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Bogomolets National Medical University Department of Human Bogomolets National Medical University Department of human anatomy GUIDELINES Academic Subject HUMAN ANATOMY Matter Module № 2 Content module 16 № Theme of the V, VII, IX cranial nerves. lesson Course І-st Amount of hours 3 Kyiv 2017 1. The relevance of the topic: The trigeminal nerve is one of the largest and most important cranial nerve because it is their sensitive fibers innervates the front of the head, the dura of the anterior and middle cranial fossae, as well as teeth. Also motor fibers innervate muscles of mastication and certain muscles of the neck, palate and middle ear. The facial nerve innervates facial muscles and certain muscles of the neck. Its sensitive branches innervate the taste sensitivity of the anterior two thirds of tongue. Vegetative or nodal fibres participate in the formation of vegetative nodes of the head. Branches of the glossopharyngeal nerve innervate the mucous membrane of the posterior third of the tongue, mucosa of pharynx, tonsils, tympanic cavity. The knowledge acquired in the study V, VII, IX pairs of cranial nerves constitutes the ground for many branches of practical medicine, such as neurology, stomatology, maxillofacial surgery and others. 2.Specific objectives : After lesson the student should know and be able to: 1. To demonstrate on preparation the ophthalmic, maxillary, and mandibular nerves at the point of exit from the skull. 2. To determine the fiber composition of the ophthalmic, maxillary and mandibular nerves. 3. Describe and demonstrate sensitive branches of nerves and areas of their actions. To name and show muscles, which are innervated by branches of the mandibular nerve. 4. To name the nucleus of the VII cranial nerve. 5. To demonstrate the exit of the facial nerve from the brain and skull. Describe the nerve in the facial canal. 6. Identify and demonstrate the course of the muscular branches of the facial nerve, areas of innervation. 7. To describe the intermediate nerve: nucleus, node, its branches, areas of innervation, function, communication with other nerves. 8. To determine the nuclei of glossopharyngeal nerve. 9. To describe the course of the trunk of the glossopharyngeal nerve. 10. To be able to determine the composition of the fibers of the IX cranial nerve. 11. To describe the course of the sensory fibers of the IX cranial nerve, identify the areas of innervation. 12. To describe the course of the motor fibers of the IX cranial nerve, identify the areas of innervation. 3. A basic training level Before class the student should know and be able to: 2.1. To identify the main challenges of modern neurology and neurosurgery , clinical direction. 2.2. To know the names of the 12 pairs of cranial nerves. 2.3. Anatomy of the musculo-skeletal system: knowing the structure of the skull bones and skulls in general, the structure of the temporomandibular joint, muscles of the head and neck. 2.4 To know the anatomy of the central nervous system (the brain and spinal cord). 2.5. To know the anatomy of the oral cavity. 2.5. To know and demonstrate the anatomy of the middle ear. 2.6. Be able to draw schematically the structure of the reflex arc (simple, complex). 2.7 . Own classification of the nervous system; N. trigeminus The trigeminal nerve N. ophthalmicus The ophthalmic nerve N. maxillaris The maxillary nerve N. mandihularis The mandibular nerve N. facialis The facial nerve N. glossopharyngeus The glossopharyngeal nerve 4. The organization of the educational material content. The educational material is described in logical sequence usinganatomical preparations of the human skull, separate wet anatomical preparations of the human brain, structural-logical schemes, tables, figures, reflecting the main issues of the topic of practical training. The content of the topic. The trigeminal nerve originates from three sensory nuclei (mesencephalic, principal sensory, spinal nuclei of trigeminal nerve) and one motor nucleus (motor nucleus of the trigeminal nerve) extending from the midbrain to the medulla. A nucleus (pl. nuclei) is a collection of nerve cell bodies within the central nervous system. At the level of the pons, the sensory nuclei merge to form a sensory root. The motor nucleus continues to form a motor root. These roots are analogous to the dorsal and ventral roots of the spinal cord. In middle cranial fossa, the sensory root expands into the trigeminal ganglion. A ganglion (pl. ganglia) refers to a collection of the nerve cell bodies outside the central nervous system. The trigeminal ganglion is located lateral to the cavernous sinus, in a depression of the temporal bone. This depression is known as the trigeminal cave. The peripheral aspect of the trigeminal ganglion gives rise to 3 divisions: ophthalmic (V1), maxillary (V2) and mandibular (V3). The motor root passes inferiorly to the sensory root, along the floor of the trigeminal cave. Its fibres are only distributed to the mandibular division. The ophthalmic nerve and maxillary nerve travel lateral to the cavernous sinus exiting the cranium via the superior orbital fissure and foramen rotundum respectively. The mandibular nerve exits via the foramen ovale entering the infra-temporal fossa. (Note – be aware that while we talk about the nerves exiting the cranial cavity, the sensory components can also be said to be entering the cranial cavity, since they are afferent fibres). Ophthalmic nerve gives rise to 3 terminal branches: frontal, lacrimal and nasociliary, which innervate the skin and mucous membrane of derivatives of the frontonasal prominence derivatives: • Forehead and scalp • Frontal and ethmoidal sinus • Upper eyelid and its conjunctiva • Cornea (see clinical relevance) • Dorsum of the nose Parasympathetic Supply: Lacrimal gland: Post ganglionic fibres from the pterygopalatine ganglion (derived from the facial nerve), travel with the zygomatic branch of V2 and then join the lacrimal branch of V1. The fibres supply parasympathetic innervation to the lacrimal gland. Maxillary nerve gives rise to 14 terminal branches, which innervate the skin, mucous membranes and sinuses of derivatives of the maxillary prominence of the 1st pharyngeal arch: • Lower eyelid and its conjunctiva • Cheeks and maxillary sinus • Nasal cavity and lateral nose • Upper lip • Upper molar, incisor and canine teeth and the associated gingiva • Superior palate Parasympathetic Supply: • Lacrimal gland: Post ganglionic fibres from the pterygopalatine ganglion (derived from the facial nerve), travel with the zygomatic branch of V2 and then join the lacrimal branch of V1. The fibres supply parasympathetic innervation to the lacrimal gland. • Nasal glands: Parasympathetic fibres are also carried to the mucous glands of the nasal mucosa. Post-ganglionic fibres travel with the nasopalatine and greater palatine nerves (branches of V2) Mandibular nerve gives rise to four terminal branches in the infra-temporal fossa: buccal nerve, inferior alveolar nerve, auriculotemporal nerve and lingual nerve. These branches innervate the skin, mucous membrane and striated muscle derivatives of the mandibular prominence of the 1st pharyngeal arch. Sensory supply: • Mucous membranes and floor of the oral cavity • External ear • Lower lip • Chin • Anterior 2/3 of the tongue (only general sensation; special taste sensation supplied by the chorda tympani, a branch of the facial nerve) • Lower molar, incisor and canine teeth and the associated gingiva Motor Supply: • Muscles of mastication; medial pterygoid, lateral pterygoid, masseter, temporalis • Anterior belly of the digastric muscle and the mylohyoid muscle (these are suprahyoid muscles) • Tensor veli palatini • Tensor tympani Parasympathetic Supply: • Submandibular and Sublingual glands: Post-ganglionic fibres from the submandibular ganglion (derived from the facial nerve), travel with the lingual nerve to innervate these glands. • Parotid gland: Post-ganglionic fibres from the otic ganglion ganglion (derived from the glossopharyngeal nerve, CN IX), travel with the auriculotemporal branch of the V3 to innervate the parotid gland. The course of the facial nerve is very complex. There are many branches, which transmit a combination of sensory, motor and parasympathetic fibres. Anatomically, the course of the facial nerve can be divided into two parts: • Intracranial – the course of the nerve through the cranial cavity, and the cranium itself. • Extracranial – the course of the nerve outside the cranium, through the face and neck. Intracranial The nerve arises in the pons, an area of the brainstem. It begins as two roots; a large motor root, and a small sensory root (the part of the facial nerve that arises from the sensory root is sometimes known as the intermediate nerve). The two roots travel through the internal acoustic meatus, a 1cm long opening in the petrous part of the temporal bone. Here, they are in very close proximity to the inner ear. Still within the temporal bone, the roots leave the internal acoustic meatus, and enter into the facial canal. The canal is a ‘Z’ shaped structure. Within the facial canal, three important events occur: • Firstly the two roots fuse to form the facial nerve. • Next, the nerve forms the geniculate ganglion (a ganglion is a collection of nerve cell bodies). • Lastly, the nerve gives rise to the greater petrosal nerve (parasympathetic fibres to glands), the nerve to stapedius (motor fibres to stapedius muscle), and the chorda tympani (special sensory fibres to the anterior 2/3 tongue). The facial nerve then exits the facial canal (and the cranium) via the stylomastoid
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