Magdolna Hornyak, MD

• Professor, Interdisciplinary Pain Centre, University of
• Freiburg Medical Centre, Freiburg, Germany

Its upper end divides into two crura enclosing a triangular depression called triangular fossa mens health quizzes 10 mg alfuzosin buy fast delivery. Antitragus is a small elevation opposite to tragus from which it is separated by an intertragic notch androgen hormone pills discount alfuzosin 10 mg on-line. Lobule of the ear hangs below the antitragus as a large skin covered flap of fibrofatty tissue prostate 41 alfuzosin 10 mg purchase. Eminentia triangularis man health muscle optimal generic 10 mg alfuzosin overnight delivery, which corresponds to the triangular fossa between the crura of the antihelix prostate supplement reviews alfuzosin 10 mg purchase. Spine of helix Incisura terminalis Tragus Clinical correlation · Pinna is a source of several graft materials for the surgeons. Muscles the muscles of the auricle are divided into two groups: extrinsic and intrinsic. The anterior and superior muscles arise from epicranial aponeurosis and are inserted into the upper part of the helix and upper part of the cranial surface of the auricle, respectively. The auricularis posterior arises from the mastoid process and gets inserted into eminentia concha. The intrinsic muscles are small muscular slips, which pass between the cartilaginous parts of the auricle. Actions the extrinsic muscles may play a role in positioning of the auricle to catch the sound, while intrinsic muscles may change the shape of the auricle. Skin the skin covering the auricle is closely adherent to the underlying cartilage and fibrofatty tissue. Sometimes coarse hair projects out of the tragus, antitragus, intertragic notch, and helix in elderly males. The cranial surface and posterior part of the lateral surface is supplied by the posterior auricular branch of the external carotid artery. The anterior part of the lateral surface is supplied by the superficial temporal artery. Clinical correlation Involvement of pinna in herpes zoster of geniculate ganglion (Ramsay Hunt syndrome): Clinically, it is acknowledged that a few fibres of the facial nerve accompany the auricular branch of vagus and supply the skin in the region of concha and eminentia conchae, as vesicles are seen in these regions during involvement of the geniculate ganglion of the facial nerve by herpes zoster virus. The communication between the auricular branch of vagus and facial nerves takes place within the petrous temporal bone. Venous Drainage the veins accompany the arteries and drain into superficial temporal and external jugular veins. Nerve Supply Motor supply: All the extrinsic and intrinsic muscles of the auricle are supplied by the facial nerve. Therefore, to examine the tympanic membrane the pinna has to be pulled upwards, backwards, and laterally, to bring the two parts in alignment. Parts the external auditory meatus is divided into two parts: cartilaginous and bony. The skin covering the cartilaginous part is thick, and contains hair and ceruminous (pilosebaceous) glands, which secrete ear wax. Floor and posterior wall are supplied by the auricular branch of vagus (note that it is the only cutaneous branch of the vagus nerve). Clinical correlation · the infection and boils of the external auditory meatus cause very little swelling but are very painful because the skin lining is firmly adhered to the underlying cartilage and bone. The irritation of auricular branch of vagus during syringing may reflexly produce persistent cough called ear cough, vomiting, and even death due to sudden cardiac inhibition. Clinical correlation · Since the hairs are confined to the outer part of the meatus, the furuncles (infection of hair follicles) develop only in this part. This is because in infants the bony part of external auditory meatus is not developed and tympanic membrane is directed mainly downwards. The skin lining the bony part of meatus is thin and continuous with the cuticular layer of the tympanic membrane. About 4 mm lateral to the tympanic membrane (about 20 mm deep to concha), the bony meatus presents a narrowing called isthmus. The foreign body lodged medial to isthmus gets impacted and are difficult to remove. Sometimes the anterior wall of bony part presents a foramen (foramen of Huschke), permitting infection back and forth from parotid gland. In the newborn, the bony canal is not developed and is represented by a tympanic ring of bone. Consequently the external auditory meatus is shorter in children, and therefore, deep insertion of ear speculum may damage the tympanic membrane. Development the external auditory meatus develops as an ectodermal invagination of first pharyngeal cleft. It becomes filled with ectodermal cells forming a solid mass called meatal plug, which is canalized before birth. The auricle develops from six mesodermal tubercles around the external opening of the first pharyngeal cleft. The failure of canalization of meatal plug results in atresia of the external auditory meatus, while failure of fusion of tubercles will give rise to accessory auricles. It is placed obliquely making an angle of about 55° with the floor of the external acoustic meatus. The tympanic membrane faces downwards, forwards, and laterally as though to catch the sounds reflected from the ground. Consequently the anterior wall and the floor of external auditory meatus are longer than the posterior wall and the roof. Arterial Supply the external auditory meatus is supplied by the following arteries: 1. Outer cuticular layer of stratified squamous epithelium, which is continuous with the skin lining the external auditory, meatus. Inner mucosal