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Questions and Answers
What is the primary action of the medial pterygoid muscle when combined with its counterpart on the opposite side?
What is the primary action of the medial pterygoid muscle when combined with its counterpart on the opposite side?
Which structure serves as the origin for the large deep head of the medial pterygoid muscle?
Which structure serves as the origin for the large deep head of the medial pterygoid muscle?
What is the nerve supply to the medial pterygoid muscle?
What is the nerve supply to the medial pterygoid muscle?
In terms of movement, what do alternating contractions of both medial and lateral pterygoids achieve?
In terms of movement, what do alternating contractions of both medial and lateral pterygoids achieve?
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Where do the fibers of the medial pterygoid muscle insert?
Where do the fibers of the medial pterygoid muscle insert?
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What is the primary role of the articular disc in the temporomandibular joint?
What is the primary role of the articular disc in the temporomandibular joint?
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Which muscle is primarily responsible for protracting the mandible?
Which muscle is primarily responsible for protracting the mandible?
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What is the most common cause of temporomandibular joint dysfunction?
What is the most common cause of temporomandibular joint dysfunction?
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Which structure is specifically attached to the body of the mandible at the level of the oblique line?
Which structure is specifically attached to the body of the mandible at the level of the oblique line?
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What is the source of vascular supply to the temporomandibular joint?
What is the source of vascular supply to the temporomandibular joint?
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Which of the following nerves provides sensory innervation to the temporomandibular joint?
Which of the following nerves provides sensory innervation to the temporomandibular joint?
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What symptom can be indicative of a tumor or infection in the muscles of mastication?
What symptom can be indicative of a tumor or infection in the muscles of mastication?
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What is typically the direction of uncomplicated jaw dislocation?
What is typically the direction of uncomplicated jaw dislocation?
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Where does the temporalis muscle primarily originate?
Where does the temporalis muscle primarily originate?
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Which structure provides a connection between the disc and the mandibular head?
Which structure provides a connection between the disc and the mandibular head?
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Which type of dislocation of the jaw may occur during extreme trauma to the skull base?
Which type of dislocation of the jaw may occur during extreme trauma to the skull base?
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What type of articulation occurs between the condyle of the mandible and the articular fossa?
What type of articulation occurs between the condyle of the mandible and the articular fossa?
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What technique is used to reduce a dislocated jaw?
What technique is used to reduce a dislocated jaw?
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What condition can result from habitual clenching of the mouth?
What condition can result from habitual clenching of the mouth?
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Which of the following statements about the masticatory muscles is correct?
Which of the following statements about the masticatory muscles is correct?
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Which of the following infections can present with 'lockjaw' or trismus?
Which of the following infections can present with 'lockjaw' or trismus?
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What is the primary action of the temporalis muscle?
What is the primary action of the temporalis muscle?
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Which part of the masseter muscle is responsible for protruding the mandible?
Which part of the masseter muscle is responsible for protruding the mandible?
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What nerve supplies both the masseter and temporalis muscles?
What nerve supplies both the masseter and temporalis muscles?
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On which surface of the mandible is the lateral pterygoid muscle primarily inserted?
On which surface of the mandible is the lateral pterygoid muscle primarily inserted?
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Which action is performed by the lateral pterygoid muscle?
Which action is performed by the lateral pterygoid muscle?
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Which muscle assists in side-to-side movements of the mandible?
Which muscle assists in side-to-side movements of the mandible?
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What provides the main nerve supply to the lateral pterygoid muscle?
What provides the main nerve supply to the lateral pterygoid muscle?
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Which muscles are primarily responsible for the closing of the mouth?
Which muscles are primarily responsible for the closing of the mouth?
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What is the action of the medial pterygoid muscle?
What is the action of the medial pterygoid muscle?
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Which muscle is responsible for contralateral deviation of the mandible?
Which muscle is responsible for contralateral deviation of the mandible?
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Where does the medial pterygoid muscle originate?
Where does the medial pterygoid muscle originate?
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What is a major clinical condition associated with masticatory muscle disorders?
What is a major clinical condition associated with masticatory muscle disorders?
