Ear Anatomy PDF

THE EAR I & II  THE EAR IS AN ORGAN OF HEARING IS ALSO CONCERNED WITH MAINTAINING BODY EQUILIBRIUM/BALANCE COMPOSED OF 3 MAIN PARTS: THE EXTERNAL, MIDDLE AND INTERNAL EAR THE OUTER EAR IS CALLED THE PINNA AN...

THE EAR I & II  THE EAR IS AN ORGAN OF HEARING IS ALSO CONCERNED WITH MAINTAINING BODY EQUILIBRIUM/BALANCE COMPOSED OF 3 MAIN PARTS: THE EXTERNAL, MIDDLE AND INTERNAL EAR THE OUTER EAR IS CALLED THE PINNA AND IS MADE OF RIDGED CARTILAGE COVERED BY SKIN. SOUND FUNNELS THROUGH THE PINNA INTO THE EXTERNAL AUDITORY/ACOUSTIC MEATUS , A SHORT TUBE THAT ENDS TO THE TYMPANIC MEMBRANE. SOUND CAUSES THE TYMPANIC MEMBRANE AND ITS TINY ATTACHED BONES (OSSICLES) IN THE MIDDLE PORTION OF THE EAR TO VIBRATE, AND THE VIBRATIONS ARE CONDUCTED TO THE NEARBY COCHLEA. THE SPIRAL-SHAPED COCHLEA IS PART OF THE INNER EAR; IT TRANSFORMS SOUND INTO NERVE IMPULSES THAT TRAVEL TO THE BRAIN. THE FLUID-FILLED SEMICIRCULAR CANALS ATTACH TO THE VESTIBULE & COCHLEA AND NERVES IN THE INNER EAR SEND INFORMATION ON BALANCE AND HEAD POSITION TO THE BRAIN. THE EUSTACHIAN (AUDITORY) TUBE VENTILATE THE MIDDLE EAR SPACE, ENSURING THAT ITS PRESSURE REMAINS AT NEAR NORMAL ENVIRONMENTAL AIR PRESSURE, IT ALSO DRAINS FLUID FROM THE MIDDLE EAR INTO THE THROAT (PHARYNX) BEHIND THE NOSE. © 2014 WebMD, LLC. All rights reserved.  THE EXTERNAL EAR AURICLE/PINNA EXTERNAL ACOUSTIC MEATUS TYMPANIC MEMBRANE/EARDRUM  THE AURICLE IT IS COMPOSED OF A SINGLE CRUMPLED PLATE OF ELASTIC CARTILAGE WHICH IS LINED ON BOTH SIDES WITH SKIN. THE LOWEST PART OF THE AURICLE CONSISTS ONLY OF CONNECTIVE TISSUE COVERED BY SKIN AND IS TERMED THE LOBULE. TRAPS SOUND WAVES AND CHANNELS THEM THROUGH TO THE EXTERNAL ACOUSTIC MEATUS.  THE AURICLE BLOOD SUPPLY NERVE INNERVATION  LYMPHATIC DRAINAGE PRE-AURICULAR POST AURICULAR SUPERFICIAL CERVICAL NODES  THE EXTERNAL ACOUSTIC MEATUS IS ALSO CALLED THE EXTERNAL AUDITORY MEATUS/CANAL CONDUCTS SOUNDS WAVES TOWARDS THE TYMPANIC MEMBRANE (EARDRUM) IS ABOUT 24MM LONG (MEDIAL 2/3RD-16MM BONY AND LATERAL 1/3RD -8MM CARTILAGINOUS) THE BONY PART IS FORMED BY THE TYMPANIC PLATE OF THE TEMPORAL BONE. THE CARTILAGINOUS PART IS FILLED WITH FIBROUS TISSUE AND IS LINED WITH SKIN WHICH IS ADHERENT TO THE PERICHONDRIUM AND CONTAINS HAIRS, SEBACEOUS GLANDS AND CERUMINOUS (WAX) GLANDS.  