1. EAR
DEVELOPMENT

2. DEVELOPMENT OF EAR
EXTERNAL EAR
SOUND COLLECTING ORGAN
MIDDLE EAR
SOUND CONDUCTING ORGAN
INTERNAL EAR
CONVERTS SOUND WAVES INTO NERVE IMPULSE
CONTAINS VESTIBULOCOCHLEAR ORGAN
CONCERNED WITH EQUILIBRIUM AND HEARING

3. DEVELOPMENT OF INTERNAL EAR
1---OTIC PLACODE—THICKENING OF ECTODERM
ON EACH SIDE OF RHOMBENCEPHALON
INVAGINATES AND FORMS---
2---OTIC PIT
3---OTIC VESICLE/OTOCYST
PRIMORDIUM OF MEMBRANOUS LABYRINTH

6. DEVELOPMENT OF INTERNAL EAR
OTIC VESICLE
1---VENTRAL COMPONENT
a—SACCULE
b---COCHLEAR DUCT
2---DORSAL COMPONENT
a---UTRICLE
b---SEMICIRCULAR CANALS
c ---ENDOLYMPHATIC DUCT—A DIVERTICULUM
FROM THE VESICLE

8. DEVELOPMENT OF INTERNAL EAR
• STATOACCOUSTIC GANGLION
• GROUP OF CELLS WHICH BREAKS AWAY
FROM THE OTIC VESICLE
• ALSO RECEIVES CELLS FROM NEURAL CREST
• SPLITS INTO---1—COCHLEAR PART
• ---2---VESTIBULAR PART

9. DEVELOPMENT OF INTERNAL EAR
COCHLEAR AND VESIBULAR PARTS SUPPLY THE
SENSORY CELLS OF—
1—ORGAN OF CORTI
2---SACCULE
3---UTRICLE
4---SEMICIRCULAR CANALS

10. DEVELOPMENT OF INTERNAL EAR
• SACCULE COCHLEA AND ORGAN OF CORTI
• TUBULAR OUTPOCKETING FROM THE LOWER
END OF SACCULE– THE COCHLEAR DUCT
• APPEARS IN THE 6th WEEK
• PENETERATES THE SURROUNDNG MESENCHYME
IN A SPIRAL FASHION
• COMPLETES 2.5 TURNS AT THE END OF 8th WEEK
• FORMS THE MEMBRANOUS COCHLEA

12. DEVELOPMENT OF INTERNAL EAR
SACCULE [ CONTD ]
CONNECTION OF COCH DUCT WITH THE
SACCULE IS REDUCED TO A NARROW DUCTUS
REUNIENS
MESENCHYME SURROUNDING THE COHLEAR
DUCT DIFFERENTIATES INTO CARTILAGENOUS
OTIC CAPSULE

13. DEVELOPMENT OF INTERNAL EAR
• MEMBRANOUS LABYRINTH ENLARGES AND
VACUOLES APPEAR IN CARTILAGENOUS
CAPSULE IN THE 10th WEEK
• VACUOLES BECOME CONFLUENT TO FORM
PERILYMPHATIC SPACE
• MEMBRANOUS LABYRINTH SUSPENDED IN A
FLUID [ PERILYMPH ] IN THE PERILYMPHATIC
SPACE
• CARTILAGENOUS CAPSULE OSSIFIES TO FORM THE
BONY LABYRINTH

14. DEVELOPMENT OF INTERNAL EAR
PERILYMPHATIC SPACE RELATED TO COCHLEAR
DUCT DEVELOPS INTO---
1—SCALA VESTIBULI SEPARATED FROM THE
COCHLEA BY THE VESTIBULAR MEMBRANE
2---SCLA TYMPANI SEPARATED FROM THE
COCHLEA BY THE BASILAR MEMBRANE
LAT WALL OF COCH DUCT REMAINS ATTACHED
TO THESURROUNDING CARTILAGE BY SPIRAL
LIGAMENT
MEDIAN ANGLE OF COCH. DUCT IS CONNECTED TO AND
IS SUPPORTED BY A LONG CARTILAGENOUS PROCESS—THE
MODIOLUS FUTURE AXIS OF COCHLEA

