Middle Ear Anatomy : Ossicles, Mastoid, Intratympanic Muscles, Blood Supply & Lymphatics " Part 2 " скачать в хорошем качестве

Middle Ear Anatomy : Ossicles, Mastoid, Intratympanic Muscles, Blood Supply & Lymphatics " Part 2 "

Mastoid Complex The mastoid antrum (2 mL volume in adults) connects to the attic via the aditus. Its air cell system includes: Various cell types (zygomatic, tegmen, perisinus, etc.) Three pneumatization patterns: cellular (well-developed), diploetic (marrow-containing), and sclerotic (non-pneumatized) Important surgical landmarks like MacEwen's triangle Korner's septum: A potentially misleading bony partition during surgery Middle Ear Contents Ossicular Chain Three bones conduct sound: Malleus (9 mm long): Head/neck in attic Handle embedded in tympanic membrane Processes for ligamentous attachments Incus: Body articulates with malleus Long process (prone to necrosis) connects to stapes via lenticular process Stapes: Footplate (3 × 1.4 mm) in oval window Posterior crus longer/thicker than anterior Head articulates with incus Muscles Tensor tympani: CN V3-innervated Tenses tympanic membrane via malleus Stapedius: CN VII-innervated (smallest human muscle) Dampens loud sounds via stapes Paralysis causes hyperacusis Neurovascular Structures Tympanic plexus (on promontory): Formed by Jacobson's nerve (CN IX) and caroticotympanic nerves Provides sensory and secretomotor (parotid) innervation Arterial supply: Six branches from external/internal carotid systems Mainly from maxillary and stylomastoid arteries Venous drainage: To pterygoid plexus and superior petrosal sinus Clinical Correlations Several anatomical features have surgical importance: The cog and sinus tympani represent challenging areas for complete cholesteatoma removal Korner's septum may mislead surgeons during mastoidectomy Facial nerve dehiscences create infection/injury vulnerability The stapes' long process is often the first ossicular structure eroded in disease Round window membrane serves as a landmark for singular neurectomy