layer is lined by low columnar epithelium, which is continuous with the mucous lining of the middle, ear. Parts the tympanic membrane is divided into two parts: pars tensa and pars flaccida. Its periphery is thickened to form a fibrocartilaginous rim called annulus tympanicus, which fits into the tympanic sulcus. From the margins of the notch the anterior and posterior malleolar folds in mucous membrane of tympanic cavity pass to gain attachment to the lateral process of the malleus. The handle of the malleus is firmly attached to the inner surface of the pars tensa. This part is rendered tough by the inward pull of the tensor tympani muscle, attached to the root of handle of the malleus and radial fibres. This part is thin and lax because intermediate fibrous layer here is replaced by loose areolar tissue. Surfaces Lateral surface of the tympanic membrane is concave towards the meatus and directed downwards, forwards, and laterally. Here the handle of the malleus is crossed medially by chorda tympani nerve, which runs forwards between the fibrous and mucosal layer at the junction of pars flaccida and pars tensa. The outer surface is supplied by deep auricular artery, a branch from first part of maxillary artery. The inner surface is supplied by (a) anterior tympanic artery, a branch from first part of maxillary artery, and (b) posterior tympanic artery, a branch from stylomastoid artery arising from posterior auricular artery. Anterior half of the lateral surface is supplied by the auriculotemporal nerve (V3). Clinically, the tympanic membrane is divided into four quadrants by means of two imaginary lines passing through the umbo. One is drawn along the handle of the malleus and the other at right angle to it through the umbo. Clinical correlation · Perforation of the tympanic membrane: It may result from an external injury or middle ear infection (otitis media). The color, curvature, presence of lesions, and position of malleus are features of special importance. When tympanic membrane is illuminated for examination, a cone of light is reflected in the anteroinferior quadrant of the membrane from umbo, the point of maximum concavity, which marks the attachment of the handle of the malleus. Sometimes an incision is given in the tympanic membrane (myringotomy) to drain the pus from the middle ear. The incision is usually given in the posteroinferior quadrant to avoid injury to the chorda tympani nerve, which crosses the inner aspect of the membrane in the upper part. Development the tympanic membrane develops from first pharyngeal membrane consisting, from superficial to deep, of three layers: ectoderm, mesoderm, and endoderm. Therefore, the tympanic membrane also consists of three layers from superficial to deep these are: 1. The three layers of tympanic membrane are likened to the three layers of trilaminar embryonic disc. It contains three auditory ossicles, which transmit sound vibrations from tympanic membrane in its lateral wall to the internal ear via its medial wall. The tympanic cavity is really the intermediate portion of a blind diverticulum from the respiratory mucous membrane of the nasopharynx. From front to back, the diverticulum consists of pharyngotympanic tube, tympanic cavity, and mastoid antrum. Handle of malleus Cone of light Size and Shape the middle ear is shaped like a cube, compressed from side to side. The mucous membrane lining of the middle ear invests all the structures within it and forms several folds, which project into the cavity giving it a honey-comb appearance. Communication the middle ear communicates: with nasopharynx through pharyngotympanic tube. Posteriorly with mastoid antrum and mastoid air cells through aditus to antrum called aditus ad antrum. Epitympanum (attic), a part above the tympanic membrane containing head of malleus, body, and short process of incus. Mesotympanum, a part opposite to tympanic membrane containing handle of malleus, long process of incus, and stapes. Floor: the floor is also formed by a thin plate of bone, which separates the tympanic cavity from the jugular bulb. Sometimes it is congenitally deficient and the jugular bulb then projects into the middle ear, being separated from cavity only by mucosa. The tympanic branch of glossopharyngeal nerve pierces the floor between the jugular fossa and lower opening of the carotid canal and enters the tympanic cavity to take part in the formation of tympanic plexus. The upper part of anterior wall presents two openings or canals, the upper one for the tensor tympani muscle and the lower one for the auditory tube. The bony partition between the two canals extends backwards along the medial wall in the tympanic cavity as a curved lamina called processus cochleariformis. Posterior wall: the posterior wall separates the tympanic cavity from mastoid antrum and mastoid air cells, and presents the following features: 1. Aditus ad antrum, an opening in the upper part through which tympanic cavity communicates with the mastoid antrum. Fossa incudis, a small depression close to the aditus, lodging the short process of the incus. Pyramid, a hollow conical bony projection below the aditus containing stapedius muscle whose tendon appears through its summit, passes forwards to be attached to the neck of the stapes. Vertical part of facial canal runs in the posterior wall just behind the pyramid and descends up to the stylomastoid foramen. Posterior canaliculus for chorda tympani, a small aperture for emergence of this nerve. Medial wall: It separates the tympanic cavity from the internal ear; thus it is actually formed by the bony lateral wall of the internal ear. Promontory, a rounded prominence in the centre