Chapter 8: Nervous System: Lecture Program 8.1: Overview (including Cranial Nerves) To accompany Illustrated Anatomy of the Head and Neck 4th Edition 1 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Lecture Program 8.1: Outline NERVOUS SYSTEM OVERVIEW Central Nervous System Peripheral Nervous System Cranial Nerves 2 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Lecture Program 8.1: Learning Objectives 1. 2. 3. 4. 5. Define and pronounce all the key terms and anatomic terms in this lecture. Describe the components of the nervous system and outline the actions of nerves. Discuss the divisions of the central and peripheral nervous systems. Identify and trace the routes of the cranial nerves on a diagram and skull. Discuss the innervation of each of the cranial nerves. 3 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Lecture Program 8.1: Learning Objectives (continued) 8. 9. 10. Discuss the nervous system pathology associated with the head and neck region. Correctly complete the review questions and activities for this lecture. Integrate an understanding of head and neck nerves into clinical dental practice. 4 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview 5 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview The nervous system is an extensive, intricate network of neural structures that activates, coordinates, and controls all functions of the body. The nervous system causes muscles to contract resulting in facial expressions and even joint movements, such as those involved in mastication and speech. 6 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview The system stimulates glands to secrete and regulates many other systems of the body such as the vascular system and digestive system. The nervous system also allows sensation to be perceived, such as pain and touch during dental treatment. 7 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview The nervous system has two main divisions: central and peripheral. Figure 8-1 8 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview Figure 8-2 9 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Case Study 8.0 Age 84 yrs Scenario Sex Female Height 5’ 4” Weight 275 lbs Chief Complaint “What can I do to keep my mouth healthy?” Medical History Recent history of a cerebrovascular accident - her speech is not affected but her right side has physical limitations, especially in the oral region Blood pressure now controlled by medication; working on obesity A patient of record is concerned about her oral health. A full examination was performed and a clinical photograph was taken as well as a full mouth radiographic series. Current Medications Social History Antidepressant Anticoagulant Antihypertensives Retired high school teacher She is overdue for her maintenance appointment and needs a periodontal evaluation. 10 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview The neuron is the cellular component of the nervous system and is composed of a cell body and neural processes. A nerve is a bundle of neural processes outside the central nervous system and in the peripheral nervous system. Figure 8-1 11 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview A synapse is the junction between two neurons or between a neuron and an effector organ, where neural impulses are transmitted. Figure 8-1 12 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview In order to function, most tissue, structures, and organs have innervation, a supply of nerves to the body part. A nerve allows information to be carried to and from the brain, which is the central information center. 13 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview An accumulation of neuron cell bodies outside the central nervous system is a ganglion (plural, ganglia) such as the trigmeninal ganglion. Figure 8-8 14 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview: Afferent and Efferent Nerves Nerves are of two types: afferent and efferent. Figure 8-1 15 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview: Afferent and Efferent Nerves An afferent nerve or sensory nerve carries information from the periphery of the body to the brain (or spinal cord). Thus an afferent nerve carries sensory information such as taste, pain, and proprioception to the brain. 16 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview: Afferent and Efferent Nerves An efferent nerve or motor nerve carries information away from the brain (or spinal cord) to the periphery of the body. Thus an efferent nerve carries information to the muscles in order to activate them, often in response to information received by way of the afferent nerves. 17 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview: Afferent and Efferent Nerves Figure 8-1 18 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview The plasma membrane of a neuron, like all other cells, has an unequal distribution of ions and electric charges between the two sides of the membrane. The fluid outside of the membrane has a positive charge; the fluid inside has a negative charge. This charge difference is a resting potential and is measured in millivolts. 