TSR Med Students' Society Part III

Exams over! Now to go drink beer and play games.

Nice one. Eugh, my exams start in exactly a month's time.

That's certainly better than coming back from Christmas straight after new year. Bloody King's.

That sucks. I go back next week for another two weeks of lectures and then two weeks worth of study leave before exams.

Nice one. Eugh, my exams start in exactly a month's time.

That sucks. I go back next week for another two weeks of lectures and then two weeks worth of study leave before exams.

Ah I'm so jealous! We never get study leave. They tell us its not possible to revise for our exams (it definitely is).

Got up at 7 to see my girlfriend off and had to go back to sleep as I was far too tired - not looking good for next week's lectures!

There is absolutely no chance that i'll be able to stay awake for all of those 9am starts; my body clock is a mess.

There is absolutely no chance that i'll be able to stay awake for all of those 9am starts; my body clock is a mess.

There is absolutely no chance that i'll be able to stay awake for all of those 9am starts; my body clock is a mess.

I'm just trying to revise some (very basic) respiratory stuff, and my book's saying that after a quiet expiration, intrathoracic pressure is about -0.5 kPa. I don't quite understand why, if it is negative relative to atmospheric pressure, air does not continue to enter the lungs, as gasses go from a region of high to low pressure, right? Is it due to some elastic tension in the lungs, or perhaps the intercostal muscles? But further, if it does reach 0 (or +ve as in forced expiration) what prevents the lungs collapsing? The book also says that the terms 'intrapleural pressure' and 'intrathoracic pressure' are interchangeable, does that mean that the pressure inside the thorax is always the same as the pressure inside the pleural membranes? Thanks!

One of the slides in that lecture confused me; the one that said that intrapleural pressure becomes positive during forced expiration. All other sources i've come across say that intrapleural pressure is always negative. This makes more sense, as the lungs would collapse under a positive intrapleural pressure. The negative pressure is down to the lymphatic system draining pleural fluid and the elasticity of the lungs (inward force) opposing the elasticity of the chest (outward force) giving a greater intraplueral volume and therefore a lower pressure.

Hmm, that would make more sense, however, even Pocock & Richards says that intrapleural pressure becomes positive during forced expiration, up to 10 kPa. So I don't really know what to think!