Skull Anatomy (PDF)

1 Skull Facial bones calvarium Mandible (brain case) Skull vault Skull base The bones of calvarium and face are joined at immovable fibrous joints- except f...

1 Skull Facial bones calvarium Mandible (brain case) Skull vault Skull base The bones of calvarium and face are joined at immovable fibrous joints- except for TM joint which is movable cartilaginous joints. The skull vault  It is made up of several flat bones joined at sutures.  The bones consist of diploic space (cancellous layer containing vascular spaces) sandwitched between inner and outer tables of cortical bones.  The skull is covered by Periosteum (pericranium) which is continuous with the fibrous tissue in the sutures.  The diploic veins within the skull are large valveless vessels with thin walls. The communicates with the meningeal veins, the dural sinuses & the scalp veins.  The paired parietal bones are joined at the sagittal suture.  The parietal foramina are paired foramina close to the midline in the parietal bones.the are often seen on radiographs.  The frontal bone is joined to the parietal bones at the coronal suture.  Frontal bone formed by 2 frontal bones that join at the metopic sutures.  Metopic suture normally disappears by 2 1/2 of age, but persists into adulthood in 10% of people and may be incomplete. If metopic suture persists frontal sinuses are not developed.  The junction of the coronal and sagittal = Bergma.  The occipital bone is joined to the parietal at the lambdoid.  The lambdoid and sagittal sutures are joined at the lambdo.  2 Coronals Sagittal S. Lambdoid S. Bregma Lambda The side of the skull 1. Frontal + parietal bones (above). 2. Greater wing of sphenoid+squamous part of temporal bone (below). Sutures of the side of the skull Sphenosqumosal Sphenofrontal & Squamosal Bet. Sphenooparietal Bet. Bet. Greater wing of Sphenoid Temporal sphenoid& Temporal Parietal Bone bone bone bone Frontal Parietal N.B.: 1- The H shaped intersection of these sutures = Pterion which is surface mark of the anterior branch of the middle meningeal artery on lateral skull radiography. 2- The asterion : is the point where the squamosal suture meets the lambdoid. Suture.  3 The skull base The inner aspect "From anterior to posterior" -A- -B- -C- -D- Sphenoid bone  Cribriform  Lesser wings  Part of Occipital bone. plates of the anteriorly. squomous ethmoid in the  Greator temporal bone. midline. wingsposteriorly.  Petrous  Crista galli  Body with temporal bone.  Orbital elevated sella plates of the frontal turcica in the bones midline. Individual bones of skull base -A- * Orbital plates of the frontal bones:  Thin and irregular. → Separate the ant. Cranial fossa and the orbital cavity. * Cribriform plate of ethmoid bone:  Thin and depressed. → Seperates the ant. Cranial fossa from the nasal cavity. * Crista galli:  Superior perpendicular projection of the cribriform plate of ethmoid.  Continuous with the nasal septum from below on the frontal skull radiographs. -B- The sphenoid bone: *Body. **greater wing. ***lesser wing. * The body of sphenoid: Fig. (48) FG.  It uses the sphenoid sinuses.  Grooved laterally by the Carotid sulcus in which cavernous sinus and carotid A. run.  Has a deep fossa superiorly called Sella tursica on which lies the pituitary gland.  4  Anterior to sella tursica there is prominence called Tuberculum sellae.  Anterior to it’s a groove called Sulcus chiasmaticus where the optic chiasma lies and leads to optic canal on each side.  On either side of sella there is anterior clinoid process.  Posteriorly bounded by Dorsum sellae which is continuous with the clivus.  Posterior clinoid processes are post. Projections of the dorsum sellae.  The floor of sella is formed of thin bone called Lamina dura which may be eroded by raised ICP or pituitary tumors. -C- Temporal bone Which may be eroded by raised ICF or pituitary tumors Squamous part Petrous part Mastoid part Styloid process Forms part of the Houses the middle Inf. projections vault and part of and inner ears and the base. forms part of skull base. The zygomatic process projects from the outer side of the squamous temporal bone and continues with the zygomatic arch. -D- The occipital bone  Forms part of skull vault and post. Part of the skull base.  Has the Foramen magnum in the midline and the clivus.  The occipital condyles for articulation with atlas vertebra.  5 Cranial fossae  Anterior cranial fossa: o Limited posteriorly by the sphenoid ridge and ant. by Clinoid process. o Contains the frontal lobes of the brain.  Middle cranial fossa: o Limited ant. By the sphenoid ridge and ant. Clinoid process. o Limited post. By :  Midline :( Post. Clinoid process & Dorsum sellae).  Laterally :( petrous ridges). o Contains :  Temporal lobes of the brain.  Pituitary gland.  Most of the foramena of skull base.  Posterior crainial fossa: (Largest & deepest). o Limited ant. By :  Dorsum sellae and post clinoid Processes.  Petrous ridges. o Limited post. By: goove of the transverse sinus. o It contains :  Anteriorly → pons + medulla.  Posteriorly → cerebellum  Continuous with the spinal cord through foramen magnum. 6  7 Radiological features of skull base and vault I- Plain films  Standard projections are: lateral, OF20, Town's.  SMV: is used for of skull base and demonstrate most of the foramina. 1- The pituitary fossa: * Lateral view is the most frequently used for its assessment. * OF20: * F030 *SMV. *Dimensions (on lat view): 11-16m length, 8-12mm depth. *The dorsum sella have well def. margins ant. and post. *Pneumatization of sphenoid sinus may be: -Rudimentary -Presellar -sellar, extending under entire sella (most common). -Extensive (when involving the dorsum). *The degree of pneumatization has implication on trans-sephanoidal pituitary surgery *J-shaped, Omega, or hourglass sella = elongation of pituitary fossa with prominent sulcus chiasmaticus. (Normal variant) (5% in children). 2-Middle meningeal vessels: *A prominent groove on the inner table of skull vault. *Run from the foramen spinosum → squamous temporal bone then dividing into anterior and posterior branches. 3-Diploic markings: *Large irregular less well defined venous channels running in the diploic space. *A stellate confluence is often seen on the parietal bone on the lateral radiograph (fig. 1.3 –no.33) 4-Dural sinuses: *They are wide channels that groove the inner table e.g. the transverse sinus grooves: - Best seen on Town's projections. - Running from the region of the internal occipital protuberance laterally to the mastoids before becoming the sigmoid sinus.  8 5-Supra-orbital artery : Runs from the orbit to the groove on the outer table of the frontal bone (appears on the OF projection). 6-Superficial temporal art. Runs superiorly from the region of the external auditory meatus → grooves the outer table of its temporal and parietal bones (appears on lat. Projection). 7-Arachnoid granulation pits: Small irregular impressions on inner table related to the superior sagittal sinus. 8-Metobic suture: May persist in 10% of people. 9-Spheno-occipital synehondnosis: *Bet. Ant. part of the bone, sphenoid body. It's fuses at puberty but may persists and be mistaken for # base of skull in lat. Radiography. *Intraoccipital or "Mendosal sutures" are often seen extending from the lamdoid suture and should not be mistaken for facture base of skull on lat. Skull radiographs. *Wormian bones: are small bony islands that may be seen in suture lines particularly in relation to lamdoid suture. They are greater in number in infants. **Thickness of the skull vault :( not uniform) -Thin parietal convexities (appear radiolucent). -Thick parts of frontal bone. -Thick internal and external occipital protuberance. -Thick muscular attachments of the occipital bones esp. in males. II- C.T. Image  9 - Gives excellent visualization of skull base and foramina when narrow high resolution Images are obtained. - MRI with narrow section thickness slices is excellent for demonstration of soft tissue contents of skull foramena esp. Cranial Nerves. **The neonatal and growing skull: At birth: overlapping of the cranial bones due to moulding.  