19 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview The rapid depolarization of the cell membrane results in an action potential, which then causes propagation of the nerve impulse along the membrane. An action potential is a temporary reversal of the electric potential along the membrane for a brief period (less than a millisecond). Figure 8-1 20 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview The action potential begins at one spot on the membrane but spreads to adjacent areas of the membrane, propagating the impulse along the length of the cell membrane. After passage of the action potential, there is a brief period—the refractory period—during which the membrane cannot be stimulated. 21 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Overview To have the impulse cross the synapse to another cell requires the actions of chemical agents or neurotransmitters from the neuron, which are discharged with the arrival of the action potential. Figure 8-1 22 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Central Nervous System: Synapse and Neurotransmitters Applegate EJ. The Anatomy and Physiology Learning System, ed 3. Elsevier, 2006 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 23 Clinical Note: Anesthesia Many local anesthetic agents such as lidocaine, as used in dentistry, mimic inhibitory neurotransmitters by decreasing sensory neurons’ ability to generate an action potential, thus producing localized anesthesia. Anesthesia is the loss of feeling or sensation resulting from the use of certain drugs or gases that serve as inhibitory neurotransmitters. 24 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Central Nervous System 25 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Central Nervous System One of the major divisions of the nervous system, the central nervous system (CNS) includes both the brain and spinal cord. Figure 8-1 26 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Central Nervous System One of the major divisions of the nervous system, the central nervous system (CNS) includes both the brain and spinal cord. Figure 8-2 27 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Central Nervous System The system of membranes is the meninges, which has three layers: dura mater, arachnoid mater, and pia mater. Figure 8-4C 28 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Central Nervous System The dura mater also surrounds and supports the large venous channels (dural sinuses) carrying blood from the brain toward the heart such as the cavernous sinus in the head. Figure 6-12 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 29 Central Nervous System Applegate EJ. The Anatomy and Physiology Learning System, ed 3. Elsevier, 2006 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 30 Central Nervous System Figure 8-4C 31 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Central Nervous System: Brain The major divisions of the brain include: the cerebrum, the cerebellum, the brainstem, and the diencephalon. Figure 8-3 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 32 Central Nervous System: Brain The cerebrum is the largest division of the brain and consists of two cerebral hemispheres. The cerebellum is the second largest division of the brain, after the cerebrum. Figure 8-3 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 33 Central Nervous System: Brain The brainstem has a number of divisions including the medulla, pons, and midbrain. Figure 8-4A 34 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Central Nervous System: Brain The medulla is closest to the spinal cord. The pons connects the medulla with the cerebellum and with higher brain centers. The midbrain includes relay stations for hearing, vision, and motor pathways. Figure 8-4A 35 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Central Nervous System: Brain Superior to the brainstem, the diencephalon primarily includes the thalamus and hypothalamus. The thalamus serves as a central relay point for incoming nerve impulses. The hypothalamus regulates homeostasis. Figure 8-4A 36 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Central Nervous System: Spinal Cord The other component of the CNS, the spinal cord, runs along the dorsal side of the body and links the brain to the rest of the body. Figure 8-4A 37 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Dissection Brain and Spinal Cord Figure 8-4B 38 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Imaging Brain and Spinal Cord Figure 8-4B Figure 8-4D: MRI 39 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Peripheral Nervous System 40 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Peripheral Nervous System The other major division of the nervous system, the peripheral nervous system (PNS), is composed of all the nerves stretching their pathways among the CNS and the receptors, muscles, and glands. Figure 8-1 41 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Peripheral Nervous System The other major division of the nervous system, the peripheral nervous system (PNS), is composed of all the nerves stretching their pathways among the CNS and receptors, muscles, and glands. Figure 8-2 42 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Peripheral Nervous System The PNS is further divided into the afferent nervous system or sensory nervous system, which carries information from receptors to the brain or spinal cord, and the efferent nervous system or motor nervous system, which carries information from the brain or spinal cord to muscles or glands. 