ANATOMY OF EXTERNAL ANDMIDDLE EAR

                                                    BY

                     K.S RAMA RAJU

EXTERNAL EAR:-PINNA:-

EMBRYOLOGY:PERIOD OF DEVLOPMENT=4th-6thwk OF INTRAUTERINE LIFE CONTRIBUTION ARCHES= 1st &2nd BRANCHIAL ARCHES 1st ARCH=TRAGUS, 2nd ARCH=REST OF PINNA 6 HILLOCKS ARE FORMED FROM CONDENSATION OF MESODERM OF 1st AND 2nd ARCHES

ANOMALIES: PRE AURICULAR SINUS ABNAORMAL SHAPES OF PINNA:

1. BAT EAR

2. WILDERMUTH'S EAR

3. MOZART'S EAR MICROTIA SYNOTIA MELOTIA

ANATOMY OF PINNA: FRAMEWORK : MADE OF YELLOW ELASTIC CARTILAGE EXCEPT LOBULE CYMBA CONCHA: BENEATH IT LIES MAC EWEN'S TRIANGLE,A LANDMARK FOR MASTOID ANTRUM INCISURA TERMINALIS BETWEEN TRAGUS AND ANTERIOR CRUS OF HELIX DEVOID OF CARTILAGE SITE OF INCISION FOR ENDAURAL APPROACHLIGAMENTS OF PINNA:1. 2 EXTRINSIC LIGAMENTS:2. INTRINSIC LIGAMENTS :MUSCLES OF PINNA: 3 EXTRINSIC MUSCLES1. AURICULARIS ANTERIOR 2. AURICULARIS SUPERIOR 3. AURICULARIS POSTERIOR4. THESE MUSCLES SUPLIED BY TEMPORAL & POSTERIOR AURICULAR BRANCH OF FACIAL NERVE

ARTERIAL SUPPLY OF PINNA: SUPPLIED BY BRANCHES OF EXTERNAL CAROTID ARTERY

POSTERIOR AURICULAR ARTERY:

1. MEDIAL SURFACE (EXCEPT LOBULE)

2. CONCHA

3. MIDDLE AND LOWER PORTIONS OF HELIX

4. LOWER PART OF ANTIHELIX

AURICULAR BRANCH OF SUPERFICIAL TEMPORAL ARTERY:

1. UPPER PORTIONS OF HELIX AND ANTIHELIX

2. TRIANGULAR FOSSA

3. TRAGUS

4. LOBULE

NERVE SUPPLY:SENSORY INNERVATION FROM:

1. GREATER AURICULAR NERVE

2. LESSER OCCIPITAL NERVE

3. AURICULAR BRANCH OF VAGUS NERVE

4. AURICULO TEMPORAL NERVE

5. FACIAL NERVE

EXTERNAL AUDITORY MEATUS:

EMBRYOLOGY:DEVLOPS FROM 1st BRANCHIAL CLEFT AT 16th EMBRYONIC WEEK CELLS PROLIFERATE FROM BOTTOM OF ECTODERMAL CLEFT TO FORM MEATAL

PLUG WHICH LATER RECANALISES STARTING FROM DEEPER PART

ANOMALIES:

1. COMPLETE ATRESIA

2. SHALLOW DEPRESSION OF CANAL

3. CHANGE IN THE CURVATURE

4. STENOSIS

ANATOMY OF E.A.C:LENGTH =24mm

1. CARTILAGENOUS PART=8mm

2. BONY PART=16mm FISSURE OF SANTORINI:VERTICAL FISSURE IN THE ANTERIOR PART OF CARTILAGE OF EAC

THROUGH THIS THE PAROTID AND MASTOID INFECTION APPEARS IN THE CANAL &VICE VERSA

ROOF OF E.A.C=SQUAMOUS TEMPORAL BONE MOST OF THE CANAL=TYMPANIC BONESUTURES: ANTERIOR TYMPANO SQUAMOUS SUTURE POSTERIOR TYMPANO MASTOID SUTURECONSTRICTIONS: JUNCTION BETWEEN CARTILAGE AND BONY PORTIONS ISTHMUS(5mm FROM T.M)ANTERIOR RECESS: DEEP TO ISTHMUS,ANTERO-INFERIOR PART OF CANAL WALL DIPS FORWARDS FORMING RECESS WHICH IS

DIFFICULT TO SPOT

ARTERIAL SUPPLY OF E.A.C:

ROOF AND ANTERIOR PART OF CANAL=AURICULAR BRANCH OF SUPERIOR TEMPORAL ARTERY POSTERIOR PORTION OF CANAL=AURICULAR BRANCH OF POSTERIOR AURICULAR ARTERY

