Snell's Clinical Anatomy - Head and Neck PDF

58-year-old woman woke up one morning finding the and her blood pressure was very high. To make the diagnosis, A right side of her face feeling peculiar and heavy." On looking in the mirror, she saw that the comer of her mouth on the right side was drooping and her right lo...

58-year-old woman woke up one morning finding the and her blood pressure was very high. To make the diagnosis, A right side of her face feeling peculiar and heavy." On looking in the mirror, she saw that the comer of her mouth on the right side was drooping and her right lower e~ the physician had to have knowledge of the facial muscles, the laryngeal muscles, and their nerve supply. The facial paralysis, slurred speech, high blood pressure, and absence of lid seemed to be lower than her left. When she attempted any other abnormal findings suggested a diagnosis of a left- to smile, the right side of her face remained immobile and sided cerebral hemorrhage (stroke), secondary to high blood masklike. While eating her breakfast, she noticed that her food pressure. However, because a left-sided cerebral hemorrhage tended to stick on the inside of her right cheek and liquid dri~ would cause paralysis of only the musdes of the lower part of bled out the corner of her mouth. On taking her dog for a walk. the right side of the face. this was not the diagnosis. she found to her amazement that she could not whistle for his This patient had paralysis of the muscles of the entire return to her side; her lips just would not pucker. right side of the face. Only a lesion of the right facial nerve, Upon examination, the woman~ primary care physician which supplies the muscles, could cause this. Fortunately, this found paralysis of the muscles of the entire right side of the patient was suffering from Bel I palsy, the prognosis was excel- face. Also, this patient talked with 111 slightly slurred speech lent, and she had a complete recovery. CHAPTER OUTLINE Overview Interior of the Skull Neck Osteology Meninges Skin and Superficial Fascia Adult Skull Venous (Dural) Blood Sinuses Neck Muscles Mandible Pituitary Gland (Hypophysis Neck Triangles Neonatal Skull Cerebri) Deep Cervical Fascia HyoidBone Brain Root of the Neck Scalp Orbit and Eye Head and Neck Arterlea Muscles Eyelids Carotid System Sensory Nerve Supply Lacrimal Apparatus Subclavian System Arterial Supply Orbit Venous Drainage Nerves Head and Neck Veins Lymph Drainage Blood and Lymph Vessels Intracranial Veins Eyeball Movements Extracranial Veins Face Eye Structure Facial Skeleton Head and Neck Lympla Skin Temporal, lnfratemporal, Drainage Sensory Nerves and Pteryaopalallne Pericervical Collar Nodes Arterial Supply Foaae Cervical Regional Nodes Venous Drainage Temporal Fossa Deep Cervical Nodes Lymph Drainage Infratemporal Fossa Facial Muscles (Muscles of Facial Pterygopalatine Fossa Cranial Nervee Expression; Mimetic Muscles) Arteries Olfactory Nerves (CN I) Facial Nerve Nerves Optic Nerve (CN D) 609 610 CHAPTER 12 Head and Neck Oculomotor Nerve (CN ID} Ear Pineal Gland Trochlear Nerve (CN IV) External Ear Thyroid Gland Trlgemlnal Nerve (CN V) Tympanic Membrane Parathyroid Glands Abducens Nerve (CN VI) Middle Ear Facial Nerve (CN VD) Internal Ear Radiographic Anatomy Vestlbulocochlear Nerve (CN VDI) Radiographic Appearance of the Glossopharyngeal Nerve (CN IX) D18atiw S,.tem Skull Vagus Nerve (CN X) Oral Cavity Cerebral Arteriography Accessory Nerve (CN XI) Pharynx Computed Tomography Hypoglossal Nerve (CN XII) Esophagus Scans Magnetic Resonance Imaging Cenic:a1 Pleme Ruplratory Sy8tem Cutaneous Branches Nose Surface Anatomy Muscular Branches (Neck} Nasal Cavity Surface Landmarks of the Phrenlc Nerve Paranasal Sinuses Head Larynx Neck Surface Landmarks Brachlal Pleme Trachea Autonomic Nervom S,.tem Sympathetic Part Enclocrlne System Parasympathetic Part Pituitary Gland (Hypophysis Cerebri} LEARNING OBJECTIVES The purpose of this chapter Is to examine the anatomy 2. Identify the meninges surrounding the braJn of the head and neck In the context of normal f\lllctlonal and the folds of dura mater that subdlvlde organization and common clinical conditions. the cranium. Explain the functional/clinical significance of this arrangement. Describe the Osteology innervation of the dura mater. 3. Trace the Bow of blood Into the cranial cavity, 1. Identify the bones of the skull, hyoid, and cervical indlcattng the maJor anastomoses and collateral spine. and their major features, in dry osteology routes. Describe the formation of the cerebral specimens and in standard medical imaging. arterial circle and explain Its functional and Describe the functional aspects of these structures. clinical significance. 2. Identify the components of the 4. Identify the dural venous sinuses, Indicating temporomandlbular joint (TMJ). Describe the their relations to the cranial meninges. Trace mechanisms of opening and closing the jaws. the communications of the venous sinuses with 3. Identify the muscles of mastication, their the extracrantal venous system and explain attachments, sources of innervation, and major the functlonal/clintcal significance of this actions in chewing. arrangement. 5. Explain the anatomical basts for epidural, Scalp and Face subdural, and subarachnotd cranial hemorrhages. 1. Describe the boundaries and structure of the scalp. 6. Identify each of the cranial nerves as It leaves 2. Identify the major muscles of facial expression, the cranial cavity. Indicate the relationships of their actions, and their Innervation. each nerve to particular cranial fossae, to the 3. Describe the Innervation of the face and scalp. folds of dura mater, and to venous sinuses along Predict the deficit expected following injury to its course. Also Indicate the foramlna used In each of the major nerve branches. exiting the cranium, and any major accompanying 4. Trace the flow of blood through the face and scalp. structures (e.g., blood vessels). 5. Trace the pattern of lymph drainage from the 7. Identify the major components of the braJn and scalp and face. their functional significance. Interior of the Skull Orbit and Eye 1. Identify the cranial fossae, the major bony 1. Identify the bony elements of the orbit. Indicate components and boundaries of each, and the the major structures surrounding the orbit, and major contents of each. the position of the eyeball relative to the orbit.  Overview 611 2. Identify the extraocular muscles, their actions, 2. Trace the 8ow of blood through the subclavtan and their nerve supply. Predict the functional artery and Its major branches. Note the regions deficit resulting from damage to each muscle. supplied by each branch, the relationship of Describe the method of clinical testing of the the branches to surrounding structures, and Individual extraocular muscles and their nerves. anastomoses between the branches. 3. Identify the major nerves of the orbit, their 3. Identify the primary intracranial and extracranlal functional components, their main branches, and veins. Trace the Oow of blood through the jugular their destinations. Predict the functional deficit system of veins, noting the regions drained by resulting from damage to each nerve. each of the tributaries and Interconnections 4. Trace the flow of blood into and out of the orbit between the major veins. and orbital structures. 4. Trace the routes of lymphatic drainage In the 5. Identify the main components of the eyelids. head and neck. Indicate the major aggregations of Describe the mechanics of movement of the eyelids. lymph nodes and their relations to neighboring 6. Identify the components of the lacrimal structures. Differentiate the patterns in the right apparatus. Trace the pathway a tear takes from and left sides. the lacrimal gland to the inferior nasal meatus. 7. Follow the course of autonomic nervous Neural Organization supply to orbital structures, indicating the pre- and postgangllonic sources of innervation. 