Diploic spaces are not developed.  Vascular markings are not visible.  Sinuses are not aireated.  Sutures are straight lines.  Fontanels are open and wormian bones are seen.  Skull vault=8times that of facial bones on the lat. Skull radiography.  At 2-3 mon.: 2 pairs of lateral fontanelles close.  At 6-8 mon.: ant. fontanelle closes.  By 6 mon. suture have narrowed to < 3mm. by 1y they begin to interlock.  By 2 ys.: 1- Serrated appearance of adult sutures appears. 2- Diploic spaces begin to appear. **Adult proportions of vault and face are attained at 7 ys, (fascial bone occupy similar volume to the cranium). **Skull changes in old age: the cranium become thinner, & maxilla & mandible with the loss of dentition & resorption of alveolar process. Normal calcifications of skull I) Pineal body: midline structure situated behind the third ventricle & 50% of adults over 20 years &in most elderly subjects is calcified. II) Habenular commissure: Just ant. To the pineal gland often calcifies in association with it in a C shaped curve with its concavity towards the pineal gland. III) Glomus of the choroid plexus: in the atria of the lateral ventricles is frequently calcified.Calcification is usually symmetrical & bilateral. IV) Dural calcifications: occur anywhere,But, Frequently seen in the: a) falx & tentorium cerebelli. b) The petroclinoid &interclinoid ligament (dural reflections that run form petrous apex to the dorsum sellae & ( ) ant. & post. Clinioid processes).  10 V) Arachinoid granulations: usually close to vault along sup. Longitudinal venous sinus. VI) Basal ganglia & dentate nucleus: may show punctuate calcification. VII) ICA: may be calcified especially in the region of the siphon. VIII) Lens of eye. Facial bone 1)Several contribute to the bony skeleton of the face including mandible, maxilla & zygomata. 2)Orbits, nose & paranasal sinuses form bony cavities contained by the facial skeleton. The Zygoma 1)This forms the eminence of the cheek & it is also known as malar bone. 2)Its anterior end reinforces the lateral & inferior margins of the orbital rim. 3)It forms the lateral boundary of the temporal fossa & infratemporal fossa. 4)Assessed radiologically OM projection & on Town's & SMV views. The nasal Bones * Attached to each other & the nasal process of the frontal bone. The bony orbit 4 walls + 2 fissures + 1 groove * Four sided pyramidal bone cavity. * The base forms the orbital rim. * Lat., Med., Sup. and inf. Walls converge posteromedially to the apex. *The optic foramen opens into the apex transmitting Optic N- and Ophthalmic art. * Lat. Orbital wall: - Strong, formed by : o Zygomatic bone (infront). o Greater wing of sphenoid (behind).  11 - Separates the orbital cavity from temporal fossa. * Sup. Orbital wall: - Weak, formed by : o Orbital plate of frontal bone (infront). o Lesser Wing of sphenoid (behind). - Separates the orbital cavity from ant. cranial fossa. * Med. Orbital wall: - Thin, formed by : o Maxillary. o Lacrimal. Bones. o Ethmoid. - Separates the orbital from the lacrimal cavity. N.B.: Lamina papyracea : paper- Thin bone bet.The orbit and ethmoid. * Inf. Orbital wall: - Formed by the orbital process of the maxillary bone. - Separates the orbital from the maxillary sinus. N.B.: The orbit has a supero-lateral depression for lacrimal sac & duct. * It also has the : o Sup. Orbital fissure. o Inf. Orbit. Fissure + periorbata. o Infra- orbital groove. * Sup. Orbital fissure:  Triangular slit. bet. greater and lesser wings of sphenoids.  It transmits : o 1st division of the 5th, 3rd, 4th, 6th cranial nerves. o Ophthalmic veins. o Branch of middle meningeal art. * Inf. orbital fissure:  A slit bet. lat. & Inf. orbital walls.  It connects the orbit with : o Pterygopalatine fossa (posteriorly). o Infratemporal fossa (anteriorly).  It transmits : o Infra-orbital n. (branch of maxillary division of the 5th). o Infra-orbital art. (branch of maxillary art). o Inf. opthalamic vein.  12 * Infra-orbital groove:  It runs in the floor of the orbit from the inf. orbit. Fissure → infra- orbital canal → infra orbital foramen in the maxillary bone. Carrying the infra-orbital nerve * Periorbata  Fibrous covering of the orbital cavity continuous with the dura through optic canal and superior orbital fissure. It closes the inferior orbital fissure separating orbit from the infratemporal and pterygopalatine fossa.Radiology of the bony orbit X-ray:  Best projections: OF20 and OM.  Asymmetry ( ) sup.Orbital fissures is common.  Innominate line: Straight line from the supero-lateral to the inferomedical rim. Caused by reflection of the X-ray beam hitting the curved greater wing of sphenoid tangentially.  The optic foramen < 7mm in diameter.  The ophthalmic art. may have a separate foramen or key-hole (if not completely separated) opening with the optic foramen.  The floor of the orbit & the infraorbital canal is seen on the OM & OM30 projectioins. CT:  The bony orbit & its soft tissue contents are demonstrated very well by CT.  Axial or coronal images may be obtained coronal imaging shows the floor of the orbit & is useful for the assessment of trauma where # is suspected. MRI:  It is more variable for demonstration of the soft tissue contents of the orbit than the bone. The nasal cavity - Extends from the external nose ant. →to nasopharynx posteriorly. - Divided by the nasal septum. - Floor form the roof of the oral cavity and consists of : o Palatine process of the maxilla anteriorly. o Palatine bone posteriorly.  13 - Lateral wall consists of : o Maxillary, palatine, lacrimal and ethmoid bones. o 3 curved turbinates dividing the cavity into sup., middle, inf. meati. o The space above the sup. turbinate is spheno-ethmoidal recess. - Spheno-ethmoidal recess drains the sphenoid air cells. - Superior meatus drains post. group of ethmoidal air cells. - Middle meatus drains ant. Group of ethmoidal air cells (open at the hiatus semilunaris) + maxillary sinuses + frontal sinus (opens into most ant. opening of the middle meatus). - Inf. meatus drains, naso-lacrimal duct. - Blood supply of the nasal cavity :  The sphenopalatine a.: Terminal part of the maxillary artery. It has medial branches to nasal septum & lat branches to the lat wall of the nose & turbinates.  The greater palatine a.: supplies some of the lower part of the nasal cavity by branches passes through incisive foramen.  The sup. Labial branch of the facial a.: supply anteroinferior part of the nasal septum & nasal alae.  Ethamoidal branches of the ophthalmic a.: supply sup. Part of the nasal cavity. N.B.:Little's area: vascular region of mucosa in the ant. &inf. Part of the nasal septum supplied by branches sphenopalatine, greater palatine & facial arteries.This is acommon site of epistaxis. The para-nasal sinuses Frontal Ethmoidal Sphenoid Maxillary - Above the - Lie bet. nose & medial med. wall of the part of orbit inner orbit and lat. wall and outer tables of the nose. of frontal bone. - Consist of - They vary labyrimth of greatly in size bony cavities. and are often asymmetric.  14 -Sphenoid sinuses - Paired cavities in the body of the sphenoid. - May be not separated from each other & may be subdivided into smaller bony cells. - Relationship :  Sup.: Sella turcica with pit.gland & optic chiusm  Lat.: cavernous sinus and contents.  Inf.: roof of the nasopharynx.  Ant.: closely related to ethamoid air cells. it may be difficult to distinguish a boundary. Maxillary sinuses 4 processes Body Orbital pr. Zygomatic Aveolar pr. Palatine pr. pr.  15 - The maxillary ostium opens into the infandibulum. - Infundibulum is a channel bet.