Question 42

The phrenic nerve branches from the cervical plexus.

The phrenic nerve is primarily formed from the cervical plexus, specifically from the C3, C4, and C5 nerve roots. This nerve plays a crucial role in innervating the diaphragm, which is essential for respiration.

A) Brachial plexus

The brachial plexus is responsible for innervating the upper limb and does not contribute to the formation of the phrenic nerve. Therefore, this option is incorrect in the context of identifying the plexus that branches to form the phrenic nerve.

B) Sacral plexus

The sacral plexus mainly supplies the lower limb and pelvic region. It does not have any direct connection to the phrenic nerve, making this option incorrect as well.

C) Lumbar plexus

While the lumbar plexus innervates parts of the lower body, it does not give rise to the phrenic nerve. Thus, this option is also incorrect in relation to the question.

D) Cervical plexus

The cervical plexus is the correct answer as it contains the nerve roots (C3, C4, and C5) that combine to form the phrenic nerve, which is essential for controlling the diaphragm and facilitating breathing.

Conclusion

The correct answer is D) Cervical plexus, as it directly gives rise to the phrenic nerve, unlike the other options which do not contribute to its formation. Understanding the anatomical relationships of the nervous system is essential for recognizing how specific functions, such as respiration, are regulated.