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Many are minor segmentation anomalies and may be incidental radiological or osteological findings medicine to stop runny nose buy exelon overnight delivery. More severe anomalies may lead to craniocervical instability (Piper and Traynelis 1998). Innervation the lumbosacral junction is innervated by branches derived from the fourth and fifth lumbar spinal nerves. The sympathetic trunks cross it anterolaterally, while the obturator nerves and lumbosacral trunks pass close laterally. The relations of the lumbosacral facet joints are similar to those of the lumbar facet joints (see above). Its surfaces carry 738 Muscles hyaline cartilage that varies from thin veils to small islands. Semispinalis capitis Sternocleidomastoid Splenius capitis Rhomboid minor Rhomboid major Trapezius Deltoid Levator scapulae Supraspinatus Infraspinatus Ligaments the anterior sacrococcygeal ligament consists of irregular fibres that descend on the pelvic surfaces of both sacrum and coccyx, and is attached in the same way as the anterior longitudinal ligament. The deep posterior sacrococcygeal ligament passes from the back of the fifth sacral vertebral body to the dorsum of the coccyx and corresponds to the posterior longitudinal ligament. On each side, the lateral sacrococcygeal ligaments connect the coccygeal transverse processes to the inferolateral sacral angles, completing foramina for the fifth sacral spinal nerves. Similarly, the intercornual ligaments connect the sacral and coccygeal cornua, and a fasciculus connects the sacral cornua to the coccygeal transverse processes. Vascularsupply the arterial supply of the sacrococcygeal junction is derived from the inferior lateral sacral and median sacral arteries. InnervationThe innervation of the sacrococcygeal junction is derived from the lower two sacral and the coccygeal nerves. Segments are also connected by extensions of the anterior and posterior sacrococcygeal ligaments. In adult males all segments unite comparatively early, but in females union is later. The apex of the terminal segment is connected to overlying skin by white fibrous tissue. The true back muscles are characterized by their position and by their innervation by branches of the posterior (dorsal) rami of the spinal nerves. The true back muscles below the neck lie deep to the posterior layer of the thoracolumbar fascia. In the lumbar region, where the layers of the thoracolumbar fascia are well defined, they occupy the compartment between its posterior and middle layers. The most superficial of these run between the upper limb and the axial skeleton, and consist of trapezius, latissimus dorsi, levator scapulae and the rhomboid muscles. Beneath this layer lie the serratus posterior group, superior and inferior, which are variably developed but usually thin muscles whose function may be respiratory or possibly proprioceptive. Trapezius, levator scapulae, rhomboid major, rhomboid minor and latissimus dorsi are described on pages 816, 818 and 821 respectively, serratus posterior superior and inferior are described on pages 941, 942. The more superficial layers contain the splenius muscles in the neck and upper thorax, and the erector spinae group in the trunk as a whole. The deeper layers include the spinotransverse group, which is itself layered into semispinalis, multifidus and the rotatores, and the suboccipital muscles. The lumbar intertransversarii mediales, thoracic intertransversarii and medial parts of cervical posterior intertransversarii are innervated by dorsal rami, but the others are supplied by ventral rami (Commentary 5. On the left only the skin, superficial and deep fasciae (other than gluteofemoral) have been removed; on the right, sternocleidomastoid, trapezius, latissimus dorsi, deltoid and external oblique have been dissected away. It is reason- the ligamentum nuchae is not a ligament of the neck, for it does not connect adjacent bones and lacks the internal structure typical of a ligament. It is a unique arrangement of tendons and fascia between the posterior muscles of the neck. It is attached to the external occipital protruberance superiorly, and the tip of the C7 spinous process inferiorly. In its superior half it consists of the aggregated tendons of the most medial fibres of the cervical portion of trapezius. Because of their longitudinal arrangement, these tendons have been described as forming the funicular portion of the ligamentum nuchae (Mercer and Bogduk 2003). In its inferior half, the funicular portion is joined by the obliquely orientated tendons of splenius capitis and rhomboid minor. Across the midline the tendons of splenius capitis are continuous with those of rhomboid minor on the other side, and they interweave with the tendons of the reciprocal sets of muscles to produce the raphenous structure of the ligamentum nuchae. From the ventral surface of the dorsal raphe, a median fascial septum extends deeply towards the vertebral column and separates semispinalis capitis from its opposite partner. A lateral expansion of the septum extends laterally ventral to semispinalis capitis, separating it from multifidus and semispinalis cervicis. The median continuation of the septum reaches the tips of the cervical spinous processes, and extends into the cervical interspinous spaces as far as the ligamentum flavum. Spinalis thoracis tubercle of the atlas, and it blends with the posterior atlanto-occipital and posterior atlanto-axial membranes. Passing through these membranes, it is attached to the posterior surface of the dura mater (Dean and Mitchell 2002). Only the dorsal raphe affords attachment to muscles; no muscles arise from the median septum. Longissimus thoracis 5 Splenius capitis Attachments Splenius capitis arises from the mastoid process and the rough surface on the occipital bone just below the lateral third of the superior nuchal line. The lower fibres insert into the tips of the spinous processes of the seventh cervical and upper three or four thoracic vertebrae and the intervening supraspinous ligaments. Between sternocleidomastoid and trapezius it forms part of the floor of the posterior triangle of the neck, above and behind levator scapulae. Innervation Splenius capitis is innervated by lateral branches of the second and third cervical dorsal rami. Actions Acting unilaterally, and synergistically with the contralateral sternocleidomastoid, splenius capitis rotates the head to the same side. It arises from the transverse process of the atlas, the tip of the transverse process of the axis and the posterior tubercle of the third cervical vertebra. Its fibres pass downwards and medially, wrapping around the other posterior intrinsic neck muscles, to insert into the third to sixth thoracic spinous processes. It consists of fascicles that assume systematic attachments to homologous parts of the skull, the cervical, thoracic and lumbar vertebrae, the sacrum and the ilium. Individual muscles are defined by the attachments of their fascicles and the regions that they span. SpinalisSpinalis thoracis is the most medial portion of erector spinae in the thoracic region. It consists of fascicles that arise from the spinous processes of the upper thoracic vertebra and insert into the spinous processes of the eleventh and twelfth thoracic and first two lumbar vertebrae. The fascicles are arranged in an overlapping series of increasingly longer, flat arcs. The shortest fascicles have the lowest origin and highest insertion, and the longest fascicles have the highest origin and lowest insertion. Laterally, the muscle blends intimately with longissimus thoracis and is considered by some to be a component of that muscle. When present, spinalis cervicis consists of paramedian fibres that arise variously from the spinous processes of the axis and the third and fourth cervical vertebrae, and insert into the lower part of the ligamentum RelationsSplenius cervicis lies deep to serratus posterior superior, the rhomboids and trapezius. It covers the upper parts of the erector spinae and the lower semispinalis muscles. Innervation Splenius cervicis is innervated by lateral branches of the lower cervical dorsal rami. ActionsActing unilaterally, splenius cervicis rotates the upper cervical vertebra, in the same way that the splenius capitis rotates the head. Iliocostalis cervicis consists of slender fascicles that arise by long tendons from the posterior tubercles of the fourth, fifth and sixth cervical vertebrae. They descend over the posterior thorax to insert into the third to sixth ribs at their angles. The fibres arise from the back of the transverse process of the seventh cervical vertebra and the superior borders of the angles of the upper six ribs; they lie lateral to iliocostalis cervicis, and insert into the upper borders of the angles of the lower six ribs. The lumbar part is formed by fleshy fascicles that arise from the tips of the first four lumbar transverse processes and the posterior surface of the middle layer of thoracolumbar fascia lateral to these tips. These fascicles descend to the ilium in a laminated fashion, such that those from higher levels cover those from lower levels.