(Fig. 1-12): o Infero-medial aspect of the orbit laterally. o Uncinate process medially. Extends Continuous with Bears the Roof of the superomedially to the zygomatic teeth. mouth. the medial rim of arch. the orbit. Body pyramidal with apex projecting superomedially Surfaces Ant. Post. Super. Medial. Directed Forms the ant. -Smooth and -Forms of lat. Wall of downwards and wall of the infra- triangular & lower part of the laterally forming temporal fosa -Separates the nasal cavity the contour of the (infratemporal sinus from the -Has the middle cheek sur.) orbital cavity meatus into which the (orbital sinus drains surface) (Nasal surface) (It has a superpior projection called (uncinate process) Ostiomeatal complex Ostium infundibulum middle meatus. Radiology of the nasal cavities I ) Plain Films: A-Frontal sinuses: 1- Not visible until 2ys.  16 2- Achieves adult proportions at 14ys. 3- Asymmetry is common and adevelopment may occur. 4- Absence of both may associate persistence of metopic suture. B-Ethmoidal sinuses: They have the similar rate of development of frontal. C- Sphenoidal sinuses: Pneumatization begins at 3ys. D-Maxillary sinuses: 1- 1st to appear and are visible radiological few weeks after birth. 2- Tooth bearing alveolar processes begin to develop at 6ys. 3- Full pneumatization appears in early adulthood with complete eruption of permanent dentition. II) C.T:. 1- Axial or coronal planes provide excellent visualization. 2- Attention should be paid to ostio-meatal complex & sup. meatus and spheno-ethmoid. 3- Pneumatized sinuses contain noting but air. III) MRI 1- Demonstrates the sinuses as the bony septa which are no signal structures. 2- Sandwitched between high-signal mucosal layers. 3- Air has law-signal intensity. The mandible *Composed of 2 halves united at the symphesis menti. - Each half has: (horizontal body – vertical ramus) joined at the angle of mandible. - Ramus has 2- sup. projections (coronoid process ant.- condylar process post.) separated by mandibular notch. - Coronoid process gives attachment to the temporalis ms. - Condylar process articulates with the skull at tempromandibular j. - Body bears :  Alveolar border and teeth sockets.  17  Mandibular canal (transmits the alveolar vessels & nerve)  Has proximal opening (mandibular foramen) (on inner aspect).  Distal opening (mental foramen) (on outer aspect). Tempromandibular joint -The articular surface consist of: - Temporomandibular fossa posteriorly. Covered by fibrous cartilage. - Articular tubercle anteriorly. -There is a fibrocartilagenous disc dividing the joint into upper & lower compartments. This disc has Ant. band attached to lat. Middle thin zone Post. band attached to pterygoid ms. attached to the joint the temporal bone by capsule. bands of fibers called transitional zone. The teeth  In the child: 20 milk teeth, each quad. has: (2 incisors - 1 canine -2 molars)  In the adult: 32 permanent: Each quad. has: (2 incisors -1 canine -2 premolar -3 molar)  The relevant quadrant is referred to by 2 arms of a cross ┌ ,┐,└...  The position of the tooth is relative to the midline of the cross.  Permanent tooth is referred to be a number, milk by capital letter. -e.g.: 2nd Rt.lower, premolar in adult → 5┐. -e.g.: 2nd. Lt.upper, molar in a child → └E.  Each tooth has : o Root → embedded in a socket. o Neck → covered by mucous memb. of mouth.  Crown: Exposed intraoral part covered by enamel (hardest & most radio-opaque part in the human body).  Dentine: has a radiographic density similar to compact bone.  18  Pulp cavity: Radiolucent middle of the tooth, continuous with the root canal that transmits nerves and vessels.  Roof and neck are surrounded by peri-odontal membrane (radiolucent line) which is surrounded by dense white line of bone called lamina dura. Radiology of mandible and teeth Plain Films C.T. Dental pantomography anthrography - Mandible is seen on: -High -Gives panoramic image -Done with 0F, 0F20, OM, OM30 and resolution for: injection of lateral projects. C.T. for *Dental arches. radio-opaque - Special oblique view TMJ. *Mandible. contrast into the for rami if # is suspected. *TMJ. synovial spaces - Special views for -MRI is *Maxilla: using special under TMJ and a full excellent equipment that moves radiographic radiographic study of it for joint around patients face. control. includes images of both anatomy. joints with mouth open -N.B.: contrast and closed. should not pass - The teeth can be from one radiographed on small compartment to films placed close up another. against then inside the mouth which provide excellent detail. N.B.: - Smphysis menti fuses at 2ys. - Complete eruption of milk teeth at 2ys. - Dentition develops in the mandible and maxilla during childhood and their calcification seen on radiographs at 3yrs. - 1st permanent molar erupts at 6ys of age. - All the permanent dentition is present by the age of 12 or 13ys except 3rd molar (wisedom teeth) at early adulthood. - The mandibular canal and mandibular and mental formina may be identified or radiographs of the mandible.  19 The oral cavity  The oral cavity forms the passage from the lips to the oropharynx.  The parotid gland opens into its lat. wall.  The submandibular and sublingual open into its floor.  The roof is formed by: (Hard palate ant. – Soft palate post.). The soft palate : (separates the oro- and nasopharynx).  From the lat. wall of the pharynx 2 muscles are inserted into it(Fig.582 FG) o Levator veli palatine: o Tensor veli palatine: they elevate the soft palate during swallowing to prevent nasal reflex.  From the middle of soft palate the uvula hangs and 2 pairs of muscles run from its base to the tongue and pharynx. o Palatoglossus: o Palatopharyngens: + overlying mucosa into whose concavity the palatine tonsil lie. The muscles at the tongue: o Intrinsic → change the shape of tongue. o Extrinsic → paired muscles that move the tongue.  Genioglossus: (fig 361 FG)  oFrom the inner surface of symphesis menti → fans out to form the ventral surface of the tongue. oIt is inferior fibers form a tendon to the hyoid bone.  Hyoglossus& chondroglossus: sheets of muscles arising from the bone to the sides of tongue.  Styloglossus: from the styloid process to the side of the tongue.  N.B.: A median raphea divides the tongue into two half. The floor of the mouth : formed by muscles that support tongue.  The mylohyaid muscle: from the mylohyoid line on the inner surface of the mandible to the hyoid bone on either side.  20 o Above it: the inferior fibers of gennioglossus pass from hyoid → to symphesis. o Below it: ant.belly of digastric pass from the hyoid to shympsis menti.  Post. belly of digastric: from mastoid process to lat. aspect of the hyoid.  Stylohyoid: from styloid process to hyoid. Lymphatic drainage of the oral cavity:  Submental.  Submandibular  retropharyngeal.  Deep cervical Radiology of the oral cavity - C.T. and MRI are very useful in detection of any infiltrating tumors. - MRI gives better soft tissue contrast than C.T. and can image in coronal sagittal as well as axial planes, so, MRI is superior to C.T. in this area. The salivary gland ‫هام‬ I- The parotid gland ** Pyramidal in shape (base above, apex below). 1- The largest gland and has superficial and deep parts. 2- Lies behind the angle of the jaw and in front of the ear. 3- Large superficial and small deep parts are continuous behind the ramus of the mandible via the isthmus : oThe deep part:  Extends medially to the carotid sheath and lat. wall of the pharynx separated from them by styloid process and muscles.  It lies between the ramus of the mandible anteriorly and EAM posteriorly. o The superficial part:  Lies anterior to the tragus of the ear.  21  Related posteriorly to (mastoid process – sternomastoid ms.) & anteriorly to (post. ramus of mandible – masseter ms.).  