produced by first (basal) turn of the cochlea. The tympanic branch of the glossopharyngeal nerve ramifies on it to form tympanic plexus. Oval window (fenestra vestibuli), a reniform aperture located above and behind the promontory. Round window (fenestra cochleae), a small round opening below and behind the promontory which in life, is closed by fibrous secondary tympanic membrane. Sinus tympani, a depression behind the promontory between fenestra vestibuli and fenestra cochleae, which indicates the position of ampulla of the posterior semicircular canal. Prominence of oblique part of the facial canal that extends backwards and downwards above the oval window until it joins the vertical part of the facial canal in the posterior wall of the tympanic cavity. Sometimes the bony covering of the facial nerve may be absent, thus exposing the nerve for injuries and infection. Prominence of lateral semicircular canal of the internal ear, which is seen as a small ridge high up in the angle between the medial and posterior walls. The chorda tympani nerve, a branch of facial nerve passes across the tympanic membrane lying lateral to the long process of the incus and medial to the handle of the malleus. It enters the tympanic cavity through the posterior canaliculus in the posterior wall and leaves through the anterior canaliculus medial to the petrotympanic fissure. They conduct sound vibrations from tympanic membrane to the oval window and subsequently to the inner ear fluid. It has head, neck, handle (manubrium), a lateral process, and an anterior process. The head and neck lie in the epitympanum, whereas the handle is embedded in the fibrous layer of tympanic membrane. The lateral process forms a knob-like projection on the outer surface of the tympanic membrane and provides attachment to the anterior and posterior malleolar folds. The head of malleus articulates with the body of the incus forming the incudomalleolar joint (saddle type of synovial joint).

Damage to the internal capsule caused by hemorrhage or infarction prostate cancer webmd 10 mg alfuzosin purchase visa, leads to loss of sensations and spastic paralysis of the opposite half of the body (contralateral hemiplegia) androgen hormone 2 ep2 buy on line alfuzosin. Each lateral ventricle is a C-shaped cavity lined with ependyma within each cerebral hemisphere prostate cancer zinc supplementation alfuzosin 10 mg purchase free shipping. Each lateral ventricle communicates with the 3rd ventricle through the interventricular foramen (of Monro) mens health rat race 10 mg alfuzosin order. Retrolentiform part Sublentiform part Corticopontine fibres Arterial supply of internal capsule the different parts of the internal capsule are supplied by the following arteries: 1 prostate cancer 0 to 10 10 mg alfuzosin for sale. Anterior limb: by medial striate branches of the anterior cerebral artery and lateral striate branches of the middle cerebral artery. Posterior limb: by lateral striate branches of the middle cerebral artery and branches of the anterior choroidal artery. Central part: the central part or body lies mostly within the parietal lobe and extends from interventricular foramen in front to the splenium of the corpus callosum behind. The floor from lateral to medial side is formed by: body of caudate nucleus, stria terminalis, thalamostriate vein, and thalamus. The roof is formed by the body of the corpus callosum and the medial wall is formed by septum pellucidum. Anterior horn: It is the anterior extension of the central part into the frontal lobe and lies in front of interventricular foramen and behind the posterior surface of the genu of corpus callosum. It is triangular in coronal section and presents roof, floor, and anterior, medial, and lateral walls. Cerebrum 397 Vertical line at the level of interventricular foramen Anterior horn of lateral ventricle Central part of lateral ventricle Collateral trigone are formed by septum pellucidum and head of caudate nucleus, respectively. Posterior horn: It is the backward extension of the central part into the occipital pole. In coronal section, the posterior horn presents: medial wall, lateral wall, roof, and floor. The medial wall consists of two convexities, the upper one - the bulb of posterior horn is formed by the forceps major of corpus callosum and the lower one - the calcar avis is formed by the calcarine sulcus. The roof, lateral wall, and floor are formed by the tapetum of the corpus callosum. Inferior horn: It is the largest horn and is considered as direct continuation of the main ventricular cavity into the temporal lobe. In coronal section, it appears as a transverse slit and presents the roof and the floor. The floor is formed medially by the hippocampus and laterally by collateral eminence. The lateral part of the roof is formed by tapetum of the corpus callosum and medial part by the tail of caudate nucleus and stria terminalis. The pia mater covering the ependyma along this C-shaped line is invaginated by the fringe-like tuft of capillaries of blood vessels into the central part and inferior horn to form the choroid plexus of the lateral ventricle. The line of invagination of the choroid plexus into the lateral ventricle is called choroid fissure. The roof is formed by anterior part of the body of corpus callosum, the floor by rostrum of corpus callosum, anterior wall by genu of corpus callosum. The medial and lateral walls 398 Textbook of Anatomy: Head, Neck, and Brain Golden Facts to Remember " Largest part of the brain " Most conspicuous cerebral sulcus " Dominant cerebral hemisphere (in right handed people) " Largest bundle of commissural fibres of the brain " Most important and largest