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Clinical observations suggest that in humans the gland also receives secretomotor fibres through the chorda tympani medications ibs discount 4.5 mg exelon with mastercard. Infection may (potentially) spread further, usually to the parapharyngeal, and occasionally to the retropharyngeal, spaces or the tissue planes of the face above, when it may even reach the orbit via the inferior orbital fissure. Life-threatening cavernous sinus thrombosis is a remote possibility once infection has spread to the orbit, with further spread directly through the superior orbital fissure into the cranial cavity. Placed between the infratemporal fossa laterally and the nasopharynx medially, it functions as a neurovascular conduit. The body of the sphenoid forms the roof, the posterior boundary is the root of the pterygoid process and adjoining anterior surface of the greater wing of the sphenoid, and the anterior boundary is the superomedial part of the infratemporal surface (posterior wall) of the maxilla. The perpendicular plate of the palatine bone, with its orbital and sphenoidal processes, forms the medial boundary, and the pterygomaxillary fissure is the lateral boundary. There are two openings in the posterior wall of the pterygopalatine fossa: the foramen rotundum, which transmits the maxillary nerve, and the pterygoid canal (Vidian canal), which transmits the nerve of the pterygoid canal (Vidian nerve). The fossa communicates with the nasal cavity via the sphenopalatine foramen; with the orbit via the medial end of the inferior orbital fissure; and with the infratemporal fossa via the pterygomaxillary fissure, which lies between the back of the maxilla and the pterygoid process of the sphenoid and transmits the maxillary artery. It also communicates with the middle fossa via foramen rotundum and the pterygoid canal, and with the oral cavity via the greater palatine canal, which opens in the posterolateral aspect of the hard palate. Its proximity to these adjacent areas permits the ready spread of both tumours and infection. The main contents of the pterygopalatine fossa are the third part of the maxillary artery, the maxillary nerve and many of its branches, and the pterygopalatine ganglion. These branches may form an additional pathway by which gustatory fibres from the anterior two-thirds of the tongue may reach the facial ganglion without traversing the middle ear, and they do not synapse in the otic ganglion. Motor branches to tensor veli palatini and tensor tympani, derived from the nerve to medial pterygoid, also pass through the ganglion without synapsing. The artery has a variable and tortuous course in its short passage through the pterygopalatine fossa, where it gives off numerous branches, including the posterior superior alveolar and infraorbital arteries and the artery of the pterygoid canal (Vidian artery), and terminates in the sphenopalatine and greater palatine arteries. Chorda tympani the chorda tympani nerve enters the infratemporal fossa region by passing through the medial end of the petrotympanic fissure behind the capsule of the temporomandibular joint. The chorda tympani joins the posterior aspect of the lingual nerve at an acute angle. It carries taste fibres for the anterior two-thirds of the tongue and efferent preganglionic parasympathetic (secretomotor) fibres destined for the submandibular ganglion in the floor of the mouth. In contrast, a pericoronitis that affects a mandibular third molar tooth that communicates with the oral cavity, or, less commonly, either a dental abscess associated with this tooth, or a postoperative infection, may spread along tissue planes. Spread may be buccal; submandibular; submental; parapharyngeal; sublingual; less commonly, submasseteric; and, more rarely, infratemporal. The main symptom caused by infection of the pterygomandibular region is trismus (painful reflex muscle spasm), which usually affects medial pterygoid. There are few anatomical barriers to the posterior superior alveolar artery arises from the maxillary artery within the pterygopalatine fossa and runs through the pterygomaxillary fissure on to the maxillary tuberosity. It gives off branches that penetrate the bone here to supply the maxillary molar and premolar teeth and the maxillary air sinus, and other branches that supply the buccal mucosa. Occasionally, the posterior superior alveolar artery arises from the infraorbital artery. Infraorbital artery 552 the infraorbital artery enters the orbit through the inferior orbital fissure. It runs on the floor of the orbit in the infraorbital groove and infraorbital canal, and emerges on to the face at the infraorbital foramen to supply the lower eyelid, part of the cheek, the side of the external nose, and the upper lip. While within the infraorbital canal, it gives off the anterior superior alveolar artery, which runs downwards to supply the anterior teeth and the anterior part of the maxillary sinus. When present, it branches from the infraorbital artery within the infraorbital canal and runs inferiorly along the lateral wall of the maxillary sinus towards the region of the canine and lateral incisor teeth, anastomosing with the anterior and posterior superior alveolar arteries. Variable anastomoses exist between all three of the divisions of the trigeminal nerve with branches of the facial nerve. The connection between the lingual nerve and the chorda tympani branch of the facial is the most familiar interconnection with the mandibular nerve. Interconnections between the mental nerve and the buccal and marginal mandibular branch of the facial have been demonstrated. A branch from the auriculotemporal may join the inferior alveolar nerve within the infratemporal fossa with evident implications for referred pain. The functional significance of some of the neural connections has yet to be determined (Shoja et al 2014). The infection is life-threatening due to restricted mouth opening and a compromised airway. B, In this case, the airway was secured with awake fibreoptic intubation followed by tracheostomy. Aggressive through-and-through drainage was initiated (note the grey discolouration of the tissues). Aggressive early treatment with surgical drainage and intravenous antibiotics has reduced the mortality to approximately 5%. Anastomoses between lower cranial and upper cervical nerves: a comprehensive review with potential significance during skull base and neck operations, Part 1: Trigeminal, facial and vestibulocochlear nerves. The Maxillary nerve vascular structures are anterior to the neural at foramen rotundum structures. It passes through the pterygoid canal and anastomoses with the pharyngeal, ethmoidal and sphenopalatine arteries in the pterygopalatine fossa and with the ascending pharyngeal, accessory meningeal, ascending palatine and descending palatine arteries in the oropharynx and around the pharyngotympanic