Mr. Bell presents with the inability to move certain muscles on one side of his face. You ask him to make various facial expressions and find that on his right side he is unable to purse his lips, pull in his cheeks, elevate his upper lip, and smirk. What muscles is Mr. Bell unable to contract?

검증된 단계별 안내

Step 1: Identify the muscles responsible for the specific facial expressions Mr. Bell is unable to perform. For pursing the lips, the orbicularis oris muscle is primarily involved.

Step 2: Determine the muscle responsible for pulling in the cheeks. This action is performed by the buccinator muscle, which is located in the cheek area.

Step 3: Analyze the muscle responsible for elevating the upper lip. The levator labii superioris muscle is responsible for this movement.

Step 4: Identify the muscle involved in smirking. The zygomaticus major muscle is responsible for pulling the corners of the mouth upward and outward during a smirk.

Step 5: Conclude that Mr. Bell's inability to contract these muscles suggests dysfunction in the facial nerve (cranial nerve VII), which innervates these muscles and controls facial expressions.

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주요 개념

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Facial Muscles

Facial muscles are a group of muscles that control facial expressions. They are primarily innervated by the facial nerve (cranial nerve VII) and include muscles such as the orbicularis oris, buccinator, and zygomaticus. Dysfunction in these muscles can lead to characteristic signs of facial weakness or paralysis, as seen in conditions like Bell's palsy.

Cranial Nerve VII (Facial Nerve)

The facial nerve, or cranial nerve VII, is responsible for the motor control of the muscles of facial expression. It also carries sensory information from the taste buds of the anterior two-thirds of the tongue and provides parasympathetic innervation to salivary and lacrimal glands. Damage to this nerve can result in weakness or paralysis of the facial muscles on the affected side.

Bell's Palsy

Bell's palsy is a condition characterized by sudden, unilateral facial weakness or paralysis, often due to inflammation of the facial nerve. The exact cause is often unknown, but it may be linked to viral infections. Symptoms typically include difficulty with facial expressions, drooping of the mouth, and loss of the ability to close the eye on the affected side.