It has an antero-inferior extension or tail which wraps around the angle of the mandible. *Surfaces and relations: 1- Posteromedial surface: irregular and related to: (Fig 155, 154 FG) - Mastoid process - Sterno-mastoid ms. - Post. belly of digastric - Styloid process. - ICA and IJV (carotid sheath) - last 4 cranial nerve. 2-Anteromedial surface: - Medial pterygoid ms. - Ramus of the mandible. - Masseter muscle. 3-Superficial surface : - Skin and superficial fascia - Parotid LNs. - Great auricular nerves. *Structures within the gland: 1-Terminal part of facial nerve after emerging from the stylomastoid foramen with its (TBZ MC) temporal, zygomatic, buccal, mandibular, cervical branches. 2-ECA branching within the gland into: (Superficial temporal art.– Maxillary art). 3-Retromandibular vein (formed of: superficial temporal v. – maxillary v.). 4-Most of parotid LNs lie within the gland. *Surface anatomy of the gland: 4 points joined by straight lines (4 borders). 1- Head of the mandible. 2- Middle of masseter. 3- Point 2cm below and behind the angle of the mandible. 4- Mastoid process. * Parotid duct: (Stensen's duct): - Begins as a confluence of 2 ducts in the superficial part.  22 - Passes forwards on the masseter ms till left reaches its ant. border where it turns medially sharply. - It pierces the buccal pad of fat, buccinator ms and drains into the mouth opposite to the 2nd upper molar tooth. - It is above 5cm long. - Surface anatomy: middle 1/3 of a line joining tragus. - Small accessory parotid glands are common joining the duct along its length. II- Submandibular gland **It's mixed mucinous and serious gland → its tendency to form calculi. *Superficial part:  Continuous with the deep part around the post. Border of the mylohyoid ms.  It is wedge shaped with 3 surfaces : oLateral : occupying submandibular fossa in the inner aspect of the body of the mandible it is related to :  Nerve to mylohyoid.  Facial art. groove. oInfero-lat. covered with: (skin – superficial fascia "+platysma"- deep fascia – mandibular and cervical br. of facial nerve. – facial vein – submandular LNs. oMedial: Rests on mylohyoid ms. *Deep part:  It lies deep to mylohyoid ms and superficial to hypoglossal ms and lingual nerves. *Submandibular duct (wharton's duct):  About 5cm long and 2-4mm width.  It runs superiorly through the deep part between mylohyoid and hypoglossus ms then medial to sublingual gland to open in the floor of the mouth at the side of the frenulum of the tongue.  It is related to the lingual n. 1st lat → below → medial to duct. (Fig. 378 FG) *Nerve supply:  Parasympathetic: facial (Chorda tympani).  symphthetic: plexus around facial nerve.  23 III- Sublingual gland 1- It is the smallest of the 3. 2- It lies beneath the tongue under the mucous membrane of the floor of the mouth. 3- It raises the floor of the mouth forming the sublingual fold. 4- It is almond in shape with its long axis is directed forwards and medially. 5- It has 10-20 ductules which open in submandibular duct or open directly in the floor of the mouth. *Relations: - Lat.: Sublingual fossa in the inner side of the mandible. - Below : mylohyoid ms. - Med.: Genioglossus separated from if by lingual nerve & Submandibular duct. Radiology of salivary glands A-Sialography: for details (see technique book). B-C.T. and MRI: Are important for detection of tumor of the gland and assess involvement of surrounding structures. * CT may be done after sialography to improve visualization of ducts. * High resolution MRI demonstrates the facial nerve with the gland. It is slightly lower in intensity than the surrounding gland on T1 weighted images. C-Ultrasound: May be performed through the skin or intra-oral using high frequency transducers. D-Nuclear imaging: because with salivary gland accumulates and secrete (technetium 90mm) used the nuclear imaging. Value → * used to image several gland at once. * No cannulation of the duct.  24 The orbital contents Lacrimal Ophthalmic Extra-occular Globe Optic nerve gland vessels muscles The whole is embedded in fat. 1- Orbital septum: limits the orbit anteriorly, separates the orbital contents from the eye lids. It's a thin layer of fascia that extends from orbital rim to sup. and inf. tarsat plate.(Fig.316,FG) 2- Peri-orbata: fascial layer lining the bony cavity at the orbit and is continuous with the dura mater of the brain through the superior orbital fissure and optic canal. 3- The globe: Composed of : a. Cornea: transparent post. part. b. Sclera: opaque post. part. c. Limbus: corneo-scleral junction. *The mid coronal plane of the globe is the equator. 4- Tenon's capsule: fascial layer covering the sclera from the limbus to the exit of the optic nerve from the eye. It fuses with the fascia of the extrinsic ocular muscular at their insertion. 5- Conjunctiva: Covers the anterior aspect of the eye, it is a mucous memb. reflected from the inner surface of the eye lid and fuses with the limbus. 6- Six extra-ocular muscles: 4 recti and 2 oblique : A. Superior, inferior, lateral and medial recti arise from a common tendinous origin called annulus of Zinn which is attached to the superior orbital fissure. These muscles are inserted into the sclera. B. Superior oblique muscle:  Arises from the sphenoid bone.  Passes through the trochlea (tendinous ring attached to the frontal bone superior and medial to the orbit).  It then passes posteriorly to insert into upper outer surface of the globe posterior to equator.  25 C. Inferior oblique muscle:  Arises from the ant. part of the orbital floor and Inserted into Outer Middle Inner Posteriorly Anteiorly Vascular layer Retina (sclera) (cornea) (uveal tract) (post.) The junction the limbus Post Ant. Post Ends ant. short (choroid) (ciliary body and nerve fibres distance behind iris) gives the converges to ciliary body ciliary (muscles) form the optic responsible for nerve at optic (ora serrata) accommodations. disc. lower outer part of the globe behind the equator. D. Levator palpebrae superioris:  Arises from inferior surface of the lesser wing of sphenoid (see fig. 1-10).  Inserted into upper eye lid behind the orbital septum.  Blood supply: o Ophthalmic art. o Superior and inferior ophthalmic vein → cavernous sinus. 7- The optic nerve: - Is a direct extension of the brain 4mm thick. - Covered by dura, arachnoid and piamatter. - Has 4 parts: o Intra-ocular: begins at the optic disc. o Intra-orbital: within the muscle cone. o Intra-canalicular: within the optic canal. o Intra-cranial: bet. optic canal and optic chiasma. Internal anatomy and covering of the eye 3 layers of the globe N.B.: the macula has greatest conc. Of cones and is responsible for central vision, lies temporal to the optic disc. Ant. Segment: Is that part ant. to the lens  26 Ant.chamber Post.chamber Bet. cornea and iris Bet. iris and lens Filled with aqueous humour and continuos through the pupil. Post. Segment: Is that part post. to the lens  Filled with a gelatinous material (vitreous body).  Has condensed outer part (hyaline membrane).  There is potential space between the vitreous and retina (subhyaloid space) in pathological conditions fluid or blood may accumulate in this space. Radiology of the orbit and eye 1)Plain Films: 1- The orbital margins may be demonstrated by 0F20, OM and OM30. 2- The floor of the orbit is undulated and not well defined. 3- The cornea & eye lids are demonstrated by lateral radiography of the eye using small dental films and low exposure. 4- The floor of the orbit is assessed by C.T. in trauma. 2)Ultrasound: 1- High frequency transducers image the ant.seg. 2- Low frequency transducers image the post.seg. 3- Scans are performed usually in transverse (axial) and longitudinal (sagittal) planes.  Aqueous & vitreous chambers → Anechoic  Cornea and lens →→→→→→ Echogenic  Choroid, retina and sclera →→→Hypo-echoic (and are not distinguishable from each other).  