tube. Through these complex anastomoses, the artery of the pterygoid canal contributes to the supply of part of the pharyngotympanic tube, the tympanic cavity and the upper part of the pharynx. It may also anastomose with the artery of the foramen rotundum and so communicate with branches of the cavernous portion of the internal carotid artery. They can be subdivided into those that come directly from the nerve, and those that are associated with the pterygopalatine parasympathetic ganglion. Named branches from the main trunk are meningeal, ganglionic, zygomatic, posterior, middle and anterior superior alveolar and infraorbital nerves. Named branches from the pterygopalatine ganglion are orbital, nasopalatine, posterior superior nasal, greater (anterior) palatine, lesser (posterior) palatine and pharyngeal. Meningeal nerve the meningeal branch of the maxillary nerve arises within the middle cranial fossa and runs with the middle meningeal vessels. Ganglionic branches Zygomatic nerve Pharyngeal artery the pharyngeal branch of the maxillary artery passes through the palatovaginal canal, accompanying the nerve of the same name, and is distributed to the mucosa of the nasal roof, nasopharynx, sphenoidal air sinus and pharyngotympanic tube. There are usually two ganglionic branches that connect the maxillary nerve to the pterygopalatine ganglion. The zygomatic branch of the maxillary nerve leaves the pterygopalatine fossa through the inferior orbital fissure together with the maxillary nerve. The posterior superior alveolar nerve leaves the maxillary nerve in the pterygopalatine fossa. Greater (descending) palatine artery the greater palatine artery leaves the pterygopalatine fossa through the greater (anterior) palatine canal, within which it gives off two or three lesser palatine arteries. The greater palatine artery supplies the inferior meatus of the nose, then passes on to the roof of the hard palate at the greater (anterior) palatine foramen and runs forwards to supply the hard palate and the palatal gingivae of the maxillary teeth. It gives off a branch that runs up into the incisive canal to anastomose with the nasopalatine artery, and so contribute to the arterial supply of the nasal septum. The lesser palatine arteries emerge on to the palate through the lesser (posterior) palatine foramen, or foramina, and supply the soft palate. Infraorbital nerve the infraorbital nerve can be regarded as the terminal branch of the maxillary nerve. It leaves the pterygopalatine fossa to enter the orbit at the inferior orbital fissure, and its subsequent course and distribution are described on page 502. Orbital branches Sphenopalatine artery the sphenopalatine artery and the greater palatine artery are the terminal branches of the maxillary artery. The sphenopalatine artery is the principal artery supplying the mucosa of the nose. It enters the nasal cavity through the sphenopalatine foramen posterior to the superior meatus. From here, its posterior lateral nasal branches ramify over the conchae and meatuses, anastomosing with the ethmoidal arteries and nasal branches of the greater palatine artery to supply the frontal, maxillary, ethmoidal and sphenoidal air sinuses. Fine orbital branches enter the orbit through the inferior orbital fissure and supply orbital periosteum.
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Reduction of sacral constituents is less common but lumbarization of the first sacral vertebra does occur; it remains partially or completely separate treatment of uti buy 4.5mg exelon fast delivery. The bodies of the first two sacral vertebrae may remain unfused when the lateral masses are fused. The dorsal wall of the sacral canal may be variably deficient, due to imperfect development of laminae and spines. Orientation of the superior sacral articular facets displays wide variation, as does the sagittal curvature of the sacrum. Asymmetry (facet tropism) of the superior facets alters the relation between the planes of the two lumbosacral facet joints. Apex the apex is the inferior aspect of the fifth sacral vertebral body, and bears an oval facet for articulation with the coccyx. The inclination of the sacrum means that it is directed cranially in the standing position. Each lateral wall presents four intervertebral foramina, through which the canal is continuous with pelvic and dorsal sacral foramina. The canal contains the cauda equina and the filum terminale, and the spinal meninges. Opposite the middle of the sacrum, the subarachnoid and subdural spaces close; the lower sacral spinal roots and filum terminale pierce the arachnoid and dura mater at that level. The filum terminale with its meningeal coverings emerges below the sacral hiatus and passes downwards across the dorsal surface of the fifth sacral vertebra and sacrococcygeal joint to reach the coccyx. The fifth sacral spinal nerves also emerge through the hiatus medial to the sacral cornua, and groove the lateral aspects of the fifth sacral vertebra. It usually consists of four fused rudimentary vertebrae, although the number varies from three to five, and the first is sometimes separate. The bone is directed downwards and ventrally from the sacral apex; its pelvic surface is tilted upwards and forwards, its dorsum downwards and backwards. The base or upper surface of the first coccygeal vertebral body has an oval, articular facet for the sacral apex. Posterolateral to this, two coccygeal cornua project upwards to articulate with sacral cornua; they are homologues of the pedicles and superior articular processes of other vertebrae. A rudimentary transverse process projects superolaterally from each side of the first coccygeal body and may articulate or fuse with the inferolateral sacral angle, completing the fifth sacral foramina. The second to fourth coccygeal vertebrae diminish in size and are usually mere fused nodules. They represent rudimentary vertebral bodies, though the second may show traces of transverse processes and pedicles. The gap between the fifth sacral body and the articulating cornua represents, on each side, an intervertebral foramen that transmits the fifth sacral spinal nerve. The dorsal ramus descends behind the rudimentary transverse process, and the ventral ramus passes anterolaterally between the transverse process and sacrum. Muscle attachments the pelvic surface gives attachment to piriformis in its second to fourth segments, to iliacus superolaterally, and to coccygeus inferolaterally. On the lateral border below the auricular surface, gluteus maximus is attached dorsal and coccygeus is attached ventral to the sacrotuberous and sacrospinous ligaments. Primary centres for the centrum and each half vertebral arch appear between the tenth and twentieth weeks. Primary centres for the costal elements of the upper three or more segments appear superolateral to the pelvic sacral foramina, between the sixth and eighth prenatal months. The lateral sacrococcygeal ligament connects the transverse process to the inferolateral sacral angle. Key: 1, promontory; 2, auricular (articular) surface; 3, attachments of interosseous sacroiliac ligaments; 4, spinous process; 5, sacral cornu (left). The median area gives attachment to the deep and superficial posterior sacrococcygeal ligaments, the superficial descending from the margins of the sacral hiatus and sometimes closing the sacral canal. The filum terminale, which is situated between the two ligaments, blends with them on the dorsum of the first coccygeal vertebra. A centre in the first segment appears about birth and its cornua may soon ossify from separate centres. Segments slowly unite: union between the first and second is frequently delayed until 30 years. C, At the twenty-fifth year: epiphysial plates for each lateral surface are marked by asterisks. It is broader caudally, and thicker and narrower in thoracic than in cervical and lumbar regions, and is also relatively thicker and narrower opposite vertebral bodies than at the levels of intervertebral symphyses. It extends from the basilar part of the