Question

Which of these changes does not occur at birth when an infant takes its first breaths?

1) Increase in oxygen levels in the blood
2) Closure of the fetal shunts
3) Expansion of the lungs
4) Activation of the diaphragm

Answer 1

The activation of the diaphragm does not occur at birth since it is already active before birth. At birth, oxygen levels in the blood increase, fetal shunts close, and the lungs expand as a part of normal physiological changes.

Step-by-step explanation:

The change that does not occur at birth when an infant takes its first breaths is the activation of the diaphragm. Upon the first breaths, the following changes happen:

• The lungs inflate and oxygen levels in the blood increase.
• Fetal shunts, such as the foramen ovale and ductus arteriosus, begin to close to redirect blood flow through the lungs for oxygenation.
• The lungs expand, reducing pressure in the pulmonary system and facilitating blood flow through the newly functional organs.

However, the diaphragm is already active before birth as the fetus 'practices' breathing movements. It does not become activated only at birth, as it is already capable of movement even before the first breath.