NERVOUS SUPPLY: ANTERIOR WALL & ROOF=AURICULOTEMPORAL NERVE(V3) POSTERIOR WALL & FLOOR=AURICULAR BRANCH OF VAGUS

VEINS: EXTERNAL JUGULAR VIEN MAXILLARY VIEN PTERYGOID PLEXUS

TYMPANIC MEMBRANE:

EMBRYOLOGY:

OUTER EPIDERMAL LAYER OF T.M=1st PHARYNGEAL GROOVE(ECTODERM)

MIDDLE FIBROUS LAYER=MESODERM INNER MUCOUS LAYER=1st BRANCHIAL POUCH(ENDODERM)

ANATOMY:

• PARS FLACCIDA=LESS STIF FDUE TO PRESENCE OF SPARSE DISORGANISED FIBROUS TISSUE 

• PARS TENSA-LARGE,STIFF,VIBRATING SURFACE OF T.M

BLOOD SUPPLY OF T.M:OUTER SURFACE OF T.M:

DEEP AURICULAR BRANCH OF MAXILLARY ARTERYINNER SURFACE OF T.M:

ANTERIOR TYMPANIC BRANCH OF MAXILLARY ARTERY POSTERIOR TYMPANIC BRANCH OF STYLOMASTOID ARTERY INFERIOR TYMPANIC BRANCH OF ASCENDING PHARYNGEAL ARTERYNERVE SUPPLY OF T.M:

LATERAL SURFACE=

ANTERIOR PART=AURICULO TEMPORAL NERVE POSTERIOR PART=VAGUS NERVE

MEDIAL SURFACE=GLOSSOPHARYNGEAL NERVE

EMBRYOLOGY OF MIDDLE EAR:PHARYNGEAL POUCH:-PROXIMAL NARROW PART=EUSTACHIAN TUBEDISTAL DILATED PART=             1.TYMPANIC CAVITY             2.ANTRUM             3. ATTIC             4.MASTOID AIR CELLSOSSICLES=   1st ARCH CARTILAGE=1.HEAD OF MALLEUS                                             2.BODY OF INCUS    2nd ARCH CARTILAGE=1.HANDLE OF MALLEUS                                               2.LONG PROCESS OF INCUS                                               3.CRURA OF STAPES   OTIC CAPSULE=FOOT PLATE OF STAPES

COMPARTMENTS AND FOLDS OF TYMPANIC CAVITY:

ATTIC COMPARTMENT:1. ANTERIOR COMPARTMENT2. POSTERIOR COMPARTMENT                       A)  SUPERIOR INCUDAL SPACE                        B) MEDIAL INCUDAL SPACE   COMPARTMENT OF MESOTYMPANUM     1.ANTERIOR MALLEOLAR FOLD      2.POSTERIOR MALLEOLAR FOLD                                      

TYMPANIC CAVITY(MIDDLE EAR):

DIVIDED IN TO 3 PARTS:1. EPITYMPANUM (ATTIC)2. MESOTYMPANUM3. HYPOTYMPANUM

LATERAL WALL OF MIDDLE EAR: FORMED BY   1.BONY LATERAL WALL OF EPITYMPANUM-               SCUTUM-EROSION CAUSE TELLTALE SIGN                   ON CT   2.TYMPANIC MEMBRANE   3.BONY LATERAL WALL OF HYPOTYMPANUM PETROTYMPANIC FISSURE:       RECIEVES:1.  ANTERIOR MALLEOLAR LIGAMENT2.  ANTERIOR TYMPANIC BRANCH OF

MAXILLARY ARTEY

CANAL OF HUGIER:MEDIAL WALL OF PETROTYMPANIC FISSURE THROUGH WHICH CHORDA TYMPANI RUNS OUT

COURSE OF CHORSA TYMPANI

ROOF OF THE MIDDLE EAR:

TEGMEN TYMPANI:  FORMED BY PETROUS AND SQUAMOUS PORTION OF TEMPORAL BONE

PETOSQUAMOUS SUTURE:ROUTE OF INFECTION IN TO EXTRA DURAL SPACE IN CHILDREN

  

FLOOR OF MIDDLE EAR:

FORMED BY :-PNEUMATISED BONE

SEPARATES FROM JUGULAR BULB

TYMPANIC BRANCH OF GLOSSOPHARYNGEAL NERVE ENTERS AT JUNCTION BETWEEN FLOOR AND MEDIAL WALL

MEDIAL WALL OF THE MIDDLE EAR:

THREE DEPRESSIONS:

1. OVAL WINDOW 2. ROUND WINDOW3. SINUS TYMPANI FACIAL NERVE CANAL DOME OF THE LATERAL

SCC:-POSTERIOR AND LATERAL TO FACIAL CANAL

ANTERIOR WALL OF MIDDLE EAR:-

LOWER 1/3rd:- PLATE OF BONE COVERING CAROTID ARTERYMIDDLE 1/3rd:- 1.EUSTACHIAN TUBE 2.CANAL FOR TENSOR  TYMPANI 

UPPER 1/3rd:-HAS ANTERIOR EPITYMPANIC SINUS ANTERIOR TO OSSICLE HEADS&CAN HIDE CHOLESTEATOMA IN CANAL WALL UP SURGERIES                                

POSTERIOR WALL:- ADITUS PROCESSUS PYRAMIDALIS VERTICAL PORTION OF FACIAL NERVE FACIAL  RECESS (SUPRAPYRAMIDAL RECESS) SINUS TYMPANI (INFRA PYRAMIDAL RECESS)

MUCOSA OF TYMPANIC CAVITY:- MUCOUS SECRETING RESPORATORY CILIATED EPITHELIUM VENTILATION ROUTE FROM MESOTYMPANUM AND

EPITYMPANUM IS VIA TWO SMALL OPENINGS1. ANTERIOR ISTHMUS TYMPANI2. POSTERIOR ISTHMUS TYMPANIPRUSSAK'S SPACE:-SITE FOR CHOLESTEATOMA      LATERALLY=PARS FLACCIDA      MEDIALLY  = NECK OF MALLEUS      INFERIORLY=LATERAL PROCESS OF MALLEUS      SUPERIORLY=LATERAL MALLEOLAR FOLD

BLOOD SUPPLY OF MIDDLE EAR:-

FROM BRANCHES OF :1. MIDDLE MENINGEAL ARTERY2. MAXILLARY ARTERY3. ASCENDING PHARYNGEAL ARTERY4. STYLOMASTOID BRANCH OF POSTERIOR AURICULAR

ARTERY NERVE SUPPLY:-SENSORY:-IXth CRANIAL NERVE THROUGH TYMPANIC

PLEXUS MOTOR:-1. TENSOR TYMPANI=MANDIBULAR DIVISION OF Vth NERVE2. STAPEDIUS=FACIAL NERVE

COMPONENTS OF TYMPANIC CAVITY:EAR OSSICLES:

MALLEUS=HEAD,NECK,ANTERIOR PROCESS,LATERAL PROCESS ,HANDLE

INCUS=BODY,SHORT PROCESS,LONG PROCESS,LENTICULAR PROCESS

STAPES=HEAD,NECK,ANTERIOR CRURA,POSTERIOR CRURA,FOOT PLATE

LONG AXIS OF STAPES IS ALWAYS HORIZONTAL

MUSCLES OF MIDDLE EAR:1. TENSOR TYMPANI2. STAPEDIUS:-SUPPLIED BY A BRANCH OF

MANDIBULAR NERVE

NERVES:3. CHORDA TYMPANI4. TYMPANIC PLEXUS

EUSTACHIAN TUBE ANATOMY:

2 PARTS BONY PART (12mm) CARTILAGENOUS PART(24mm) MUSCLES ATTACHED: TENSOR TYMPANI: N.S=MANDIBULAR NERVESEPARATES

TUBE FROM OTIC GANGLION MANDIBULAR NERVE CHORDA TYMPANI MIDDLE MENINGEAL ARTERY                                                        contd

CONTD:2.SALPHINGO PHARYNGEUS: 3.LEVATOR PALATIN.S FOR THESE MUSCLES=PHARYNGEAL PLEXUS

ARTERIAL SUPPLY OF TUBE:1.ASCENDING PHARYNGEAL ARTERY2.MIDDLE MENINGEAL ARTERY

NERVE SUPPLY OF TUBE:1.PHARYNGEAL Br OF SPHENO PALATINE GANGLION=OSTIUM2.NERVOUS SPINOSUS(Vc)=CARTILAGE PART3.TYMPANIC PLEXUS=BONY PART

MASTOID AIR CELLS SYSTEM: MASTOID ANTRUM:   AIR FILLED SPACE WITHIN PETROUS   PART OF TEMPORAL BONE RELATIONS RIDGE FORMED BY DIGASTRIC MUSCLE IN THE

MASTOID LIES LATERAL TO SIGMOID SINUS AND FACIAL NERVE(LANDMARK)

MAC EWEN,S TRIANGLE PETROUS APEX GRADENIGO'S SYNDROME KOCHER'S SEPTUM