Page 97 - Edited - Webster HEAD AND NECK - part 2-Merge PDF

HN 291 THE EAR HN 291

THE EAR HAS THREE PARTS - OUTER, MIDDLE, & INNER. The first two of these develop
st
from the 1 BRANCHIAL CLEFT & POUCH respectively. The tissue seperating cleft & pouch
becomes the TYMPANIC MEMBRANE (ear drum)
BRAINSTEM
Oticcyst ECTODERM OTIC
CYST

1 branchial becomes
st
OPTIC left MESODERM INNER
CUP EAR
1 2 ENDODERM
3 4 1 BRANCHIAL
ST
st
BRANCHIAL CLEFT becomes 1 BRANCHIAL
ARCHES OUTER EAR POUCH becomes
MIDDLE EAR & PHARYNX
AUDITORY
TUBE

TRILAMINAR
PARTITION BECOMES
TYMPANIC MEMBRANE

SCHEMATIC SECTION THROUGH FIRST
BRANCHIAL CLEFT & POUCH

SCHEME OF DEFINITIVE ARRANGEMENT (1)

SQUAMOUS TEMPORAL BONE

MIDDLE CRANIAL FOSSA→
PINNA of TEGMEN
OUTER EAR: TYMPANI PETROUS
ELASTIC TEMPORAL
CARTILAGE BONE: the MIDDLE &

SKELETON INNER EARS ARE WITHIN
INNER EAR THIS BONE. NOTE THIN
(NEURAL ROOF (TEGMEN TYMPANI)
TRANSDUCTION) OF TYMPANIC CAVITY

POSTERIOR
CRANIAL
EXTERNAL FOSSA
AUDITORY
NOTE THAT MEATUS OF
"MEATUS" OUTER EAR TYMPANIC BASI-
MEANS A CAVITY OCCIPITAL
BONE
"TUBE" -NOT
A "HOLE"

NASO-
TYMPANIC PHARYNX
BONE (PLATE)
(TEMPORAL)
CARTILAGINOUS PARTS OF AUDITORY
(PHARYNGO-TYMPANIC)
BONY TUBE

NOTICE 1. The OUTER EAR is the PINNA ("ear" of everyday parlance) & the AUDITOR MEATUS. The
latter has a lateral CARTILAGINOUS PART & a medial BONY PART.
2. The TYMPANIC MEMBRANE slopes upwards & outwords & is NOT attached to the petrons
temporal bone.
3. The THREE EAR OSSICLES in the TYMPANIC CAVITY of the MIDDLE EAR
4. The connection between MIDDLE EAR & NASO-PHARYNX-The AUDITORY (PHARYGO
TYMPANIC) TUBE, which also has bony & Cartilaginous parts.