In head and neck the parasympathetic system in innervates the
## Core Concept
The parasympathetic nervous system is one of the branches of the autonomic nervous system, which is responsible for promoting 'rest and digest' functions. In the head and neck, parasympathetic innervation is crucial for controlling various glandular and smooth muscle activities. The parasympathetic nerves in this region primarily originate from cranial nerves.
## Why the Correct Answer is Right
The correct answer involves understanding which structures in the head and neck receive parasympathetic innervation. The parasympathetic nervous system innervates various glands and smooth muscles in the head and neck, including the salivary glands (except the parotid gland), lacrimal gland, and others. Specifically, the **otic ganglion** and **pterygopalatine ganglion** are key parasympathetic ganglia in the head that relay fibers to these targets. The **submandibular gland** and **sublingual gland** receive parasympathetic innervation via the facial nerve (CN VII) through the submandibular ganglion.
## Why Each Wrong Option is Incorrect
- **Option A:** This option is not specified, but if it refers to a structure not primarily innervated by the parasympathetic system in the head and neck, such as the **parotid gland**, it would be incorrect because the parotid gland receives sympathetic innervation for its secretory function but parasympathetic for the secretion of enzymes; however, the pathway involves the glossopharyngeal nerve (CN IX) and the otic ganglion.
- **Option B:** Similarly, without specifics, if this option suggests a structure not primarily associated with parasympathetic innervation in the head and neck, it would be incorrect.
- **Option C:** This would be incorrect if it refers to a structure that does not receive significant parasympathetic innervation in the context provided.
- **Option D:** This option is the distractor and would be incorrect based on the specifics of parasympathetic innervation patterns.
## Clinical Pearl / High-Yield Fact
A key point to remember is that the **facial nerve (CN VII)** carries parasympathetic fibers that ultimately innervate the **submandibular** and **sublingual salivary glands** via the **submandibular ganglion**, and the **lacrimal gland** and **mucous membranes of the nasal and oral cavities** via the **pterygopalatine ganglion**. This is crucial for understanding the control of glandular secretions in the head and neck.
## Correct Answer Line
**Correct Answer: D.**