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The Tympanic Membrane

The tympanic membrane viewed from within. (Testut.)

The malleus has been resected immediately beyond its lateral process, in order to show the tympanomalleolar folds and the membrana flaccida.

Legend

1. Tympanic membrane.

2. Umbo.

3. Handle of the malleus.

4. Lateral process.

5. Anterior tympanomalleolar fold.

6. Posterior tympanomalleolar fold.

7. Pars flaccida.

8. Anterior pouch of Tröltsch.

9. Posterior pouch of Tröltsch.

10. Fibrocartilaginous ring.

11. Petrotympanic fissure.

12. Auditory tube.

13. Iter chordæ posterius.

14. Iter chordæ anterius.

15. Fossa incudis for short crus of the incus.

16. Prominentia styloidea.

The Tympanic Membrane

(membrana tympani) (Fig. 909, Fig. 910) separates the tympanic cavity from the bottom of the external acoustic meatus. It is a thin, semitransparent membrane, nearly oval in form, somewhat broader above than below, and directed very obliquely downward and inward so as to form an angle of about fifty-five degrees with the floor of the meatus. Its longest diameter is downward and forward, and measures from 9 to 10 mm.; its shortest diameter measures from 8 to 9 mm.

The greater part of its circumference is thickened, and forms a fibrocartilaginous ring which is fixed in the tympanic sulcus at the inner end of the meatus. This sulcus is deficient superiorly at the notch of Rivinus, and from the ends of this notch two bands, the anterior and posterior malleolar folds, are prolonged to the lateral process of the malleus.

The small, somewhat triangular part of the membrane situated above these folds is lax and thin, and is named the pars flaccida; in it a small orifice is sometimes seen.

The manubrium of the malleus is firmly attached to the medial surface of the membrane as far as its center, which it draws toward the tympanic cavity; the lateral surface of the membrane is thus concave, and the most depressed part of this concavity is named the umbo.

Structure

The tympanic membrane is composed of three strata: a lateral (cutaneous), an intermediate (fibrous), and a medial (mucous). The cutaneous stratum is derived from the integument lining the meatus. The fibrous stratum consists of two layers: a radiate stratum, the fibers of which diverge from the manubrium of the malleus, and a circular stratum, the fibers of which are plentiful around the circumference but sparse and scattered near the center of the membrane. Branched or dendritic fibers, as pointed out by Grüber, are also present especially in the posterior half of the membrane.

(Text modified from Gray's 1918 Anatomy)


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Reference

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


Cite this page: Hill, M.A. (2024, June 23) Embryology Gray0910.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Gray0910.jpg

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current06:44, 19 August 2012Thumbnail for version as of 06:44, 19 August 2012400 × 548 (78 KB)Z8600021 (talk | contribs)==The Tympanic Membrane== The tympanic membrane viewed from within. (Testut.) The malleus has been resected immediately beyond its lateral process, in order to show the tympanomalleolar folds and the membrana flaccida. ===Legend=== {| | 1. Tympanic mem