1. Identify the 12 pairs of cranial nerves. Identify Differentiate sympathetic and parasympathetic the functional component(s) contained within functions. and/or conveyed by each of the cranial nerves. Trace the course of each of the cranial nerves Temporal, lnfratemporal, and Pterygopalatine from its origin at the base of the brain to its final Regions destination(s). Indicate the avenue(s) taken in exiting the skull, and the peripheral relations 1. Define the temporal, infratemporal, and of each nerve. Predict the functional deficit(s) pterygopalatine fossae. Identify the major expected from the lesion of each nerve. structures contained in each region. 2. Describe the formation of the cervical and 2. Trace the flow of blood through the maxillary brachial plexuses of nerves, noting the spinal and superficial temporal arteries and their major segments of origin, relations to surrounding branches. Identify the regions supplied and the cervical structures, and distribution of peripheral anastomoses between branches. branches. Note the formation, relations, and 3. Identify, and trace the courses of, the nerves that distributions of the phrenic nerve and the ansa traverse the above fossae. Identify the functional cervicalis. components of each nerve, their sources, and 3. Identify the sources of autonomic innervation to their areas of termination. the head. Trace the pathways of preganglionic and postganglionic autonomic neurons in the Neck head from their origins to their final destinations. Indicate specific synapse points. Describe the 1. Describe the arrangement and fwtctions of the primary functions governed by each autonomic superficial and deep cervical fascia with respect component in the head. to the organlzatlon of the neck. 2. Identify the triangles of the neck, the boundaries Ear of each, and the major contents of each. 3. Identify the muscles in the neck, Including their 1. Identify the boundaries and contents of the attachments, innervation, and major actions. external ear, middle ear, and Internal ear. 4. Describe the vascular supply and drainage of the Describe the relations of each part of the ear neck. apparatus to Its neighboring structures. Describe 5. Describe the lymphatic drainage of the neck. the innervation of the region. 2. Relate the structures of the ear to the mechanics Vascular and Lymphatic Organization of hearing and equilibrium. 1. Trace the flow of blood through the carotid arterial Digestive System tract. Note the regions supplied by each of the major branches, the relationship of the branches 1. Define the boundaries and subdivisions of the to surrounding structures, and anastomoses oral cavity, pharynx, and esophagus. Describe between branches. Describe the locations and the main relations of each to Its surrounding functions of the carotid sinus and carotid body. structures. 612 CHAPTER 12 Head and Neck 2. Identify the muscles of the oral cavity, palate, each sinus to the surrounding oral, orbital, and auditory tube, pharynx. and esophagus and their cranial cavities. attachments, actions, and innervation. 3. Describe the pattern of innervation of the 3. Identify the extrinsic and Intrinsic muscles of the respiratory system in the head and neck. tongue. Describe the sensory and motor nerve 4. Trace the arterial supply to and venous drainage supply to the tongue. Predict the deficit expected from the components of the respiratory system. to follow an injury to each nerve. 5. Trace the lymph drainage from the respiratory 4. Describe the mechanism of swallowing. Note the components. sequence of events, the muscles responsible for 6. Identify the major morphological features of the each event, and the nerves controlling each event. larynx. 5. Describe the location, innervation, lymphatic 7. Identify the extrinsic and intrinsic muscles of the drainage, secretory drainage, and general larynx. Determine the actions of these muscles relationships of the parotid, submandibular, and their roles In sound production. and subllngual salivary glands. Describe the 8. Trace the courses of the neurovascular supply of clinical slgnUicance of the relationship between the larynx. Predict the functional consequences the parotid gland, Its duct, and the emacranial of damage to the different nerves constituting distribution of the facial nerve. this innervation. 6. Describe the pattern of Innervation of the oropharyngeal region and esophagus. Identify Endocrine System the source, region supplied, and the functional components of each nerve. 1. Identify the pituitary, pineal, thyroid, and 7. Trace the arterial supply to and venous drainage parathyroid glands. of the oropharyngeal region and esophagus. 2. Describe the relations of the endocrine organs to Identify the major blood vessels, their territories, surrounding structures. and any significant anastomoses. 3. Trace the vascular, lymph, and nervous supply of 8. Describe the location, lymphatic drainage, and the endocrine organs. general relationships of the oropharyngeal tonsils. 4. Briefty describe the primary functions of the endocrine organs. Respiratory System Radiographic and Surface Anatomy 1. Identify the components, boundaries, and 1. Identify the maJor structures In the head and relations of the nose, paranasal sinuses, larynx, neck that are visible In standard medical imaging. and trachea. 2. Identify the maJor structures that are palpable 2. Identify the drainage routes of each of the and/or have notable surface projections in a paranasal sinuses. Describe the relationship of basic physical examination of the head and neck. OVERVIEW Head injuries from blunt trauma and penetrating mis- siles are associated with high mortality and severe disabil- The head and neck region of the body contains many ity. Headaches are usuallycaused bynonsertous conditions important structures compressed Into a relatively small such as sinusitis or neuralgia; however, they can represent area. The skull, with the enclosed brain and meninges, the earliest manifestations of a lif&threatenlng disease. forms most of the head. The special senses (the eye, ear, Facial, scalp, and mouth injuries are commonly olfactory area, taste receptors) lie within the skull bones encountered ln practice and vary in seriousness from or in the cavities bounded by them. The brain gives a small skin laceration to major max:illofaclal trauma. rise to 12 pairs of cranial nerves, which leave the brain Even an untreated boil on the side of the nose can be and pass through foramina and fissures in the skull. All life threatening. Facial paralysis and unequal pupils may the cranial nerves are distributed to structures in the indicate the existence of a serious neurologic deficit. head and neck, except the 10th, which also supplies Many vital structures are present in the neck. Injuries structures In the chest and abdomen. The digestive and or pressure on the larynx or trachea can compromise respiratory systems begin In the head and traverse the the airway. Swellings can indicate the existence of a neck to reach the thorax and abdomen. Additlonally, key tumor of the thyroid gland or the presence of a malig- endocrine organs are located in the head and neck.. nant secondary lesion in a lymph node.  