Compared to a normal diaphragm, contraction of a diaphragm that ...

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Compared to a normal diaphragm, contraction of a diaphragm that is low and flat may result in which of the following?
 
  a. Compression of the thoracic cavity
  b. Enhanced venous return and thus cardiac output
  c. Greater diaphragmatic efficiency
  d. Larger than normal change in thoracic volume

Question 2

Which of the following muscles are considered primary muscles of ventilation? 1. Diaphragm 2. Intercostals 3. Scalenes 4. Sternomastoid
 
  a. 1, 3, and 4
  b. 1 and 2
  c. 3 only
  d. 1, 2, 3, and 4

[catron30]

Answer to Question 1

ANS: A
Increased lung volume causes the diaphragm to flatten out. Contraction of a flattened diaphragm can result in tension on the lower ribs that causes them to be pulled inward, which results in compression of the thoracic cavity. This condition can occur in individuals with severe gas trap-ping as a result of emphysema or asthma. To compensate for this, these individuals must recruit other muscles to enlarge the thorax. This results in less efficient breathing and excessive muscle work.

Answer to Question 2

ANS: B
The diaphragm and intercostal muscles are the primary muscles of ventilation.

[luminitza]

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TYSM