ANATOMY OF EAR.pptx (ENT) MBBS PRESENTATION

ANATOMY OF EAR

1. ANATOMY OF EAR DR. PARIMA PAL MBBS, DNB ENT ASSISTANT PROFESSOR DEPT OF ENT

2. ANAOMY OF EXTERNAL EAR It comprises of pinna external auditory canal.

3. Pinna Pinna is developed from 6 tubercles around the first branchial cleft. It is composed of yellow elastic cartilage covered by fat, sc tissue and skin. It has two surfaces- lat and medial.

4. External auditory canal It is S shaped and approximately 24 mm in length. It has two parts-outer 1/3 rd is cartilagenous and inner 2/3 rd bony. Outer part is directed backward, upward and medially and inner part is directed forward, downward and medially. It has two fissures- fissure of Santorini in the cartilagenous canal through which parotid or superficial mastoid infections can appear in meatus and vice versa. Foramen of Huschke is present in the bony part upto 4 yrs of age. About 6 mm lat to TM lies the isthmus. Beyond the isthmus lies anterior recess.

5. Nerve supply of pinna

6. Nerve supply of EAC Ant wall, floor is supplied by auricuotemporal nerve. Rest of the canal and post part of TM is supplied byauricular branch of vagus known as Arnold’s nerve. A twig of facial nerve is incorporated in the Arnold’s nerve.

7. TYMPANIC MEMBRANE It is a thin semi translucent membrane, pearly white in color lying obliquely in the medial end of EAC at an angle of 55 degree. It forms the partition between the external ear and middle ear. It is 9-10 mm tall, 8-9 mm wide and 0.1 mm thick. It is divided into 2 parts – pars tensa and pars flaccida .

8. Pars tensa It forms most of the tympanic membrane. Its periphery is thickened to form a fibrocartilagenous ring called annulus tympanicus . Its central part is tented inward at the level of the tip of malleus and it is called umbo . Cone of light is seen in th antero inferior quadrant

9. Pars flaccida is situated above the lateral process of malleus between the notch of Rivinus and the ant and post malleolar folds. Layers of tympanic membrane- 1. Outer epithelial layer 2. Inner mucosal layer 3. Middle fibrous layer which encloses handle of malleus and has radial, circular and parabolic fibres . Fibrous layer is thin in pars flaccida and the fibres are not organized.

10. Nerve supply – outer surface is supplied by auriculotemporal nerve ant part tympanic branch of vagus in post part. Inner surface is supplied by tympanic plexus.

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