Osteology 613 Clearly, many signs and symptoms related to the The anatomical posltlon of the skull Is such that region of the head and neck are determined by the ana- the lower margins of the orbits and the upper margins tomic arrangement of the various structures. This chap- of the external acoustic meatl are in the same hori- ter reviews the basic anatomy of this complicated region zontal plane. This is termed the orbltomeatal plane and highlights the clinical relevance of the structures C'Frankfurt plane"). This corresponds closely with a considered. h specifically excludes detailed consider- natural horizontal cranial plane. ation of the brain, which is best covered in a neurobiology The skull is composed of several separate bones text. united at immobile joints called IUl:Ure8. The connec- tive tissue between the bones forms autural ligament& The mandible is an exception to this rule, as it is united OSTEOLOGY to the skull by the mobile, synovtal TMJs. The bones of the skull are organized Into a cranial The skeleton of the head and neck includes the skull, skeleton that surrowids the brain and a fadal ak:el· middle ear osslcles, hyoid bone, and cervical ver- eton. The c:ranlal cavity is the space containing the tebrae. This section describes the skull and hyoid. brain. The skull vault (calvarlum) is the upper part of The ear osslcles are described later, In the section the cranium and forms the roof and side walls of the on the middle ear. The cervical vertebrae are cov- cranial cavity. The bue of the skull is the lowest part ered in Chapter 2 along with rest of the vertebral of the cranium and forms the floor of the cranial cavity colwnn. (Fig. 12.1; also see Figs. 12.5 and 12.6). / Parietal Greater wing of sphenoid Zygomatlc process of frontal Zygoma11C-- Superior orbital Squamous temporal fissure Inferior ort>ital ----11r-:-:.;;;. Zygomatic fissure Figure 12.1 Bones of the anterior aspect of the skull. 614 CHAPTER 12 Head and Neck The relatively Oat bones of the vault {frontal, pari- Adult Skull etals, and part of the occipital) are composed of Biomedical students do not need a comprehensive exterDal and Internal tables of compact bone sepa- knowledge of the detailed structure of each individual rated by a layer of spongy bone called the dlple>e skull bone. However, sufficient detail to understand (Fig. 12.2). The internal table is thinner and more cltntcally relevant applications ls essential. Students brittle than the external table. The bones are cov- ered with periosteum on both the outer and inner should be famlllar with the skull as a whole and should have a dried skull available for reference as they read surfaces. The bones of the vault form via membra- the following description. nous osslflcalfon, whereas the bones of the cranial base and the facial skeleton form via endochondral oalflcatton. Anterior View The cranium consists of the following bones, two of The frontal bone, or forehead bone, curves downward which are paired (Figs. 12.3 and 12.4): to make the upper margins of the orbits (see Fig. 12.1). Frontal bone: 1 The superdllary arches are on either side, and the Parietal bones: 2 aupraorbltal notch {or sapraorbltal foramen) ts at or Occipital bone: 1 near the orbital rim. Medially, the frontal bone articu- Temporal bones: 2 lates with the frontal processes of the maxillae and with Sphenold bone: 1 the nasal bones. Laterally, the frontal bone articulates Ethmoid bone: 1 with the zygomatlc bone. The orbital IJW1lns are bounded by the frontal bone The facial skeleton consists of the following, two of superiorly, the zygomatic bone laterally. the maxilla which are single: inferiorly, and processes of the maxilla and frontal bone Zygomatic bones: 2 medially. Maxillae: 2 The frontal bone contains two hollow spaces lined Nasal bones: 2 with mucous membrane, the frontal air lln118e8, just Lacrimal bones: 2 above the orbital margins. These sinuses communicate Vomer: 1 with the nose and serve to lighten the facial skeleton Palatlne bones: 2 and act as voice resonators. Inferior conchae: 2 The two nasal bones form the brldge of the nose. Mandible: 1 Their lower borders, with the maxillae, make the - Superficial vein of scalp Emissary vein Dlplolc vein ~~~~~~~~~~~~!~~~~~'. Superior sagittal sinus ~~~~~~iii~ Arachnoid granulation Endoeteal layer Pertcranlum of dura mater (perlosteum} Meningeal layer of dura mater ; \ ··. Arachnoid Inner table of ':.~ ·:· : ~. Cerebral artery in parietal bone ·:: ~:·:. ···:· ·:.. ~ubarachnold space.. :. Pia mater Cerebral vein In · Cerebral ccrtex subarachnold space Inferior sagittal sinus Figure 12.2 Coronal section of the upper part of the head showing the layers of the scalp, the sagittal suture of the skull, the falx cerebri, the superior and inferior sagittal venous sinuses, the arachnoid granulations, the emissary veins, and the relation of cerebral blood vessels to the subarachnoid space.  Osteology 615 Pterfon Squamous temporal l Coronal suture Parietal Greater wing Naslon Nasal Frontal process Occipital of zygomallc Lacrfmal ·~~-:F.--~ ZygomaUc Zygomatlcofaclal foramen _~- ~ lnfraortlltal foremen ~ -r-:. Neck of mandible Head of mandible FltJure 12.3 Bones of the lateral aspect of the skull. Superior temporal line Inferior tsmporal line c!!:1--:.henold. The middle cranial fossa is separated from wing of the sphenoid and drains Into the cavernous the posterior cranial fossa by the petrous part of the sinus. temporal bone. The foramen rotundum, which is situated behind the medial end of the superior orbital fissure, perfo- ANTERIOR CRANIAL FOSSA rates the greater wing of the sphenoid and transmits The anterior cranial fossa lodges the frontal lobes of the maxillary nerve from the trigeminal ganglion to the the cerebral hemispheres. It is bounded anteriorly by pterygopalatine fossa.  Osteology 619 Cristagalli / Orbital plate of frontal Optic canal Tuberculum sellae Sella turcica Posterior clinoid process 1 Foramen splnoeum Dorsum sellae Squamous part of temporal Petrous part of temporal Internal acoustic meatus Groove for superio ~ pelr088l sinus · · Hypogl088al canal ln~mal OQCipital protuberance Internal occipital crest Figure 12,6 lntemal surface of the base of the skull. The foramen ovale Iles posterolateral to the fora- sphenold. After a short distance, the artery divides Into men rotundum. It perforates the greater wing of the anterior and posterior branches. The anterior branch sphenoid and transmits the large sensory root and passes forward and upward to the pterion. Here, the small motor root of the mandibular nerve to the lnfra- bone ls deeply grooved or tunneled by the artery for a temporal fossa; the lesser petrosal nerve also passes short distance before it runs backward and upward on through it. the parietal bone. It ls at this site that the artery may The small foremen tplnosum lays posterolateral to be damaged after a blow to the side of the head. The the foramen ovale and also perforates the greater wing posterior branch passes backward and upward across of the sphenoid. The foramen transmits the middle the squamous part of the temporal bone to reach the meningeal artery from the infratemporal fossa into the parietal bone. cranial cavity. The artery then runs forward and later- The large and irregularly shaped foramen lacerum ally In a groove on the upper surface of the squamous lies between the apex of the petrous part of the part of the temporal bone and the greater wing of the temporal bone and the sphenoid bone. The inferior 620 CHAPTER 12 Head and Neck opening of the foramen Iacerum in life is filled by car- POSTERIOR CRANIAL FOSSA tilage and fibrous tissue, and only small blood vessels The posterior cranial fossa Is deep and lodges the pass through this tissue from the cranial cavity to the parts of the hindbrain, namely, the cerebellum, pons, neck. and medulla oblongata. Anteriorly, the superior bor- The carotid canal opens into the side of the foramen der of the petrous part of the temporal bone bounds Iacerum above the closed inferior opening. The internal the fossa. The posterior boundary is the internal sur- carotid artery enters the foramen through the carotid face of the equamous part of the occipital bone (see canal and immediately turns upward to reach the side Fig. 12.6). The floor of the posterior fossa ls formed of the body of the sphenoid bone. Here, the artery turns by the basilar, condylar, and aquamo111 parts of the forward in the cavernous sinus to reach the region of occipital bone and the mastoid part of the temporal the anterior clinoid process. At this point, the internal bone. carotid artery turns vertically upward, medial (see The roof of the fossa is formed by a fold of dura, the Fig. 12.30) to the anterior clinoid process, and emerges tentorium cerebelli, which intervenes between the cer- from the cavernous