bundle of projection fibres of the brain " Most common cause of hemiplegia " Largest part of the lateral ventricle " Largest horn of the lateral ventricle " Most variable horn of the lateral ventricle " Island of Reil " Most marked structural feature of the visual cortex Cerebrum Lateral sulcus (of Sylvius) Left cerebral hemisphere Corpus callosum Internal capsule Infarction of the posterior limb of the internal capsule Central part or body Inferior horn Posterior horn Insula (also called central lobe) Visual stria (of Gennari) Clinical Case Study A 57-year-old executive officer with a history of hypertension developed paralysis in the left side of his body. He was taken to the nearby neurocentre, where on examination the neurosurgeon found increased muscle tone, increased tendon reflexes and positive Babinski sign on the affected side. Name the parts of the internal capsule and mention the part in which the lesion was likely to be located. The internal capsule consists of the following five parts: anterior limb, genu, posterior limb, sublentiform part, and retrolentiform part. The lesion was likely to be located in the posterior limb because it contains corticospinal fibres and fibres of superior thalamic radiation providing motor and sensory innervation to the opposite half of the body respectively. It is the larger lateral striate (lenticulostriate) branch of the middle cerebral artery. Anatomically, the term basal ganglia include: (a) corpus striatum, (b) claustrum, and (c) amygdaloid body. Functionally, basal ganglia also include substantia nigra, red nucleus, and subthalamus. The major function of the basal nuclei is to decrease muscle tone and inhibit unwanted muscular activity. However, anteroinferior ends of these nuclei remain connected by a few bands of grey matter across the anterior limb of the internal capsule. The lentiform nucleus consists of two parts: a darker lateral part putamen and a medial paler part globus pallidus. Phylogenetically, corpus striatum forms two distinct functional units, the paleostriatum and the neostriatum. The caudate nucleus and putamen being recent in development, together form the neostriatum/ striatum. Topographically, it is almost completely divided into the caudate nucleus and the lentiform nucleus by a band of Caudate nucleus is a large comma-shaped mass of grey matter, which surrounds the thalamus and is itself surrounded by the lateral ventricle. The striatum receives fibres mainly from the cerebral cortex, thalamus, and substantia nigra. The globus pallidus sends fibres to the thalamus, subthalamus, substantia nigra, reticular formation, and red nucleus. Claustrum is a thin saucer-shaped mass of grey matter situated between the putamen and insula. Its rounded anterior part in front of interventricular foramen is called its head. In horizontal section of cerebrum, it appears wedge shaped with broad convex base directed laterally. It is divided into two parts by a vertical plate of white matter (external medullary lamina): an outer darker part, the putamen and an inner lighter part the globus pallidus. The larger lateral part, the putamen consists of densely packed small cells, and is structurally similar to the caudate nucleus. The globus pallidus is further Amygdaloid body is an almond-shaped mass of grey matter in the temporal lobe, lying anterosuperior to the tip of inferior horn of lateral ventricle. It is situated deep to uncus, which serves as a surface landmark for its location. Developmentally it is related to the basal nuclei but functionally it is included in the limbic system, and therefore, shares its functions (for details see limbic system on page 401). The limbic region was formerly called rhinencephalon because of its association to olfaction, but only a small part of it is actually concerned with smell. Phylogenetically, limbic cortex is the oldest part of the cerebral cortex and is made up of primitive type of cortical tissue called allocortex, which consists of only three layers and surrounds the hilum of the cerebral hemisphere. The limbic system plays a vital role in abstract functions such as emotions, behavior, drive, and memory. It is located caudal to the lateral half of the thalamus and inferomedial to globus pallidus. Determine how rapidly a movement is to be performed and how large the movement must be. Regulate the muscle tone and thus help in smoothening the voluntary motor activities of the body. Emotional aspects of behavior together with visceral responses accompanying these emotions, particularly the reactions of fear and anger, and emotions associated with sexual behavior which are necessary for: (a) survival of an individual including procuring of food and eating behavior, and (b) survival of the species including the sexual behavior. Because of visceral responses to activities in the limbic system, it is also known as visceral brain. Clinical correlation Lesions of basal ganglia: the lesions of basal ganglia result in various forms of unwanted involuntary movements and disturbance in the muscle tone. The Parkinsonism being the commonest disorder is described in detail in the following text. Limbic lobe, consisting of cingulate gyrus, isthmus, parahippocampal gyms, and uncus (anterior part of the parahippocampal gyrus). Since part of it receives olfactory input, it is believed that the amygdaloid body plays an important role in smellmediated sexual behavior. People in late sixties become pervasive in their sexual behavior, probably due to atrophy of amygdaloid bodies. In an adult brain, it forms a longitudinal elevation in the floor of inferior horn of the lateral ventricle and is continuous medially with the subiculum