THE EXTERNAL ACOUSTIC MEATUS BLOOD SUPPLY & VENOUS LYMPHATIC DRAINAGE DRAINAGE OUTER PART OF CANAL- SUPERFICIAL PREAURICULAR NODES TEMPORAL & POST AURICULAR BRANCHES POSTAURICULAR NODES INNER PART OF CANAL- DEEP AURICULAR SUPERFICIAL CERVICAL NODES BRANCH OF THE MAXILLARY ARTERY AND ACCOMPANYING VEIN  THE EXTERNAL ACOUSTIC MEATUS NERVE INNERVATION SKIN LINING THE ANTERIOR PART OF THE MEATUS IS SUPPLIED BY THE AURICULOTEMPORAL NERVE. SKIN LINING THE POSTERIOR PART OF THE MEATUS IS SUPPLIED BY THE AURICULAR BRANCH OF THE VAGUS NERVE.  THE TYMPANIC MEMBRANE IS A THIN TRANSLUCENT PARTITION BETWEEN THE EAM & THE MIDDLE EAR OVAL IN SHAPE PLACED OBLIQUELY AT A 55˚ ANGLE WITH THE FLOOR OF THE MEATUS OUTER SURFACE LINED WITH SKIN AND IS CONCAVE INNER SURFACE PROVIDES ATTACHMENT TO THE HANDLE OF THE MALLEUS EXTENDING UP TO ITS CENTER AND IS CONVEX MAXIMUM POINT OF CONVEXITY CALLED THE UMBO  THE TYMPANIC MEMBRANE IS THICKENED AT ITS CIRCUMFERENCE AND IS FIXED TO THE TYMPANIC SULCUS OF THE TEMP. BONE SUP. THE SULCUS IS DEFICIENT AND HERE THE MEMBRANE IS ATTACHED TO THE TYMPANIC NOTCH, FROM THE ENDS OF THE NOTCH TWO BANDS (ANT & POST) MALLEOLAR FOLDS ARE PROLONGED TO THE LAT. PROCESS OF THE MALLEUS. PARS TENSA- TIGHTLY STRETCHED PART OF MEMBRANE PARS FLACCIDA- LOOSE PART LOCATED BETWEEN THE TWO MALLEOLAR FOLDS  THE MIDDLE EAR ALSO REFERRED TO AS THE TYMPANIC CAVITY/TYMPANIUM AIR FILLED CAVITY WITHIN THE PETROUS PART OF TEMPORAL BONE BETWEEN THE INTERNAL AND EXTERNAL EAR SHAPED LIKE A CUBE, CAN BE SUBDIVIDED INTO THE TYMPANIC CAVITY PROPER AND THE EPITYMPANIC RECESS  THE MIDDLE EAR COMMUNICATIONS CONTENTS ANTERIORLY- NASOPHARYNX THROUGH THE OSSICLES: MALLEUS, INCUS &STAPES AUDITORY TUBE LIGAMENTS OF THE OSSICLES POSTERIORLY- MASTOID ANTRUM AND TWO MUSCLES: TENSOR TYMPANI AND THE MASTOID AIR CELLS. STAPEDIUS MUSCLE VESSELS SUPPLYING AND DRAINING THE MIDDLE EAR NERVES: CHORDA TYMPANI & THE TYMPANIC PLEXUS OF NERVES  THE MIDDLE EAR BOUNDARIES ROOF- TEGMENTAL WALL FLOOR- JUGULAR WALL ANTERIORLY- CAROTID WALL POSTERIORLY- MASTOID WALL LATERALLY- MEMBRANOUS WALL MEDIALLY- LABYRINTHINE WALL  THE MIDDLE EAR BLOOD SUPPLY: ANTERIOR TYMPANIC LYMPHATIC DRAINAGE: PREAURICULAR AND BRANCH OF THE MAXILLARY ARTERY, RETROPHARYNGEAL NODES POSTERIOR AURICULAR ARTERY & THE POSTERIOR TYMPANIC ARTERY OF THE STYLOMASTOID BRANCH. NERVE SUPPLY: DERIVED FROM THE TYMPANIC PLEXUS, TYMPANIC BRANCH OF THE GLOSSOPHARYNGEAL NERVE (MUCOUS VENOUS DRAINAGE: SUPERIOR PETROSAL MEMBRANE, AUDITORY TUBE, MASTOID SINUS & THE PTERYGOID PLEXUS OF VEINS. ANTRUM & AIR CELLS), SUP. & INF. CORTICOTYMPANIC NERVE (VASOMOTOR TO MUCOUS MEMBRANE)  THE MIDDLE EAR FUNCTIONS TRANSMITS SOUND WAVES FROM THE EXTERNAL EAR TO THE INTERNAL EAR THOROUGH THE CHAIN OF EAR OSSICLES TRANSFORMS THE AIRBORNE VIBRATIONS FROM THE TYMPANIC MEMBRANE TO THE LIQUID BORNE VIBRATION IN THE INNER EAR INTENSITY OF SOUND WAVES IS INCREASED TEN TIMES BY OSSICLES BUT THE FREQUENCY OF THE SOUND DOESN’T CHANGE THE EUSTACHIAN (AUDITORY) TUBE VENTILATE THE MIDDLE EAR SPACE, ENSURING THAT ITS PRESSURE REMAINS AT NEAR NORMAL ENVIRONMENTAL AIR PRESSURE, IT ALSO DRAINS FLUID FROM THE MIDDLE EAR INTO THE THROAT (PHARYNX) BEHIND THE NOSE.  THE EAR OSSICLES MALLEUS INCUS RESEMBLES A HAMMER RESEMBLES AN ANVIL IT’S THE LARGEST OF THE 3 AND MOST FOUND BETWEEN THE MALLEUS & STAPES LATERALLY PLACED PARTS : LARGE BODY WITH ARTICULAR PARTS: ROUNDED HEAD, NECK, ANTERIOR SURFACE FOR THE HEAD OF THE MALLEUS, PROCESS, LATERAL PROCESS AND THE LONG PROCESS WHICH PROJECTS HANDLE DOWNWARDS AND PARALLEL WITH THE HANDLE OF THE MALLEUS AND A TIP WITH A LENTIFORM NODULE WHICH ARTICULATES WITH THE HEAD OF THE STAPES  THE EAR OSSICLES STAPES RESEMBLES A STIRRUP IS THE SMALLEST AND MOST MEDIALLY LOCATED PARTS: SMALL HEAD WHICH ARTICULATES WITH THE INCUS, NARROW NECK GIVES INSERTION TO THE TENDON OF THE STAPEDIUS MUSCLE, TWO LIMBS/CRURA WHICH ATTACH TO THE FOOT PLATE/PIECE/BASE.  THE EAR OSSICLES JOINTS OF THE OSSICLES- INCUDOMALLEOLAR (SADDLE) JOINT AND THE INCUDOSTAPEDIAL (BALL & SOCKET) JOINT. BOTH JOINS ARE SYNOVIAL JOINTS SURROUNDED BY CAPSULAR LIGAMENTS. MUSCLES OF THE MIDDLE EAR: TENSOR TYMPANI AND THE STAPEDIUS MUSCLES, ACT SIMULTANEOUSLY TO DAMPEN DOWN THE INTENSITY OF HIGH-PITCHED SOUND WAVES THUS PROTECTING THE INTERNAL EAR.  THE TYMPANIC/MASTOID ANTRUM SMALL, CIRCULAR AIR FILLED SPACE LOCATED IN THE POSTERIOR PART OF THE PETROUS TEMPORAL BONE. MASTOID CELLS: A SERIES OF INTERCOMMUNICATING SPACES OF VARYING SIZES LOCATED USUALLY WITHIN THE UPPER PART OF THE MASTOID PROCESS. AIR CELLS ARE SUPPLIED BY: THE POST TYMPANIC ARTERY AND DRAINED BY THE MASTOID EMISSARY VEIN, POST AURICULAR VEIN AND SIGMOID SINUS. LYMPH DRAINAGE INTO THE POST AURICULAR & UPPER DEEP CERVICAL NODES. NERVE INNERVATION DERIVED FROM THE TYMPANIC PLEXUS OF THE GLOSSOPHARYNGEAL NERVE.  