sinus. ebellum below and the occipital lobes of the cerebral Lateral to the foramen Iacerum is an impression on hemispheres above (see Fig. 12.28). the apex of the petrous part of the temporal bone for The foramen magnum (see Fig. 12.29) occupies the the trigemlnal ganglion. On the anterior surface of the central area of the floor and transmits the medulla petrous bone are two grooves for nerves. The larger oblongata and its surrounding meninges, the ascend- medial groove is for the greater petrotlBI nerve, a ing spinal parts of the accessory nerves, and the two branch of the facial nerve. The smaller lateral groove is vertebral arteries. for the leuer petrosal nerve, a branch of the tympanic The hypoglOIBBI canal ls situated above the antero- plexus. The greater petrosal nerve enters the foramen Iateral boundary of the foramen magnum and transmits lacerum deep to the trigeminal ganglion and joins the the hypoglossal nerve. deep petroeal nerve (sympathetic fibers from around The jugular foramen lies between the lower border the Internal carotid artery) to form the nerve of the of the petrous part of the temporal bone and the condy- pt.erygoid canal. The lesser petrosal nerve passes for- lar part of the occipital bone. It transmits the following ward to the foramen ovale. structures in anteroposterior sequence: the inferior The abducens nerve bends sharply forward across petrosal sinus; the 9th, 10th, and 11th cranial nerves; the apex of the petrous bone, medial to the trigeminal and the large sigmoid sinus. The inferior petrosal sinus ganglion. Here, it leaves the posterior cranial fossa and descends in the groove on the lower border of the enters the cavernous sinus. petrous part of the temporal bone to reach the foramen. The arcuate eminence is a rounded eminence on the The sigmoid sinus turns down through the foramen to anterior surface of the petrous bone and is caused by become the internal jugular vein. the underlying superior semicircular canal. The Internal acoustic meatus pierces the posterior The tegmen tympani, a thin plate of bone, is a surface of the petrous part of the temporal bone. It forward extension of the petrous part of the tempo- transmits the vestibulocochlear nerve and the motor ral bone and adjoins the squamous part of the bone. and sensory roots of the facial nerve. From behind forward, it forms the roof of the mas- The internal occipital crest runs upward in the toid antrum, the tympanic cavity, and the auditory mldllne posteriorly from the foramen magnum to the tube. This thin plate of bone is the only major barrier internal occipital protuberance. The small falx cerebelli that separates Infection in the tympanic cavity from attaches to this crest over the occipital sinus. the temporal lobe of the cerebral hemisphere (see A wide groove for the tran8Vene alnus lays on each Fig. 12.70). side of the internal occipital protuberance. This groove The body of the sphenoid bone forms the median sweeps around on either side, on the internal surface part of the middle cranial fossa. In front is the IUlcus of the occipital bone, to reach the posteroinferior angle cblaBJDatls, which is related to the optic chiasm and or corner of the parietal bone. The groove next passes leads laterally to the optic canal on each side. Posterior onto the mastoid part of the temporal bone, and here, to the sulcus ls an elevation, the tuberculum tiellae. the transverse sinus becomes the sigmoid sinus. The Behind the elevation is a deep depression, the eella tur- superior petrosal sinus runs backward along the upper clca, which lodges the pituitary gland. A square plate of border of the petrous bone in a narrow groove and bone, the donum aellae, bounds the sella turclca pos- drains into the sigmoid sinus. As the sigmoid sinus teriorly. The superior angles of the dorsum sellae have descends to the jugular foramen, it deeply grooves two tubercles, the poeterior clinoid proceaee8, which the back of the petrous bone and the mastoid part give attachment to the fixed margin of the tentorlum of the temporal bone. Here, it lies directly posterior to cerebelli. the mastoid antrum. The cavernous sinus is directly related to the Table 12.l provides a summary of the major open- side of the body of the sphenold (see Figs. 12.28 ings in the base of the skull and the structures that pass and 12.29). through them.  Osteology 621 Table 12.1 Major Openings in the Base of the Skull and Structures Passing Through Them Anterior Cl'W'llal Foua Perforations in cribriform Ethmoid Olfactory nerves plate Mlcldle Cninlal Foua Optic canal --, Lesser wing of sphenoid ~ Optic nerve, ophthalmic artery Superior orbital fissure Betwee_n lesser and greater wings of Oc:ulomotor, troc:hlear, nasociliary, frontal, lac:rimal, spheno1d and abducens nerves; superior ophthalmic vein Foramen rotundum Greater wing of sphenoid =-iMaxillary division of the trigeminal nerve Foramen ovale Greater wing of sphenoid Mandibular division of the trigeminal nerve, lesser petrosal nerve Foramen spinosum Greater wing of sphenoid I Middle meningeal artery Carotid canal + foramen - Between petrous part of temporal _ Lnternal : carotid artery lacerum and sphenoid --- Posterior Cninlal Foua Foramen magnum Occipital M:dulla oblongata, spinal part of ac:c:essory nerve, - - - - - - - - - - ' " -a;;;.n- :..:d right and left vertebral arteries Hypoglossal canal _ _ Occipital Hypoglossal nerve Jugular foramen Between petrous part of temporal Glossopharyngeal, vagus, and accessory nerves; -I and condylar part of occipital I sigmoid sinus becomes internal jugular vein __ Internal acoustic meatus Petrous part of temporal Facial and vestibuloc:ochlear nerves @ Clinical Notes Skull Fractures Anterior Cranial Fossa Fractures Fractures of the skull are common in the adult but much The cribriform plate of the ethmoid bone may be damaged less so in the young child. In the infant skull, the bones are in fractures of the anterior cranial fossa. This usually more reslllent than In the adult skull, and fibrous sutural results In tearing of the overlying meninges and underlylng ligaments separate them. In the adult, the Inner table of the mucoperfosteum. The patient wlll have bleeding from the skull Is parUcularly brittle. Moreover, the sutural ligaments nose (eplstuU) and leakage of cerebrosplnal ftuld into begin to ossify during middle age. the nose (cerebroctplnal rhlnorrhea). Fractures involving The type of fracture that occurs in the skull depends the orbital plate of the frontal bone result in hemorrhage on the age of the patlent, the severity of the blow, and the beneath the conjunctiva and into the orbital cavity, causing area of skull receiving the trauma. The adult skull may be emphthalmos. The frontal air sinus may be Involved, with likened to an eggshell in that it possesses a certain limited hemorrhage into the nose. resllfence beyond which it spllnters. A severe, localized blow produces a local indentation, often accompanied by Middle Cranial Fossa Fractures splintering of the bone. Blows to the vault often result in a Fractures of the middle cranial fossa are common, series of linear fractures, which radiate out through the thin because this Is the weakest part of the base of the skull. areas of bone. The petrous parts of the temporal bones and Anatomlcally, this weakness is caused by the presence the occipital crests strongly reinforce the base of the skull of numerous foramina and canals in this region. The and tend to deflect linear fractures. cavities of the middle ear and the sphenold air sinuses are In the young child, the skull may be likened to a table particularly vulnerable. The leakage of cerebrospinal fluid tennis ball in that a localized blow produces a depression and blood from the external auditory meatus Is common. without spllntering. This common type of circumscribed The seventh and eighth cranial nerves may be Involved as lesion ls referred to as a "pond" fracture. they pass through the petrous part of the temporal bone. (continued) 622 CHAPTER 