Ear canal

Ear canal
Anatomy of the human ear.
Details
PrecursorGroove (cleft) of the first branchial arch[1]
ArteryAnterior part: superficial temporal artery
posterior part: posterior auricular artery
VeinSuperficial temporal veins, external jugular vein, pterygoid plexus
NerveAuriculotemporal nerve, great auricular nerve, auricular branch of vagus nerve
LymphSuperficial cervical lymph nodes, deep cervical lymph nodes
Identifiers
Latinmeatus acusticus externus
MeSHD004424
TA98A15.3.01.045
TA26867
FMA61734
Anatomical terminology

The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the auricle to the eardrum and is about 2.5 centimetres (1 in) in length and 0.7 centimetres (0.3 in) in diameter.

Structure

The human ear canal is divided into two parts. The elastic cartilage part forms the outer third of the canal; its anterior and lower wall are cartilaginous, whereas its superior and back wall are fibrous. The cartilage is the continuation of the cartilage framework of auricle. The cartilaginous portion of the ear canal contains small hairs and specialized sweat glands, called apocrine glands, which produce cerumen (ear wax). The bony part forms the inner two thirds. The bony part is much shorter in children and is only a ring (annulus tympanicus) in the newborn. The layer of epithelium encompassing the bony portion of the ear canal is much thinner and therefore, more sensitive in comparison to the cartilaginous portion.

Size and shape of the canal vary among individuals. The canal is approximately 2.5 centimetres (1 in) long and 0.7 centimetres (0.28 in) in diameter.[2] It has a sigmoid form and runs from behind and above downward and forward. On the cross-section, it is of oval shape. These are important factors to consider when fitting earplugs.

Disorders

Due to its relative exposure to the outside world, the ear canal is susceptible to diseases and other disorders. Some disorders include:

Earwax

Main article: Earwax

Earwax, also known as cerumen, is a yellowish, waxy substance secreted in the ear canals. It plays an important role in the human ear canal, assisting in cleaning and lubrication, and also provides some protection from bacteria, fungi, and insects. Excess or impacted cerumen can press against the eardrum and/or occlude the external auditory canal and impair hearing, causing conductive hearing loss. If left untreated, cerumen impaction can also increase the risk of developing an infection within the ear canal.

Additional images

  • Base of skull. Inferior surface.
    Base of skull. Inferior surface.
  • Left infratemporal fossa.
    Left infratemporal fossa.
  • External and middle ear, opened from the front. Right side.
    External and middle ear, opened from the front. Right side.
  • Horizontal section through left ear; upper half of section.
    Horizontal section through left ear; upper half of section.
  • Lateral head anatomy detail. Facial nerve dissection.
    Lateral head anatomy detail. Facial nerve dissection.

See also

References

  1. ^ hednk-022—Embryo Images at University of North Carolina
  2. ^ Faddis, B. T. (2008). "Structural and functional anatomy of the outer and middle ear". In W. Clark & K. Ohlemiller (Eds.), Anatomy and physiology of hearing for audiologists (pp. 93–108). Thomson Delmar Learning.
  • Veterans Health Administration web site
  • OSHA web site
  • Continuing Medical Education Ear Photographs
  • Otoscopy Tutorial w/ Images
  • "Anatomy diagram: 34257.000-1". Roche Lexicon - illustrated navigator. Elsevier. Archived from the original on 2012-07-22.