occipital bone to the anterior tubercle of C1 and the front of the body of C2, and then continues caudally to the front of the upper sacrum. B, A median sagittal section through the upper lumbar vertebral column showing discs and ligaments. B, With permission from Waschke J, Paulsen F (eds), Sobotta Atlas of Human Anatomy, 15th ed, Elsevier, Urban & Fischer. At these various levels, ligamentous fibres blend with the subjacent periosteum, perichondrium and periphery of the anulus fibrosus. The morphology and histology of the ligamentum flavum have been studied in the thoracolumbar region (Viejo-Fuertes et al 1998). On a macroscopic level, it has two layers, superficial and deep, whose fibres run in opposite directions. The superficial layer is innervated by medial branches from the dorsal roots of the spinal nerves. The most superficial fibres are the longest and extend over three or four vertebrae, the intermediate extend between two or three, and the deepest from one body to the next. The thoracic interspinous ligaments are narrow and elongated, whereas those at lumbar levels are thick and quadrilateral, and occur as closely applied pairs, the left and right ligaments being separated by a narrow or potential cleft. In the lumbar ligaments, collagen fibres run obliquely inferiorly and ventrally, and only the deepest fibres are truly ligamentous. The more dorsal fibres are derived from tendons of longissimus thoracis that dip into the interspinous space to gain attachment to the superior edge of the spinous process rather than to its tip. Distinctive interspinous ligaments are not evident at cervical levels, where they are represented by the median septum of the ligamentum nuchae as it passes between the cervical spinous processes. Its smooth, glistening fibres, attached to intervertebral discs, hyaline cartilage end-plates and adjacent margins of vertebral bodies, are separated between attachments by basivertebral veins and the venous channels that drain them into anterior internal vertebral plexuses. At cervical and upper thoracic levels the ligament is broad and of uniform width, but in lower thoracic and lumbar regions it is denticulated, narrow over vertebral bodies and broad over discs. Its superficial fibres bridge three or four vertebrae, while deeper fibres extend between adjacent vertebrae as perivertebral ligaments, which are close to and, in adults, fused with the anulus fibrosus of the intervertebral disc. The layers of the posterior longitudinal ligament and the relationship of the ligament to associated membranes in the epidural space are fully discussed by Loughenbury et al (2006). The most superficial fibres extend over three or four vertebrae, the deeper span two or three, and the deepest connect adjacent spines and are continuous with the interspinous ligament. Most of the ligament is formed by the tendons of muscles with posterior midline attachments, i. Their attachments extend from facet joint capsules to the point where laminae fuse to form spines. Here their posterior margins meet and are partially united; the intervals between them admit veins that connect the internal and posterior external vertebral venous plexuses. Their predominant tissue is yellow elastic tissue, whose almost perpendicular fibres descend from the lower anterior surface of one lamina to the posterior surface and upper margin of the lamina below. The anterior surface of the ligaments is covered by a fine, continuous, smooth lining membrane (Newell 1999). The ligaments are thin, broad and long in the cervical region, thicker in the thoracic and thickest at lumbar levels. At cervical levels, they consist of a few, irregular fibres that are largely replaced by intertransverse muscles; in the thoracic region, they are cords intimately blended with adjacent muscles; and in the lumbar 732 Joints region, they are thin and membranous. For the detailed anatomy of the lumbar intertransverse ligaments, see Bogduk (2005). The transverse ligament is stronger than the dens, which therefore usually fractures before the ligament ruptures.
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These sites are represented at thoracic levels by the tip of a transverse process and the immediately adjacent posterior surface of the rib; at cervical levels by the transverse process and posterior tubercle; and at lumbar levels by the accessory process (the transverse element) and medial half of the transverse process (the costal element) medications starting with p discount 1.5mg exelon amex. Longissimus capitis is a narrow flat band of muscle that arises from the posterior edge of the mastoid process, under cover of splenius capitis and sternocleidomastoid. It descends across the lateral surface of semispinalis capitis and inserts by a series of tendons into the transverse processes of the lower three or four cervical and upper four or so thoracic vertebrae. Longissimus cervicis is a long thin muscle that arises by tendons from the posterior tubercles of the transverse processes of the second to sixth cervical vertebra. It descends into the thoracic region, between the tendons of longissimus capitis and longissimus thoracis, to insert by tendons into the transverse processes of the upper four or five thoracic vertebrae. It consists of many small fascicles that are aggregated in a particular manner to produce a very long, and in some places thick, muscle. The lumbar part is formed by fleshy bundles that arise from the accessory process and the medial half or so of the posterior surface of the transverse process of each of the five lumbar vertebrae. Those from the first four lumbar vertebrae converge on to a common flat tendon that covers the lateral surface of the muscle and separates it from the lumbar fibres of iliocostalis, for which reason it is called the lumbar intermuscular aponeurosis. The aponeurosis commences in the mid-lumbar region, with a broad irregular base, and inferiorly it tapers to a truncated point that inserts into the medial surface of the ilium just dorsal to the ala of the sacrum. The fascicle from the first lumbar vertebra attaches rostrally and dorsally to the aponeurosis. The fascicle from the fifth lumbar vertebra inserts separately, deep to the intermuscular aponeurosis, into the ventromedial aspect of the ilium and the upper fibres of the dorsal sacroiliac ligament. Medially, the lumbar fibres of longissimus are separated from the multifidus by a wide cleavage plane filled with fat and veins. The thoracic part consists of fascicles with small, fusiform muscle bellies that have short rostral tendons and long caudal tendons. The muscle bellies are arranged in a tiered fashion across the length of the posterior thoracic wall, with the highest lying medially and the lowest lying laterally. The upper four fascicles arise from the tips of the first four thoracic transverse processes. The succeeding fascicles have bifid tendons that arise from the transverse process and the adjacent rib at each of the lower eight thoracic segments. The long caudal tendons of the thoracic fascicles of longissimus are aggregated in parallel to form a wide aponeurosis, which allows them to assume a variety of caudal insertions. The tendons of the uppermost fascicles insert into the lumbar spinous processes and their supraspinous ligament. The fascicles from the seventh to ninth thoracic segments reach the median sacral crest, and those from the tenth and eleventh thoracic segments attach transversely across the posterior surface of the third segment of the sacrum. The fascicle from the twelfth thoracic segment reaches the sacrum and dorsal segment of the iliac crest just below where the intermuscular aponeurosis of the lumbar fibres of longissimus inserts into the ilium. The aponeurosis covers the multifidus and the lumbar fibres of longissimus; it extends from the midline as far laterally as the dorsal edge of the lumbar intermuscular aponeurosis, with which it fuses. Within the lumbar intermus- Erectorspinaeaponeurosis Together, the dorsal aponeuroses of the thoracic fibres of