12 Head and Neck The third, fourth, and sixth cranial nerves may be damaged tothe nasal septum and require careful treatment under lf the lateral wall of the cavernous sinus Is tom. Blood and general anesthesia. cerebrosplnal Ould may leak Into the sphenold air sinuses and then Into the nose. Maxillofacial Fractures Maxillofacial fractures usually occur as the result of massive Posterior Cranial Fossa Fractures facial trauma. There Is extensive facial swelllng, mldface In fractures of the posterior cranial fossa, blood may escape moblllty of the underlying bone on palpation, malocclusion into the nape of the neck deep to the postvertebral muscles. of the teeth with anterior open bite, and possibly leakage of Some days later, it tracks between the muscles and appears cerebrosplnal fluid (cerebrollplnal rhhlorrbea) secondary in the posterior hiangle, close to the mastoid process. The to fracture of the cribriform plate of the ethmoid bone. mucous membrane of the roof of the nasopharynx may be Double vision (dlplopla) may be present, owing to orbital tom, and blood may escape there. Jn fractures involving the wall damage. Involvement of the lnfraorbttal nerve with Jugular foramen, the 9th, 10th, and 11th cranial nerves may anesthesia or paresthesla of the skin of the cheek and upper be damaged. The strong bonywails of the hypoglossal canal gum may occur in fractures of the body of the maxilla. Nose usually protec::t the hypoglossal nerve from Inf ury. bleeding may also occur in maxillary fractures. Blood enters the maxillary air sinus and then leaks into the nasal cavity. Fadal Bone Fractures The sites of the fractures are classified. as Le Fort type I, D, or ID. These fractures are summarized. In Figure 12.7. The developing bones of a child's face are more pliable than an adult's, and fractures may be incomplete or greenstick. Blowout Fractures of the Maxilla In adults, the presence of well-developed, air-filled sinuses and the mucoperiosteal surfaces of the alveolar parts of Asevere blow to the orbit (as from a baseball) may cause the the upper and lower jaws means that most facial fractures contents of the orbital cavity to explode downward through should be considered to be open fractures, susceptible to the floor of the orbit Into the maxillary sinus. Damage to the lnfectlon, and requiring anttblotlc therapy. lnfraorbital nerve may occur, resulting In altered sensation In the skin of the cheek, upper lip, and gum. Anatomy of Common Facial Fractures Zygoma or Zygomatrc: Arch Fracture Automobile accidents, fisticuffs, and falls are common causes of facial fractures. Fortunately, the upper part of the A blow to the side of the face can fracture the zygoma skull ls developed from membrane (whereas the remainder or zygomatlc arch. Although It can occur as an isolated ls developed from cartilage). Therefore, this part of the skull fracture, as from a blow from a clenched fist, it may be in children Is relatively flexible and can absorb considerable associated with multiple other fractures of the face, as often force without resulting in a fracture. seen In automobile accidents. Signs of fractures of the facial bones include defonnity, ocular displacement, or abnormal movement accompanied by crepltatlon and malocclusion of the teeth. Anesthesia or paresthesia of the facial skin will follow fracture of bones through which branches of the trlgemlnal nerve pass to the skin. "' I~ r' J I j -~ , l~~f/4~·' The muscles of the face are thin and weak and cause little displacement of the bone fragments (e.g., prolonged ' 8TllC plate LlgamentJI The laleral temporomandlbuJar ligament strengthens Mastoid the lateral aspect of the capsule, and its fibers run procesa downward and backward from the tubercle on the root Styloid process of the zygoma to the lateral surface of the neck of the Stylomandlbular/ mandible (see Fig. 12.9). This ligament limits the move- A ligament ment of the mandible in a posterior direction and thus protects the external auditory meatus. The aphenomandlbular ligament Iles on the medial side of the joint. It is a thin band that Is attached above to the spine of the sphenoid bone and below to the lingula of the mandibular foramen. It represents the remains of the first pharyngeal arch in this region. The stylomandlbular ligament lies behind and medial to the joint and some distance from it. It is merely a band of thickened deep cervical fascia that extends from the apex of the stylold process to the angle of the mandible. B Artlcalar Disc A fibrocartilage arttcular c Figure 12.9 Temporomandibular joint as seen from the bony surfaces and divides t lateral (A) and medial (8) aspects. Articular tu..rele Temporal fascia T~mporalis Zygomatlc process Zygomatlc , arch (cut) ,,..- Mandibular fossa Head of mandible Tendon of -- temporalis _ External auditory rneatus Mandibular notch Neck of mandible - Ramus of mandible ·-. Sternocleido· mastoid - Angle of External -- mandible carotid artery Figure 12.10 A dissection of the left temporcmandibular joint. The capsule and lateral temporomandibular ligament have been removed to reveal the interior of the joint. Note the articular tubercle and mandibular fcssa of the temporal bone and the head of the mandible. The articular disc is present within the joint cavity on the upper surface of the head of the mandible.  Osteology 625 Ar1icula.r tubercle L Synovlal membrane A Dlgastrtc (posterior belly) Dlgastrtc (anterior belly) Omohyold - - 7 i i l (superior belly) c Figure 12.11 Temporomandibular joint with the mouth closed (A) and with the mouth open (8). Note the position of the head of the mandible and articular disc in relation to the articular tubercle in each case. C. The attachment of the muscles of mastication to the mandible. The arrows indicate the direction of their actions. compartments (see Fig. 12.11). The disc is an oval plate Neroe Supply that attaches ctrcumferentlally to the capsule. It Is also Aurlculotemporal and masseteric branches of the attached in front to the tendon of the lateral pterygoid mandibular nerve muscle and by fibrous bands to the head of the mandi- ble. These bands ensure that the disc moves forward and Mooements backward with the head of the mandible during protrac- The mandible can be depressed, elevated, protruded, tion and retraction of the mandible. The upper surface of and retracted. Rotation also occurs, as In chewing. In the disc is concavoconvex from anterior to posterior to the posltlon of rest, the teeth of the upper and lower fit the shape of the articular tubercle and the mandibular jaws are slightly apart. On closw-e of the jaws, the teeth fossa; the lower surface is concave to fit the head of the come into contact (occlusion.). mandible. The synovial membrane lines the capsule in The muscles of mastication are summarized in both the upper and lower cavities of the joint. Table 12.2 and Figure 12.11. Table 12.2 Mastication Muscles Masseter Zygomatic arch Lateral surface of Mandibular division Elevates the mandible to ramus of mandible of the trigeminal occlude teeth L nerve Temporalis Floor of temporal Coronoid precess of Mandibular division Anterior and superior fibers fossa the mandible of the trigeminal elevate mandible; posterior nerve fibers retract mandible Lateral Greater wing of the Neck of mandible Mandibular division] Pulls neck of mandible pterygoid (two sphenoid and lateral and articular disc of the trigeminal forward (protraction) heads) pterygoid plate nerve Medial I pterygoid (two Tuberosity of maxilla and lateral pterygoid Medial surface of angle of mandible f'Mandibular division I ~·the trigeminal Elevates mandible heads) plate nerve 1 626 CHAPTER 12 Head and Neck MANDIBLE DEPRESSION 1!s;~~:~:~~otes As the mouth is opened, the head of the mandible rotates on the undersurface of the articular disc around a horizontal axis. To prevent the angle of the jaw Impinging u1U1ecessartly on the parotld gland and the sternocleldomastold muscle, the mandible Is pulled forward (protracted). This is