Extra-ocular muscle and optic nerve appear as echo-free structures within the echogenic retrobulbar fat. 4)C.T.: excellent modality  For assessment of extraocular contents of orbit and bony walls.  Coronal images are best for assessment of orbital floor; esp in trauma using 4mm intervals and thinner sections gives better details.  27 5)MRI: Demonstrates soft tissue of the orbit, performed in any plane.  It is valuable in demonstrating the optic nerve on vertical oblique images along the long axis of the nerve.  Demonstrates 3rd, 4th, & 6th nerves just below the ant. clinoid process. The pharynx ‫هام‬ **Muscular tube extending from the base of the skill to the level of C6.It communicates with both oral and nasal cavities.  Naso → behind nasal cavity.  Oro → behind oral  Laryngeo → behind larynx. It has 3 coats Innermost Submucous Fibrous Outermost mucous coat coat Muscular coat` Continuous with the (pharyngeo-basilar 3 constrictor ms (sup., mucosa of oral and nasal fascia) mid. &Inf.). cavity  28 N.B.: Pharngeo-basilar fascia:  Thick and gives the pharynx its shape.  Attached superiorly and the base of the skull.  Continuous with the fibrous material filling the foramen lacrum.  It is pierced only by austachian tube. **The outer most muscular coat. Anterior attachments Superior Middle Inferior Inferior extension of the  Hyoid bone Cricoid and thyroid medial pterygoid plate  Stylohyoid lig. cartilage (pterygoid hamulus) N.B.: 1) The 3 muscles fan posteriorly to insert into posterior raphae which is attached superiorly to the base of the skull ant. to the foramen magnum and is continuous downwards with the esophagus. 2) A gap ( ) the oblique & horizontal fibers of the inf. Constrictor may become a weak spot through which pharyngeal pouch may emerge. I- The nasopharynx *Site: it is the part of the pharynx bet. post. choanae and lower limit of soft palate. *It communicates:  Ant. with → nasal cavity.  Inf. with → oro-pharynx. *Boundaries:  Roof: Inf. surface of the sphenoid and clivus.  Post: upper cervical vertebrae+ Langus collis and capitis ms.  Postero-lat.: Styloid ms separates it from the carotid sheath.  Lat.: para-pharyngeal space + deep soft tissue at the infra- temporal space. **The eustachian tube opens into its lat. Wall piercing the pharengeobasilar fascia. This opening has a posterior cartilaginous ridge (Torus tuberious) behind it there is fossa of Rosenmueller. *The musculas layer:  Sup. pharyngeal constrictor.  The palatal muscles: → levator veli Palatini → tensor veli palatini. They elevate the soft palate during deglutition  29 *Lymphoid tissue: Lies in the roof and extends to the post. Wall. It's prominent superiorly forming the adenoid. *N.B.: the lymphatic drainage of the nasooharynx is mainly to jugulodigasteric node (at the mandible angle). *Spaces of the naso-pharynx: ‫هام‬ Parapharyngeal infratemporal pterygopalatine 1)Parapharyngeal : (Fig. 1.35)  Slit-like space: lat. to the nasopharynx.  Bounded by buccopharyngeal fascia (fascial plane separate the pharyngeal muscles from the muscles of mastication).  Post.→ separated from the carotid sheath by the styloid process and muscles.  Lat. → the deep part of the parotid gland.  Contents: A: ECA V : pharyneal veins. N : mandibular nerve. 2)Infratemporal: (Fig. 1.37)  Lies lat. to the naso-pharyngeal & para-naso-pharyngeal spaces and benid to post. wall of maxilla.  Extends from the base of the skull to the hyoid bone  Superiorly: It communicates with the temporal fossa through the gap ( ) the zygomatic arch & side of the skull. Medial to this a roof is formed by the inferior surface of middle cranial fossa and is pierced by foramen oval and spinosum.  Laterally: zygomatic arch, temporalis muscle and coronid process of the mandible.  Medially: lat. pterygoid plate and nasopharynx.  Post. : i. Deep part of parotid gland. ii. Styloid process and its muscles. iii. Carotid art and jugular vein.  Anteromedial limit: junction of lat. pterygoid plate with the posteromedial limit of maxilla superiorly and the post. border of perpendicular plate of palate inferiorly.  N.B.: The ant. & med. Walls of the space meet inferiorly but separated superiorly by ptrygo-maxillary fissure where the ptrygoid plates diverge from the post wall of the maxilla.  30 3)Pterygo-palatine fossa:  It is a depression of the pterygomaxillary fissure, below the apex of the orbit between the pterygoid process and post. maxilla.  It is importance is that it communicates with several cavities and may facilitate spread of pathology bet. them.  Communications: (Fig. 29 FG).  The orbit through IOF (Inf. orbit. Fissure).  The middle cranial fossa through foramen rotundum.  The infra temporal fossa laterally.  The nasal cavity through spheno-palatine foramen medially.  The oral cavity through greater palatine canal.  Contents: Maxillary division of 5th cranial nerve (pass through foramen rotandum). Pterygopalatine segment of maxillary art. II- The oro-pharynx  Site: from the lower part of the soft palate to the epiglottis. Continuous with the oral cavity anterior & laryngeoph. Below.  N.B.: oro-pharyngeal isthmus:  It forms the junction bet. oropharyngeal and oral cavity.  It is bounded on either side by folds called (palato-pharyngeal folds) or (fauces) tonsils lie inbet. III- The laryngeo-pharynx (hypo-pharynx)  Site: Between level of C3 (epiglottis) to C6 (beginning of the esophagus behind the larynx).  N.B.:  It is not opened on the larynx but on the esophagus.  It forms deep recesses on either side of the upper part of the larynx called "piriform fossea”).  During deglutition the epiglottis close the laryngeal entrance forcing bolus of food into these fossae down to the esophagus. Cross sectional anatomy of naso-pharynx :(Fig. 1.34 & 1.36)  31 1. Paired lat. pharyngeal recesses or fossae of Rosenmulleur lie postero-laterally. 2. Anterior to them is torus tubaris (a cartilaginous of eustachian tub.) 3. Ant. to T. tubaris is a recess for med by the entrance the eustachian tube. 4. Med. and lat. pterygoid plates + their muscles lie anterolat. to nasopharynx. 5. Infra-temporal space crossed by the lat. pterygoid ms. 6. Para-pharyngeal space post. to the infratemporal space and anterior to the carotid vessels. 7. Parotid gland: It's deep part lies lat. to the parapharyneal space. 8. Prevertebral ms posteriorly. 9. Maxillary antrum and nasal cavity anteriorly. Radiology of the pharynx 1-Plain film and tomography:  Lat. view of the skull and neck shows soft tissue outlines.  Lat. tomography gives improved separation of soft tissue planes.  The post. Wall of the pharynx forms a soft tissue shadow curving posteriorly from below the body of sphenoid anterior to the cervical vertebrae: it measures : o Ant. to C4: 3mm but below this become thickened but does not exceed the AP diameter of the cervical vertebrae. o In children not more than 5mm due to presence of lymphoid tissue). o Ant. to C6: 12mm (in children  Adenoids may show soft tissue shadow  Base of tongue and epiglottis → form. Ant. surface of oropharynx.  Basal projection of the skull : (post wall – Lat. wall of naso-pharynx).  AP views of the neck: shows o Piriform fossa of laryngopharynx. o Pharyngeal wall. 2-pharyngeography: (Ba swallow study of the pharynx):  Single contrast →Ba. Used (fluid 60-100%).  Double contrast → ↑ Barium density (250%).  The 1st shows any strictures or filling defects.  32  The 2nd shows any mucosal abnormalities.  Ba. Swallow shows : 1- Lining of the wall of the pharynx. 2- Piriform fossae which are: a. Lat. extension of the Ba. column in AP view. b. Have smooth distensible borders. c. Asymmetry is a normal variant. 3- Below the cricoid cartilage small indentation caused by submucous veins characterized by changing their shape on swallowing. 3-Palatal studies and videofluroscopic feeding studies:  Movement of the palate during phonation can be radiographed in the lat. Projection.  