All muscles of the pharynx are supplied by pharyngeal plexus, EXCEPT:
## **Core Concept**
The pharyngeal plexus is a network of nerve fibers that provides motor and sensory innervation to the muscles of the pharynx, except for one key exception. This plexus is primarily derived from the pharyngeal branches of the vagus nerve (cranial nerve X) and the glossopharyngeal nerve (cranial nerve IX), with contributions from the spinal accessory nerve (cranial nerve XI) for one specific muscle.
## **Why the Correct Answer is Right**
The pharyngeal plexus supplies all the muscles of the pharynx except the tensor veli palatini muscle. The tensor veli palatini muscle is unique because it is supplied by the mandibular division of the trigeminal nerve (cranial nerve V3), which is different from the innervation provided by the pharyngeal plexus. This muscle plays a crucial role in the function of the Eustachian tube and in the process of swallowing.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option would be incorrect because it is not specified, but based on the context, muscles like the superior constrictor, middle constrictor, and inferior constrictor are all supplied by the pharyngeal plexus.
- **Option B:** Similar to Option A, without specifics, we assume that if it's not the correct answer, it refers to a muscle supplied by the pharyngeal plexus.
- **Option C:** This would also refer to a muscle innervated by the pharyngeal plexus, given the exception is the tensor veli palatini.
- **Option D:** This option is incorrect because it is stated as the correct answer, implying it refers to the tensor veli palatini muscle.
## **Clinical Pearl / High-Yield Fact**
A key clinical point to remember is that the tensor veli palatini muscle, which is responsible for the equalization of middle ear pressure, is innervated by the mandibular division of the trigeminal nerve (V3). This is an exception to the general rule that all pharyngeal muscles are innervated by the pharyngeal plexus, which is primarily derived from cranial nerves IX and X.
## **Correct Answer:** D. Tensor veli palatini.