area of high pressure to an area of low pressure, it would mean that keeping gastric contents out of the esophagus is something to worry about (and keeping air from coming in from the top, where the pressure is higher...ie. atmospheric pressure). The job of the upper esophageal sphincter is to prevent air from coming in and the job of the lower esophageal sphincter to prevent gastric contents from entering the esophagus.

Hope this helps.

nice explanation Kaushik... I agree with pookiez.. I would buy a Bio book written by you too... and also, I need that discount

 

[ChemEngSoonMD]

abdominal cavity has a positive pressure gradient.

thank you

if you dont have a positive pressure gradient, what do you think makes poop come out?

 

[nonzerosum]

The thoracic location of the esophagus means that intraesophageal pressure is equal to intrathoracic pressure. When they say negative pressure, they mean that it's negative compared to atmospheric pressure. For example, if the pressure is -10 torr, it means that the pressure is 750 torr (since atmospheric pressure is 760 torr and 750 - 760 = -10).

What this means is that the intraesophageal pressure is lower than abdominal pressure (ie. the abdominal pressure is not as negative as intrathoracic/intraesophageal pressure; I can't recall its actual value off the top of my head but it might be positive relative to atmospheric pressure).

So, the problem is that there's a pressure gradient between what's in the abdomen (ie. the stomach) and the esophagus since the pressure is lower at the esophagus. Since stuff goes from an area of high pressure to an area of low pressure, it would mean that keeping gastric contents out of the esophagus is something to worry about (and keeping air from coming in from the top, where the pressure is higher...ie. atmospheric pressure). The job of the upper esophageal sphincter is to prevent air from coming in and the job of the lower esophageal sphincter to prevent gastric contents from entering the esophagus.

Hope this helps.

amazing explanation. Thanks!