and parahippocampal gyrus. The name "hippocampus" meaning "sea horse", is derived from its appearance in coronal section. Traced posteriorly the hippocampus gradually narrows and ultimately ends beneath the splenium of corpus callosum. The ventricular surface of the hippocampus is covered by a thin layer of white fibres called alveus. The fibres of alveus originate in the hippocampal cortex, course towards the medial border of hippocampus where they converge to form a narrow strip of white matter, the fimbria of hippocampus. Phylogenetically, hippocampus represents the archicortex and consists of the following three layers: 1. In the region known as subiculum, there is gradual transition from six-layered neocortex to the threelayered archicortex. It is an almond-shaped mass of grey matter underlying the rostral part of the parahippocampal gyrus on the anteriormost part of the roof of the inferior horn of lateral ventricle. The others join the anterior commissure and are distributed to the contralateral amygdaloid body. Basal Nuclei and Limbic System 403 Connections Afferents: Hippocampus receives fibres mainly from entorhinal area (area 28). The fibres leaving the hippocampus pass to: (a) the opposite hippocampus through the commissure of fornix/hippocampal commissure, (b) the septal and anterior hypothalamic regions, and (c) the mammillary body, which sends impulses to cingulate gyrus through anterior nucleus of thalamus. Formerly hippocampus was regarded as the part of olfactory system but it has no direct connections with the sense of smell in man. In man it is an integrative centre, which influences endocrine and visceral functions and emotional states through its connections with hypothalamus, septal nuclei, and the cingulate gyrus. Origin, Course, and Distribution of the Fibres the fibres of fornix arise mainly from the pyramidal cells of the hippocampus and form a thin layer of white fibres on its ventricular surface called alveus. The fibres of alveus collect on the medial margin of hippocampus to form a narrow strip of white matter, the fimbria, lying flat over the dentate gyrus. The fimbria becomes a rounded band, the crus of fornix as it arches upwards, medially and forwards underneath the splenium of corpus callosum. The two crura, one of each hemisphere, curving over the thalamus, converge and unite in the midline beneath the trunk of corpus callosum to form the body of fornix. Each column of fornix arches downwards towards the anterior commissure, and forms the anterior boundary of interventricular foramen. Then it curves posteriorly through the hypothalamus to end in the mammillary body. These fibres being located posterior to anterior commissure are referred to as postcommissural fornix. Some fibres of column pass in front of anterior commissure to end in the septal area and anterior hypothalamic region, etc. Fornix is the only tract of the cerebrum, which contains all the three types of its fibres such as projection fibres, commissural fibres, and association fibres. When traced anteriorly, dentate gyrus runs medially across the inferior surface of the uncus. The posterior end of dentate gyrus is continuous with the splenial gyrus or gyrus fasciolaris, which continues as a thin layer of grey matter over the corpus callosum called indusium griseum. The indusium griseum is the vestigial grey matter and contains two delicate longitudinal bands of fibres buried in it, the medial and lateral longitudinal striae. On the medial surface of the cerebral hemisphere, it is seen as an arched prominent bundle of white fibres below the corpus callosum, along the lower border of septum pellucidum. A careful physical examination by a neurologist revealed increased muscle tone and cogwheel type of rigidity of the joints. Parkinsonism occurs due to degeneration of substantia nigra or nigrostriate fibres. The characteristic clinical features of Parkinsonism are mask-like facies, pill-rolling movements of hands with resting tremors. Although the brain constitutes only 2% (1/50) of the total body weight, it receives 20% (1/5) of the total cardiac output and consumes 20% of the total O2 used by the body. The cerebrovascular diseases (thrombosis, embolism, and hemorrhage) are the third most common cause of death and the neurological signs depend on the site of lesion. Therefore, an adequate knowledge of the blood supply of the brain is essential for proper diagnosis and treatment of these diseases. The two vertebral arteries enter the skull through the foramen magnum and unite at the lower border of the pons to form the basilar artery, which ascends in the midline on the ventral surface of the pons and at its upper border terminates by dividing into right and left posterior cerebral arteries. Each internal carotid artery enters the cranial cavity through carotid canal and the superior part of the foramen lacerum. It then takes a sinuous course through the cavernous sinus, pierces the dural roof of the sinus, and ends immediately lateral to the optic chiasma in the region of anterior perforated substance by dividing into a larger middle cerebral artery and a smaller anterior cerebral artery. Formation the circle of Willis is formed: Anteriorly, by the anterior communicating and the anterior cerebral arteries. Laterally on each side, by the posterior communicating artery connecting the internal carotid artery with the posterior cerebral artery. The circle of Willis lies in the interpeduncular subarachnoid cistern and contributes most of the arterial blood supply to the brain. Posterior spinal artery (first intracranial branch) arises from vertebral artery and sometimes from posterior inferior cerebellar artery.