Videofluroscopy can be used to the movement of the tongue, palate ,& pharynx during feeding by suing food. 4-MRI and C.T.:  Axial C.T.: is better because it gives good details to the based the skull and bone details.  Coronal MRI: better because it does not require change of the position of the patient. Waldyer´s ring Pharyngeal tonsits Adenoids Lingual tonsits. Lat. wall of the oro-pharynx Post. wall of naso-pharynx Post. surface of the tongue The larynx ‫هام‬  It form the entry of the air and responsible for voice production.  Relations: o Post.: C3 → C6. o Ant. : Strap muscles of neck, skin and sup. fascia. o Lies in between great vessels of the neck  It is lined by mucosa which is continuous with that of the trachea below and pharynx above (stratified epith.).  33 Framework 3 single Thyroid Epiglottis Cricoid 3 paired Corniculats Arytenoids Cuniforms 1-Cricoid cartilage: - It is the anchor cartilage of the larynx. - Signet ring in shape with flat wide lamina post. and arch anteriorly. - It is joined to the thyroid cartilage above the crico-thyroid memb. and to the trachea below by the crico-tracheal memb. 2-Thyroid cartilage: Form the ant. and lat. boundary of larynx. - Formed of a pair of laminae joined anteriorly, notched from above → sup. notch thyroid (at level of C4). - Post. part of laminae has upper and lower projections forming sup. and inf. horns the inf. horn articulates with the signal of the cricoid cartilage with synovial joint. - The vocal ligaments are attached to the inner surface of he thyroid cartilage near the lower margin. 3-Epiglottis: - A leaf shaped cartilage whose narrow base or petiole is attached to inner surface of thyroid cartilage at the same point as the vocal cords (lower margin). - It projects up behind the base of the tongue and directs food boluses laterally into piriform fossae during deglutition. - Pair of mucosal folds pass laterally from the epiglottis to the pharyngeal wall called pharyngeal folds. - 3 mucosal folds pass from ant. surface of the epiglottis to the base of the tongue 2 lat. and 1 central forming pair of recesses called valleculae. - Pair of mucosal folds extend from the lateral margin of the epiglottis posteriorly to the arytnoid cartilage called ary-epiglottic folds. Together with the epiglottis define the laryngeal entrance.  34 4-Paired anytenoids: - Sit on the supero-lat. margin of the signet of the circoid cartilage. - Bear antero-inf. vocal processes which give rise to vocal cords. 5-Paired corniculates: - Sit on to of aryntenoids. 6-Paired cuniforms: - Lie in the free margin of ary-epiglottic fold. Cavity Divided by upper (vestibular or false folds) & lower (true cords) pairs of mucosal folds into 3 parts: Upper Space in between Lower Space between vestibular Laryngeal ventricle ( ) Infraglottic larynx Folds & laryngeal entrance false and true vocal Between vocal cords folds. & tracheal enterance  The laryngeal ventricle may extend anterosuperiorly forming a small pouch called the saccule of the larynx.  The term glottis refers to the true vocal cords & the triangular space ( ) them when open called Rima golltidis.  The infraglottic larynx is elliptical in Cross section superiorly & circular inferiorly as it merges with trachea. **N.B.:Hyoid bone: o U-shaped bone ( ) the mandible & the thyroid cartilage. o Has a small central body & along extension on each side called greater horns. o Smaller horns (lesser horns) arise from its upper surface o The tip of each greater horn is attached to the styloid process by stylohyoid ligament. o The hyoid bone is attached to the mandible, tongue, styloid process and pharynx by middle pharyngeal constrictor. **N.B:  35  The thyrohyoid memb.: Arises from oblique line on the thyroid cartilage and inserts in the inferior part of the hyoid bone.  The thyrohyoid lig. Is a midline thickening of the membrane.  The lat. thyrohyoid ligaments: the thickened posterior part of the same membrane, passes from the superior horns of thyroid cartilage to the greater horns of the hyoid bone. Radiology of the larynx Plain Tomography Xeroradiogrphy contrast laryngeography A- Plain radiography:  Lateral views: Is the most useful as larynx is not obscured by overlying bones.  Air in the pharynx and larynx provides intrinsic contrast with soft tissue walls.  The hyoid bone and laryngeal cartilages are seen.  The hyoid, cricoid and arytenoid are hyaline cartilages and may calcify or undergo true ossification. *N.B.: Calcification is often irregular, but may be homogenous with dense cortex and less dense medulla.  The other cartilages are composed of yellow elastic fibrocartilage & do not calcify.  The lateral thyrohyoid ligaments contain tri-ticeal cartilage which may calcified cartilages “Do not mistake them for F.B.”  Base of tongue, vallecula, epiglottis, ary-epiglottic folds, true and false cords may be identified. B- Tomography:  Useful in AP views when bone densities are blurred to allow better details.  He true and false cords are best seen in this view.  The piriform fossae are seen on either side of proximal larynx. C- Xeroradiography: D- Conrast-larryngeography: see techniques.  36 E- CT & MRI:  Cross section imaging using CT provide excellent anatomical detail of the larynx & surrounding structures.  MRI sagittal & coronal imaging is also possible.  The cartilages are of low density on CT unless calcified which occurs increasingly with age.  On MRI: They are of high signal intensity as they contain fatty marrow.  The mucosa of the subglottic larynx & the ant. Commissure should not be thicker than 1mm on MRI images.  The true cords (ligament) are of low signal intensity & the false cords (fat containing) are of high signal intensity. Cross-secional anatomy of the larynx. Supra-glottic glottic infra-glottic. *Supraglottic level:  The larynx is ant. to the pyriform sinuses separated from them by argepiglottic fold.  At higher level: o The hyoid bone and thyroid cartilage are seen. o Epiglottis, valleculae, base of the tongue may at identified posterior to hyoid bone. o The sterno-mastoid ms are seen postero-lat. with carotid and heath medial to them. *Glottic level:  A complete ring of cartilage is seen: o The thyroid cartilage anteriorly. o Cricoid and arytenoids cartilage posteriorly.  The vocal processes are identified giving attachment to the vocal ligaments and defining the level of he glottis.  Ant. & Post. commissures (fusion of vocal cords).  Both commisures appear thin when cords are abducted and appear thickened during adduction of cords (phonation).  The larynx is elliptical in shape at the level of true cords and triangular at higher level (level of false cords). At this level, the false cords form the lat. Wall of the larynx & the ary-epiglottic folds form the post wall.  The thyroid cartilage is ant.  37 *Infra-glottic level:  Just below the cords.  The larynx is elliptical.  The crico-thyroid is ant. and cricoid is posterior.  Inf. thyroid horns are posterolat. to cricoid.  At lower level, the larynx is circular and cricoid forms a complete ring.  Post of thyroid gland lobes are seen lat. with neck vessels postero- laterally.  EJV and to sternomastoid muscles. Thyroid gland  The thyroid gland derived from the 1st and 2nd pharyngeal pouch.  38  It consists of 2 lobes joined by a midline isthmus.  The 2 lobes are 4cm in height extending from thyroid cartilage superiorly to 6th tracheal ring inferiorly.  The lobes are often asymmetrical (Rt. > Lt.)  The isthmus is at the level of C6 from 2nd → 4th tracheal ring.  The gland is invested with the trachea and larynx and the pharynx and esophagus in pretracheal fascia.  The carotid sheath lies postero-laterally behind these structures on either side are prevertebral muscle.  Anterior to the gland are the strap muscles of the neck & the sternomastoid.  Superficially: the ant. jugular vein runs in the midline and the ext. jugular vein runs on either side.  