longissimus and the thoracic fibres of iliocostalis lumborum form a wide sheet of parallel tendons known as the erector spinae aponeurosis. It is attached to the lumbar spinous processes and supraspinous ligaments, the median sacral crest, the third sacral segment, the dorsal segment of the iliac crest and the medial end of the iliac crest, and covers multifidus and the lumbar fibres of both longissimus and iliocostalis. Significantly, the erector spinae aponeurosis is formed exclusively by the tendons of the thoracic fibres of longissimus thoracis and iliocostalis lumborum; it does not give rise to the lumbar fibres of these muscles, which are attached independently to the ilium. Some of the more superficial fibres of multifidus may insert into the deep surface of the erector aponeurosis over the sacrum, but otherwise the substantive insertion of multifidus is into the sacrum. A portion of the uppermost fibres of gluteus maximus arise from the dorsal surface of the inferolateral corner of the erector spinae aponeurosis. The lumbar intermuscular aponeurosis is a ventral extension of the erector spinae aponeurosis, separating the lumbar fibres of longissimus from those of iliocostalis. RelationsErector spinae is covered in the lumbar and thoracic regions by the thoracolumbar fascia, and by serratus posterior inferior below and the rhomboids and splenii above. In the lumbar region, it lies in the compartment between the posterior and middle layers of the thoracolumbar fascia. InnervationErector spinae is innervated by the lateral branches of the dorsal rami of the cervical, thoracic and lumbar spinal nerves. At lumbar levels, lateral branches innervate iliocostalis and intermediate branches innervate longissimus. Actions the thoracic and lumbar components of erector spinae are powerful extensors of the vertebral column. Acting concentrically and bilaterally they can extend the thoracic and lumbar spines whereas acting unilaterally they can laterally flex the trunk. From the upright posture, the trunk can flex forwards under the influence of gravity. When the trunk is fully flexed, many parts of erector spinae cease to contract and become electromyographically silent. In this position, flexion is limited by passive tension in the back muscles, and tension in the thoracolumbar fascia, the posterior spinal ligaments and the intervertebral discs. Similarly, lateral flexion under gravity is controlled by the contralateral erector spinae, with input from the abdominal oblique muscles. The function of the cervical and capital components of erector spinae has not been determined. These are small muscles with very little force capacity, and are poorly orientated to exercise extension or to control flexion of the head or cervical spine. Axial rotation of the head draws longissimus capitis around the perimeter of the cervical spine, orientating it perhaps so that it is able to restore the head to neutral from the rotated position. Rotatores are not obviously present at lumbar and cervical levels, where they may be represented by some of the deeper fascicles of multifidus. Spinotransverse group the spinotransverse muscle group consists of muscles where the fascicles span between a spinous process and the transverse elements of vertebrae at various levels below. The muscles are grouped according to the length of their fascicles and the region that they cover Table 43. Rotatores have the deepest and shortest fascicles, and span one and two segments, whereas the fascicles of multifidus span two, three, four or five segments, and those of semispinalis span about six segments. At each segmental level, multifidus is formed by several fascicles that arise from the caudal edge of the lateral surface of the spinous process and from the caudal end of its tip. They radiate caudally to insert into the transverse elements of vertebrae two, three, four and five levels below (Macintosh et al 1986). These sites are represented at cervical levels by the superior articular processes, at thoracic levels by the posterior surface of each transverse process near its base, and at lumbar levels by the mammillary processes. Fascicles that extend beyond the fifth lumbar vertebra insert into the dorsal surface of the sacrum. The first pair lies between the first and second thoracic vertebrae, and the last between the eleventh and twelfth thoracic vertebrae. Multifidus Multifidus 742 Muscles are covered at cervical levels by splenius, at thoracic levels by spinalis thoracis, and at lumbar levels by the erector spinae aponeurosis. In the neck, semispinalis capitis lies mainly deep to splenius and trapezius, but a small portion may be exposed to form the uppermost part of the floor of the posterior triangle of the neck. InnervationRotatores, multifidus, semispinalis thoracis and semispinalis cervicis are all innervated by the medial branches of the dorsal rami of the appropriate spinal nerves. Semispinalis capitis is innervated by descending branches of the greater occipital nerve (C2) and the third cervical nerve (C3). Semispinalis cervicis Semispinalis thoracis ActionsAll the spinotransverse muscles are extensors. They extend the vertebrae from which they arise, or the head in the case of semispinalis capitis. The predominantly longitudinal orientation of their fascicles precludes any substantive action as rotators. Although rotatores have been presumed to rotate the thoracic vertebrae, this action has not been validated. Intertransversarii second lumbar vertebrae insert into the dorsal segment of the iliac crest.
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Its final 5 cm medications that interact with grapefruit purchase cheap exelon on line, the filum terminale externum, fuses with the investing dura mater, and then descends to the dorsum of the first coccygeal vertebral segment. A few strands of nerve fibres, which probably represent the roots of rudimentary second and third coccygeal spinal nerves, adhere to its upper part. They cross the subarachnoid space and traverse the dura mater separately, uniting in or close to their intervertebral foramina to form the (mixed) spinal nerves. Since the spinal cord is shorter than the vertebral column, the more caudal spinal roots descend for varying distances around and beyond the cord to reach their corresponding foramina. In so doing, they form a divergent sheaf of spinal nerve roots, the cauda equina, which is gathered round the filum terminale in the spinal theca, mostly distal to the apex of the cord. Note the fusiform cervical and lumbar enlargements of the cord, and the changing obliquity of the spinal nerve roots as the cord is descended. The cauda equina is undisturbed on the right but has been spread out on the left to show its individual components. E, the lower end of the spinal cord, filum terminale and cauda equina exposed from behind. F, A spinal cord segment showing the mode of formation of a typical spinal nerve and the gross relationships of the grey and white matter. Dorsal spinal roots bear ovoid swellings, the spinal ganglia, one on each root proximal to its junction with a corresponding ventral root in an intervertebral foramen. Dorsal roots are usually said to contain only afferent axons (both somatic and visceral), which are the central processes of unipolar neurones in the spinal root ganglia, but they may also contain a small number (3%) of efferent fibres and autonomic vasodilator fibres. Each ganglionic neurone has a single short stem that divides into a medial (central) branch that enters the spinal cord via a dorsal root, and a lateral (peripheral) branch that passes peripherally to a sensory end organ. The central branch is an axon while the peripheral one is an elongated dendrite (but when traversing a peripheral nerve is, in general structural terms, indistinguishable from an axon). The region of spinal cord associated with the emergence of a pair of nerves is a spinal segment but there is no actual surface indication of segmentation. Distal to the foramen magnum, within the vertebral column, the dura is