---

MEDICINE 101

Lungs

Here's a set of lungs from a pig.   They're about the same size as your lungs and, no offence, but they're also identical. They don't look very big but if we stretched out all these fine membranes they'd cover a racquetball court.  And it's jammed into a sac about the size of a 3 litre milkbag.

Notice that the lungs are each covered by a thin clear membrane.   It looks and feels like industrial strength plastic wrap.   That's called the PLEURA Ð and inflammation of it is called pleurisy.

But the lungs themselves begin up here, at the throat.  Food and air travels down the throat, and then splits off.  The esophagus takes the food and the larnyx or voicebox handles the air.  The vocal cords are stretched across the top of the larynx and they vibrate when air passes through them.  The vibration produces speech if you're human or an oink if you're a pig.

Below the larnyx is the trachea, a large tube of bone that divides into two bronchi.   An infection here is bronchitis.    Then the bronchi divide into smaller tubes called bronchioles, then divide again into smaller and smaller tubes until they become too small to see.   All of these tiny bronchioles in the lung end in a microscopic dead end, sort of a like a cul de sac.  It's called the alveoulus and it's where the real work of the lung gets done. 

Alveolus means grape in Latin and you can see by this model .. it is like a little grape .. or a very small balloon.  The wall of the alveolus is a rich supply of blood vessels and when you take a big breath in, air (and oxygen) rushes down through all this tubing and comes into millions of these tiny grape-like sacs- and then, a simple process occurs. The oxygen in the air goes directly into the blood vessels, to be carried off to thirsty cells throughout the body.   It isn't pumped across the capillary wall, it doesn't pass go and collect 200 dollars - it just flows into the blood.   That's all there is to it - breath after breath after breath, your lungs inflate with air (blows up lung) cleverly sucking the life-giving oxygen out of the air every time.  And with the used-up air, you're exhaling, or talking away, even as I am now, completely oblivious to the wonder and complexity of it all.  If you stop and think about it (gasp) it's enough to take your breath away.