Middle layer arises from lower border of the posterior one-third of the zygomatic arch prostate cancer 15 year survival rates by stage 10 mg alfuzosin visa. Superficial fibres pass downwards and backwards at 45° to be inserted into the angle and lower posterior half of the lateral surface of the ramus of the mandible androgen hormone structure purchase alfuzosin cheap online. Middle fibres pass vertically downwards to insert into the central part of the ramus men health tips cheap alfuzosin 10 mg buy on line. Deep fibres pass vertically downwards to insert into the upper part of the mandibular ramus and its coronoid process prostate cancer outside the prostate alfuzosin 10 mg buy on line. More laterally mens health 092012 buy discount alfuzosin 10 mg on-line, the back of maxilla replaces the palatine bone as the anterior boundary of the entrance of the fossa - the pterygomaxillary fissure. Posterior: Pterygoid process and adjoining part of the anterior surface of the greater wing of the sphenoid. Medial: Upper part of the perpendicular plate of palatine orbital and sphenoidal process of the palatine. Lateral: the fossa opens into the infratemporal fossa through pterygomaxillary fissure. Superior: Under surface of the body of the sphenoid and orbital process of the palatine. The lateral part of the roof is open and here fossa opens into the orbit through inferior orbital fissure. Inferior: Pyramidal process of the palatine bone in the angle between the maxilla and the pterygoid process. Nerve supply the masseter is supplied by a masseteric nerve, a branch from anterior division of the mandibular nerve. Infratemporal Fossa, Temporomandibular Joint, and Pterygopalatine Fossa 151 Table 10. The maxillary nerve, the second division (V2) of the trigeminal nerve is purely sensory. Course and Relations It arises from the convex anterior border of the trigeminal ganglion, pierces the trigeminal cave of dura to reach the lower part of the lateral wall of the cavernous sinus. The nerve leaves the middle cranial fossa through foramen rotundum to reach the pterygopalatine fossa. The infraorbital nerve (in fact a continuation of maxillary nerve) runs forward along the floor of the orbit in the infraorbital groove and canal in succession and appears on the face, through infraorbital foramen. Therefore in its course the maxillary nerve traverses four regions in succession: the middle cranial fossa, the pterygopalatine fossa, the orbit and the face. In the pterygopalatine fossa the pterygopalatine ganglion is suspended from the maxillary nerve by two roots. Then it breaks up to form superior dental plexus, which supplies the molar teeth and adjoining part of the gum. Middle superior alveolar nerve passes downward and forward along the lateral wall of the maxillary sinus, joins superior dental plexus and supplies the premolar teeth. Anterior superior alveolar nerve runs in the anterior wall of the maxillary sinus through a bony canal called canalis sinuosus and divides into dental and nasal branches: (a) the dental branches join the superior dental plexus and supply the canine and incisor teeth. Nasal branches supply the skin of the side of nose and the mobile part of the nasal septum. The superior dental plexus is formed by posterior, middle, and anterior superior alveolar nerves. It is situated in the alveolar process of the maxilla above the sockets of the teeth. Branches and Distribution the maxillary nerve gives off the following branches: A. Zygomatic nerve enters the orbit through inferior orbital fissure and divides on the lateral wall of the orbit into: (a) a zygomaticotemporal branch, which passes through a foramen in the zygomatic bone to supply the skin of the temple, and (b) a zygomaticofacial branch, which passes through the foramen in the zygomatic bone to supply the skin of the face. Posterior superior alveolar nerve enters the one or two foramina on the posterior surface of the body of maxilla the branches of maxillary nerve are summarized in the Table 10. Infratemporal Fossa, Temporomandibular Joint, and Pterygopalatine Fossa 153 Table 10. It carries preganglionic parasympathetic fibres from superior salivatory nucleus (located in the lower part of the pons). The postganglionic fibres arise from the cells in the ganglion and supply secretomotor fibres to the lacrimal gland, glands of the nose, palate, nasopharynx, and paranasal sinuses. Sympathetic root: It is derived from sympathetic plexus around internal carotid artery via nerve of pterygoid canal. These fibres pass through the ganglion without relay and provide vasomotor supply to the mucus membrane of the nose, palate, pharynx, and paranasal air sinuses. It serves as a relay station for the secretomotor fibres to the lacrimal gland and mucus glands of the nose, palate, pharynx, and paranasal sinuses. Location It is located deeply in the upper part of the pterygopalatine fossa, suspended from maxillary nerve by two short roots. Sensory root: It is derived from maxillary nerve and passes through the ganglion without interruption to be distributed through the branches of the ganglion. Branches of Distribution the branches of the ganglion are actually the branches of maxillary nerve, which passes through the ganglion without relaying. While passing through the ganglion, they incorporate the parasympathetic and sympathetic fibres of the ganglion. The orbital branches (2 or 3 in number) enter the orbit through inferior orbital fissure and supply orbital periosteum, ethmoidal air