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ANATOMY
Medicine Made Simple
, Ear
External ear
3 parts Middle ear
Inner ear
External ear
Comprises of auricle/pinna and the external
acoustic meatus
Auricle-mostly cartilaginous with skin closely
applied
External acoustic meatus-
i. S shaped canal
ii. 1.5 inches long
iii. Directed medially upwards forwards then medially backwards,finally medially forwards
downwards
iv. Conduct sound waves from the concha to tympanic membrane
v. Medial 2/3 is bony and lateral 1/3 is cartilaginous
vi. Bony part – narrower, formed by tympanic plate of temporal bone and the squamous
temporal bone, lined by thin skin firmly adherent to the periosteum
vii. Cartilaginous part – Lined by skin containing
hair, sebaceous glands and wax glands
(modified sweat glands - ceruminous)
viii. Nervous supply –
Anterior ½ by auriculotemporal nerve
Posterior ½ by auricular branch of Vagus nerve
Tympanic membrane
Separates external acoustic meatus from middle ear
Derived from all 3 dermal layers
Oval shaped, faces downwards, forwards and
laterally
Translucent except at margins
Placed obliquely at an angle of 55 with the floor of
the meatus
Has outer and inner surfaces
Thickened circumferentially which is attached to the tympanic sulcus of the temporal bone and
superiorly attached to the tympanic notch where the sulcus is deficient
Outer surface– concave, lined by skin
Inner surface – convex, provide attachment to the handle of the malleus
Point of maximum convexity – umbo, lies at the tip of the handle of the malleus
Greater part of the membrane tightly stretched –pars tensa
Loose part between the two malleolar folds, thin and lax – pars flaccida
Pars flaccida – crossed internally by chorda tympani and more likely to rupture than pars tensa
1
ANATOMY
Medicine Made Simple
, Ear
External ear
3 parts Middle ear
Inner ear
External ear
Comprises of auricle/pinna and the external
acoustic meatus
Auricle-mostly cartilaginous with skin closely
applied
External acoustic meatus-
i. S shaped canal
ii. 1.5 inches long
iii. Directed medially upwards forwards then medially backwards,finally medially forwards
downwards
iv. Conduct sound waves from the concha to tympanic membrane
v. Medial 2/3 is bony and lateral 1/3 is cartilaginous
vi. Bony part – narrower, formed by tympanic plate of temporal bone and the squamous
temporal bone, lined by thin skin firmly adherent to the periosteum
vii. Cartilaginous part – Lined by skin containing
hair, sebaceous glands and wax glands
(modified sweat glands - ceruminous)
viii. Nervous supply –
Anterior ½ by auriculotemporal nerve
Posterior ½ by auricular branch of Vagus nerve
Tympanic membrane
Separates external acoustic meatus from middle ear
Derived from all 3 dermal layers
Oval shaped, faces downwards, forwards and
laterally
Translucent except at margins
Placed obliquely at an angle of 55 with the floor of
the meatus
Has outer and inner surfaces
Thickened circumferentially which is attached to the tympanic sulcus of the temporal bone and
superiorly attached to the tympanic notch where the sulcus is deficient
Outer surface– concave, lined by skin
Inner surface – convex, provide attachment to the handle of the malleus
Point of maximum convexity – umbo, lies at the tip of the handle of the malleus
Greater part of the membrane tightly stretched –pars tensa
Loose part between the two malleolar folds, thin and lax – pars flaccida
Pars flaccida – crossed internally by chorda tympani and more likely to rupture than pars tensa
1
