INTRODUCTION:
It is a thin, translucent partition
between the external acoustic meatus and the middle ear.
- Shape: Oval Shaped.
- Measurement: 9×10 mm
- Location: It is placed obliquely at the angle of the 55° with the floor of the Meatus.
FEATURES:
The membrane has 2 Surfaces:-
Outer Surface:
- It is free, concave and lined by a thin skin.
Inner Surface:
- It provides attachment to the handle of the malleus.
- It is convex.
- At the tip of the handle of the malleus lies the point maximum convexity called UMBO.
- The membrane is thickened at its circumference which is fixed to the tympanic membrane is lightly stretched called PARS TENSA.
- The part between the two malleolar fold is loose is known as PARS flaccida.
- It is crossed internally by chorda tympani. It is more liable to rupture.
- The membrane is held tense by the inward pull of the tensor tympani muscle which is inserted into the upper end of the handle of malleus.
STRUCTURE:
The tympanic membrane is composed of the 3
types:-
- Outer cuticular layer of skin.
- Middle Fibrous layer: It is made up of Superficial radiating fibers and deep circular fibers. The Fibrous layer is replaced by loose areolar tissue in pars flaccida.
- Inner mucous layer: It is lined by the low ciliated columnar epithelium.
ARTERIAL SUPPLY:
- The outer surface is supplied by AURICULAR branch of the maxillary artery.
- The inner surface is supplied by the anterior and posterior tympanic artery.
VENOUS DRAINAGE:
- Outer surface drains into the external jugular vein.
- Inner surface drains into the transverse sinus.
LYMPHATIC DRAINAGE:
It
drains into preauricular and Retropharyngeal Lymph Nodes.
NERVE SUPPLY:
Outer surface:
- Anteroinferior part:- supplied by Auriculotemporal nerve.
- Anterosuperior part:- supplied by the temporal branch of the vagus nerve.
Inner surface:
- It is supplied by tympanic branch.
APPLIED ANATOMY:
- Tympanic membrane perforation.
- Myringotomy:- In this, the membrane is incised to drain pus present in the middle ear.
- Myringectomy:- Removal of tympanic membrane.