Questions and Answers
Which branch of the facial nerve innervates the frontalis muscle responsible for elevating the eyebrows?
What could be a significant consequence of paralysis of the orbicularis oculi muscle?
Which muscle is primarily responsible for elevating the upper lip during facial expressions?
The zygomaticus major muscle is responsible for which facial action?
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Which facial muscle plays a crucial role in compressing the cheeks against the teeth?
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What is the primary role of the depressor labii inferioris muscle in facial expression?
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The zygomatic branch of the facial nerve primarily innervates which muscle?
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What action is primarily facilitated by the orbicularis oris muscle?
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What is the primary function of the platysma muscle?
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Which nerve innervates the trapezius muscle for its motor function?
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What is the origin of the anterior belly of the digastric muscle?
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What is the function of the sternohyoid muscle?
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Where does the sternothyroid muscle insert?
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Which muscle is innervated by the facial nerve (CN VII)?
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What is the role of the upper fibers of the trapezius muscle?
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Which of the following statements is true regarding the infrahyoid muscles?
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What is the primary function of the sternocleidomastoid muscle during bilateral contraction?
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Which of the following statements best describes the auricularis muscles?
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What nerve innervates the anterior, middle, and posterior scalene muscles?
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Which condition is associated with injury to the facial nerve (CN VII)?
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In terms of their function, how do the scalene muscles primarily assist during forced inspiration?
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What direction does the anterior scalene muscle pull during contraction?
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What is the origin of the posterior scalene muscle?
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Which of the following actions is NOT associated with the function of the sternocleidomastoid muscle?
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What is the primary function of the mylohyoid muscle?
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Which of the following muscles is innervated by the ansa cervicalis?
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Which structure is the insertion point for the inferior belly of the omohyoid muscle?
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What innervates the levator scapulae muscle?
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Which muscles share the same innervation?
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Where does the levator scapulae muscle originate?
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What is the primary function of the splenius cervicis muscle?
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Which structure does the longus colli muscle insert at?
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What is the primary function of the external intercostal muscles?
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What is the innervation of the internal intercostal muscles?
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Which part of the internal intercostal muscles is responsible for elevating the ribs during inspiration?
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Where do the subcostal muscles originate?
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What is the main role of the transversus thoracis muscle?
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Which part of the diaphragm is associated with the lumbar vertebrae?
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What occurs when the diaphragm contracts?
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Which intercostal muscles assist in forced expiration?
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Study Notes
Facial Nerve and Muscles
- Facial nerve (CN VII) divides into five major branches: temporal, zygomatic, buccal, mandibular, and cervical.
- Each branch has specific muscle functions, crucial for localizing facial nerve injuries.
- Frontalis muscle (part of occipitofrontalis) elevates eyebrows and creates forehead wrinkles; innervated by temporal branch.
- Orbicularis oculi muscle closes the eyelids; its paralysis can lead to corneal dryness (e.g., Bell’s palsy); innervated by zygomatic and temporal branches.
- Levator labii superioris muscle elevates the upper lip, exposing teeth when smiling; innervated by zygomatic and buccal branches.
- Zygomaticus major muscle raises the mouth corners to create a smile; innervated by zygomatic and buccal branches.
- Buccinator muscle compresses cheeks against teeth, aiding in chewing and blowing; innervated by the buccal branch.
- Depressor labii inferioris muscle lowers the bottom lip for expressions of sadness or pouting.
- Auricularis muscles (anterior, superior, posterior) pull ears backward; mostly vestigial due to limited movement in humans; innervated by temporal branch.
- Facial nerve injury results in facial expression paralysis on the affected side, leading to asymmetry and conditions like Bell's palsy.
Neck Muscles
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Sternocleidomastoid Muscle:
- Origin: Manubrium and medial third of the clavicle.
- Insertion: Mastoid process and superior nuchal line.
- Functions: Rotates head, flexes neck, extends head; innervated by spinal accessory nerve (CN XI) and C2-C3 branches.
