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Base of skull

8 Pages

Course Code
Dirk De Clercq

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Basicranium and pharynx Base of skull: bones • occipital, temporalis, sphenoid, vomer, palatines and maxillae • parts of parietals and zygomatics visible basicranial foramina and structures passing thru • incisive foramen o right behind incisors in maxillae o transmits structures from nasal septum  nasopalatine nerve  sphenopalatine artery—terminal branch of maxillary artery (from external carotid) • passes through pterygomaxillary fissure canal • palatine foramina (right behind molars) o greater and lesser palatine nerves and vessels  sensory nerves from maxillary division of CN V  nerves pass through pterygopalatine ganglia  sensory innervation to palate + parasymp taste fibers from VII o greatergoes forward; lessergoes backward on soft palate • foramen ovale o CN V : mandibular nerve o lesser petrosal nerve from middle ear cavity • Foramen lacerum o Jagged opening at junction of occipital, petrous part of temporal and pterygoid part of sphenoid bone o Occupied by cartilage o Small structures passing thru, not significant o Internal carotid artery with sympathetic plexus passes above it o Pterygoid canal starts in front of foramen lacerum, goes into bone  Carries parasymp and taste fibers of VII  Picks up sympathetics on way to pteropalatine ganglia • Foramen spinosum o Sits on edge of spine of sphenoid bone o Middle meningeal vessels; can follow grooves from inside of skull o Meningeal branch of CN V (when return to skull); supplies dura • Carotid canal o Internal carotid artery with carotid plexus enters skull • Jugular foramen o Border of occipital and temporal bones o CN IX, X, XI and internal jugular vein o inferior petrosal sinus enters at front of foramen o sigmoid sinus enters at back of foramen • Stylomastoid foramen o b/w mastoid and styloid process o CN VII: primary motor branch, some sensory • Foramen magnum o Spinal cord, vertebral arteries, spinal accessory nerves (ascending branches of accessory) • Hypoglossal canal (foramen) o CN XII • Condylar canal (fossa)--variable o Back of condyles o Goes to sigmoid sinus o Transmits Emissary vein from sigmoid sinus, vertebral veins, meningeal branch of occipital arch • Mastoid foramen: can be variable o Emissary veins from sigmoid sinus • No valves in system!! o Blood can go inside-out or outside-in Other basicranial features • Choanae (internal nares) o Back of hard palate; two canals o Marks boundary between nasal cavity & nasopharynx • Medial and lateral pterygoid plates of sphenoid o attachment for pterygoid muscles (chewing muscles) and tensor palatine • hamulus of medial pterygoid plate o projection of medial plate: styloform process o pulley for tendon of tensor veli palatini • articular tubercle and mandibular fossa (glenoid) o make up temperomandiublar joint (jaw joint) • pharyngeal tubercle o anterior to foramen magnum o attachment of pharynx to base of skull o one of pharyngeal constrictors attaches • styloid process o slender, 1 inch long o stylopharyngeus muscle, stylohyoid muscle, styloglossus muscle attach o stylohyoid and stylomandibular ligaments attach • auditory tube and external auditory meatus o junction between nasopharynx and middle ear • mastoid processes o sternocleidomastoid and posterior belly of digastric attach o hollow; full of air cells, which are connected to middle ear cavity • occipital condyles o sides of foramen magnum o related to articulation with atlas vertebrae o nodding • external occipital protuberance (inion) o attachment of neck (nuchal) muscles Pharynx (gen’l stuff) • fibromuscular tube • runs along prevertebral fascia from base of skull (pharyngeal tubercle) to inferior border of cricoid cartilage (anterior) and C6 (posterior) • common route for air and food • extends from back of nasal and oral cavities to esophagus • ends where it becomes esophagus and gives off larynx and trachea (anteriorly) • 5 layers (from inside out) o mucosa—lines everything on inside o submucosa o fibrous fascia (pharyngeal basilar fascia) o muscles o buccopharyngeal fascia • pharynx regions o nasopharynx • posterior extension of nasal cavities superior to soft palate • opens thru choanae (internal nares) • contains pharyngeal tonsils or adenoids • form the roof • when inflamed, can block ear tube • contains opening of auditory (pharyngotympanic or Eustachian) tubes • superolateral corner o oropharynx • continuous with oral cavity • extends from soft palate to epiglottis • contains palatoglossal (palate to tongue) and palatopharyngeal (palate to pharynx) arches, palatine tonsils b/w arches o laryngopharynx • posterior to larynx • from epiglottis to lower border of cricoid cartilage, where it becomes continuous w/ esophagus • contains aditus (inlet) of larynx and its piriform recesses • aditus is covered by epiglottis during swallowing • food can get lodged in piriform recesses • can feel laryngeal prominence of trachea o where vocal folds attach o choking is usually above vocal foldsblock larynx o cut below vocal folds—tracheotomy Muscles of pharynx o external muscles: three constrictors o all attach to tendinous midline o circular sphincters for peristalsis o slight overlap b/w superior and middle constrictors and b/w middle and inferior constrictors o not well differentiated o laterally: gaps (see more below) o Superior constrictor  From pterygomandibular raphe and pterygoid hamulus to median raphe and pharyngeal tubercle • Pterygomandibular raphe: boundary b/w buccinator and superior constrictor o Middle constrictor  From hyoid bone and inferior end of stylohyoid ligament to median raphe o Inferior constrictor  From thyroid and cricoid cartilages to median raphe o Internal muscles: longitudinal o Elevate pharynx o Stylopharyngeus  From styloid process to thyroid cartilage  Starts externally then becomes internal o Palatopharyngeus  From palate to thyroid cartilage, side of pharynx and esophagus o Salphingopharyngeus  Considered part of palatopharyngeus  From cartilaginous part of auditory tube (salphinx) to pharynx • Allows you to pull on tube to open ear passage (like on airplane when you chew gum or yawn) o Innervation o Most innervation comes from pharyngeal plexus o Sensory of mucosa: CN IX
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