16. DEVELOPMENT OF INTERNAL EAR
SPIRAL ORGAN OF CORTI
DIFFERENTIATES FROM CELLS IN THE WALLS OF
COCHLEAR DUCT
GANGLION CELLS OF 8th NERVE MIGRATE ALONG
THE COILS OF COCHLEA
FORMS THE SPIRAL GANGLION
NERVE PROCESSES EXTEND FROM THE
GANGLION TO THE SPIRAL ORGAN WHERE THEY
TERMINATE ON THE HAIR CELLS

17. DEVELOPMENT OF INTERNAL EAR
SPIRAL ORGAN OF CORTI
EPITHELIAL CELLS OF THE COCHLEA FORM TWO
RIDGES---
1—INNER RIDGE [SPIRAL LIMBUS ]
2---OUTER RIDGE
OUTER RIDGE FORMS 3—4 ROWS OF HAIR
CELLS—SENSORY CELLS OF AUDITORY SYSTEM
HAIR CELLS COVERED BY TECTORIAL MEMBRANE

19. DEVELOPMENT OF INTERNAL EAR
ORGAN OF CORTI [CONTD]
TECTORIAL MEMBRANE IS ATTACHED TO SPIRAL
LIMBUS AND ITS TIP IS ON HAIR CELLS
ORGAN OF CORTI FORMED BY—1-TECT MEMB
---2-HAIR CELLS
IMPULSES RECEIVED BY THE ORGAN OF CORTI
ARE TRANSMITTED TO---SPIRAL GANGLION
FROM THERE TO CNS BY THE AUDITORY FIBRES
OF 8TH CRANIAL NERVE

20. DEVELOPMENT OF INTERNAL EAR
UTRICLE AND SEMICIRCULAR CANALS
SEMICIRCULAR CANALS APPEAR AS FLAT
OUTPOCKETINGS OF THE UTRICLE
CENTRAL PORTIONS OF THE WALLS OF THESE
DISAPPEAR FORMING 3 SEMICIRCULAR CANALS
1—POSTERIOR
2—SUPERIOR/ANTERIOR
3—LATERAL/HORIZONTAL

22. DEVELOPMENT OF INTERNAL EAR
SEMICIRCULAR CANALS[CONTD]
ONE END OF EACH CANAL DILATES TO FORM
CRUS AMPULLARES
IMPULSE GENERATED IN SENSORY CLLS OF
CRISTAE AND MACULAE AS A RESULT OF
CHANGE IN POSITON ARE TRANSMITTED BY
VESTIBULAR FIBRES

23. DEVELOPMENT OF INTERNAL EAR
MACULAE ARE SENSORY AREAS IN THE WALLS
OF UTRICLE AND SACCULE
CELLS IN THE AMPULLAE FORM A CREST----
CRISTA AMPULLARIS CONTAINING SENSORY
CELLS FOR THE MAINTENANCE OF EQUILIBRIUM

24. DEVELOPMENT OF MIDDLE EAR
TYMPANIC CAVITY AND AUDITORY TUBE
• TYMPANIC CAVITY DERIVED FROM THE ENDODERM OF
1st PHARYNGEAL POUCH
• POUCH EXPANDS LATERALLY
• COMES INTO CONTACT WITH 1st PHARYNGEAL
CLEFT
• DISTAL PART FORMS TUBOTYMPANIC RECESS
• WIDENS AND FORMS THE TYMPANIC CAVITY
• PROXIMAL PART REMAINS NARROW AND FORMS THE
AUDITORY TUBE THROUGH WHICH TYMP CAVITY
COMMUNICATES WITH THE NASOPHARYNX

26. DEVELOPMENT OF MIDDLE EAR
OSSICLES
MALLEUS AND INCUS FROM THE CARTILAGE OF
1st ARCH
STAPES FROM THE CARTILAGE OF 2nd ARCH
REMAIN EMBEDDED IN THE SURROUNDING
MESENCHYME TILL THE 8th MONTH
OSSICLES ARE FREE WHEN THE MESENCHYME
DISSOLVES

27. DEVELOPMENT OF MIDDLE EAR
OSSICLES [CONTD ]
WHEN FREE BECOME SURROUNDED BY THE
ENDODERMAL EPITHELIUM OF TYMPANIC
CAVITY
EPITHELIUM CONNECTS THEM TO THE WALL OF
THE CAVITY
SUPPORTING LIGAMENTS DEVELOP LATER

