External ear, Biology

EXTERNAL EAR -

  1. It is an oval shaped, some what funnel like, skin covered flap of elastic cartilage and muscles.
  2. It's outer stiff ridge is called hellix. Lower flexible lobe is lobule. Cavity is known as auricle or Concha.
  3. It collects sound waves and direct them to canal i.e. external auditory meatus.
  4. It is trumpet shaped in rabbit. Situated on lateral side of head part.
  5. Immovable as oticularis muscles are vestigeal, movable in rabbit.
  6. External auditory meatus run up to tympanum. It is 'S' shaped tube to prevent hard objects hitting the tympanum directly, in rabbit tube is long & straight.
  7. Canal is supported by elastic cartilage in the outer portion & by temporal bone in the inner portion.
  8. Outer region of canal bears hair to cheek dust particle.
  9. Inner region consists of ceruminous gland or wax gland to secreate cerumen or ear wax to protect lining of meatus & tympanum.
  10. Pinnae absent in platypus, whales seal, walrus & sea cow etc.
  11. Tympanum or tympanic membrane is thin, oval, tightly stretched on a cartilage i.e. Annular tympanicus.
  12. It is composed of connective tissue with fibres radiating from the central region called umbo.
  13. It's external part is ectodermal, middle part is mesodermal & inner part is endodermal in origin.

2348_man ear structure.png

Ear of Man

742_rabbit ear.png

Ear of Rabbit

Posted Date: 10/3/2012 2:42:33 AM | Location : United States







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