43 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Peripheral Nervous System A nerve cell leading from the eye to the brain and carrying visual information is a part of the afferent nervous system. A nerve cell leading from the brain to the muscles controlling the eye’s movement is a part of the efferent nervous system. Figure 8-1 44 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Peripheral Nervous System: Somatic and Autonomic The efferent division of the PNS is further subdivided into the somatic nervous system and the autonomic nervous system. Figure 8-2 45 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Peripheral Nervous System: Somatic and Autonomic The somatic nervous system (SNS) is a subdivision of the efferent division of the peripheral nervous system and includes all nerves controlling the muscular system and external sensory receptors. The SNS involves both receptors and effectors. 46 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Peripheral Nervous System: Somatic and Autonomic The autonomic nervous system (ANS) is the other subdivision of the efferent division of the peripheral nervous system. This system operates without any conscious control as the caretaker of the body. Autonomic fibers are efferent nerves, and they always occur in two-nerve chains: the first nerve carries autonomic fibers to a ganglion, where they terminate near the cell bodies of the second nerve. 47 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Autonomic Nervous System: Sympathetic and Parasympathetic The ANS itself has two nervous system subdivisions: sympathetic and parasympathetic. Figure 8-2 48 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Autonomic Nervous System: Sympathetic and Parasympathetic The sympathetic nervous system is involved in “fight-or-flight responses” such as the shutdown of salivary gland secretion with certain medications. The parasympathetic nervous system is involved in “rest-or-digest” responses such as the stimulation of salivary gland secretions. 49 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Parasympathetic Nervous System Parasympathetic fibers associated with the glands of the head and neck region are carried within various cranial nerves and are briefly described here, as well as in greater detail later. Their ganglia are located in the head, and therefore parasympathetic neurons in this region may be either preganglionic neurons (before relaying in the ganglion) or postganglionic neurons (after relaying in the ganglion). 50 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Nervous System Applegate EJ. The Anatomy and Physiology Learning System, ed 3. Elsevier, 2006 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 51 Brain Review - Ventral View Fehrenbach MJ, editor, Dental Anatomy Coloring Book, WB Saunders, Philadelphia, 2007 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 52 Brain Review - Ventral View Fehrenbach MJ, editor, Dental Anatomy Coloring Book, WB Saunders, Philadelphia, 2007 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 53 Brain and Spinal Cord ReviewLateral Sagittal View Fehrenbach MJ, editor, Dental Anatomy Coloring Book, WB Saunders, Philadelphia, 2007 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 54 Brain and Spinal Cord ReviewLateral Sagittal View Fehrenbach MJ, editor, Dental Anatomy Coloring Book, WB Saunders, Philadelphia, 2007 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 55 Brain and Spinal Cord Review ID 1 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 56 Nervous System Cranial Nerves 57 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Cranial Nerves The cranial nerves are an important part of the PNS. All 12 paired cranial nerves are connected to the brain at its base and pass through the skull by way of fissures or foramina. Figure 8-5 58 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Cranial Nerves The cranial nerves are an important part of the PNS. All 12 paired cranial nerves are connected to the brain at its base and pass through the skull by way of fissures or foramina. Figure 8-6 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 59 Cranial Nerves Some cranial nerves are either afferent or efferent, and others have both types of neural processes. Both Roman numerals (I to XII) and anatomic terms are used to designate the cranial nerves. 