sinuses, and secretomotor fibres to the lacrimal gland. The greater palatine nerve passes through greater palatine canal and foramen to supply posteroinferior quadrant of the lateral wall of the nose. The lesser palatine nerves pass through lesser palatine canals and foramina to supply secretomotor fibres to mucus membrane and glands on the inferior surface of soft palate and hard palate. The nerves of lateral set supply lateral wall of the nasal cavity while those of medial set supply roof and nasal septum. It runs anteroinferiorly in a groove on the nasal septum and leaves the nasal cavity through the incisive foramen to enter the oral cavity where it supplies the anterior part of hard palate. The pharyngeal branch passes through palatovaginal canal and supply the nasopharynx. Consequently the individual suffers from running nose and eyes, for this reason the nerve of pterygoid canal is called nerve of hay fever and the pterygopalatine ganglion is termed ganglion of hay fever. Within the fossa it lies in front of the pterygopalatine ganglion and divides into its terminal branches. The branches of the third part of the maxillary artery and its distribution are described in detail on page 138 of this chapter. Infratemporal Fossa, Temporomandibular Joint, and Pterygopalatine Fossa 155 Golden Facts to Remember " Key muscle of the infratemporal fossa " All the principal muscles of mastication close the mouth except " Clinically the most important branch of maxillary artery is " Peripheral heart in the region of head and neck " Chief elevator of the lower jaw " All the branches of anterior division of mandibular nerve are motor except " All the branches of posterior division of mandibular nerve are sensory except " Most common nerve block given in dentistry " Most common dislocation of temporomandibular joint " Ganglion of hay fever " Most common cause of dislocation of temporomandibular joint Lateral pterygoid muscle Lateral pterygoid, which opens the mouth Middle meningeal artery Lateral pterygoid muscle Masseter Buccal nerve, which is sensory and supplies mucus membrane and skin of the cheek Mylohyoid nerve, which is motor and supplies mylohyoid muscle and anterior belly of digastric muscle Inferior alveolar nerve block Anterior dislocation Pterygopalatine ganglion Blow to the chin when mouth is widely open (as in laughing or yawning) Clinical Case Study A medical student was yawning in the anatomy lecture. The young lecturer walked to the student and hit him on the chin when he yawned widely again. Following a blow on chin the student got up immediately and wanted to say sorry to the teacher, but he could not say so because he failed to close his jaws. He took him to the orofacial surgeon who reduced the dislocation and the student was relieved of his agony. Mention the type of temporomandibular joint and name the bones taking part in its formation. The bones taking part are head (condyle) of the mandible and mandibular fossa and articular eminence of squamous part of the temporal bone. From anterior to posterior the parts of the intraarticular disc are: (a) anterior extension, (b) anterior thick band, (c) thin intermediate zone, (d) posterior thick band, and (e) bilaminar posterior extension. It is reduced as follows: the mandible is depressed posteriorly by exerting pressure on last molar teeth with thumbs and simultaneously the assistant elevates the chin (also refer to page 148). In the region of neck, thyroid and trachea are routinely examined by clinicians to diagnose their disorders. Therefore, detailed knowledge of anatomy and relations of these structures is extremely important. The hormones secreted by the thyroid gland include triiodothyronine (T3), tetraiodothyronine (T4; commonly called thyroxine), and calcitonin, which subserve the following functions: 1. It is the only endocrine gland, which is located superficially in the body, hence accessible for physical examination. It is the only endocrine gland that depends on external environment for raw material, iodine, to synthesize its hormones. It is the only endocrine gland, which does not pour its hormones into blood immediately after formation but stores them and then releases them in blood for use as and when required. Parts and Features It is H-shaped and consisting of vertical right and left lateral lobes and a horizontal isthmus connecting them across the midline. Sometimes a small pyramidal lobe projects upwards from the isthmus usually to the left of the midline. Each lateral lobe of the gland extends upwards to the oblique line of the thyroid cartilage and below up to the 5th or 6th tracheal ring. The isthmus extends across the midline in front of the 2nd, 3rd, and 4th tracheal rings. Therefore, to avoid hemorrhage during thyroidectomy, the thyroid gland is removed along with the true capsule. In case of prostate gland, the venous plexus lies between its true and false capsules and, therefore, during surgical removal of prostate gland (prostatectomy), prostate gland is removed; leaving behind both the capsules. Each lobe of the thyroid gland is 5 cm long, 3 cm wide, and 2 cm thick (5 Ч 3 Ч 2 cm). The thyroid gland is usually larger in females and further increases in size during menstruation and pregnancy. Clinical correlation · Sometimes the thyroid tumor extends backwards, as the capsule is thin along the posterior borders of the lateral lobes, compressing the adjacent structures without forming a visible swelling on the front of the neck. Thus thyroid swellings