THE INTERNAL EAR ALSO KNOWN AS THE LABYRINTH LIES IN THE PETROUS PART OF TEMPORAL BONE CONSIST OF A BONY LABYRINTH WITHIN WHICH A MEMBRANOUS LABYRINTH LIES. MEMBRANOUS LABYRINTH IS FILLED WITH FLUID CALLED THE ENDOLYMPH AND IS SEPARATED FROM THE BONY LABYRINTH VIA ANOTHER FLUID CALLED THE PERILYMPH  THE BONY LABYRINTH CONSISTS OF 3 PARTS: THE COCHLEAR (ANTERIORLY), THE VESTIBULE ( IN THE MIDDLE) AND THE SEMICIRCULAR CANALS (POSTERIORLY). COCHLEA- BONY AND RESEMBLES A SHELL OF A COMMON SNAIL, FORMS THE ANTERIOR PART OF THE LABYRINTH. HAS A CONICAL CENTRAL AXIS KNOWN AS THE MODIOLUS AROUND WHICH THE COCHLEAR CANAL MAKES 2,75 TURNS  THE BONY LABYRINTH A SPIRAL RIDGE OF THE BONE ( SPIRAL LAMINA) PROJECTS FROM THE MODIOLUS AND PARTLY DIVIDES THE COCHLEAR INTO THE SCALA VESTIBULI AND THE SCALA TYMPANI. THIS DIVISION IS COMPLETED BY THE BASILAR MEMBRANE. AT ITS APEX THE SCALA VESTIBULI COMMUNICATES WITH THE SCALA TYMPANI VIA A SMALL OPENING (HELICOTREMA) THE FUNCTION OF THE COCHLEA IS TO TRANSFORM THE VIBRATIONS OF THE COCHLEAR LIQUIDS AND ASSOCIATED STRUCTURES INTO A NEURAL SIGNAL. THIS OCCURS AT THE ORGAN OF CORTI, WHICH IS LOCATED ALL ALONG THE COCHLEA  THE BONY LABYRINTH VESTIBULE- CENTRAL PART OF THE BONY LABYRINTH. LIES MEDIAL TO THE MIDDLE EAR AND OPENS INTO THE MIDDLE EAR AT THE FINESTRA VESTIBULI WHICH IS CLOSED BY THE FOOTPLATE OF THE STAPES. 3 SEMICIRCULAR CANALS OPEN INTO ITS POST. WALL, WHILE ITS MEDIAL WALL IS RELATED TO THE IAM THE UTRICLE AND SACCULE WITHIN THE VESTIBULE RESPOND TO CHANGES IN THE POSITION OF THE HEAD WITH RESPECT TO GRAVITY  THE BONY LABYRINTH SEMICIRCULAR CANALS- THERE ARE 3 THEY ARE LINED WITH CILIA (MICROSCOPIC CANALS LOCATED ( ANT./SUP., POST. & HAIRS) AND FILLED WITH A LIQUID LATERALLY). SUBSTANCE, KNOWN AS ENDOLYMPH. THEY LIE POSTERIOR/RSUPERIOR TO THE EVERY TIME THE HEAD MOVES, THE VESTIBULE AND ARE AT RIGHT ANGLES TO ENDOLYMPH MOVES THE CILIA. THIS WORKS EACH OTHER. AS A TYPE OF MOTION SENSOR, AS THE MOVEMENTS OF THE CILIA ARE EACH CANAL IS DILATED AT ONE END TO COMMUNICATED TO THE BRAIN. FORM THE AMPULLA AND OPEN INTO THE VESTIBULE VIA 5 OPENINGS. THE SEMICIRCULAR CANALS RESPOND TO ROTATIONAL MOVEMENTS  THE MEMBRANOUS LABYRINTH IS A CONTINUOUS ENCLOSED CAVITY FILLED WITH ENDOLYMPH. CONTAINS SPECIALIZED EPITHELIUM ( RECEPTORS FOR SOUND FOR ORGAN OF CORTI), MACULAE FOR STATIC BALANCE & THE CRISTAE FOR KINETIC BALANCE. CONSIST OF 3 MAIN PARTS: SPIRAL DUCT OF THE COCHLEA/ORGAN OF HEARING, THE UTRICULE & SUCCULE/ ORGAN FOR STATIC BALANCE AND THE SEMICIRCULAR DUCTS/ORGANS FOR KINETIC BALANCE THE END