distinct from the tissues that line the vertebral canal, and separated from them by the epidural space (see below). The spinal dura mater forms a tube whose upper end is attached to the edge of the foramen magnum and to the posterior surfaces of the second and third cervical vertebral bodies, and also by fibrous bands to the posterior longitudinal ligament, especially towards the caudal end of the vertebral canal. It invests the thin spinal filum terminale, descends to the back of the coccyx, and blends with the periosteum. It is closed above by fusion of the spinal dura with the edge of the foramen magnum, and below by the posterior sacrococcygeal ligament that closes the sacral hiatus. It contains loosely packed connective tissue, fat, a venous plexus, small arterial branches, lymphatics and fine fibrous bands that connect the theca with the lining tissue of the vertebral canal. These bands, the meningovertebral ligaments, are best developed anteriorly and laterally. There is also a midline attachment from the posterior spinal dura to the ligamentum nuchae at atlanto-occipital and atlantoaxial levels (Dean and Mitchell 2002). The shape of the space within each spinal segment is not uniform, though the segmental pattern is metamerically repeated. In the lumbar region, the dura mater is apposed to the walls of the vertebral canal anteriorly and attached by connective tissue in a manner that permits displacement of the dural sac during movement and venous engorgement. Adipose tissue is present posteriorly in recesses between the ligamentum flavum and the dura. The connective tissue extends for a short distance through the intervertebral foramina along the sheaths of the spinal nerves. Like the main thecal sac, the root sheaths are partially tethered to the walls of the foramina by fine meningovertebral ligaments. Local anaesthetics injected near the spinal nerves, just outside the intervertebral foramina, may spread up or down the epidural space to affect the adjacent spinal nerves or may pass to the opposite side. The paravertebral spaces of Spinal cord and spinal nerves: gross anatomy A variety of pathological processes can occur within the epidural space, compressing the dura and resulting in pain and potential neurological disturbance. For a review of the morphology of the epidural space and a discussion of the nature of the lining layer of the vertebral canal, see Newell (1999). The first crosses behind the vertebral artery where it is attached to the dura mater, and is separated by the artery from the first cervical ventral root. The last of the dentate ligaments lies between the exiting twelfth thoracic and first lumbar spinal nerves and is a narrow, oblique band that descends laterally from the conus medullaris. Changes in the form and position of the dentate ligaments during spinal movements have been demonstrated by cine-radiography. Beyond the conus medullaris, the pia mater continues as a coating of the filum terminale. Subdural space the subdural space is a potential space in the normal spine because the arachnoid and dura are closely apposed (Haines et al 1993). It does not connect with the subarachnoid space but continues for a short distance along the cranial and spinal nerves. Injection of fluid into the subdural space may damage the cord either by direct toxic effects or by compression of the vasculature. At sites where vessels and nerves enter or leave the subarachnoid space, the arachnoid mater is reflected on to the surface of these structures and forms a thin coating of leptomeningeal cells over the surface of both vessels and nerves. Thus a subarachnoid angle is formed as nerves pass through the dura into the intervertebral foramina. At this point, the layers of leptomeninges (arachnoid and pia) fuse and become continuous with the perineurium. Such an arrangement seals the subarachnoid space so that particulate matter does not pass directly from the subarachnoid space into nerves. This layer is concentrated in the dorsal and ventral regions, and forms a highly perforated, almost lace-like structure that is focally compacted to form the dorsal, dorsolateral and ventral ligaments of the spinal cord. Dorsally, the intermediate layer is adherent to the deep aspect of the arachnoid mater and forms a discontinuous series of dorsal ligaments that attach the spinal cord to the arachnoid. The dorsolateral ligaments are more delicate and fenestrated, and they extend from the dorsal roots to the parietal arachnoid. As the intermediate layer spreads laterally over the dorsal surface of the dorsal roots, it becomes increasingly perforated and eventually disappears. A similar arrangement is seen over the ventral aspect of the spinal cord but the intermediate layer is less substantial. The intermediate layer is structurally similar to the trabeculae that cross the cranial subarachnoid space, i. The ligamentum denticulatum is a flat, fibrous sheet on either side of the spinal cord between the ventral and dorsal spinal roots. These prolongations, the spinal nerve sheaths or root sheaths, gradually lengthen as the spinal roots become increasingly oblique. Each individual dorsal and ventral root runs in the subarachnoid space with its own covering of pia mater. Each root pierces the dura separately, taking a sleeve of arachnoid with it, before joining within the dural prolongation just distal to the spinal ganglion. The dural sheaths of the spinal nerves fuse with the epineurium, within or slightly beyond the intervertebral foramina. At the cervical level, where the nerves are short and the vertebral movement is greatest, the dural sheaths are tethered to the periosteum of the adjacent transverse processes. In the lumbosacral region, there is less tethering of the dura to the periosteum, though there may be an attachment posteriorly to the facet joint capsule. The ventral, hypaxial, ramus is connected to a corresponding sympathetic ganglion by white and grey rami communicantes. It innervates the prevertebral muscles and curves around in the body wall to supply the lateral muscles of the trunk. Near the mid-axillary line, it gives off a lateral branch that pierces the muscles and divides into anterior and posterior cutaneous branches. The main nerve advances in the body wall, where it supplies the ventral muscles and terminates in branches to the skin. Spinal nerves are united ventral and dorsal spinal roots, attached in series to the sides of the spinal cord.
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Medial palpebral arteries Superior and inferior medial palpebral arteries arise from the ophthalmic artery below the trochlea treatment narcissistic personality disorder cheap exelon 3 mg on-line. They descend behind the nasolacrimal sac to enter the eyelids, where each divides into two branches that course laterally along the edges of the tarsal plates, forming the superior and inferior arches and supplying the eyelids. They anastomose with branches of the supraorbital, zygomatico orbital and lacrimal arteries. External (dorsal) nasal artery the external nasal artery is a termi nal branch of the anterior ethmoidal artery, which arises from the ophthalmic artery. It emerges at the junction of the nasal bone and the lateral nasal cartilage and supplies the skin covering the external nose. Frontal (anterior) branch the frontal branch passes upwards towards the frontal tuberosity and supplies the muscles, skin and peri cranium in this region. It anastomoses with its contralateral fellow and with the supraorbital and supratrochlear branches of the ophthalmic artery. Parietal (posterior) branch the parietal branch is larger than the frontal branch of the superficial temporal artery. It curves upwards and backwards, remains superficial to the temporal fascia, and anastomoses with its contralateral fellow and with the posterior auricular and occipi tal arteries. Accompanied by the greater occipital nerve, the occipi tal artery enters the back of the scalp by piercing the investing layer of deep cervical fascia that connects the cranial attachments