Question

Directions:

1. Insert the balloon through the open bottom of a modified 2-liter soda bottle and up over the neck of the bottle. Pull the end of the balloon over the edges of the neck of the bottle. The balloon is held open by the neck of the bottle.

   

2. Place the plastic bag over the bottom (open) end of the 2-liter bottle and use the rubber band to hold it in place. This will serve as the diaphragm. To inflate the lung, blow into the balloon just before you fasten the rubber band. You can also wrap tape over the edges of the plastic bag to minimize air leaks

3. Grasp the bottom of the plastic bag and pull it down and push it up. Watch as the "lungs" (the balloon) expand and contract as you do this. The balloon has to change size because the air space between the balloon and bottle must remain constant. (Well, it would if the seal around the plastic bag and bottle were perfect).

     

You may block the "trachea" (the neck of the bottle) so that the air supply is cut off and watch as nothing happens when the "diaphragm" is pushed in and out.

This model isn’t perfect. None of the joints are air tight as they would be in a real thoracic cavity. Pull the “diaphragm down and watch the lungs expand . If you hold it in place, the lungs will collapse again over time. This is because of leaks and is not how real lungs work. Pushing the diaphragm in and pulling it out over and over does give you an idea of how lungs work. As the diaphragm tightens, contracts (pull down on the plastic bag) the lungs fill with air. As the diaphragm relaxes (push up on the plastic bag) air is expelled from the lungs .

There are several different ways we breath, i.e. expand our thoracic cavity so that our lungs can expand. You have just made a demonstration model of the diaphragm at work. You can also use your rib cage to expand and contract so that you can inhale and exhale. There are muscles between and around your ribcage which you can use to change the size of your thoracic cavity.

This is approximately what your model of a lung will look like.

1. Put a hand on your lower ribcage and try moving your ribs out and in. Does air also move in and out?

2. Someone with an upper back or neck injury may not have the options of using diaphragm or ribs to breath. They can learn to use the clavicle and the muscles attached to expand their thoracic cavity a small amount and breathe independently for short periods of time. Put your hand on you clavicle and try to raise and lower just that bone without using your diaphragm or your ribs. It isn’t easy but you should be able to get a little air into and out of your lungs this way. How effective do you think this way of breathing is?

3. When you take a really deep breath you use all these muscle groups to help. Take a really deep breath and notice that your ribs expand, your lower abdomen comes out (a sign that the diaphragm has contracted) and your shoulders lift a little (the upper chest and clavicle are working). Now take a relaxed breath. Only your abdomen should go in and out. The movement of your abdomen is a result of the contracting diaphragm pushing on the contents of your “gut” which forces your abdomen to push out.  

Do you breath in or out when your diaphragm contracts?\

4. If a hole were poked in your thoracic wall (the wall of the pop bottle – the hole should be at least the diameter of a pencil)

a. what would happen when you tried to breath? (This is a pneumothorax).

b. Is the space between the balloon and plastic bottle still required to remain constant?

5. Would it be possible to live with a paralyzed diaphragm? Explain your answer.

Answer 1

Please find the answers below:

Answer 1: Yes. The rib cage surrounds the lungs in the thoracic cavity from all sides. As the ribs move up and down, the internal and external intercoastal muscles associated with the ribs tend to move the lungs as well thus causing the lungs to inflate and expand. This helps in moving the air in and out.

Answer 2: There are two modes of respiration, first and most commonly used is abdominal mode and second is thoracic mode. The abdominal mode of respiration utilizes diaphargm-mediated generation of air pressure and thus movement of air. On the other hand, the thoracic-mode of respiration uses the force generated by movement of internal muscles of the ribs and upper thorax to help the lungs expand. This thoracic respiration is less effective than abdominal mode but can definitely help in sustaining life.

Answer 3: The diaphragm undergoes contraction and relaxation to generate space and pressure in the thoracic cavity. The abdominal pressure decreases, volume increases and the air moves inside the lungs with contraction of diaphragm. On the other hand, the abdominal pressure increases, volume decreases and the air moves outside the lungs with relaxation of diapharagm.

Answer 4:

Part a: If a hole is poked into the thoracic wall, the air pressure would leak and the constant pressure would not sustain. This would prevent the total build up of air pressure and gradually the lungs will collapse.

Part b: As the air pressure would drop, the pneumothorax and the lungs would tend to stick to each other since these are the most closely related membranes in the thoracic cavity. This further diminishes the air pressure in the lungs making it difficult to breath.