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Previous Years NEET MDS Question Discussion
1. Which of the following structures does not pass through cavernous sinus?
- Middle cerebral artery
- Occulomotor nerve
- Abducent nerve
- Trochlear nerve
ANSWER (a)
The cavernous sinus is a paired dural venous sinus located within the cranial cavity. It is divided by septa into small ‘caves’ – from which it gets its name.
The cavernous sinuses are located within the middle cranial fossa, on either side of the sella turcica of the sphenoid bone (which contains the pituitary gland). They are enclosed by the endosteal and meningeal layers of the dura mater.
The borders of the cavernous sinus are as follows:
- Anterior – superior orbital fissure.
- Posterior – petrous part of the temporal bone.
- Medial – body of the sphenoid bone.
- Lateral – meningeal layer of the dura mater running from the roof to the floor of the middle cranial fossa.
- Roof – meningeal layer of the dura mater that attaches to the anterior andnmiddle clinoid processes of the sphenoid bone.
- Floor – endosteal layer of dura mater that overlies the base of the greater wing nof the sphenoid bone.
CONTENTS
Travels through cavernous sinus
- Abducent nerve (CN VI)
- Internal carotid artery (with venous and sympathetic plexus around it)
Travels through lateral wall
- Occulomotor nerve
- Trochlear nerve
- Ophthalmic nerve
- Maxillay branches of trigeminal nerve
2. Posterior one third of tongue is innervated by
- Accessory nerve
- Glossopharyngeal
- Hypoglossal
- Lingual
ANSWER (b)
All of the muscles of the tongue, intrinsic and extrinsic, are innervated by the hypoglossal nerve (CN XII).
The one exception is the palatoglossus muscle which is supplied by the vagus nerve (CN X).
Sensory information is provided by the glossopharyngeal nerve (CN IX),
Glossophaygeal nerve
- It carries general sensory information from the of mucosa of the posterior one-third of the tongue, and special sensory information from the vallate papillae.
- The glossopharyngeal nerve (CN IX) leaves the skull through the jugular foramen.
- It then descends down the lateral surface of the stylopharyngeus muscle and passes through the oropharyngeal triangle.
- The nerve then reaches the oropharynx, from where it enters the tongue just inferiorly to the styloglossus and hyoglossus muscles.
3. Mylohyoid nerve is a branch of
- Main trunk of mandibular nerve
- Anterior division of mandibular nerve
- Facial nerve
- Inferior alveolar nerve
ANSWER (d)
Branches Of Mandibular Nerve
- From main trunk
- Meningeal branch
- Nerve to medial pterygoid
- From anterior trunk
- Masseteric nerve—passing posterior to the tendon of temporalis, this branch approaches the masseteric muscle on its deep aspect.
- Deep temporal nerves—two branches arise generally from this—an anterior and posterior division. Sometimes, a third (intermediate) branch may be found.
- Lateral pterygoid nerve—this branch enters the deep surface of the muscle.
- Buccal branches
- From posterior trunk
- Auriculotemporal nerve—this branch has two roots and is closely related to the middle meningeal artery.
- Lingual nerve—this nerve carries two parts of information—that is related to the trigeminal nerve for sensation from the tongue (general somatic afferent), but also carries with it a branch from the facial nerve— the chorda tympani nerve for special sensory fibers of taste from the front two-thirds of the tongue, but also preganglionic parasympathetic fibers to the submandibular ganglion.
- Inferior alveolar nerve—this is a dual motor and sensory nerve. It gives rise to the motor branches to the mylohyoid and anterior belly of digastric muscles.
4. Posterior communicating artery is a branch of
- Internal carotid artery
- External carotid artery
- Middle cerebral artery
- Posterior superior cerebellar artery
ANSWER (a)
Cerebral part of internal carotid artery and its branches
Three large branches
- Anterior cerebral artery (A): it is a terminal branch of the internal carotid artery originating from the communicating segment (C7).
- Middle cerebral artery (M): it is the second and largest terminal branch of the internal carotid artery, also originating from the communicating segment (C7).
- Ophthalmic arteryalso stemming from the ophthalmic segment (C6), this artery passes through the optic canal, ultimately entering the orbit and supplying its contents.
Three smaller branches
- Superior hypophyseal artery (S): it stems from the ophthalmic segment (C6), supplying the infundibulum and median eminence of the hypothalamus, as well as the pars tuberalis of the anterior pituitary gland.
- Posterior communicating artery (P): it originates from the communicating segment (C7) and anastomoses with posterior cerebral artery coming off the basilar artery, contributing to the formation of the circle of Willis.
- Anterior choroidal artery (A): also originating from the communicating segment (C7).
5. Which of the following is not a branch of cavernous segment of internal carotid artery?
- Cavernous branch
- Inferior hypophyseal branch
- Meningeal branch
- Ophthalmic branch
ANSWER (d)
- CERVICAL SEGMENT
None - PETROUS (HORIZONTAL) SEGMENT
- caroticotympanic artery
- Vidian artery
- CAVERNOUS SEGMENT
- Cavernous branches
- Meningeal branches
- Hypophyseal branches
- CEREBRAL (SUPRACLINOID) SEGMENT
- ophthalmic artery
- superior hypophyseal artery
- posterior communicating artery
- anterior choroidal artery
- anterior cerebral artery
- middle cerebral artery