accomplished by the Temporomandibular Joint contraction of the lateral pterygoid muscle, which pulls The TMJ lies immediately in front of the external forward the neck of the mandible and the articular disc auditory meatus. The great strength of the lateral so that the latter moves onto the articular tubercle (see temporomandlbular ligament prevents the head of the Fig. 12.11). The forward movement of the disc is limited mandible from passing backward and fracturing the by the tension of the fibroelastic tissue, which tethers tympanic plate when a severe blow falls on the chin. the disc to the temporal bone posteriorly. The articular disc of thetemporomandibular joint may Depression of the mandible is brought about by become partially detached from the capsule, and thls results in its movement becoming noisy and producing contraction of the digastrics, the geniohyoids, and the an audible click during movements at the Joint. mylohyoids. The lateral pterygoids play an important role by pulling the mandible forward. Temporomandibular Joint Dislocation MANDIBLE ELEVATION The movements in depression of the mandible are Dislocation sometimes occurs when the mandible Is depressed. In this movement, the head of the mandible reversed. First, the head of the mandible and the disc and the articular disc both move forward until they reach move backward, and then the head rotates on the lower the summit of the articular tubercle. In this posltlon, surface of the disc. the Joint ls unstable, and a minor blow on the chb1 or Elevation of the mandible Is brought about by a sudden contraction of the lateral pterygoid muscles, contraction of the temporalls, the masseter, and the as in yawning, may be sufficient to pull the disc forward medial pterygolds. The head of the mandible ls pulled beyond the summit. In bilateral cases, the mouth is fixed backward by the posterior fibers of the temporalis. The In an open position, and both heads of the mandible articular disc ls pulled backward by the fibroelastlc lie ln front of the articular tubercles. Pressing the tissue, which tethers the disc to the temporal bone gloved thumbs downward on the lower molar teeth and posteriorly. pushing the Jaw backward easily achieve reduction of the dislocation. The downward pressure overcomes the tension of the temporalls and masseter muscles, and the MANDIBLE PROTRUSION backward pressure overcomes the spasm of the lateral The articular disc is pulled forward onto the anterior pterygold muscles. tubercle, carrying the head of the mandible with it. All movement thus takes place in the upper cavity of the joint. In protrusion, the lower teeth are drawn forward over the upper teeth, which ls brought about by con- traction of the lateral pterygoid muscles of both sides, Neonatal Skull assisted by both medial pterygolds. The newborn skull, compared with the adult skull, has a disproportionately large crantwn relative to the face MANDIBLE RETRACTION (Fig. 12.12). The neonatal face to cranium size ratio Is The articular disc and the head of the mandible are approximately 1:8, whereas the adult face to cranium pulled backward into the mandibular fossa. Retraction ratio Is approximately 1:1. Growth of the oral apparatus is brought about by contraction of the posterior fibers (upper and lower jaws, teeth, muscles of mastication, of the temporalis. and tongue) and respiratory system (nasal cavities and paranasal sinuses) during childhood results in a great LATERAL CHEWING MOVEMENTS increase in length of the face. Alternately protruding and retracting the mandible on The bones of the skull are smooth and unilaminar, each side produces lateral motions. For this to take as they have no diploe. Most of the skull bones are place, a certain amount of rotation occurs, and the ossified at birth, but the process is incomplete, and muscles responsible on both sides work alternately and the bones are mobile on each other, being connected not in unison. by fibrous tissue or cartilage. The bones of the vault Important Temporomandlbular Jolnt Relatlons are not closely knit at sutures, as In the adult, but are Anteriorly: Mandibular notch and the masseterlc separated by Wlossified membranous Intervals called nerve and artery (see Fig. 12.45) fontanelles ("soft spots"). Cllnlcally, the anterior and Posteriorly: Tympanic plate of the external auditory posterior fontanelles are most Important and are easily meatus (see Fig. 12.9A) and the glenoid process of the examined In the midllne of the vault. parotld gland The anterior (bregmatic) fontanelle ls diamond Laterally: Parotid gland, fascia, and skin (see Fig. 12.87) shaped and Iles between the two halves of the frontal Medlally: Maxillary artery and vein and auriculotem- bone in front and the two parietal bones behind. The poral nerve fibrous membrane forming the floor of the anterior  Osteology 627 Anterior fontanelle i-:------:->.-.~:-- Frontal Posterior suture fontanelle lntennaxillary suture MandIble TYf11l'BlliC membrane Tympanic part of temporal bone A B Figure 12,12 Neonatal skull as seen from the anterior (A) and lateral (B) aspects. fontanelle ossifies and closes by 18 months of age. The The Dl81told procea is not present at birth and devel- posterior (lambdolcl) fontanelle is triangular and lies ops later in response to the pull of the stemocleidomas- between the two parietal bones In front and the occlpl- told muscle when the child moves his or her head. tal bone behind. This fontanelle usually closes by the At birth, the mastoid antrum Iles about 3 mm deep end of the 1st year. Two smaller fontanelles are located to the floor of the suprameatal triangle. As growth of on each side of the skull. The anterolateral (spheno&- the skull continues, the lateral bony wall thickens so dal) fontanelle is at the junction of the frontal, parietal, that at puberty the antrum may lie as much as 15 mm squamous temporal, and greater wing of the sphenoid from the surface. bones. The po8terolateral (mastoldal) fontanelle is Two separate right and left dentary bonee, joined by at the junction of the temporal, parietal, and occipital a midllne symphyseal joint, form the lower jaw at birth. bones. The two dentaries fuse at the symphysla mend by the The tympanlc part of the temporal bone is merely end of the first year and fonn the single mandible. a C-shaped ring at birth, compared with a C-shaped The angle of the mancllble is obtuse at birth. The curved plate in the adult. Thus, the external audi- head is level with the upper margin of the body, and the tory meatus ls almost entirely cartllagtnous In the coronold process ltes at a superior level to the head. newborn, and the tympanlc membrane (eardrwn) ls The angle assumes the adult shape after eruption of the nearer the surface. Although the tympanic membrane permanent teeth, and the head and neck grow so that is nearly as large as In the adult, it faces more infe- the head comes to lie higher than the coronoid process. riorly. During childhood, the tympanic plate grows In old age, the size of the mandible reduces when the laterally, forming the bony part of the meatus, and teeth are lost. As the alveolar part of the bone becomes the tympanic membrane comes to face more directly smaller, the ramus becomes oblique in position so that laterally. the head is bent posteriorly. 1@ Clinical Notes Fontanelles Tympanic Membrane Palpation of the fontanelles enables the physician to At. birth, the tympanlc membrane faces more downward determine the progress of growth in the surrounding bones, and less laterally than In maturity. When examined with the degree of hydration of the baby (e.g., if the fontanelles the otoscope, it Iles more obllquely In the Infant than In are depressed below the surface, the baby is dehydrated), the adult. and the state of the intracranial pressure (a bulging fontanelle Indicates raised lntracranlal pressure). Forceps Delivery and the Facial Nerve Samples of cerebrosplnal ftuld can be obtained by passing a long needle obliquely through the anterior fontanelle into The mastoid process is not developed in the neonate, the subarachnoid space or even into the lateral ventricle. and the facial nerve Is relatively exposed and dose to Clinically, it is usually not possible to palpate the anterior the surface as it emerges from the stylomastoid foramen. fontanelle alter 18 months, because the frontal and parletaJ Thus, forceps used in a difficult delivery can damage the bones have enlarged to close the gap. nerve. 