29. DEVELOPMENT OF MIDDLE EAR
MASTOID PROCESS
DURING LATE FOETAL LIFE TYMP CAVITY
EXPANDS TO FORM MASTOID ANTRUM
LOCATED IN THE PETROMASTOID PART OF
TEMPORAL BONE
AFTER BIRTH EPITHELIUM OF TYMPANIC CAVITY
INVADES THE DEVELOPING MASTOID PROCESS
LATER EPITHELIUM LINED SACS ARE FORMED
MIDDLE EAR CONTINUES TO GROW THROUGH
PUBERTY

32. DEVELOPMENT OF EXTERNAL EAR
EXTERNAL AUDITORY MEATUS
• FROM THE DORSAL PART OF 1st PHARYNGEAL
GROOVE
• ECTODERMAL CELLS AT THE BOTTOM OF THIS
FUNNEL SHAPED TUBE PROLIFERATE TO FORM
MEATAL PLUG
• IN LATE FOETAL PERIOD CENTRAL CELLS
DEGENERATE
• MEATUS RELATIVELY SHORT AT BIRTH
• ATTAINS ADULT LENGTH AROUND 9th YEAR

33. DEVELOPMENT OF EXTERNAL EAR
TYMPANIC MEMBRANE
SOURCES
1st PHARYNGEAL MEMBRANE
EXTERNAL COVERING FROM SURFACE
ECTODERM
INTERNAL COVERING FROM ENDODERM OF
TUBOTYMPANIC RECESS
MESODERM OF Ist &2nd ARCH GROWS B/W THE
TWO LAYERS AND FORMS THE FIBROUS STRATUM
MAJOR PART OF THE MEMB FIRMLY ATTACHED TO THE
HANDLE OF MALLEUS

34. DEVELOPMENT OF EXTERNAL EAR
AURICLE
SOURCE
SIX MESENCHYMAL SWELLINGS ----
AURICULAR HILLOCKS
ARISE ALONG THE MARGIN OF 1st GROOVE
FUSE AND FORM THE DEFINITIVE AURICLE

36. CONGENITAL ANOMALIES OF EAR
1---CONGENITAL DEAFNESS---
a—CONDUCTIVE
b---NERVE
CAUSES
1--MOSTLY GENETIC FACTORS
2--MAY BE ASSOCIATED WITH OTHER HEAD AND
NECK ABNORMALITIES
3 1st ARCH SYNDROME—INCUS &MALLEUS
INVOLVED

37. CONGENITAL ANOMALIES OF EAR
CONGENITAL DEAFNESS [CONTD ]
4--RUBELLA DURING 7th & 8th WEEK MAY CAUSE
MALDEVELOPMENT OF SPIRAL ORGAN
5--MATERNAL GOITER
6--CONGENITAL FIXATION OF THE STAPES

38. CONGENITAL ANOMALIES OF EAR
AURICILAR ABNORMALITIES [ COSMETIC ]
1—PREAURICULAR SINUS—PIT LIKE CUTANEOUS
DEPRESSION—TRIANGULAR AREA ANTERIOR
TO THE AURICLE
CAUSE? ABNORMAL DEVELOPMENT OF
HILLOCKS
FAMILIAL AND OFTEN BILATERAL

39. CONGENITAL ANOMALIES OF EAR
2—AURICULAR APPENDAGES
CAUSE—DUE TO FORMATION OF ACCESSORY
HILLOCKS
USUALLY ANTERIOR TO AURICLE
MORE OFTEN UNILATERAL

41. CONGENITAL ANOMALIES OF EAR
3—ANOTIA
ABSENCE OF AURICLE
COMMONLY ASSOCIATED WITH 1st ARCH SYN
4—MICROTIA
SMALL AURICLE
5—ATRESIA OF EXT ACCOUSTIC MEATUS
FAILURE OF MEATAL PLUG TO CANALIZE

44. CONGENITAL ANOMALIES OF EAR
6—CONGENITAL CHOLESTEATOMA
REST OF EPITHELIAL CELLS
APPEAR AS WHITE CYST LIKE STRUCTURES
MEDIAL TO OR WITHIN THE TYMPANIC
MEMBRANE
ORIGIN FROM MEATAL PLUG
REST---GROUP OF CELLS THAT HAVE BECOME
DISPLACED AND LIES IN TISSUE OF ANOTHER
CHARACTER