can be distinguished clinically from other swellings in the region of the neck. True capsule: It is formed by the peripheral condensation of the fibrous stroma of the gland. The important features of the false capsule are: (a) It is thin along the posterior border of the lateral lobe. It extends up to the oblique line of thyroid cartilage where 158 Textbook of Anatomy: Head, Neck, and Brain Muscles attached on the oblique line of thyroid cartilage Thyrohyoid muscle Superior thyroid artery 1. Thyroid and Parathyroid Glands, Trachea, and Esophagus 159 Vagus nerve Superior laryngeal nerve Superior border is related to anastomosis between the anterior branches of two superior thyroid arteries. Along this border inferior thyroid vein emerge and thyroidea ima artery (when present) enters. It runs downwards and forwards in company with the external laryngeal nerve, which it leaves near the upper pole of the thyroid lobe. The anterior branch first descends along the anterior border of the lobe and then continues along the upper border of the isthmus to anastomose with its fellows of opposite side. The posterior branch descends along the posterior border of the lobe to anastomose with the ascending branch of the inferior thyroid artery. Superior thyroid artery supplies the upper one-third of the lobe and upper half of the isthmus. Inferior thyroid artery: It is a branch of thyrocervical trunk from the first part of the subclavian artery. It first runs upwards along the medial border of scalenus anterior, and then passes medially behind the carotid sheath to reach the back of the thyroid lobe, where it is intimately related to the recurrent laryngeal nerve. The figure also shows intimate relationship of the external and recurrent laryngeal nerves with the superior and inferior thyroid arteries, respectively. The ansa-cervicalis is embedded in the anterior wall of the sheath while cervical sympathetic chain lies posterior to sheath in front of prevertebral fascia. It is related to (a) longitudinal arterial anastomosis between superior and inferior thyroid arteries, and (b) parathyroid glands. Two tubes Superior laryngeal nerve External carotid artery Superior thyroid artery Anterior branch Posterior branch Thyroidea ima artery Inferior thyroid artery Thyrocervical trunk Subclavian artery Arch of aorta External laryngeal nerve Recurrent laryngeal nerve Relations of Isthmus the isthmus is horizontal and presents two surfaces - anterior and posterior and two borders - superior and inferior. Anterior surface is related to: (a) strap muscles (sternohyoid and sternothyroid) and (b) anterior jugular veins. The inferior thyroid artery supplies lower two-third of the lobe and lower half of the isthmus. Thyroidea ima artery (in 30% cases): It is a branch of the brachiocephalic trunk or may arise directly from the arch of aorta. Middle thyroid vein: this short, wide venous channel emerges at the middle of the lobe to soon enter the internal jugular vein. Inferior thyroid vein/veins: They emerge at the lower border of the isthmus, form plexus in front of the trachea and then run downwards to drain into the left brachiocephalic vein. Sometimes a fourth vein, the thyroid vein (of Kocher) emerges between the middle and inferior thyroid veins to drain into the internal jugular vein. Superior thyroid vein: It emerges at the upper pole of the thyroid lobe, runs upwards and laterally, and drains into the internal jugular vein. The upper group drains into the prelaryngeal (lying in front of the larynx) and upper deep cervical (jugulodigastric) lymph nodes. The lower group drains into pretracheal and lower deep cervical lymph nodes and group of lymph nodes along the recurrent laryngeal nerves. Those from lower part of isthmus drain into retrosternal or brachiocephalic nodes lying in the superior mediastinum. The upper lymphatics follow superior thyroid artery and lower lymphatics follow the inferior thyroid arteries. The parasympathetic supply is derived from the vagus and recurrent laryngeal nerves. The sympathetic supply is derived from the superior, middle, and inferior cervical sympathetic ganglia, but mainly from the middle one. Thyroid and Parathyroid Glands, Trachea, and Esophagus 161 Prelaryngeal nodes Posterior belly of digastric muscle Jugulodigastric nodes the parafollicular cells or C-cells lie mainly between the basement membrane and the follicular cells. It reduces the blood calcium level by reducing the reabsorption of the calcium by the renal tubules.

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Diseases

• Mental retardation gynecomastia obesity X linked
• Sirenomelia
• Acrokeratoelastoidosis of Costa
• Typhus
• Acute necrotizing ulcerative gingivitis
• Bardet Biedl syndrome
• Dystonia musculorum deformans type 1
• Anorchidism
• Idiopathic pulmonary fibrosis

References

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• Stadlbauer V, Krisper P, Aigner R, et al. Effect of extracorporeal liver support by MARS and Prometheus on serum cytokines in acute-on-chronic liver failure. Crit Care. 2006;10(6): R169.
• Kyle RA, Therneau TM, Rajkumar SV, et al. Long-term follow-up of 241 patients with monoclonal gammopathy of undetermined significance: the original Mayo Clinic series 25 years later. Mayo Clin Proc 2004;79(7):859-866.
• Tang NL, Hui J, Yong CK, et al. A genomic approach to mutation analysis of holocarboxylase synthetase gene in three Chinese patients with late-onset holocarboxylase synthetase deficiency. Clin Biol Chem 2003;36:145.