628 CHAPTER 12 Head and Neck Hyoid Bone of the occipltofrontalls muscle (see below and Fig. 12.14). The lateral margins of the aponeurosls are The hyoid bone is a mobile single bone in the midline attached to the temporal fascia. The aubaponeurodc of the neck below the mandible and next to the larynx. apace ls the potential space deep to the eplcranial It does not articulate with any other bones. The hyoid aponeurosis. It is limited In front and behind by the bone Is U-shaped and consists of a body and two origins of the occipitofrontalis muscle, and it extends greater and two lellel' comua {Fig. 12.13). It attaches laterally as far as the attachment of the aponeurosis to the skull by the stylohyold llgament and to the thy- to the temporal fascia. roid cartilage by the thyrohyold membrane. The stylo- Loose areolar tissue. This occupies the subaponeu- hyoid ligament may ossify to greater or lesser degrees. rotic space (see Fig. 12.2) and loosely connects the The hyold bone fonns a base for the tongue and is eplcranlal aponeurosls to the pertosteum of the skull suspended In position by muscles that connect It to (the perlcranlum). This is the plane of movement the mandible. to the styloid process of the temporal of the scalp, that ls, when the scalp moves, the first bone, to the thyroid cartilage, to the sternum, and to three layers (SCA) sllde along this layer relative to the the scapula. The major muscles that attach to the hyoid underlying perlosteum. The areolar tissue contains a bone are shown in Figure 12.13. few small arteries. but It also contains some impor- tant emissary veins. The eml11ary velll8 are valveless SCALP and connect the superficial veins of the scalp with the diploic veins of the skull bones and with the intracra- The scalp extends from the superciliary arches anteri- nial venous sinuses. orly to the external occipital protuberance and supe-- Perlcranlwn. The pertcranlum ls the perlosteum rlor nuchal lines posteriorly and to the temporal covering the outer surface of the skull bones. The lines laterally. lt consists of five layers (see Flg. 12.2). pertcranlum Is continuous with the perlosteum on Conveniently. the first letters of each layer together the ilmer surface of the skull bones (endoateum) at spell SCALP. making recall easier. The first three layers the sut\ll'eS between the Individual skull bones. are intimately bound together and move as a unit. SJcin. This Is thick and hair bearing and contains numerous sebaceous glands. Muscles Connective tissue beneath the skfn. This Is a dense The ocdpltofrontaUs (eplc:ranlua) ls the sole skeletal fibrofatty layer containing fibrous septa that unite the muscle in the scalp (see Fig. 12.14). It ls summarized skin to the underlying eplcranlal aponeurosls. This in Table 12.3. The muscle consists of paired frontal and layer contains nwnerous blood vessels. The arter- occipital bellies connected by the expansive epicranial ies are derived from both the external and internal aponeurosis. This muscle is responsible for movement of carotid arteries, and free anastomoses occur between the scalp. Note that when this muscle contracts, the first them. three layers of the scalp (SCA) move together as a unit. Aponeurosis ( epicranial). This is a thin, tendinous The loose areolar tissue of the fourth layer of the scalp sheet that unites the occipital and frontal bellies allows the aponeurosls to move on the pertcranlum. Greater hom (comu) Stylohyoid / I Thyrohyoid , ligament Sternohyoid I Lesser horn (oornu) Dlgaatrlc and stylohyold A Anterosuperlor aspeict B Right upec:t Flgun1 12.13 Hyoid bone from the anterosuperior (A) and right (B) aspects.  Scalp 629 Auricularis posterior Levator labll auperlorls alaeque nasl Levator labii superioris Zygomatlcus minor Zygomaticus major Platysma Figure 12.14 Muscles of the scalp and of facial expression. The frontal bellies of the occipltofrontalts can raise the The aurlculotemporal nerve, a branch of the man- eyebrows 1n expressions of surprise or horror. dibular division of the trigemlnal nerve, ascends over the side of the head from in front of the auricle. Its Sensory Nerve Supply terminal branches supply the skin over the temporal region. The main trunks of the sensory nerves Ile In the dense connective tissue layer (the "C" layer) of the scalp. The Cervical spinal nerve branches: nerves are arranged ln two main groups: (1) branches The lesaer ocdpltal nerve (C2), a branch of the cer- of the trtgemlnal nerve located anterior to the ear and vical plexus, ascends along the posterior edge of the (2) branches of cervical spinal nerves located posterior stemocleidomastoid muscle and supplies the scalp to the ear (Fig. 12.15). Moving laterally from the anterior over the lateral part of the occipital region and the midllne. the following nerves are present. skin over the medial surface of the auricle. TrlgemlDal brancha: The greater occipital nerve, a branch of the pos- The mpratrochlear nerve, a branch of the ophthal- terior ramus of the second cervical nerve, ascends mic division of the trtgemlnal nerve, winds around over the back of the scalp and suppltes the skin as far the superior orbital margin and supplies the scalp. forward as the vertex of the skull. It passes backward close to the median plane and reaches nearly as far as the vertex of the skull. The tupraOl'bltal nerve, a branch of the ophthalmic Arterial Supply division of the trigeminal nerve, winds around the The scalp has a rich blood supply to nourish the hair superior orbital margin and ascends over the forehead. follicles, and, for this reason, the smallest cut bleeds It supplies the scalp as far backward as the vertex. profusely. As with the cutaneous nerves, the arteries The zygomadcotemporal nerve, a branch of the max- run through the dense connective tissue layer (the "C" illary division of the trtgeminal nerve, supplies the layer) of the scalp, typically follow the nerves, and form scalp over the temple. an extensive, freely anastomosing network. Moving 630 CHAPTER 12 Head and Neck Table 12.3 Scalp and Face Muscles ScalpMUlde Occipitofrontalis Epieranial Facial nel'\te Moves scalp on skull Occipital belly aponeurosis and raises eyebrows Frontal belly OrbiC\daris oc:uli Medial palpebral ligament Lateral palpebral Facial nerv-;IOoses eyelids and Palpebral part Medial palpebral ligament rap he -- I di~tes lacrimal sac Orbital part and adjoining bone Loops return to Throws skin around origin I orbit into folds to --~teet eyeball Corrugator supercilii Superciliary arch - - r s kin of eyebrow Facial nerve I Vertical wrinkles of I forehead, as in frowning Compressor nasi I Frontal process of maxm;-IAponeurosis of th;-i Facial nente Compresses mobile I -I i;;idge of the n~ I nasal cartilages Dilator naris - Maxilla -: Ala of the nose Facial nerve Widens nasal apertu~ Procerus Nasal bone Skin between Facial nente Wrinkles in the skin of eyebrows the nose OrbiC\daris oris I Maxilla. mandible, and skin Encircles oral orifice Facial nerve ~ompresses lips together --~- Up Diiator Mmc:lu Levator labii superioris alaeque nasi Levator labii superioris I Zygomaticus minor Arise from bones and Facial nerve Separate lips Zygomaticus major fascia around oral aperture Levator anguli oris and insert into substance Risorius of lips Depressor anguli oris Depressor labii inferioris Mental is Buecinator uter surface of lveolar margins of Facial nerve 1 Compresses cheeks and lips against teeth axilla and mandible d pterygomandibular ament -----;. Platysma See Table 12.5 I laterally from the anterior mldllne, the following arter- branches, which supply the skin over the frontal and ies are present (see Fig. 12.15): temporal regions. The posterior auricular artery, a branch of the exter- The supralrOChleer and the supraorbltal arteries, nal carotid artery, ascends behind the auricle to sup- branches of the ophthahnic artery (a branch of the inter- ply the scalp above and behind the auricle. nal carotid artery), ascend over the forehead in com- pany with the supratrochlear and supraorbltal nerves. The ocdpltal artery, a branch of the external carotid artery, ascends from the apex: of the posterior tri- The superfldal temporal artery, the smaller termi- angle in company with the greater occipital nerve nal branch of the external carotid artery, ascends and pierces the trapezius muscle to reach the scalp. in front of the auricle in company with the aurtculo- It supplies the skin over the back of the scalp and temporal nerve. lt divides into anterior and posterior reaches as high as the vertex of the skull.  