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Which muscle inserts on the articular capsule of the TMJ?
Which muscle inserts on the articular capsule of the TMJ?
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Which nerve innervates the medial pterygoid muscle?
Which nerve innervates the medial pterygoid muscle?
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What action does the lateral pterygoid muscle primarily perform?
What action does the lateral pterygoid muscle primarily perform?
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Which part of the masseter muscle provides clenching force during emotional stress?
Which part of the masseter muscle provides clenching force during emotional stress?
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Which action is NOT associated with the temporalis muscle?
Which action is NOT associated with the temporalis muscle?
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Which muscle assists in rotary motion of chewing?
Which muscle assists in rotary motion of chewing?
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Study Notes
Myofascial Pain and Dysfunction
- Common causes include nocturnal bruxism (teeth grinding), habitual mouth clenching, and whiplash injuries.
- Temporomandibular joint (TMJ) dysfunction arises from imbalanced forces in mastication muscles, with bruxism being a primary contributor.
Symptoms and Conditions
- Muscle spasms in mastication (trismus) can indicate underlying tumors or infections such as tetanus, which may cause symptoms like "lockjaw."
- Inflammation or infection of muscles can result in myositis and painful jaw movement.
- Tumors, though rare, can form in the masticator space surrounded by deep cervical fascia, extending from adjacent structures.
Jaw Dislocation
- Uncomplicated jaw dislocation typically occurs in a forward direction, especially when the mouth is wide open.
- Notably, upward or backward dislocation requires significant trauma to the skull base or bony structures near the joint.
- Reduction technique involves pressing down on molar teeth while lifting the chin to reposition the mandible.
Articular Disc and Joint Function
- The upper surface of the articular disc is concavoconvex and fits the articular tubercle and mandibular fossa.
- The inferior compartment attaches firmly to the mandibular neck, allowing for controlled movement of the jaw.
- Sensory innervation of the joint capsule comes from the mandibular division of the trigeminal nerve, particularly the auriculotemporal nerve.
Muscles of Mastication
- Comprise four primary muscles: Temporalis, Masseter, Medial Pterygoid, and Lateral Pterygoid.
- All muscles are derived from mesoderm of the first pharyngeal arch and innervated by the mandibular division of the trigeminal nerve.
Temporalis Muscle
- Fan-shaped and located in the temporal fossa, covered by temporal fascia.
- Originates from the floor of the temporal fossa and the deep surface of temporal fascia.
- Inserts at the apex and anterior border of the coronoid process of the mandible.
- Action includes elevating the mandible to close the mouth and retracting it when protruded.
Masseter Muscle
- Thick, quadrilateral muscle covering the lateral surface of the ramus of the mandible.
- Dual origins: superficial part from zygomatic bone and deep part from zygomatic arch.
- Inserts on the lateral surface of the ramus and angle of the mandible.
- Responsible for powerful jaw closure and mandible protrusion.
Lateral Pterygoid Muscle
- Conical muscle with two heads: upper (smaller) from the greater wing of the sphenoid and lower (larger) from the lateral pterygoid plate.
- Inserts into the neck of the mandible and the articular capsule of the TMJ.
- Actions include depressing and protruding the mandible, along with lateral movements.
Medial Pterygoid Muscle
- Thick muscle situated in the infratemporal fossa with superficial and deep heads.
- Originates from the maxillary tuberosity and lateral pterygoid plate.
- Inserts into the medial surface and angle of the ramus of the mandible.
- Elevates the mandible and assists lateral pterygoid in protruding the jaw.
Clinical Anatomy
- Masticatory muscle disorders cover a broad range of issues, including myofascial pain, myositis, and neoplasms.
- Understanding the anatomy and function of these muscles is crucial for diagnosing and treating TMJ disorders effectively.
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Description
Explore the various causes of myofascial pain and dysfunction, focusing on common culprits such as nocturnal bruxism, habitual clenching, and whiplash injuries. Understand how these factors contribute to temporomandibular joint (TMJ) dysfunction and the resulting muscle imbalances. Take this quiz to enhance your knowledge of clinical anatomy related to TMJ disorders.
