Tmj is which type of joint
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The textbook library doesn't have a dedicated anatomy entry with the exact classification wording, so here is the complete answer from established anatomical knowledge:
TMJ - Type of Joint
The temporomandibular joint (TMJ) is classified as:
| Classification Level | Type |
|---|---|
| By structural type | Synovial joint |
| By shape/movement | Modified condylar (bicondylar) joint |
| By movement type | Ginglymoarthrodial joint |
Why "Ginglymoarthrodial"?
The TMJ is unique because it performs two types of movements, enabled by an articular disc that divides the joint into two compartments:
- Lower compartment (condyle + disc): Hinge (ginglymoid) movement - mouth opening/closing (rotation)
- Upper compartment (disc + temporal bone): Gliding (arthrodial) movement - protrusion, retraction, and lateral excursion (translation)
This combination of hinge + gliding makes it a ginglymoarthrodial joint - the only joint of this type in the human body.
Key Structural Features
- Articular surfaces covered by fibrocartilage (not hyaline cartilage, which is unique among synovial joints)
- Contains an articular disc (fibrocartilaginous meniscus) dividing it into upper and lower joint spaces
- Has a synovial membrane lining both compartments
- Condyle of the mandible articulates with the mandibular fossa and articular eminence of the temporal bone
Summary Answer
The TMJ is a synovial, modified condylar (ginglymoarthrodial) joint - it is a hinge joint that also allows gliding movements.
Seventh cranial nerve leaves cranial cavity through which foramen: a) Stylomastoid foramen b) Foramen ovale c) Internal acoustic meatus d) Jugular foramen
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The textbook confirms the answer. Here is the complete explanation:
Answer: a) Stylomastoid foramen
The 7th cranial nerve (facial nerve) leaves the cranial cavity through the stylomastoid foramen.
Course of the Facial Nerve - Step by Step
| Segment | Location | Key Event |
|---|---|---|
| Origin | Pons (cerebellopontine angle) | Motor root + sensory root arise |
| Enters cranial bone | Internal acoustic meatus | Enters with CN VIII (vestibulocochlear) |
| Inside petrous temporal bone | Facial canal (Fallopian canal) | Roots fuse; geniculate ganglion forms |
| At geniculate ganglion | Petrous bone | Gives off greater petrosal nerve |
| Descending segment | Facial canal | Gives off nerve to stapedius + chorda tympani |
| Exits cranial cavity | Stylomastoid foramen | Nerve emerges into the face |
| Terminal branches | Posterior border of parotid | Divides into temporal, zygomatic, buccal, marginal mandibular, cervical |
"The facial nerve continues along the bony canal...before leaving the cranium through the stylomastoid foramen."
- Kanski's Clinical Ophthalmology, 10th Ed.
Why the other options are wrong
- b) Foramen ovale - transmits CN V3 (mandibular branch of trigeminal nerve)
- c) Internal acoustic meatus - where the facial nerve enters the petrous bone (not where it exits the skull)
- d) Jugular foramen - transmits CN IX (glossopharyngeal), CN X (vagus), and CN XI (accessory)
Key Memory Point
The facial nerve travels a long, winding course inside the facial canal of the petrous temporal bone before finally exiting at the stylomastoid foramen, after which it enters the parotid gland and fans out into its five terminal branches.
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