Scalp 631 Zygomaticotemporal ner1e Figure 12.15 Superior view of the sensory nerve supply and arterial supply to the scalp. Venous Drainage part of the posterior triangle; the plexus in tum drains into the vertebral veins or the internal jugular vein. The supratrochlear and supraorbltal velm unite at The veins of the scalp freely anastomose with one the medial margin of the orbit to form the faclal vela another and are connected to the dlploic veins of the (Fig. 12.16). skull bones and the lntracranlal venous sinuses by The superftdal temporal veln unites with the mull- valveless emissary veins (see Ftg. 12.2). lary vein in the substance of the parotid gland to form the retromandlbuJar vein. The poeterlor auricular vein unites with the poete- Lymph Drainage rlor dlvlalon of the retromandlbular vein, just below Lymph vessels in the anterior part of the scalp and the parotid gland, to form the external Jugu1ar vein. forehead drain into the submandlbuJar lymph noclea The ocdpltal vein drains into the subocdpltal (Fig. 12.17). Drainage from the lateral part of the scalp venous plexus, which Iles beneath the floor of the upper Maxillary vein Superficial cervical nodes Submental nodes SIDnandilJular nodes Anterior cervical nodes Laryngeal nodes Figure 12.16 Main veins of the head and neck. FiguN 12.17 Lymph drainage of the head and neck. 632 CHAPTER 12 Head and Neck Clinical Notes Clinical Significance of the Scalp Structure Often, a wound caused by a blunt object such as a baseball bat closely resembles an lnc:lsed wound. This Is It ls important to realize that the skin, the subcutaneous because the scalp is split against the unyielding skull and tissue, and the epicranial aponeurosis (scalp layers SCA) the pull of the occlpttofrontalls muscles causes a gaping are closely united to one another and are separated from wound. This anatomic fact may be of considerable forensic the perlosteum by loose areolar tissue. The skin of the Importance. scalp possesses numerous sebaceous glands, the ducts of which are prone to infection and damage by repeated hair treatment (e.g., combing and brushing). For this reason, Life-Threatening Scalp Hemorrhage aebaceoua cym of the scalp are common. Note that all the superficial arteries supplying the scalp ascend from the face and the neck. Thus, in an emergency Scalp Lacerations situation, encircle the head just above the ears and eyebrows wlth a tie, shoelaces, or even a piece of string The scalp has a profuse blood supply to nourish the hair and tie it tlghl Then, Insert a pen, pencil, or stick into the folllcles. Even a small laceration of the scalp can cause loop and rotate it so that the tourniquet exerts pressure on severe blood loss. It is often difficult to stop the bleeding the arteries. of a scalp wound because the arterial walls are attached to fibrous septa in the subcutaneous tissue (C layer) and Scalp Infections are unable to contract or retract to allow blood clotting to take place. Local pressure appJled to the scalp ls the only Jnfectfons of the scalp tend to remain localized and are satisfactory method of stopping the bleeding (see below). usually painful because of the abundant fibrous tissue in It is common for large areas of the scalp to be cut off the subcutaneous layer. the head as a person is projected forward through the Occasionally, an infection of the scalp spreads by the windshield in automobile accidents. Because of the profuse emissary veins, which are valveless, to the skull bones, blood supply, it Is often possible to replace large areas of causing osteomyellds. Infected blood In the dlpJolc veins scalp that are only hanging to the skull by a narrow pedlcle. may travel by the emissary veins farther into the venous Appropriate vascular suturing reduces the chance of sinuses and produce venous sinus thromboala. necrosis. Blood or pus may collect in the potential space deep The tension of the epicranial aponeurosis, produced by to the epicranial aponeurosis (the L layer of the scalp). It the tone of the occlpttofrontalls muscles, ls important in tends to spread over the skull, being limited In front by the all deep wounds of the scalp. If the aponeurosls has been orbital margin, behind by the nuchal lines, and laterally by divided, the wound will gape open. For satisfactory healing the temporal lines. On the other hand, subperlosteal blood to take place, the opening in the aponeurosls must be or pus is limited to one bone because of the attachment of closed with sutures. the periosteum to the sutural ligaments. above the ear Is Into the 1Uperftclal parolid (preau- rlcular) nodes. Lymph vessels in the part of the scalp above and behind the ear drain into the mastoid nodee. Vessels in the back of the scalp drain into the oedpltal......,._:::...AQ;lii;;ijj~ nodes. Lesser wing ~I·-..._ -If 81)hGn01d I \ I I Grealer wfng of-....... sphanold FACE Squamous t~I The face Is the area from the superclllary arches supe-- Lactimal rlorly to the lower margin of the mandible inferiorly Zygomatlc and to the auricles laterally. It contains the orbits, nose, mouth, and ears and therefore houses the interfaces for vision, respiration, olfactlon, taste, food process- ing, vocalization, and hearing between the Internal and external environments. Further, the face ls critical for individual identity, and facial expression is a highly evolved means of nonvocal communication. Facial Skeleton A B The bones that form the front of the skull are shown in Figure 12.18 (also see the earlier discussion of the Ftgure 12.18 A. Bones of the front of the skull. anterior and lateral views of the skull). The superior B. Lymph drainage of the face.  Face 633 Supratrochlear nerw lnfratrochlear nerw Supraorbital Su ratrochlear vein ne upraorbhal vein Laaimal nerve Zygomatieotemporal Supraorbltal arte Zygomaticotemporal\ vein Zygomatk:otsmpora nerve artery l Superficial temporal Auriculotemporal ' / vein Superflclal temporal artery Lacrimal vein nerve. Temporal Lacrimal art& Zygomaticofacial Zygomaticofacial branch Zygomaticofacial arte ), vein nerve ?JiZygomatic lnfraorbilal artery·~.+---' - lnfraorbital vein lnfraorbital nerve A~~~iil branch Tl'answrse facial artery Transverse faclal Extemal nasal nerve vein Buccal External nasal artery branch Faclal artery Facial vein Mandlbular Mental arterv-- - -~-1Mental vein \ branch Cervical branch A B C D Figure 12.19 A. Sensory nerve supply to the skin of the face. B. Branches of the facial nerve to muscles of facial expres- sion. C. Arterial supply of the face. D. Venous drainage of the face. orbital margins and the area above them are formed by gland (Figs. 12.19A and 12.20), which is supplied by the the frontal heme, which contains the frontal air sinuses. gre4t auricular nerve (C2 and 3). The overlap of the The lateral orbital margin is formed by the zygomatlc three divisions of the trigeminal nerve is slight com- bone, and the inferior orbital margin is formed by the pared with the considerable overlap of dennatomes.zygomatt