The parathyroid glands lie close to the deep surface of the gland & may be intracapsular. *Cross sectional anatomy:  At the level of C6 the gland appears as 2 triangles of tissue connected at the isthmus around the trachea.  Each triangle is: 3cm depth and 2cm width with convex anterior surface.  Anteriorly: strap muscles of the neck, sterno-mastoid and jugular veins.  Postero-laterally: carotid sheath.  Trachea and esophagus in between. *Blood supply and lymphatic drainage:  Sup. thyroid art.: 1st branch of the external carotid.  Inf. thyroid art.: From thyrocervical trunk from subclavian art.  Thyroid ima art.: From brachiocephalic art. (Variant) or aortic arch.  Sup. hyoid vn: into IJV.  Middle thyroid vein: into IJV.  Inf. thyroid veins: → Lt. brachio-cephalic vein. *Lymphatic drainage: into it thoracic duct. Radiology of the thyroid Plain X-ray U.S. Isotopic scanning C.T. MRI A) Plain-X-ray: Only seen if enlarged to displace the trachea or barium filled esophagus.  39 B) Ultrasound:  Done using ↑ frequency transducer.  Normal thyroid gland has a homogenous echotexture of medium echogenicity.  The strap muscles appear as structures of ↓ echogenicity.  Carotid vessels appear as anechoic structures on either side.  Its vascularity can be detected with color flow imaging. C) Isotopic scanning:  Provides functional rather than anatomical details.  Useful for identifying ectopic thyroid tissue.  Technetium 99m-or iodine labeled agents are used. D) C.T.:  Used in axial planes.  Shows soft tissue area of high attenuation because of "I content".  Imaging with short scan times during infusion of contrast gives best details. E) MRI:  On T2-weighted images.  The gland is higher signal intensity than the surroundings. **Ectopic thyroid tissue: The thyroid gland develops from an out pouching of the pharynx & descends into the neck passing anterior to the hyoid bone &trachea. Maldevelopment may cause thyroid tissue to be found anywhere along a line from the base of the tongue to its normal. Less commonly thyroid tissue may migrate interiorly to the mediastinum or even to pericardium or myocardium. The thyroglossal duct may persist as a midline structure extending superiorly from the isthmus of the gland & a thyroglossal cyst may be found at any site related to it. More commonly (40%) part of the duct persists as the pyramidal lobe of the gland extending superiorly from isthmus or the medial part of either lobe. Para thyroid glands  Small lentiform structures 2-6 (usually 4) in number.  40  6mm length x 4mm transverse x 2mm AP.  They lie posterior to thyroid within its fascial sheath.  The superior develop from 4th pharyngeal pouch and do not migrate.  The inferior develop from 3rd pharyngeal pouch and migrate with the thymus inferiorly.  Mal. descent → ectopic sides: o Most commonly just below inferior pole of the thyroid. o Superior mediastinum. o Behind esophagus.  BL. Supply : mainly from Inf. Thyroid a. Radiology of the parathyroids C.T. Isotopic scanning  Normally not seen unless enlarged.  Imaged using subtraction  C.T. can detect ectopic glands. technique.  They appear as lower attenuation than  Both thyroid and para- thyroid tissue. thyroid take thalium 201chloride.  The thyroid only takes up technetium 99-m. by computerized subtraction of the technetium image from thalium image parathyroid appear. *U.S.: seen as hypoechoic structures lying posterior to the thyroid gland. The Neck vessels  41 The carotid a.a. in the neck -Left CCA → arise from arch of aorta. -Rt. CCA → arise from brachiocephalic trunk behind the rt. sternoclavicular joint. -The CCAs passes upwards and slightly laterally accompanied by : oIJV on the lat. aspect. oVagus n. posteriorly ( ) the 2 structures -The 3 structures are invested in carotid sheath. -At the level of C4, the CCA bifurcates into : Ext. carotid a. Internal carotid a. - Passes ant. then curves slightly - Contains superiorly from the posterior as it ascend to enter the origin to the base of the skull. substance of parotid gland. Maintaining the relationship of - Ends by dividing into : the CCA with the IJV and vagus *Maxilary a. nerve in the carotid sheath. *Superficial temporal a. - Has a localized dilatation ant its origin. - Has no branches in the neck. *Anatomical relations of common carotid artery within carotid sheath: -Post: Sympathetic trunk → prevertebral muscles → transverse processes of C4 to C6. -Med: * At lower level:  Trachea, oesuphegus (with recurrent laryngeal n. ( ) them). *At higher level:  larynx, pharynx, recurrent laryngeal nerve → medially.  Thyroid → anteromedially. -Antero-lat.:  Above level of the cricoid cartilage: oonly skin and fascia and medial border of sternomastoid.  Below that level: sternomastoid and strap muscles. *Anatomical relations of internal carotid a. within carotid sheath:  42 - Post : Sympathetic trunk → prevertebral ms → transverse processes of C1- C3. - Medially : Lateral wall of the pharynx. - Antero. Lat.: o Covered throughout its length by sternomastoid muscle. o On its upper part: styloid process and muscles separate it from ECA. - N.B.: At the base of the skull the ICA bcome ant. to IJV and enters carotid canal, the internal jugular vein and vagus nerve passes through the jugular formen. *Anatomical relations of external carotid artery: - Med.: oAt lower level → lat. wall of pharynx. oAt higher level → styloid process separates it from ICA. - Antero lat.: oAt 1st → ant. part of sternomastoid. oThen passes deep to post. belly of digasteric and styloid before entering the substance of parotid gland. *Branches of external carotid artery : Fig. 443 F.G. - They anastmose with : oEach other. oOpposite side. oICA branches. oSubclavian a. branches. 1- Sup. thyroid a. : * Arise close to origin. * Pass inferiorly to supply thyroid. * Anastomose with inf. thyroid a. 2- Ascending pharyngeal a.: * Ascends deep to ECA on lat. wall of pharynx. * Supplies: -Pharynx. -Meninges → through meningeal braches passes through foramen lacerum.  43 3- Lingual a.: (Fig. 446 F.G.) Arise anteriorly and runs upwards and medially then curve forwards and down wards towards the hyoid bone then run under the muscles arise from that bone to supply tongue and floor of the mouth. *N.B.: The lingual a. may arise with the fascial artery as a common trunk, lingulo fascial trunk. 4- Fascial a. :( Fig. 449 FG): - Emerges abase level of hyoid. - Pass upwards deep to the ramus of mandible grooving the posterior part of the submandibular gland → hooks around the inf. border of the ramus of the mandible. - Supplies : oMuscles and tissues of face. oSubmandibular gland. oSoft palate and tonsils. 5- Occipital a.: - Emerges posterior opposite to origin fascial a. - Cross the IJV and ICA to the post. part of the scalp. - Supply: oScalp. oGive muscular branches to the neck. oGive meningeal branches → supply dura of posterior cranial fossa. oIn 2/3 of people, it give fine stylomatoid a. → which pass through stylomastoid F. to supply middle and inner ear. 6- Post. auricular a.: - Arise post. pass ( ) styloid process and parotid gland. - Supply : oScalp, parotid, ear pinna. oMuscular branches to neck. oIn 1/3 population give rise to stylomastoid a. 7- Superficial temporal artery: - Smaller of 2 terminal branches.  44 - Arise within the parotid gland and crosses over the post. part of the zygomatic arch to give ant. and posterior branches. - Supply : oScalp and pericranium. oGive branches to : - Parotid - TMJ. - External ear. - Anastmose with lacrimal and palpebral branches of ophthalmic a. 8- Maxillary artery: (Fig. 455)  The longer of the 2 terminal branches. o Arise within the parotid gland and divided into 3 parts by lat. pterygoid ms:  1st (mandibular) part: passes deep to the neck of the mandible.  2nd (pterygoid) part: Runs forward ( ) tendon of temporalis and inf. head of lat. pterygoid.  3rd part (pterygopalatine) : pass ( ) upper and lower heads of lat. ptyerygoid and enter pterygo palatine fossa through pterygomexillary fissure.  