External ear Flashcards
Parts
Auricle
External acoustic canal
Tympanic membrane
Auricle
External pinna except its lobule and the outer part of the external acoustic canal ✓✓
Elastic cartilge w skin
Skin
Tight on lateral part,loose on medial part
Incisura Terminalis
No cartilage bw the tragus and crus of helix (endaural approach)
Concha
Reconstruction surgery on middle ear
Depressed nasal bridge
Grafts of skin and cartilage (pinna)»_space; nasal ala
EAC
Concha to tympanic membrane 24mm Posterior wall Outer part is directed up, back and medial Inner part is downward,forwards,medially
Tympanic membrane
Up back or laterally pull karna chahiye
Cartilaginous and bony
Outer 3rd a continuous from pinna, fissures of santorini through which infection can pass through. Skin covering the cartilaginous canal is thick & contains thick and contains ceruminous and sebaceous glands that secrete wax. Hair is confined to the outer canal so furuncles onli there
Bony part
It forms inner two-thirds (16 mm). Skin lining the bony canal is thin and continuous over the tympanic membrane.
It is devoid of hair and ceruminous glands.
Isthmus
About 6 mm lateral to tympanic membrane, the bony meatus presents a narrowing called isthmus. Foreign bodies, lodged medial to the isthmus, get impacted, and are difficult to remove.
Anterior recess
Anteroinferior part of the deep meatus, beyond the isth-mus, presents a recess called anterior recess, which acts as a cesspool for discharge and debris in cases of external and middle ear infections
Foramen of Huschke
(Figure 1.2). Anteroinferior part of the bony canal may present a def i ciency (foramen of Huschke) in children up to the age of four or sometimes in adults, permitting infections to and from the parotid.
Tympanic membrane
.It forms the partition between the external acoustic canal and the middle ear. It is obliquely set and as a result, its pos-terosuperior part is more lateral than its ant you eroinferior part.
It is 9–10 mm tall, 8–9 mm wide and 0.1 mm thick. Tym-panic membrane can be divided into two parts:
Pars tensa
- PARS TENSA It forms most of tympanic membrane. Its periphery is thick-ened to form a fi brocartilaginous ring called annulus tym-panicus, which fi ts in the tympanic sulcus. The central part of pars tensa is tented inwards at the level of the tip of mal-leus and is called umbo. A bright cone of light can be seen radiating from the tip of malleus to the periphery in the anteroinferior quadrant.
PARS FLACCIDA (SHRAPNELL’S MEMBRANE)
PARS FLACCIDA (SHRAPNELL’S MEMBRANE) This is situated above the lateral process of malleus between the notch of Rivinus and the anterior and posterior malleal folds (earlier called malleolar folds). It is not so taut and may appear slightly pinkish
Layers of Tympanic Membrane
Outer epithelial layer, which is continuous with the skin lining the meatus.
• Inner mucosal layer, which is continuous with the mucosa of the middle ear.
• Middle f i brous layer, which encloses the handle of mal-leus and has three types of fi bres—the radial, circular and parabolic
Relations of Tympanic Membrane
Superiorly: Middle cranial fossa
Posteriorly: Mastoid air cells and the facial nerve
Inferiorly: Parotid gland
Anteriorly: Temporomandibular joint Posterosuperior part of deeper canal near the tympanic membrane is related to the mastoid antrum. “Sagging” of this area may be noticed in acute mastoiditis.
Greater auricular nerve (C2,3) Lesser occipital (C
Auriculotemporal (V
Auricular branch of vagus (CN X)
Facial nerve
Greater auricular nerve (C2,3) Lesser occipital (C
Auriculotemporal (V
Auricular branch of vagus (CN X)
Facial nerve
External Auditory membrane and Tympanic
Greater auricular nerve
Auriculotemporal nerve
