From Embryology

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Middle Ear - Incus

Left incus. A. From within. B. From the front.

  • named from resemblance to an anvil
    • more like a premolar tooth, with two roots, which differ in length, and are widely separated from each other.
  • consists of a body and two crura
Adult Incus Anatomy
Component Description
Body (corpus incudis) somewhat cubical but compressed transversely anterior surface is a deeply concavo-convex facet facet articulates with the head of the malleus
Short Crus (crus breve; short process) somewhat conical in shape projects almost horizontally backward attached to the fossa incudis, in the lower and back part of the epitympanic recess
Long Crus (crus longum; long process) descends nearly vertically behind and parallel to the manubrium of the malleus bending medialward, ends in a rounded projection, the lenticular process lenticular process is tipped with cartilage, and articulates with the head of the stapes

(text modified from Gray's Anatomy)


Human incus development timing:[1]

  • 16 weeks - force lines start through two cortical fascicles in the long process
  • 17 to 20 weeks - two cortical fascicles progressively extend in a rostro-caudal direction
  • 21 weeks - occupy the whole extension of the long process
  • 22 weeks - fusion of both cortical fascicles begins.
  • 30 weeks - strengthened by the crossing of bone trabeculae from one cortical to another. Two fascicles come out of the incus body, surrounding the medullary cavity and going in the direction of the short process.

  1. <pubmed>18581276</pubmed>

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Gray H. Anatomy of the human body. (1918) Philadelphia: Lea & Febiger.

Cite this page: Hill, M.A. (2024, June 13) Embryology Gray0917.jpg. Retrieved from

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current02:49, 20 May 2011Thumbnail for version as of 02:49, 20 May 2011600 × 379 (44 KB)S8600021 (talk | contribs)==Middle Ear - Incus== Left incus. A. From within. B. From the front.