of trapezius and sternocleidomastoid. Tortuous branches run between the skin and the occipital belly of occipitofrontalis, anastomosing with the opposite occipital, posterior auricular and superficial temporal arteries, as well as with the transverse cervical branch of the subclavian artery. These branches supply the occipital belly of occipitofrontalis and the skin and pericranium associated with the scalp as far forwards as the vertex. Mental artery the mental artery arises from the first part of the maxil lary artery as a terminal branch of the inferior alveolar artery. It emerges on to the face from the mandibular canal at the mental foramen, sup plies muscles and skin in the chin region, and anastomoses with the inferior labial and submental arteries. Posterior auricular artery the posterior auricular artery arises in the neck from the external carotid artery and ascends between the auricle and mastoid process. It supplies 499 cHapTeR Supraorbital artery the supraorbital artery leaves the orbit through the supraorbital notch or foramen. It divides into superficial and deep branches that supply the skin and muscle of the upper eyelid, forehead and scalp. It anastomoses with the supratrochlear artery, frontal branch of the superficial temporal and its contralateral fellow. Posterior auricular and occipital veins the posterior auricular vein arises in a parietooccipital network that also drains into tributaries of the occipital and superficial temporal veins. It descends behind the auricle to join the posterior division of the retromandibular vein in, or just below, the parotid gland, to form the external jugular vein. It receives a stylomastoid vein and tributaries from the cranial surface of the auricle, drains the region of the scalp behind the ear and drains into the external jugular vein. The occipital vein begins in a posterior network in the scalp, pierces the cranial attachment of trapezius, turns into the suboccipital triangle and joins the deep cervical and vertebral veins. Emissary veins connect the occipital vein to the intracranial venous sinuses via the mastoid and parietal foramina and through the posterior condylar canal and occipital protuberances. Supratrochlear vein the supratrochlear vein starts on the forehead from a venous network connected to the frontal tributaries of the superficial temporal vein. Veins from this network form a single trunk that descends to the bridge of the nose, near the midline and parallel with its contralateral fellow. They then diverge, each joining a supraorbital vein to form the facial vein near the medial canthus of the eye. Vessels from the rest of the forehead, temporal region, upper half of the lateral auricular aspect and anterior wall of the external acoustic meatus drain to the superficial parotid nodes, which lie just anterior to the tragus, either on or deep to the parotid fascia. These nodes also drain lateral vessels from the eyelids and skin of the zygomatic region, and their efferent vessels pass to the upper deep cervical nodes. A strip of scalp above the auricle, the upper half of the cranial aspect and margin of the auricle, and the posterior wall of the external acoustic meatus all drain to the upper deep cervical and posterior auricular nodes. The posterior auricular nodes are superficial to the mastoid attachment of sterno cleidomastoid and deep to auricularis posterior, and drain to the upper deep cervical nodes. The auricular lobule, floor of the external acoustic meatus and skin over the mandibular angle and lower parotid region all drain to the superficial cervical or upper deep cervical nodes. Super ficial cervical nodes lie along the external jugular vein superficial to sternocleidomastoid. It passes medially above the orbital opening, pierces orbicu laris oculi and unites with the supratrochlear vein near the medial canthus of the eye to form the facial vein. After receiving the supra trochlear and supraorbital veins, it travels obliquely downwards by the side of the nose, passes under zygomaticus major, risorius and platysma, descends to the anterior border and then passes over the surface of masseter. It crosses the body of the mandible and runs down in the neck to drain into the internal jugular vein. The facial vein ini tially lies behind the more tortuous facial artery but crosses the artery at the lower border of the mandible. The uppermost segment of the facial vein, above its junction with the superior labial vein, is also called the angular vein; any infection of the mouth or face can spread via the angular veins to the cavernous sinuses, resulting in thrombosis. Posterior auricular nodes Occipital nodes Tributaries Near its origin, the facial vein connects with the superior ophthalmic vein, both directly and via the supraorbital vein, and so is linked to the cavernous sinus. The facial vein receives tributaries from the side of the nose and, below this, an important deep facial vein from the pterygoid venous plexus. It also receives the inferior palpebral, superior and inferior labial, buccinator, parotid and masseteric veins, and other tributaries that join it below the mandible. Superficial temporal vein A widespread venous network across the scalp receives branches from the supratrochlear, supraorbital, posterior auricular and occipital veins. Anterior and posterior tributaries from this network unite above the zygomatic arch to form the superficial temporal vein on each side. The vein accompanies its artery, usually lying behind it; crosses the posterior root of the zygoma; and enters the parotid gland, where it joins the maxillary vein to form the retromandibular vein. Tributaries the tributaries are the parotid veins, rami draining the temporomandibular joint, anterior auricular, transverse facial and middle temporal veins. The middle temporal vein receives the orbital vein (formed by the lateral palpebral veins), pierces the temporal fascia and then passes back between the layers of the fascia to join the super ficial temporal vein just above the level of the zygomatic arch. Submental nodes Submandibular nodes To upper deep cervical nodes Buccal, mental and infraorbital veins 500 the buccal, mental and infraorbital veins drain the cheek and chin regions and pass into the pterygoid venous plexus. The occipital region of the scalp drains partly to the occipital nodes, and partly to a vessel that runs along the posterior border of sterno cleidomastoid to the lower deep cervical nodes. Occipital nodes are commonly superficial to the upper attachment of trapezius but occa sionally lie in the superior angle of the posterior triangle. There are usually three submandibular nodes, internal to the deep cervical fascia in the submandibular triangle. One lies at the anterior pole of the submandibular gland, and two flank the facial artery as it reaches the mandible. Submandibular nodes drain a wide area, including vessels from the submental, buccal and lingual groups of nodes, and their efferents pass to the upper and lower deep cervical nodes. The external nose, cheek, upper lip and lateral parts of the lower lip drain directly to the submandibular nodes; the afferent vessels may have a few buccal nodes along their course and near the facial vein. The mucous mem brane of the lips and cheek drains to the submandibular nodes, and the lateral part of the cheek drains to the parotid nodes. The central part of the lower lip, buccal floor and tip of the tongue all drain to the submental nodes, which lie on mylohyoid between the anterior bellies of the digastric muscles. These nodes receive afferents bilaterally, some decussating across the chin; their efferents pass to the submandibular and juguloomohyoid nodes.