Branches : o Of 1st part : o Middle meningeal a.:  Enter skull through f. spinosum.  Supply dura and bone of cranium. o Accessory meningeal a.:  Pass through F. ovale  May arise from middle meningeal a. o Inf. dental a. → supply structures of lower jaw. o Of 2nd part : Branches to : o Masseter. o Pterygoid. o Temporalis. o Of 3rd part: o Sup. dental a.:  Arise as artery enters pterygo-palatine fossa.  Supply structures of upper jaw. o Infra-orbital a.:  Enter orbital cavity through infra orbital fissure.  Supply contents of orbit. o Greater palatine a. :  Pars through greater palatine foramen.  45  Supply tonsils, ums, mm and palate of roof of mouth. o Sphenopalatine : ( terminal branch)  Pass from sphenopalatine foramen to nasal cavity.  Supply nasal structures and sinuses. Radiology of the carotid vessels 1-U.S.: - CCA and bifurcation imaged using ↑ frequency probe (7.3-10mk/z). - ECA and ICA can be identified by : oSuperior thyroid branch of ECA. oCarotid sinus at the root of ICA. - U.S. is useful for assessment of inner wall of vessels which should appear smooth in normal patient. 2-Angiography: - Performed : oEither conventional or oDigital system to "subtract". - Provided visual map of vessels injected. - Content can be injected into : oArch of aorta. oSelective inject in CCA. oSelective inject in ECA (rare). oSelective injection ICA (to assess IC pathology). Variations in the anatomy:  Left. CCA may arise with the brachiocephalic trunk (commonest var in aortic arch vessels "seen in 22% of population").  Right CCA may arise from arch of aorta.  CCAs arise from single trunk.  Cong. Absence of internal or external carotid a. may occur rarely. 3-C.T. and MRI: - Carotid vessels may be identified by both modalities.  46 - Pathology in neck may displace or involve the vessels. - Symmetry ( ) 2 sides should be evident in normal cases. - MRI advantages : oImage vessels at any plane. oVessels may be imaged at the thoracic inlet without any form of bone artifact. oCoronal imaging allows assessment of their origin from aortic arch. oMRA → used to visualize vessels and their branches. Venous drainage of the head and neck 1. Fascial vein: - Drains: 1- ant. part of scalp. 2- fascial structures. - Arise from angle of the eye and runs postero-inferiorly to the angle of the mandible. - It drains into IJV. 2. Retromandibular vein: - Formed by joining of : o Superficial temporal vein (drains scalp). o Maxillary vein (drain infra temporal fossa). - It runs downwards through the parotid gland deep to fascial nerve and superficial to ECA. - Ends by dividing into : o Ant. branch → join fascial v. → to drain in IJV. o Post. auricular v. to form the external jugular vein. 3. IJV: - Formed at the jugular forman as a continuation of sigmoid sinus. - Descends in the carotid sheath lat. to its artery and passes behind the medial end of clavicle to joint the subclavian veins. - Tributaries (Fig. 488 F.G.): o Vein drains inf. petrosal sinus. o Fascial vein. o Lingual veins. o Superior and middle thyroid veins. - Thoracic duct drains at the junction ( ) lt. IJV and Lt. subclavian. - Right lymphatic duct usually drain at the junct a. ( ) rt. IJV and rt. subclavian.  47 4. The ext. jugular vein: - Descends superficial to sternomastoid and pierces the cervical fascia above the mid point of clavicle to enter the subclavian vein. 5. Ant. jugular vein: - Arises at the level of the hyoid bone near the midline, it passes downwards and laterally, passing deep to sternomastoid to enter the EJV behind the clavicle. - Jugular arch → V. shaped communication ( ) the 2 ant. jugular veins above the, manibrium sterni. - The vertebral vein → exit from transverse formen of C6 and runs downwards and forwards to drain into subclavian vein. Radiology of veins of the head and neck - They are not imaged specifically. - The neck veins are identified on cross sectional imaging techniques such (U.S., C.T. and MRI). * The subclavian a.a in the neck Origin: - The right subclavian → from the bifurcation of the brachiochephalic trunk. - The left subclavian → arch of aorta in front of the trachea at level of T5- T4 disc space and ascend on the left of the trachea to behind the left sternoclavicular joint → from this point both a.a have some course. Parts: - Both a.a are divided into 3 parts by scalenus ant. muscle (passes from transverse processes of the upper cervical vertebrae o the inner border of the 1st rib. o 1st part: arches over of apex of the rung and lies deeply in the neck. o 2nd part: Passes laterally behind scalenus ant. muscle which separates it from subclavian vein. o 3rd part: Passes to the lat. border of the 1st rib → to become axillary artery. Branches : A. Branches of 1st part :  48 1- Vertebral a. : - Enter the transverse foramen of C6 and passes through transverse fromina of C6-C1 then arches medially and enter cranial cavity through foramen magnum. - In neck → supplies : o Vertebral ms. o Spinal cord. 2-Internal mammary a. : - Descends behind costal cartilages of ribs about 2cm from lat. border of the sternum. - It supplies the anterior mediastinum, ant. pericardium, the sternum and ant. chest wall. 3-Thyrocervical trunk: - Arise close to medial border of scalenus. - Trifurcates immediately into 3 branches: o Inf. thyroid → pass lower pole of thyroid. o Subscapular supply muscles of shoulder. o Transverse cervical region and share in the scapular anastmosis. B. Branches of the 2nd part: Costocervical artery: (may arise from 1st part on left side). - It divides into : o Superior intercostal a. o Deep cervical branches. C. Branches of the 3rd part: dorsal scapular artery. * The subclavian veins in neck - Start as continuation of axillary vein at the outer border of 1st rib. - Ends by joining to IJV to form brachiosephalic vein. - It grooves the superior surface of the rib 1st. - Relations : oAnt.: clavicle. oPost: Scalenus ant. muscle separating it from subclavian a. - Tributaries : oEJV (on both sides). oThoracic duct (on lt. side). oRight lymphatic duct (on right side). At junction with brachiocephalic vein.  49 Radiology of subclavian vessels 1. Angiography: - Subclavian arteries are bet. demonstrated by angiography. - Subclavian veins are best demonstrated by venography with an injection into one of the veins in the arm. 2. U.S.: - Difficult technique as subclavian vessels are overlaid by bone and lung and neither of them transmits U.S. wanes. 3. C.T. and MRI: - Subclavian vessels can be imaged by both modalities. - C.T. → visualization is improved by IV contrast. - MRI: o Allow imaging of the vessels along their axis. o Breathing make MRI difficult. The brachial plexus 46 ‫الرسم ص‬ Roots → Trunks → Divisions → Cords → Nerve trunks C5-T1 (post ∆ of the (behind the (at the neck) clavicle) axilla) C5/C6-Cy-C8/T1 Ant. Post. - Roots from C5-T1. - Roots unite to form 3 trunks (upper C5/C6, Middle C7, lower C8/T1). - Each trunk divides into (Ant. – post.) division. oThe ant. divisions supply the flexor and the post. division supply the extensor divisions of the arm. - 3 cords are formed from divisions : oAnt. divisions of middle and upper trunk → lat. cord. oAnt. division of lower trunk → medial cord. oPost. divisions of three trunks → post. cord. - The main nerve trunks of the arm arise from these cords : oMedial cord continues as ulnar n. oLat. cord continues as musculo-skeletal n. o Median nerve formed of fibers from both medial and lat. cords.  50 oPost. cord gives radial and axillary n. Radiology of brachial plexus - In traumatic plexopathy → CT and CT myelography can be used. - In all other circumstances brachial plexus is imaged by MRI. oOn MRI nerves are iso-or hypo-intense compared with muscles on T1 or T2 weighted images. oT1 weighted images is best as nerves are surrounded by fat. oAxial coronal and sagittal images are used for imaging.