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Scalene Muscles:
- Anterior: Elevates the first rib; innervated by ventral rami of C4-C6.
- Middle: Assists in elevating first rib; innervated by ventral rami of C3-C8.
- Posterior: Elevates the second rib; innervated by ventral rami of C6-C8.
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Platysma Muscle:
- Origin: Fascia of upper thorax and lower neck.
- Insertion: Lower mandible border and skin of lower face.
- Function: Tenses neck skin, depresses mandible; innervated by cervical branch of facial nerve (CN VII).
-
Trapezius Muscle:
- Origin: External occipital protuberance, spinous processes of C7-T12.
- Insertion: Lateral third of the clavicle, acromion, scapula spine.
- Functions: Elevates/upwardly rotates scapula, extends neck; innervated by spinal accessory nerve (CN XI) and C3-C4.
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Digastric Muscle:
- Anterior belly: Origin at digastric fossa, innervated by mylohyoid nerve (CN V3).
- Posterior belly: Origin at mastoid notch, innervated by facial nerve (CN VII).
- Function: Depresses mandible, elevates hyoid during swallowing.
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Infrahyoid Muscles:
- Sternohyoid: Depresses hyoid; innervated by ansa cervicalis (C1-C3).
- Sternothyroid: Depresses thyroid cartilage; innervated by ansa cervicalis (C1-C3).
- Thyrohyoid: Depresses hyoid or elevates thyroid cartilage; innervated by C1 via hypoglossal nerve (CN XII).
- Omohyoid: Depresses and stabilizes hyoid; innervated by ansa cervicalis (C1-C3).
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Mylohyoid Muscle:
- Origin: Mylohyoid line of mandible, insertion at hyoid body and midline raphe.
- Function: Elevates mouth floor, hyoid during swallowing; innervated by mylohyoid nerve (CN V3).
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Levator Scapulae Muscle:
- Origin: Transverse processes of C1-C4; insertion at scapula's medial border.
- Function: Elevates scapula, assists neck lateral flexion; innervated by dorsal scapular nerve (C5) and cervical nerves (C3-C4).
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Longus Colli Muscle:
- Origin: Anterior surfaces of T1-T3, transverse processes of C3-C5; insertion varies by part.
- Function: Flexes neck, aids in rotation; innervated by ventral rami of C2-C6.
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Splenius Muscles:
- Capitis: Extends, rotates, laterally flexes head; innervated by dorsal rami of cervical spinal nerves.
- Cervicis: Similar functions for the neck.
Thoracic Wall Muscles
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External Intercostals:
- Origin: Inferior border of upper rib; insertion: superior border of lower rib.
- Function: Elevates ribs during inspiration; innervated by intercostal nerves (T1-T11).
-
Internal Intercostals:
- Origin: Same as external; have interosseous (depress ribs) and interchondral (elevate ribs) parts.
- Innervated by intercostal nerves (T1-T11).
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Innermost Intercostals:
- Origin and insertion same as internal; assists in forced expiration; innervated by intercostal nerves (T1-T11).
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Transversus Thoracis:
- Origin: Lower sternum and xiphoid; insertion: costal cartilages of ribs 2-6.
- Function: Weakly depresses ribs; innervated by intercostal nerves (T2-T6).
-
Subcostal Muscles:
- Origin: Internal surface of lower ribs; insertion: superior borders of inferior ribs.
- Function: Depresses ribs, assisting expiration; innervated by intercostal nerves (T1-T11).
-
Diaphragm:
- Origin: Xiphoid process, lower ribs, lumbar vertebrae; insertion at central tendon.
- Primary muscle of inspiration: contracts to enlarge thoracic cavity, decreasing intra-thoracic pressure.
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Description
Test your knowledge on the functions and divisions of the facial nerve after it leaves the stylomastoid foramen. This quiz will help you understand the implications of injuries to its branches, aiding in the localization of facial nerve damage. Gain a deeper understanding of facial muscle functions and their neurological control.