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Phoneticians divide the tongue into the tip medicine allergy order exelon 6mg mastercard, anterior edge, the front part of the dorsum, the centre and back parts of the remaining dorsum, and a most posterior part (the root). The harmonic spectra of individual voices differ and will also vary depending upon the mode of phonation adopted. In the human vocal tract, the fundamental frequency and its harmonics are transmitted to the column of air that extends from the vocal cords to the exterior, mainly through the mouth. Part of the airstream can also be diverted through the nasal cavities when the soft palate is depressed to allow air into the nasopharynx. The supralaryngeal vocal tract acts as a selective resonator whose length, shape and volume can be varied by the actions of the muscles of the pharynx, soft palate, fauces, tongue, cheeks and lips; the relative positions of the upper and lower teeth, which are determined by the degree of opening and protrusion or retraction of the mandible; and alterations in the tension of the walls of the column, especially in the pharynx. Thus, the fundamental frequency (pitch) and harmonics produced by the passage of air through the glottis are modified by changes in the supralaryngeal vocal tract. The fundamental frequency and its associated harmonics may also be raised or lowered by appropriate elevation or depression, respectively, of the hyoid bone and the larynx as a unit by the selective actions of the extrinsic laryngeal muscles. Effectively, these movements shorten or lengthen the resonating column, and to some extent also alter the geometry of the walls of the air passages. Analysis of the human voice shows that it has a very similar pattern of harmonics for all fundamental frequencies, determined by the vocal tract acting as a selective filter and resonator. This maintains a constant quality of voice without which intelligibility would be lost (recorded speech played back without its harmonics is completely unintelligible). Each human voice is unique; it has been suggested that the unique frequency spectrum of each individual voice could be used for personal identification. During articulation, the egressive airstream is given a rapidly changing specific quality by the articulatory organs, the lips, oral cavity, tongue, teeth, palate, pharynx and nasal cavity. The discipline of phonetics primarily deals with the way in which speech sounds are produced, and consequently with the analysis of the mode of production of speech sounds by the vocal apparatus. In order to analyse the way in which the articulators are used in different speech sounds, words are broken down into units called phonemes, which are defined as the minimal sequential contrastive units used in any language. The human vocal tract can produce many more phonemes than are employed in any one language. Not all languages have the same phonemes, and within the same language, the phonemes can vary in different parts of the same country and in other countries where that language is also spoken. Reproducing phonemes that are not used in native speech is difficult because such phonemes require unfamiliar positioning of the speech organs. A native speaker of any language can quickly recognize the origins of anyone attempting to use their language as a second language. The second-language speaker will usually speak it with an accent characteristic of their own first language because they are using the familiar configurations of their vocal tract for each phoneme instead of the correct positioning. Similarly, the manner of articulation can vary from a complete closure to a slight narrowing. A narrowing that is sufficient to produce turbulence of the air in the vocal tract, and which is perceived as a rustling sound, is termed a fricative. Approximants involve a degree of closure insufficient to produce turbulence but with closure greater than that for a vowel. Nasals involve a stoppage in the oral cavity with the soft palate lowered to allow airflow through the nose, and, unlike stops, they can be sustained. Consonants can be produced with the vocal folds vibrating, when they are termed voiced, or without vocal fold vibration, in which case they are termed unvoiced. The best way to illustrate these classificatory systems in operation is by contrasting the production of different consonant pairs in which only one or two parameters have been changed. The /p/ of peat, the /b/ of beat and the /m/ of meat are all bilabial stops, meaning that they are produced by bringing together the lips. The contrast between the /b/ and the /p/ is in the differing way in which the airstreams are produced. The /m/ differs from the other two stops in being a nasal in which the soft palate is lowered to allow air to escape through the nasal cavity; unlike the other two stops, it can be sustained as in a sound of approval. Bilabial stops can be contrasted with the labiodental fricatives /f/ of feet and the /v/ of veal, both of which are produced by retracting the lower lip beneath the upper teeth. Neither involves a complete closure but both produce a significant constriction of the vocal tract with audible turbulence: the /f/ is unvoiced, while the /v/ is voiced. The sh sound (//) in ship is also a fricative involving a grooving of the tongue and is associated with significant audible turbulence; it may be contrasted with the lateral approximant /l/ in law, in which the sides of the tongue are lowered. In this case, it is the nature of the stricture that is different and the degree of closure. The sh sound in ship can be compared to the /k/ in keen, where the position of the tongue is different: in /k/ the tongue blade contacts the soft palate, while in sh the tongue tip or the blade contact the postalveolar region. The most dramatic example of the difference between voiced and unvoiced sounds may be appreciated if the /s/ sound in sip is compared with the /z/ in zip. The position of the tongue and other articulators is exactly the same for both /s/ and /z/; the difference between them is the presence or absence of phonation. A comprehensive summary of the organic disorders of voice due to laryngeal structural changes and neurological disease, as well as psychogenic voice disorders. A discussion of the routes of lymphatic drainage from the larynx and related structures. Atkinson M, McHanwell S 2002 Basic Medical Science for Speech and Language Therapy Students. A description of all aspects of laryngeal anatomy, together with a very useful bibliography. A book dealing with the evaluation, diagnosis and management of sensory and motor disorders of the larynx. Clark J, Yallop C, Fletcher J 2007 An Introduction to Phonetics and Phonology, 3rd ed. Fayoux P, Devisme L, Merrot O et al 2004 Histologic structure and development of the laryngeal macula flava. Hatley W, Samuel S, Evison G 1965 the pattern of ossification in the laryngeal cartilages: a radiological study. An older textbook that contains a lot of useful information not otherwise readily available. Kochilas X, Bibas A, Xenellis J et al 2008 Surgical anatomy of the external branch of the superior laryngeal nerve and its clinical significance in head and neck surgery. Liu M, Chen S, Liang L et al 2013 Microcomputed tomography visualisation of the cricoarytenoid joint cavity in cadavers. Maranillo E, Leon X, Orus C et al 2005 Variability in nerve patterns of the adductor muscle group supplied by the recurrent laryngeal nerve. Maranillo E, Vazquez T, Ibanez M et al 2008 Anatomic study of human laryngeal ganglia: number and distribution. Monfared A, Gorti G, Kim D 2002 Microsurgical anatomy of the laryngeal nerves as related to thyroid surgery. Mu L, Sanders I 2009 the human cricothyroid muscle: three muscle bellies and their innervation patterns. Sato I, Shimada K 1995 Arborization of the inferior laryngeal nerve and internal nerve on the posterior surface of the larynx. Storck C, Gehrer R, Fischer C et al 2011 the role of the cricothyroid joint anatomy in cricothyroid approximation surgery. Strauss S 2000 Sonographic appearance of cricoid cartilage calcification in healthy children. Vazquez T, Cobiella R, Maranillo E et al 2009 Anatomical variations of the superior thyroid and superior laryngeal arteries. This chapter will provide a description of head and neck development based primarily on data from studies on human embryos.