60 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 61 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE I The first (I) cranial or olfactory nerve transmits smell from the nasal mucosa to the brain and thus functions as an afferent nerve. The nerve enters the skull through the perforations in the cribriform plate of the ethmoid bone to join the olfactory bulb in the brain. Bath-Balogh M and Fehrenbach MJ. Illustrated Dental Embryology, Histology, Anatomy, ed 3. Saunders, Philadelphia, 2011. Figure 8-6 62 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Dissection CRANIAL NERVE I Figure 9-24 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 63 CRANIAL NERVE II The second (II) cranial or optic nerve transmits sight from the retina of the eye to the brain and thus functions as an afferent nerve. From Applegate EJ: The anatomy and physiology learning system, ed 3, St. Louis, Saunders 2006. Figure 8-6 64 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE II The optic nerve enters the skull through the optic canal of the sphenoid bone on its way from the retina. Figure 3-19 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 65 CRANIAL NERVE III The third (III) cranial or oculomotor nerve serves as an efferent nerve to some of the eye muscles that move the eyeball. Figure 8-6 66 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE III The oculomotor nerve lies in the lateral wall of the cavernous sinus and exits the skull through the superior orbital fissure of the sphenoid bone on its way to the orbit. Figure 3-19 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 67 CRANIAL NERVE IV The small fourth (IV) cranial or trochlear nerve also serves as an efferent nerve for one eye muscle, as well as proprioception, similar to the oculomotor nerve but without any parasympathetic fibers. Figure 8-6 68 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE IV Similar to the oculomotor nerve, the trochlear nerve runs in the lateral wall of the cavernous sinus and exits the skull through the superior orbital fissure of the sphenoid bone on its way to the orbit. Figure 3-19 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 69 CRANIAL NERVE V The fifth (V) cranial or trigeminal nerve has both an efferent component for the muscles of mastication, as well as some other cranial muscles, and an afferent component for the teeth, tongue, and oral cavity, as well as most of the skin of the face and head. Figure 8-6 70 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Dissection CRANIAL NERVE V The sensory root of the trigeminal nerve has three nerve divisions: ophthalmic, maxillary, and mandibular. Figures 8-7A, B 71 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE V The ophthalmic nerve (division) provides sensation to the upper face and scalp. The maxillary and mandibular nerves (divisions) provide sensation to the middle and lower face, respectively. Figure 8-8 72 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. Dissection CRANIAL NERVE V Each of the three nerves or divisions of the sensory root of the trigeminal nerve enters the skull in one of three different locations in the sphenoid bone. Figure 8-7B 73 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE V The ophthalmic nerve or division enters through the superior orbital fissure. The maxillary nerve or division enters by way of the foramen rotundum. The mandibular nerve or division passes through the skull by way of the foramen ovale. Figure 8-6 74 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE V The motor root of the trigeminal nerve accompanies the mandibular nerve of the sensory root and also exits the skull through the foramen ovale of the sphenoid bone. Figure 8-6 75 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE V The trigeminal nerve is the most important cranial nerve to the dental professional because it innervates relevant tissue, structures, and organs of the head and neck. Figure 8-8 76 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE VI The sixth (VI) cranial or abducens nerve or abducent nerve serves as an efferent nerve to one of the muscles that moves the eyeball, similar to the oculomotor and trochlear nerves. Figure 8-6 77 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE VI Similar to both of those cranial nerves, the abducens nerve exits the skull through the superior orbital fissure of the sphenoid bone on its way to the orbit. Figure 3-19 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 78 CRANIAL NERVE VII The seventh (VII) cranial or facial nerve carries both efferent and afferent components. The nerve carries an efferent component for the muscles of facial expression and for the preganglionic parasympathetic innervation of the lacrimal gland (relaying in the pterygopalatine ganglion) as well as the submandibular and sublingual salivary glands (relaying in the submandibular ganglion). Figure 8-20 Applegate EJ. The Anatomy and Physiology Learning System, ed 3. Elsevier, 2006 Drake RL, et al. Gray’s Anatomy for Students, ed 2, Churchill Livingson, 2010 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 79 CRANIAL NERVE VII Figure 8-21 Figure 8-22 80 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE VII The facial nerve leaves the cranial cavity by passing through the internal acoustic meatus, which leads to the facial canal inside the temporal bone. Figure 8-6 81 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE VII Finally, the facial nerve exits the skull by way of the stylomastoid foramen of the temporal bone. This nerve is also important to dental professionals because it innervates relevant tissue of the head and neck and travels through the parotid gland. Figure 