Chapter 13, Problem 1DYKB

_____ 1. Which cranial nerve is responsible for innervating the intrinsic and extrinsic tongue muscles?

1. a. accessory (CN XI)
2. b. glossopharyngeal (CN IX)
3. c. trigeminal (CN V)
4. d. hypoglossal (CN XII)

Summary Introduction

Introduction:

There are $12$ pairs of cranial nerves which originate towards the inferior surface of the brain. The cranial nerves are a part of the peripheral nervous system. The naming of cranial nerves is based on the positions. The naming begins from the anteriorly placed nerves.

Answer to Problem 1DYKB

Correct answer:

The hypoglossal nerve innervates intrinsic tongue muscle as well as the extrinsic tongue muscles. Therefore, option d. is correct.

Explanation of Solution

Reason for the correct statement:

Option d. is given as “hypoglossal (CN XII)”. There are nine pairs of cranial nerves which have somatic functions with the autonomic or sensory roles. The CN XII has only somatic motor function. This nerve innervates the extrinsic and intrinsic tongue muscles. Hence, intrinsic and extrinsic tongue muscles are innervated by hypoglossal or CN XII.

Hence, option d. is correct.

Reasons for incorrect statements:

Option a. is given as “accessory (CN XI)”. CN XI innervates the sternocleidomastoid and trapezius muscles. Hence, option a. is incorrect.

Option b. is given as “glossopharyngeal (CN IX)”. CN IX receives touch and taste sensation from one-third of the tongue and also innervates the parotid salivary gland and pharynx muscles. Hence, option b. is incorrect.

Option c. is given as “trigeminal (CN V)”. CN V innervates the muscles of mastication and receives sensory signals from the anterior scalp, meninges, nasal cavity, oral cavity, and face. Hence, option c. is incorrect.

Hence, options a., b., and c. are incorrect.

Conclusion

The hypoglossal nerve innervates the extrinsic and intrinsic muscles of the tongue.