3-18 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 82 CRANIAL NERVE VIII The eighth (VIII) cranial or vestibulocochlear nerve serves as an afferent nerve for hearing and balance. This nerve conveys signals from the inner ear to the brain. Figure 8-6 83 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE VIII The nerve enters the cranial cavity through the internal acoustic meatus of the temporal bone. Figure 3-19 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 84 CRANIAL NERVE IX The ninth (IX) cranial or glossopharyngeal nerve carries an efferent component for the pharyngeal muscle, the stylopharyngeus muscle, and the preganglionic gland parasympathetic innervation for the parotid salivary gland (relaying the otic ganglion). The nerve also carries an afferent component for the oropharynx and for taste and general sensation from the base of the tongue, and thus is the afferent limb of the gag reflex. Figure 7-2 Figure 2-17 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 85 CRANIAL NERVE IX The glossopharyngeal nerve passes through the skull by way of the jugular foramen, between the occipital and temporal bones. Figure 3-19 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 86 CRANIAL NERVE IX After supplying the ear, parasympathetic fibers leave the skull through the foramen ovale of the sphenoid bone as the lesser petrosal nerve. Figure 3-32 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 87 CRANIAL NERVE IX These preganglionic fibers (parasympathetic fibers) then terminate in the otic ganglion. The otic ganglion is located near the medial surface of the mandibular nerve of the trigeminal or fifth cranial nerve, just inferior to the foramen ovale. Figure 8-20 88 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE X The tenth (X) cranial or vagus nerve carries a large efferent component for the muscles of the soft palate, pharynx, and larynx and for parasympathetic fibers to many organs in the thorax and abdomen including the thymus gland, heart, and stomach. The nerve carries a smaller afferent component for a small amount of skin around the ear and for taste sensation for the epiglottis. 89 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE X The vagus nerve passes through the skull by way of the jugular foramen, between the occipital and temporal bones. This nerve is important to dental professionals because it innervates relevant tissue of the head and neck. Figure 3-19 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 90 CRANIAL NERVE XI The eleventh (XI) cranial or accessory nerve functions as an efferent nerve for the trapezius and sternocleidomastoid muscles as well as for muscles of the soft palate and pharynx. Figure 2-23 Figure 2-21 91 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE XI The accessory nerve exits the skull through the jugular foramen, between the occipital and temporal bones. This nerve is important to dental professionals because it innervates relevant tissue of the head and neck. Figure 8-6 92 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. CRANIAL NERVE XII The twelfth (XII) cranial or hypoglossal nerve functions as an efferent nerve for both the intrinsic and extrinsic muscles of the tongue. The nerve exits the skull through the hypoglossal canal in the occipital bone. The hypoglossal nerve is important to dental professionals because it innervates the tongue. Figure 3-19 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 93 Parasympathetic Nervous System and Cranial Nerves Drake RL, et al. Gray’s Anatomy for Students, ed 2, Churchill Livingson, 2010 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 94 Brain and Cranial Nerves ReviewVentral Surface Showing Nerve Attachment Fehrenbach MJ, editor, Dental Anatomy Coloring Book, WB Saunders, Philadelphia, 2007 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 95 Brain and Cranial Nerves ReviewVentral Surface Showing Nerve Attachment Fehrenbach MJ, editor, Dental Anatomy Coloring Book, WB Saunders, Philadelphia, 2007 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 96 Cranial Nerves and Skull ReviewInternal View of Skull Base Fehrenbach MJ, editor, Dental Anatomy Coloring Book, WB Saunders, Philadelphia, 2007 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 97 Cranial Nerves and Skull ReviewInternal View of Skull Base Fehrenbach MJ, editor, Dental Anatomy Coloring Book, WB Saunders, Philadelphia, 2007 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 98 Cranial Nerve Supply to Oral Cavity Review Fehrenbach MJ, editor, Dental Anatomy Coloring Book, WB Saunders, Philadelphia, 2007 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 99 Cranial Nerve Supply to Oral Cavity Review Fehrenbach MJ, editor, Dental Anatomy Coloring Book, WB Saunders, Philadelphia, 2007 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 100 Cranial Nerve Review ID 2 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 101 Cranial Nerve Review ID 3 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 102 Nervous System Table Summary 103 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved. 104 Copyright © 2012 by Saunders, an imprint of Elsevier Inc. All rights reserved.